JPH07322283A - Video camera with white balance adjustment device - Google Patents

Abstract

PURPOSE:To revise a white balance adjustment operation characteristic by using a green object area detection and follow light/rear light state discrimination means so as to apply correction when a position signal of an aperture device is compared with a threshold level thereby discriminating whether or not an object is resident indoor or outdoor. CONSTITUTION:An image is photoelectric-converted by a CCD 2 and three primary color signals R, G, B are extracted from a separation circuit 3. A matrix circuit 6 generates a luminance signal Y and color difference signals R-Y, B-Y. A selection circuit 21 and an A/D converter 22 sample the signals and convert them into digital signals, which are outputted. An integration device 23 receives a switching signal S2, integrates the digital signal for each area of 64 divisions of a screen area and the result is stored in a memory 26. Each of 64-sets of luminance evaluation values Yij, R-Y luminance evaluation values rij and B-Y luminance evaluation values bij is obtained through sequential selection. When there is a large difference between the Yij in the middle of the screen and the Yij at the circumferential part, it is discriminated to be a rear light state, and the region of rij<ro and bij<bo is discriminated to be green and to get dark, and a correction value decision circuit 42 decides a correction value. An indoor/outdoor discrimination circuit 43 receives an aperture position signal and the correction value from a hole sensor 12 to decide whether or not an object is resident indoor or o outdoor based on the data white balance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance adjusting device for controlling white balance based on an image pickup video signal obtained from an image pickup device.

[0002]

2. Description of the Related Art In a color video camera, it is necessary to control white balance in order to correct a difference in wavelength distribution of light depending on a light source. In this control, the ratio of the three primary color signals of red (hereinafter R), blue (hereinafter B), and green (hereinafter G) is 1:
It is performed by adjusting the gain of each color signal so that the ratio becomes 1: 1. Generally, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-35792 (H04N9 / 73), the integrated values of the color difference signals RY and BY of the screen become zero (the value taken at the time of achromatic color photographing). The method of adjusting the gain is widely used.

The difference in the wavelength distribution of the light source is generally represented by the color temperature (unit: Kelvin: K). Usually, the color temperature of natural light has a bluish color of 5000 K or more, and the color temperature of artificial light has a reddish color of 5000 K or less. Normally, considering that natural light exists outdoors and artificial light exists indoors, only the gain correction in the direction of increasing the R signal and decreasing the B signal is performed when shooting outdoors.
On the contrary, it is considered that only the gain correction in the direction of increasing the B signal and decreasing the R signal should be performed when photographing indoors.

Therefore, the applicant of the present application, from the brightness signal level in the picked-up video signal or the diaphragm control signal for controlling the diaphragm value of the diaphragm mechanism so that this brightness signal becomes the optimum level, the indoor photographing state or the outdoor photographing state. JP-A-4-296192 discloses a white balance adjusting device configured to determine whether the state is a state and change the characteristics of the white balance adjusting operation according to the result.
It is proposed in the Gazette.

[0005]

When the diaphragm control signal is used for indoor / outdoor discrimination as in the prior art, the discrimination is quite inaccurate due to the hysteresis of the diaphragm.

Therefore, if the aperture value of the aperture mechanism is detected by a hall element or the like, the aperture value can be detected with high accuracy, and therefore the accuracy of discrimination between indoors and outdoors can be improved, but this method is applied to a system for correcting backlight or forward light. If is adopted, the aperture will be opened more when the backlight is corrected than when it is not corrected, and it is determined that it is darker than it actually is. That is, although the outdoor shooting is performed, the aperture value is reduced by the backlight correction, and the indoor shooting is erroneously determined. On the contrary, in the indoor shooting, when the forward light correction is performed, the aperture value becomes large, and it is erroneously determined as the outdoor shooting.

Further, even under the same illuminance, the degree of opening of the diaphragm becomes large due to the difference in reflectance caused by the difference in color of the subject. For example, when a large amount of green vegetation having a lower reflectance than other colors enters the screen, even if it is relatively bright outdoors, the aperture tends to open, and it is erroneously determined to be indoor shooting.

[0008]

SUMMARY OF THE INVENTION According to the present invention, the amount of both RY and BY color difference signals for each of a plurality of areas set by dividing an image pickup screen is detected as a color evaluation value to perform color evaluation. Gain adjusting means for performing a white balance adjusting operation for adjusting the gains of both red and blue color signals based on the value, and an image pickup device for adjusting the brightness level of the picked-up image signal to a target value for realizing an optimum exposure state. A diaphragm mechanism that adjusts the amount of incident light, diaphragm position detection means that outputs a diaphragm position signal whose level changes according to the diaphragm amount of the diaphragm mechanism, and a comparison between the diaphragm position signal and a threshold value to determine whether it is an indoor shooting condition or an outdoor shooting condition. An indoor / outdoor discrimination means for discriminating whether or not a backlight condition or a forward light condition occurs, and a correcting means for correcting the aperture position signal level or the threshold value according to the backlight condition or the forward light condition. Aperture after correction by discrimination means It constitutes a comparison of 置信 No. and the threshold, and changes the characteristics of the white balance adjustment operation in accordance with the comparison result.

As another means, a green subject detecting means for detecting the area occupied by a green subject on the image pickup screen based on the color evaluation value and a correction for the diaphragm position signal level or the threshold value depending on the area. The present invention is characterized in that a correction means is provided, the aperture position signal after correction is made by the indoor / outdoor discrimination means, and the threshold value is compared, and the characteristic of the white balance adjustment operation is changed according to the comparison result.

[0010]

With the above-described structure, when a backlit state occurs or a green subject occupies a large area on the image pickup screen, the aperture of the aperture mechanism opens even if it is used for outdoor shooting, and vice versa. When a light condition occurs, the aperture of the aperture mechanism closes even when shooting indoors. The erroneous discrimination is prevented by giving the value.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram of an automatic white balance adjusting circuit of a color video camera according to this embodiment. The light that has passed through the lens group 1 enters through a diaphragm mechanism 40, which will be described later, is imaged on the CCD 2 and is photoelectrically converted, and then is converted into three primary color signals of R, G and B by a color separation circuit 3. Taken out. The R and B signals of these three primary color signals are input to the camera process and matrix circuit 6 together with the G signal through the R and B amplifier circuits 4 and 5, respectively, and based on these, the luminance signal Y and the red and blue signals, respectively. Color difference signals R-Y and B-Y
Is created and supplied to the video circuit 7 to be subjected to known processing. Further, the Y, RY, and BY signals are simultaneously supplied to the selection circuit 21.

The selection circuit 21 receives the luminance signal Y and the color difference signals RY and B according to the selection signal S1 from the timing circuit 25.
One of the three signals of -Y is sequentially selected for each field, and Y → (RY) → (BY) → Y → (R
-Y) → ... is output to the A / D converter 22 in the subsequent stage every one field. The selection signal S1 is created based on the vertical sync signal obtained from the sync separation circuit 24 as described later.

The A / D converter 22 samples one of the luminance signal Y and the color difference signals RY and BY selected by the selection circuit 21 at a predetermined sampling period and converts the sampled value into a digital value. This value is output to the integrator 23.

The timing circuit 25 is based on the camera process and the vertical and horizontal synchronizing signals from the matrix circuit 6 and the fixed oscillator output for driving the CCD 2, and the image pickup screen is shown in FIG. Areas A11, A12, A13 ... A88, that is, Aij
It is divided into (i, j: 1 to 8), and a switching signal S2 for taking out the output of the selection circuit 21 in these areas in time division is output to the integrator 23 for each area.

Upon receipt of the switching signal S2, the integrator 23 adds the A / D conversion value of the output of the selection circuit 21 for each field over one field period, that is, digitally integrates for every 64 fields, and the 1 When the integration for the field is completed, this integrated value is stored in the memory 26 as an evaluation value. As a result, the digital integration value of the luminance signal Y corresponding to 64 regions in a certain arbitrary field is 64 luminance evaluation values y.
It will be obtained as ij. Further, in the next field, since the digital integration value of the color difference signal R-Y is selected by the selection circuit 21, as a result of integration in each area of the integrator 23, the digital integration value of the color difference signal R-Y is 64. It is obtained as the color evaluation value rij. Further, since the color difference signal BY is selected in the next field,
The digital integrated value of each area of the color difference signal BY is obtained as 64 color evaluation values bij. Thus, when the integration of the three fields of the luminance signal Y, the color difference signals RY, and BY is completed, the luminance evaluation value yij and the color evaluation value rij,
The values of 64 areas of bij are stored in the memory 26. After that, the same operation as described above is repeated, the luminance evaluation value yij in the next field, the color evaluation value rij in the next field, and the color evaluation value b in the next field.
ij will be sequentially updated.

The latest color evaluation value r obtained as described above
ij and bij are sent to the screen evaluation circuit 27 and the following equation 1
And the screen color evaluation values Vr and Vb of the entire screen of each color difference signal are calculated based on Equation 2 and Equation 2.

[0017]

[Equation 1]

[0018]

[Equation 2]

The numbers 1 and 2 are obtained by dividing the total sum of all 64 color evaluation values rij and bij of each region by the number of regions and
The average value for each area is calculated as the screen color evaluation value. The screen color evaluation values Vr and Vb are supplied to the gain control circuits 29 and 30, respectively.

The gain control circuit 29 controls the gain of the R amplifier circuit 4 so that the screen color evaluation value Vr becomes zero. Similarly, the gain control circuit 30 controls the gain B so that the screen color evaluation value Vb becomes zero.
The gain of the amplifier circuit 5 is controlled. Furthermore, both gain control circuits 2
The gain control characteristics in 9 and 30 are the indoor / outdoor discrimination circuit 43 described later.
It is changed according to the discrimination result from.

The reference level of the color difference signals input to the integrating circuit 23, that is, the zero level is preset to the level obtained when a perfect achromatic surface is photographed, and therefore each color difference signal is positive. It goes without saying that not only the value of but also a negative value can be taken.

The latest color evaluation values rij and bij stored in the memory 26 are input to the color distribution determination circuit 41 to determine the distribution status of a specific color in the image pickup screen. Here, the specific color means the color temperature distribution range of the shaded portion on the coordinate axis with the two color evaluation values in FIG. 3 as the vertical and horizontal axes, that is, the color evaluation value rij is smaller than the discrimination reference value r0, and the color evaluation value is When bij falls within a range smaller than the discrimination reference value b0 and both color evaluation values are within this range, the corresponding portions are displayed in a substantially green color on the screen.

The color distribution judgment circuit 41 plots the evaluation values of both colors for each area on the coordinate axes of FIG. 3 to judge whether or not they exist within the range of the shaded area, and the number of areas within the range. And has a function of counting the color evaluation value rij and the discrimination reference value r0 as shown in FIG.
, A single pulse-shaped comparison output is generated only when rij <r0. Similarly, the color evaluation value bij and the discrimination reference value b0 are compared by the comparator 52, and when bij <b0. Only one pulse-shaped comparison output is issued, and both comparison outputs are input to the AND gate 53 to take the logical sum and this A
The output of the ND gate 53 is counted by the counter 54.
These comparison and counting operations are executed for all 64 areas, and when the determination of all areas is completed, the count value N of the counter 54 is input to the correction value determination circuit 42 in the subsequent stage, and then the counter 54 is reset. The same operation is repeated again.

On the other hand, the brightness evaluation value yij is the exposure control circuit 4
3 is supplied. The exposure control circuit 43 has a structure as shown in FIG. The brightness evaluation value yij is alternatively input to the integrators 71 and 72 via the switch 70 and integrated over one field period. In the exposure control, the brightness levels in the central area AC in the center and the peripheral area AS in the periphery are compared for the backlight and forward light correction, and if there is backlight or forward light correction, the brightness levels are corrected. Do a job. As shown in FIG. 2, the central area AC is composed of the central 16 areas among the above-mentioned 64 areas, and the peripheral area AS is composed of the peripheral 48 areas. If the central area AC has an area S1 and the peripheral area AS has an area S2, then 3S1 = S2.

The switching signal S3 is issued from the timing circuit 25, and if the input brightness evaluation value yij is a value within the 16 areas forming the central area AC, the brightness evaluation value is input to the integrator 71 and vice versa. If the value is within the 48 areas forming the peripheral area AS, the switch 70 is switched so that the brightness evaluation value is input to the integrator 72.

Each of the integrators 71 and 72 adds all the brightness evaluation values input over one field period, and outputs the added output as the brightness levels Y1 and Y2. That is, the brightness level Y1 corresponds to the sum of the brightness evaluation values in the central area AC, and the brightness level Y2 corresponds to the sum of the brightness evaluation values in the peripheral area AS.

The luminance level Y1 is input to the simple averaging circuit 79, the normalizing circuit 73 and the weighting circuit 75. Similarly, the luminance level Y2 is the simple averaging circuit 79 and the normalizing circuit 74.
And the weighting circuit 76.

In the normalization circuit 73, the brightness level Y1 is divided by the area S1 of the central region AC to calculate the brightness level per unit area in the central region AC. Similarly, in the normalization circuit 74, the brightness level Y2 is calculated. Is divided by the area S2 of the peripheral region AS to calculate the luminance level per unit area in the peripheral region AS.

In the weighting circuit 75, the central area AC determined by the priority determining circuit 77, which will be described later, is assigned to the brightness level Y1.
By multiplying the weighting amount m1 of
Then, the brightness level Y2 is multiplied by the weighting amount m2, and the respective calculation results are input to the weighting averaging circuit 78.

The priority determining circuit 77 determines whether the ratio of the brightness level per unit area in the central area AC to the brightness level per unit area in the peripheral area AS is larger or smaller than the reference value R. The weighting amounts m1 and m2 of both areas are determined according to the determination result. Specifically, {(Y2 / S
2) / (Y1 / S1)}> R is satisfied, that is, when comparing the brightness levels per unit area, when the peripheral area AS is considerably higher than the central area AC, a light source or the like intrudes into the periphery and is positioned at the center. It is determined that the main subject is in the backlit state, and in order to correct the backlit state, only the weighting amount at the center is increased to m1 = 3 and m2 = 1.

On the other hand, {(Y2 / S2) / (Y1 / S
1)} ≦ R is satisfied, that is, when the peripheral area AS is not much different from the central area AC when comparing the brightness levels per unit area, it is determined that the backlight state is not present, and compared with the above case. By reducing the weighting amount in the center, m1 = 1,
m2 = 1.

The simple averaging circuit 79 calculates the brightness level per unit area of the entire screen as a simple average value Z1 without considering weighting, and Z1 = (Y1 + Y2) /
(S1 + S2) is established.

The weighted average circuit 78 divides the added value of the outputs of both weighted circuits 75 and 76 by the sum of the products of the respective weighted amounts and the areas of both regions as shown in Formula 3, and weighted average value Z.
It is calculated as 2.

[0034]

[Equation 3]

The simple average value Z1 and the weighted average value Z2 calculated as described above are input to the division circuit 80, where Z
The calculation of 1 / Z2 is executed, and the calculation result is input to the target level control circuit 81.

The target level control circuit 81 variably controls the target level at the time of exposure adjustment, and is optimal when there is no backlight, that is, when the weighting amounts m1 and m2 are both 1 and the entire screen has a uniform weighting amount. Let P0 be the optimum target level that obtains such a screen, and the target level P at the time of backlight compensation is P = P0 × Z
Calculate with 1 / Z2. The target level P set in this way
Is applied to the + side input terminal of the comparison circuit 82 in the subsequent stage.

The comparison circuit 82 outputs the luminance signal Y to the LPF 83.
The detected luminance signal level is input to the-side input terminal and compared with the target level input to the + side input terminal, and the iris motor 50 is driven so that the luminance signal level matches the target level P. Issue a control signal.

This target level P is also input to the subtraction circuit 84, and M = P-P0 is subtracted, and this subtraction value becomes the variation amount M of the target level and is output to the correction value determination circuit 42. .

Here, for example, assuming that the backlight level is such that the brightness level Y2 of the peripheral area AS is 10 times the brightness level Y1 of the central area AC, the above calculation is performed.
(66/52) × P0, and the target level rises. Therefore, the variation amount M also has a positive value.

The iris motor 50 drives the diaphragm mechanism 40 arranged in front of the CCD 2 to adjust the amount of light incident on the CCD 2. When the brightness signal level from the LPF 83 is smaller than the target level P, When the diaphragm amount of the diaphragm mechanism 40 is reduced, and conversely is larger than the target level P, the diaphragm amount is increased.

As shown in FIG. 6, the diaphragm mechanism 40 includes a movable blade 124 having a V-shaped notch 124a on the lower side and a movable blade 12 having a V-shaped notch 125a on the upper side.
5 supports the respective arm portions 124b and 125b with the support shafts 126 and 1
The rotor 129 is pivotally supported at 27, and the rotor 129
Is pivotally supported by the camera body with a support shaft 140, so that it is arranged inside the lens barrel of the camera.
A rectangular aperture opening 128 is formed by a and 125a. By locating this aperture 128 on the optical axis, incident light can reach the CCD 2 through this aperture opening 128.

When the rotor 129 is rotated counterclockwise, the movable blade 125 moves downward, and conversely the movable blade 124 moves upward, increasing the area of the aperture opening 128 and increasing the aperture amount. Becomes smaller, the diaphragm is opened, and the amount of incident light increases. When the rotor 129 is rotated in the clockwise direction, the movable blade 125 moves upward and the movable blade 124 moves downward to reduce the area of the aperture opening 128, increase the aperture amount, and close the aperture. The amount of incident light is suppressed and reduced.

In FIG. 6, 122 is a Hall sensor for detecting the diaphragm position of the mechanical diaphragm mechanism 40 arranged in the optical image pickup system, and is fixed to the arm portion 125b of the movable blade 125 of the diaphragm mechanism 40. It is fixed to the camera chassis in the vicinity of the magnet 141, and when the rotor 129 rotates and the diaphragm amount changes, the hall sensor 122 and the magnet 141.
The distance between them changes, which changes the output level of the hall sensor 122. That is, the output level of the hall sensor 122 rises as the magnet 141 approaches and the magnetic force from the magnet 141 increases. That is, when the hall sensor 122 is arranged at the reference position, the distance X from the reference position is increased.
When becomes short, the sensor output level E increases.

The output of the Hall sensor 122 becomes a diaphragm position signal. When the diaphragm amount is small, the diaphragm position signal level becomes small, and conversely, when the diaphragm amount is large, the signal level becomes large.

The correction value determination circuit 42 includes the number N of areas from the color distribution determination circuit 41 and the variation amount M from the exposure control circuit 43.
Are input together, the correction value is calculated based on the calculation formula of the correction value Q = a × N + b × M, and the indoor / outdoor discrimination circuit 43 in the subsequent stage is calculated.
Entered in. As will be described later, this correction value increases the area of the green subject in the image pickup screen when the indoor / outdoor determination is performed using the aperture position signal indicating the aperture amount of the aperture mechanism 40 in the indoor / outdoor determination. Is a value for preventing an erroneous determination from occurring due to backlight correction.

The indoor / outdoor discrimination circuit 43 includes a hall sensor 12
The aperture position signal and the correction value Q from 2 are input, and it is determined based on these data whether the shooting is performed indoors or outdoors. Next, this determination method will be described in detail.

In the normal state, that is, when the green subject is not present on the image pickup screen and is not in the backlit state, the correction value Q becomes zero, and the diaphragm position signal level is compared with the discrimination threshold Vref. Then, the diaphragm position signal level becomes the threshold value V
If it is higher than ref and is on the aperture close side, it is determined to be outdoor photography, and conversely, if the aperture position signal level is lower than the threshold value Vref and is on the aperture open side, it is determined to be indoor photography.

By the way, when the threshold value Vref is set to a fixed value, when a green subject occupies a large area on the image pickup screen during outdoor shooting, the reflectance for green light is low, so that it is compared with other colors even under the same illuminance. When the exposure control circuit 43 determines that it is dark, the diaphragm mechanism 40 drives the diaphragm in the opening direction, and moves from the diaphragm position when there is no green subject under the same illuminance. That is, unless a green subject occupies a large area on the screen under certain illuminance,
The aperture position signal level in FIG. 7 is L1, but if the green subject occupies a large area, the aperture position signal level will drop to L2 and fall below the threshold value Vref. It will be mistaken for shooting.

Therefore, a correction value Q from the correction value determination circuit 42 is used to correct the diaphragm position signal level. That is, the area occupied by the green subject on the image pickup screen is defined as the number of areas N, and this is multiplied by a coefficient a to obtain a value a.
By inputting × N as the correction value Q to the indoor / outdoor discrimination circuit 43, adding this correction value Q to the diaphragm position signal level, and increasing the correction value Q from L2 to L1 by the correction value Q as indicated by arrow 90 in FIG. The position is closer to the diaphragm closing side than the threshold value Vref, and misjudgment is avoided.

Similarly, when a backlit state occurs during outdoor photography, the above-described backlight correction operation is executed by the exposure control circuit 43, and the weighting of the high-brightness portion in the peripheral area AS is reduced, so that the backlit is performed under the same conditions. If the aperture position signal level in FIG. 8 without correction is moved from the aperture level L3 to the level L4 in the aperture opening direction and the threshold value is fixed at Vref, it may be erroneously determined to be indoor photography because the threshold value is exceeded. become. Therefore, also in this case, a value b × M obtained by multiplying the variation amount M by the coefficient b in the correction value determination circuit 42 is input as the correction value Q to the indoor / outdoor discrimination circuit 43, and the correction value Q is set as the aperture position signal level. Is added and is increased from L4 to L3 as indicated by an arrow 91 in FIG. 8, the position is closer to the diaphragm than the threshold value, and erroneous determination is avoided.

The coefficients a and b are set in advance by experiments so that the optimum indoor / outdoor discrimination can be executed. When the correction value determination circuit 42 determines the correction value, the number of regions N and the variation amount M can simultaneously contribute to the correction value determination. In other words, in the above two situations, that is, in the case where the green subject occupies a large area on the image pickup screen and is in the backlit state, the correction amount is further increased.

The discrimination result obtained by the indoor / outdoor discrimination circuit 43 is input to the gain control circuits 29 and 30. Here, normally, the gain control circuit 29 receives the input screen color evaluation value V
When r is equal to or greater than zero, the gain Gr of the R amplifier circuit 4 is decreased as the evaluation value increases, and when equal to or less than zero, the gain Gr is increased as the evaluation value decreases, and the gain control is similarly performed. In the circuit 30, the gain Gb of the B amplifier circuit 5 is reduced as the evaluation value increases when the screen color evaluation value Vb is zero or more, and the gain Gb increases as the evaluation value decreases when the screen color evaluation value Vb is zero or less. And adjust so that both screen color evaluation values are always at zero level.

By the way, as described above, in outdoor shooting in which natural light is present, since the natural light has a bluish color with a color temperature of 5000 K or more, the gain correction is performed to suppress the B signal compared to the R signal in outdoor shooting. It is preferable to carry out.

Therefore, when the outdoor photographing condition is determined, the screen color evaluation value Vr is indicated by the solid lines in FIGS. 9 and 10.
Is fixed and the screen color evaluation value Vb is negative, the gain is fixed at 1. That is, the operation is performed so that the gain adjustment is not substantially performed. This prevents the gain Gr from decreasing even when the screen color evaluation value Vr increases during outdoor shooting.

Further, in indoor photography in which artificial light is present, since the artificial light has a reddish color with a color temperature of 5000 K or less, gain correction is performed so as to suppress the R signal compared to the B signal during indoor photography. Is preferred. Therefore, when it is determined to be the indoor shooting state, the gain is fixed to 1 in the portion where the color evaluation value Vr is negative and the color evaluation value Vb is positive, as indicated by the solid lines in FIGS. 11 and 12. This makes it possible to prevent the gain Gb from decreasing even when the screen color evaluation value Vb increases during indoor shooting.

As described above, by switching the white balance adjustment operation based on the indoor / outdoor judgment, stable white balance adjustment becomes possible.

Although the diaphragm position signal level is changed by the correction value Q in the above embodiment, as another method, the diaphragm position signal level is not corrected and the threshold value Vref is set to the arrow 92, 93 in FIG. 7 or 8. The same effect can be obtained by performing the correction in which the correction amount Q is subtracted from the threshold value Vref as described above. That is, even if the diaphragm position signal level is L2 or L4, it is possible to recognize both outdoor shooting when L2 and L4 by reducing the threshold value Vref by the correction value Q.

Further, in the above-mentioned embodiment, the countermeasure against the backlight compensation is shown. However, when a so-called illuminant such as a light source is photographed at the center of the screen as a main subject, the so-called forward lighting is performed.
In a normal exposure adjustment operation, since the weighting amounts are equal over the entire screen and the weighting at the center is not large, the exposure adjustment is performed so as to suppress the luminance of the high-luminance subject that is desired to be photographed with the high luminance. Therefore, it is preferable to perform a process of increasing the weighting amount of the central area AC even in the normal light. Specifically, the priority determination circuit 77
In the case where {(Y2 / S2) / (Y1 / S1)} <U (U is a reference value that is the boundary of occurrence of the forward light state, a value that maintains the relationship of U <R), The weighting amount is m1 =
2, m2 = 1.

By changing the weighting amount at the time of forward light, for example, if the brightness level Y1 of the central area AC is 10 times the brightness level Y2 of the peripheral area, the target value P is calculated based on the calculation formula at the time of backlight correction. , P = (55/84) × P0
And becomes smaller than the target value P0, and the fluctuation amount M = P−
P0 becomes a negative value. The correction value Q also becomes a negative value due to this variation M.

Here, for example, when a high-brightness subject is photographed during indoor photographing, and when the weighting amount at the center is small as shown in FIG. 13, the diaphragm position signal level becomes L5, which is below the threshold value Vref. Although it is determined to be indoors, when the weighting amount at the center is increased as a measure against forward light as described above, the diaphragm mechanism 40 operates in the direction to close the diaphragm, the diaphragm position signal level becomes large at L6, and the threshold Vr.
Beyond ef, the image is misidentified as outdoor photography.

Therefore, as in the case of the backlight correction, the aperture position signal level is corrected by the correction value Q. In this case, since the correction value Q is a negative value, the aperture position signal level is negative. If the correction value Q is added, as a result, as shown by the arrow 94 in FIG. 13, the value is reduced from L6 to L5, and it can be determined that the indoor shooting is performed. Incidentally, also in the case of this measure against the forward light, the threshold value Vref may be corrected instead of the correction to the diaphragm position signal, and by subtracting the negative correction value Q from the threshold value Vref, as shown by an arrow 95 in FIG. The threshold value is substantially increased, and it is possible to discriminate indoors even at level L6.

Further, the gain control characteristics in the gain control circuits 29 and 30 can be changed as shown in FIGS. 14 to 17 apart from the above embodiment. That is, when it is determined to be in the outdoor shooting state, as shown in FIG. 14 and FIG. 15, the gain change straight line in the portion where the screen color evaluation value Vr is positive and the screen color evaluation value Vb is negative is gradually made to substantially reduce the gain. Make adjustment difficult.
This prevents the gain Gr from decreasing even when the screen color evaluation value Vr increases during outdoor shooting.

Further, when it is judged that the indoor photographing state is set, as shown in FIG. 16 and FIG. 17, the gain adjustment line is made gentle in the portion where the screen color evaluation value Vr is negative and the color evaluation value Vb is positive. To make it hard to work. As a result, at the time of indoor shooting, even if the screen color evaluation value Vb becomes large, the gain Gb
Can be suppressed.

In the above embodiment, the A / D converter 22 and the integrator 23 are connected to the luminance signal Y, the color difference signals RY and BY.
It is shared in order to extract the level of 3 signals of each region by digital integration, and the integrated value of each signal could only be updated in 3 field cycles, but the A / D converter and the integrator were It goes without saying that each signal level can be updated for each field if it is provided exclusively for each signal. It goes without saying that the operation of a series of circuit blocks from the screen evaluation circuit 27, the color distribution determination circuit 41 to the correction value increasing / decreasing circuit 43 in FIG. 1 can be processed by software using a microcomputer.

[0065]

As described above, according to the present invention, even in a situation where a green subject occupies a large area on the image pickup screen, or in a situation where a backlit state or a frontlit state occurs, indoor shooting or outdoor shooting is possible. Whether or not shooting is possible can be detected with high accuracy, and when the characteristics of the white balance adjustment operation are changed based on the detection result, white balance adjustment suitable for indoor and outdoor shooting can be realized.

[Brief description of drawings]

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

FIG. 2 is a diagram illustrating division of a screen.

FIG. 3 is a diagram illustrating a distribution of color evaluation values of a green subject.

FIG. 4 is a block diagram of an essential part of an embodiment of the present invention.

FIG. 5 is a block diagram of an essential part of an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a diaphragm mechanism according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a discrimination method in an indoor / outdoor discrimination circuit 43 according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a discrimination method in an indoor / outdoor discrimination circuit 43 according to an embodiment of the present invention.

FIG. 9 is a diagram showing a gain control characteristic of an R signal during indoor shooting according to an embodiment of the present invention.

FIG. 10 is a diagram showing a gain control characteristic of a B signal during indoor shooting according to an embodiment of the present invention.

FIG. 11 is a diagram showing a gain control characteristic of an R signal during outdoor shooting according to an embodiment of the present invention.

FIG. 12 is a diagram showing a gain control characteristic of a B signal during outdoor shooting according to an embodiment of the present invention.

FIG. 13 is a diagram illustrating a discrimination method at the time of forward light in the indoor / outdoor discrimination circuit 43 according to the embodiment of the present invention.

FIG. 14 is a diagram showing a gain control characteristic of an R signal during outdoor shooting according to another embodiment of the present invention.

FIG. 15 is a diagram showing a gain control characteristic of a B signal during outdoor shooting according to another embodiment of the present invention.

FIG. 16 is a diagram showing a gain control characteristic of an R signal during indoor shooting according to another embodiment of the present invention.

FIG. 17 is a diagram showing a gain control characteristic of a B signal during indoor shooting according to another embodiment of the present invention.

[Explanation of symbols]

 23 integrator 4 R amplifier circuit 5 B amplifier circuit 40 aperture mechanism 122 hole sensor 43 indoor / outdoor discrimination circuit 41 color distribution determination circuit 42 correction value determination circuit 44 exposure control circuit 29 gain control circuit 30 gain control circuit

Claims (2)

[Claims] 1. A color evaluation value detecting means for obtaining, as a color evaluation value, an amount of both RY and BY color difference signals for each of a plurality of areas set by dividing an imaging screen, and the color evaluation value. Based on the gain adjustment means that performs white balance adjustment operation to adjust the gain of both red and blue color signals, and the amount of light incident on the image sensor so that the brightness level of the imaged video signal reaches the target value to achieve the optimum exposure state. The aperture mechanism that adjusts the aperture position, the aperture position detection means that outputs the aperture position signal whose level changes according to the aperture amount of the aperture mechanism, and the aperture position signal and the threshold value are compared to determine whether the indoor shooting state or the outdoor shooting state. In a video camera with a white balance adjusting device, which has an indoor / outdoor discrimination means for discriminating, and which changes the characteristics of the white balance adjusting operation according to the output of the indoor / outdoor discrimination means, the occurrence of a backlight condition or a forward lighting condition is judged. Judgment means and reverse It is characterized by comprising a correction means for correcting the aperture position signal level or the threshold value according to the state or the illuminating state, and comparing the aperture position signal after the correction with the threshold value by the indoor / outdoor discrimination means. Video camera with balance adjustment device. 2. A color evaluation value detecting means for obtaining, as a color evaluation value, amounts of both RY and BY color difference signals for each of a plurality of areas set by dividing an image pickup screen, and the color evaluation value. Based on the gain adjustment means that performs white balance adjustment operation to adjust the gain of both red and blue color signals, and the amount of light incident on the image sensor so that the brightness level of the imaged video signal reaches the target value to achieve the optimum exposure state. The aperture mechanism that adjusts the aperture position, the aperture position detection means that outputs the aperture position signal whose level changes according to the aperture amount of the aperture mechanism, and the aperture position signal and the threshold value are compared to determine whether the indoor shooting state or the outdoor shooting state. In a video camera with a white balance adjusting device, which has an indoor / outdoor discrimination means for discriminating, and which changes the characteristics of the white balance adjusting operation according to the output of the indoor / outdoor discrimination means, in an image pickup screen based on the color evaluation value. The surface occupied by the green subject A green subject detecting means for detecting a product and a correcting means for correcting the diaphragm position signal level or the threshold value according to the area are provided, and the indoor / outdoor discrimination means compares the corrected diaphragm position signal with the threshold value. A video camera with a white balance adjustment device.