JPH0955949A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the change in white balance accociated with the change of picture constitution under the same light source and to realize stable color correction control. SOLUTION: A low light clip circuit 971 extracts the highlight part of a picked up image, and a luminosity discrimination accuracy operation circuit 977 operates the reliability of the discriminated result. When color temperature information of a light source is included, an MIX circuit 986 sets a gain control value for WB adjustment based on the color temperature of the light source from image data of an R-color in the highlight part and image data of the R-color and a B-color in an area except for the highlight part. The gain control value is set by a counter 987 at a prescribed period, and the period is changed in accordance with the operated result of the reliability of the light source discrimination accuracy operation circuit 977. When the color temperature of the light source is decided, the setting period of the gain control value is prolonged and the flufctuation of WB adjustment can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus using an image pickup element such as a CCD, and more particularly to white balance adjustment of a picked-up image.

[0002]

2. Description of the Related Art In a color video camera or a still video camera that converts an optical image incident on a lens into an electric signal and captures it, a CCD (Charge Coupled Devic) used.
When the spectral sensitivity characteristics of the image sensor such as e) are constant and the color temperature of the light source of the subject changes, color shift occurs in the captured image. Normally, the white balance of the image capture signal is adjusted to correct this color shift. It is supposed to be taken.

The white balance is the level ratio (R / G) of the R, G, and B color components of the captured image based on the image data of the high-luminance portion (white portion) including the color temperature information of the light source in the captured image. , B / G) can be adjusted, but in a conventional color video camera or still video camera, a CCD having a linear photoelectric conversion characteristic that outputs a voltage proportional to the amount of incident light is used. Since the dynamic range for the luminance range is insufficient and the color temperature information of the light source cannot be accurately extracted from the high-luminance portion in the imaging screen, the white balance adjustment method using the image data of the high-luminance portion is not adopted. .

That is, as shown in the characteristic of FIG. 14, the image sensor used in the conventional video camera is a linear type which outputs a voltage proportional to the amount of incident light having a light intensity (gradient of characteristic) as a proportional coefficient. When the image pickup is performed by controlling only the exposure time of the image pickup sensor, which has photoelectric conversion characteristics, the range of the amount of incident light with respect to the dynamic range (area A1) is narrow,
The image of the high-luminance portion (area A2) including the color temperature information of the light source overflows. Especially, complementary color single plate CC
In the case of using D, the color modulation carrier is saturated and the color rotates, so that the dynamic range becomes narrower in view of color reproducibility.

Therefore, if the white balance is adjusted based on the image data of the high-brightness portion where accurate color temperature information of the light source cannot be obtained, the color misregistration will be worsened.

The amount of incident light is limited by the diaphragm to change the slope of the characteristic like the characteristic, and the dynamic range of the image sensor is expanded by controlling the amount of incident light and the exposure time to prevent the overflow of the high-luminance portion. It is possible to capture images, but S / N of the main subject part
Such exposure control cannot be performed because the ratio is deteriorated, and the white balance adjustment based on the image data of the high brightness portion is not adopted.

As described above, since reliable light source information cannot be obtained from the high-luminance portion due to the photoelectric conversion characteristics of the image sensor, conventionally, as an alternative to this, based on the image signal of a relatively bright and low-saturation portion. White balance is being adjusted.

That is, the image signals of the R, G, and B color components are converted into a Y signal (luminance signal) and a C signal (color signal), and the C signal is below a predetermined level and the Y signal is below a predetermined level. The white balance is adjusted using the image signals of the above portions as reference levels.

Further, the white balance adjustment data is updated at a predetermined cycle so that the color shift can be corrected even when the color balance of the photographing screen changes due to the change of the light source of the subject or the change of the screen configuration. It is like this.

[0010]

By the way, for example, when the photographing screen is changed like the case of photographing a moving body under the same light source,
If the white balance adjustment is performed according to the change of the photographing screen, the color balance fluctuates every time the moving body changes, and the image becomes rather unpleasant. Therefore, it is not preferable to frequently perform the white balance adjustment. Therefore, conventionally, the update cycle of the white balance adjustment data is set to be relatively long, and the white balance adjustment value is held even if the photographing screen changes slightly.

However, if the update cycle of the white balance adjustment is made too long, when the light source of the subject changes, the white balance adjustment may not be performed and color misregistration may occur. Therefore, it is preferable to change the light source of the subject. Although it is better to update the white balance adjustment, the conventional white balance adjustment method estimates the color temperature information of the light source from the image data of the relatively bright and low-saturation area, so the color temperature of the light source can be calculated accurately. It cannot be estimated, and it is difficult to update the white balance adjustment according to the change in the light source of the subject.

The present invention has been made in view of the above problems, and an image is picked up using an image pickup device having a logarithmic compression type photoelectric conversion characteristic, and the white balance update period is set based on the color temperature of the light source of the picked-up image. The present invention provides an image pickup device that can perform color correction appropriately by controlling the light source according to changes.

[0013]

According to the present invention, there is provided an image pickup means comprising a plurality of photoelectric conversion elements having a logarithmic characteristic for converting incident light into an electric signal logarithmically compressed with respect to its light quantity and outputting the electric signal. Area extraction means for extracting a predetermined high-brightness area from the image captured by the imaging means, determination means for determining the presence or absence of a light source in the extracted high-brightness area, and accuracy for calculating the determination result of the determination means. Calculating means, detecting means for detecting the color temperature of the light source from the high brightness area, data generating means for generating white balance adjustment data of the captured image based on the detected color temperature of the light source, and at a predetermined cycle Data generation control means for generating the white balance adjustment data, and cycle change for changing the generation cycle of the white balance adjustment data according to the calculation result of the accuracy calculation means. Those and the stage.

With the above structure, the subject light image is converted into an electrical signal logarithmically compressed with respect to the subject brightness and is imaged, and the color temperature of the light source included in a predetermined high brightness region in the picked-up image at a predetermined cycle. Data for white balance adjustment is generated based on Further, the determination accuracy of the presence or absence of the light source in the high brightness region is calculated, and the generation period of the white balance adjustment data is changed according to this accuracy.

For example, when the determination accuracy with the light source is high,
It is estimated that the color temperature of the light source of the subject is stable, so the update cycle of the data for white balance adjustment is set long, and problems such as fluctuations in color correction due to unnecessary white balance adjustment are prevented. To be done.

[0016]

1 is a block diagram of an image pickup apparatus according to the present invention. The image pickup apparatus 1 is an optical system that guides reflected light (a subject light image) from a subject to an image pickup system, an image pickup system that converts the subject light image into an electric signal and takes it in, and a signal processing of an image signal picked up by this image pickup system. And a signal processing system for performing.

The optical system includes a lens system 2 for forming a subject light image on the image pickup surface of the image pickup system, an iris 3 for protecting the CCD image sensor 6 when the image is not picked up, and an iris driver 4 for controlling the driving of the iris 3. Consists of. The iris driver 4 controls opening / closing of the iris 3 based on an exposure control value input from an exposure control calculation circuit 95 described later.
That is, the iris driver 4 opens the iris 3 immediately before the CCD image sensor 6 starts the image pickup operation, closes the iris 3 after a predetermined exposure time, and cuts the incident light to the CCD image sensor 6 when the image is not picked up. Cut off.

The image pickup system detects incident light by R (red), G (green),
Dichroic prism 5 for decomposing into B (blue) three primary color components, and three CCDs for photoelectrically converting the subject light image of each of the R, G, and B color components output from this dichroic prism 5 into an electric signal Image sensor 6 (R),
6 (G), 6 (B) and their CCD image sensor 6
The timing generator 7 controls the driving of (R), 6 (G), and 6 (B).

In this embodiment, the image pickup system is a three-plate type C
Although it is composed of a CD image sensor, it may be composed of a single-plate CCD image sensor.

The CCD image sensor 6 (imaging means) is
The output voltage with respect to the amount of incident light has a photoelectric conversion characteristic of a logarithmic function, and each pixel is equivalently configured by the circuit shown in FIG.

Each pixel comprises a photosensitive section 61 for photoelectrically converting the incident light quantity into a logarithmically compressed voltage and outputting the voltage, and a charge accumulating section 62 for accumulating charges based on the output voltage from the photosensitive section 61.

The photosensitive section 61 has a pn junction type photodiode PD for photoelectrically converting incident light into a photocurrent Ip proportional to its intensity and an n-channel MOS field effect for converting the photocurrent Ip into a logarithmically compressed voltage V _G. Transistor FET
(Hereinafter, referred to as MOSFET).

The anode of the photodiode PD is connected to the drain (D) and the gate (G) of the MOSFET, and the power source voltage V _DD is applied to the cathode of the photodiode PD. The gate (G) of the MOSFET is connected to the first electrode M1 of the charge storage section 62,
MOSFET source (S) and back gate (substrate)
A DC (direct current) voltage V _SS and a DC voltage V _SUB are applied to each.

Here, V _DD > V _SS > V _SUB , and
Reverse bias is applied to the photodiode PD, and MO
Reverse bias is also applied to the source (S) and drain (D) and the back gate of the SFET.

The charge storage unit 62 includes an input diode 621 for discharging excess charge, a first electrode M1 for controlling the stored charge voltage, a second electrode M2 for storing the charge, a third electrode M3 for controlling reading of the stored charge, and It is composed of a two-phase drive type CCD composed of a plurality of electrodes after the fourth electrode M4 for transferring the read accumulated charge.

A control pulse φ _D (low-level pulse signal) for controlling the start of charge storage of the charge storage section 62 is input to the input diode 621, and the gate voltage V _{G of the} MOSFET is input to the first electrode M1. It is supposed to be done.

A DC voltage V _R for adjusting the offset level of the dynamic range and a shift pulse φ _S (high level) for controlling the end of charge accumulation in the charge accumulating portion 62 are applied to the second electrode M2 and the third electrode M3. Pulse signal) and even-numbered electrodes M (2i + 2) (i = 1, 2, ...) After the fourth electrode M4 and odd-numbered electrodes M (2
i + 3) (i = 1, 2, ...) Represents a first transfer pulse .phi.1 and a second transfer pulse .phi.2 for controlling the reading of the accumulated charge.
And are applied. The first pulse φ1 and the second transfer pulse φ2 are pulse train signals that are out of phase with each other by π.

Now, the operations of the photosensitive section 61 and the charge storage section 62 will be described. The threshold voltage V _T is (V _G −V _S ) ≦
When V _T + (nkT / q) is satisfied, n channel MO
The drain (D) of the S-type field effect transistor has a subthreshold current I _DS (sub-threshol) represented by the following equation.
It is known that a minute electric current called d currrent) flows.

[0029]

[Equation 1]

In the above equation, the surface level density N _fs = 0
(That is, C _fs = 0) and (K / n) << (V _D −V _S ), then n = m, 1 << m (V _D −V _S ) / K, and ex
Since p {−m (V _D −V _S ) / K} ≈0, the above equation becomes the following equation.

[0031]

[Equation 2]

From the above equation, the threshold voltage V _T is (V _G −
V _S ) ≦ V _T + K, and (K / n) << V _D −V _S
= V _G −V _S , that is, (K / n) << (V _G −
If V _S ) ≦ (V _T + K), it can be seen that the subthreshold current I _DS flowing in the drain (D) of the MOSFET becomes an exponential function of the gate-source potential difference (V _G −V _S ). .

On the other hand, the threshold voltage V _T is expressed by the following equation and changes with (V _SS (= V _S ) −V _SUB ), so D
The C voltage V _SUB properly adjusted the (K / n) «(V G -
V _S) by setting the operating state of the MOSFET so as to satisfy the condition ≦ V _T + K, the circuit configuration, I _D = because it is I _P, the photocurrent _{I P = I DS0 · exp {} (V G -V _SS −V _T ) /
K}, and the logarithmically compressed gate voltage V _G shown below is output to the gate (G) of the MOSFET.

[0034]

(Equation 3)

[0035]

(Equation 4)

Therefore, when light is incident on the photosensitive portion 61, a photocurrent I _P proportional to the intensity of the light is applied to the photodiode P.
It flows from the cathode of D to the anode and is supplied to the drain (D) and gate (G) of the MOSFET. Then, this photocurrent I _P is converted into a logarithmically compressed voltage and is converted into a MOS.
It is output from the gate (G) of the FET. That is, in the photosensitive section 61, incident light is photoelectrically converted into a voltage logarithmically compressed with respect to the amount of incident light and is output.

On the other hand, in the charge storage section 62, a potential well is formed immediately below each of the electrodes M1, M2, ..., And the potential well immediately below the second electrode M2 corresponds to the gate voltage V _{G of the} MOSFET. The amount of charge is accumulated.

The depth of the potential well becomes deeper as the voltage applied to the corresponding electrode becomes higher, and the potential level for electric charges becomes lower. Therefore,
As the DC voltage V _R is increased, the depth of the potential well immediately below the second electrode M2 is increased, and the charge storage capacity in this well is increased.

To accumulate charges in the potential well immediately below the second electrode M2, first, the maximum amount of charge C _MAX (the amount of charge corresponding to the dynamic range of the CCD) determined by the DC voltage V _R is applied. After being injected into the well, the upper limit level of the well is lowered based on the gate voltage V _{G of the} MOSFET for a predetermined exposure time, and the amount C _Log (charge amount corresponding to the exposure amount) corresponding to the incident light amount is reduced. ) Is discharged to the input diode 621.

Therefore, at the end of the exposure control, the amount C _INT obtained by removing the amount C _Log (the charge amount logarithmically compressed with respect to the incident light amount) proportional to the gate voltage V _G from the maximum accumulation amount C _MAX in the potential well. The charge of (= C _MAX −C _Log ) is accumulated. Since the charge amount C _INT is a brightness value obtained by subtracting the brightness of the subject from the dynamic range (sensitivity range) of the charge storage unit 62, it is a negative signal obtained by inverting the subject brightness in black and white.

The charges accumulated in the potential well immediately below the second electrode M2 are input with the shift pulse φ _S when the exposure time has elapsed, and the potential level immediately below the third electrode M3 is set to the potential level immediately below the second electrode M2. The potential is lowered below the potential level, and the fourth electrode M is passed directly under the third electrode M3.
The data is read out by ejecting it to the transfer area immediately below 4.

FIG. 4 is a time chart showing charge accumulation in the charge accumulator 62 and transfer processing of accumulated charges, and FIG.
FIG. 6 is a diagram showing a potential state of the charge storage unit 62 at each timing in the time chart of FIG. Note that, in FIG. 5, the shaded portions indicate charges.

In FIG. 4, time t1 is the exposure start timing and time t4 is the exposure end timing. t
= T1, when the control pulse φ _D falls to the low level,
Electrons are injected from the input diode 621 side under the first electrode M1 into the potential well W1 immediately below the second electrode M2 (FIG. 5A), and the control pulse φ _D rises to a high level at t = t2. Then, excess electrons with respect to the well W1 pass under the first electrode M1 and the input diode 621
And the charge accumulation (exposure operation) is started at the same time (FIG. 5B).

That is, when the control pulse φ _D is input, the CCD is reset by injecting the electric charge of the maximum storage amount C _MAX into the potential well W1, and the exposure is started.

When the exposure is started, the gate voltage V _{G of the} MOSFET rises with a characteristic that it is logarithmically compressed with respect to the incident light quantity, and the potential immediately below the first electrode M1 becomes deeper in accordance with the rise in the voltage, and the above potential is generated. The charges of the well W1 of the above pass through the bottom of the first electrode M1 and are discharged to the input diode 621 (FIG. 5C).

As a result, the charge amount C _INT (= C _MAX −C _Log ) remains in the potential well W1. The charge amount C _INT is a function of the potential difference V _RG (= V _R −V _G ) between the DC voltage V _R and the gate voltage V _G , but the charge amount C _Log discharged during the exposure time is the gate voltage. Since it is based on the logarithmic characteristic of V _G, the charge amount C _INT also has the logarithmic characteristic.

When the shift pulse φ _S rises to a high level at t = t4, the level of the potential well W2 directly below the third electrode M3 becomes lower than that of the potential well W1 and remains in this well W1. The stored charge is transferred to the potential well W2 directly below the third electrode M3, the exposure is completed (FIG. 5D), and when the shift pulse φ _S falls to the low level at t = t5, the potential well is changed to the above potential well. The level of W2 becomes higher than the level of the potential well W1, the accumulated charge is transferred to the potential well (shift register) immediately below the fourth electrode M4, and the accumulated charge can be read out to the signal processing system. (FIG. 5 (e)).

Then, after this, from t = t6, the first and second
When the transfer pulses φ1 and φ2 are input, the electrodes M after the fourth electrode M4 are synchronized with the first and second transfer pulses φ1 and φ2.
(i + 3) (i = 1, 2, ...) Alternately and sequentially change to a low level, and the accumulated charge is sequentially transferred to the potential well immediately below the fourth electrode M4 to the signal processing system. Are read out (FIG. 5 (f)).

As described above, the CCD image sensor 6 has the photoelectric conversion characteristic shown in FIG. 6 because it converts the incident light from the subject into an electric signal logarithmically compressed with respect to the light amount and outputs the electric signal.

In the figure, the horizontal axis represents the amount of incident light and the vertical axis represents the output voltage from the image sensor.

As described above, the normal CCD image sensor has a linear photoelectric conversion characteristic (see FIG. 14).
), CCD output voltage range (dynamic range)
The range A1 of the amount of incident light with respect to is very narrow, and for example, a subject with a background of a ski slope or a snow scene in clear weather is CC
When shooting is performed by controlling only the exposure time of the D image sensor, the output of the high-brightness portion of the background overflows, and the density balance of the shot image is significantly impaired.

Therefore, in a camera using a normal CCD image sensor, a diaphragm for limiting the amount of incident light from a subject is provided, and the photoelectric conversion characteristic of the CCD image sensor is adjusted by adjusting the amount of incident light and the exposure time. The inclination is reduced to extend the dynamic range.

On the other hand, the CCD image sensor 6 according to the present invention has a non-linear photoelectric conversion characteristic of logarithmically compressing and outputting as shown in FIG. 6, so that the CCD output voltage range (dynamic range) D Since the range A3 of the incident light amount is extremely wide, it is not necessary to adjust the incident light amount by using a diaphragm and storage time control as in a normal CCD image sensor, and it is possible to obtain an appropriate exposure for the dynamic range A3. ing.

As described above, the DC voltage V _R determines the depth of the potential well W1 immediately below the second electrode M2, and the DC voltage V _R changes the dynamic range of the CCD image sensor 6. It has become. This is because the offset level V _L of the dynamic range of the CCD image sensor 6 is changed by the DC voltage V _R in FIG.
Is equivalent to changing.

[0055] Thus, in the CCD image sensor 6, since it is possible to correct exposure equivalent to the dynamic range D'to D by adjusting the DC voltage V _R, in this imaging apparatus 1, the DC voltage and to perform the exposure control by V _R.

Returning to FIG. 1, the timing generator 7 generates a clock for controlling the driving of the CCD image sensors 6 (R), 6 (G), 6 (B) and the correlated double sampling circuit 81, and performs exposure control calculation. Based on the exposure value input from the circuit 95, various control signals such as the control pulse φ _D , the shift pulse φ _S , the first and second transfer pulses φ1 and φ2 are generated.

The signal processing system subjects the image signal (analog signal) output from the image pickup system to predetermined signal processing and converts it to a digital signal, and an image signal converted to a digital signal (hereinafter referred to as image signal). Data) and a digital signal processing circuit 9 for performing a predetermined signal processing and outputting the data.

The analog signal processing circuit 8 includes a correlated double sampling circuit 81 (indicated by CDS in the drawing, hereinafter referred to as a CDS circuit 81) for suppressing noise of the image signal output from the CCD image sensor 6, and the above. A preamplifier 82 that amplifies the image signal to a prescribed level, a white balance circuit 83 (hereinafter referred to as a WB circuit 83) that adjusts the white balance of the image signal, and an A / D converter 84 that A / D converts the image signal. I have it.

The WB circuit 83 has three WB amplifiers (V in the figure) for adjusting the gains of the image signals of the R, G and B color components.
Indicated by CA. ), The G color image signal is set to a predetermined reference level, and the levels of the R color and B color image signals are changed from the color correction arithmetic circuit 98 to the D / A converter 99.
Adjustment is made based on the amplifier gain control values AG _R and AG _B input via.

The A / D converter 84 has three A / D converters 84 (R), 84 (G), 84 (B), and R, G, B
1 for each pixel signal forming the image signal of each color component of
Convert to 0-bit image data. This image data is used as a γ correction circuit 91, a Y matrix circuit 94, a light source discrimination circuit 97 and a color correction calculation circuit 9 in the digital signal processing circuit 9.
8 is input.

The digital signal processing circuit 9 includes a γ correction circuit 91 for correcting the γ characteristic of the image data input from the A / D converter 84, an enhancer 92 for correcting the contour of the image data, and the image data after the digital signal processing. D / A converters 93, R, G, which convert to analog signals and output
A Y matrix circuit 94 that generates luminance data from the B image data, an exposure control value (DC voltage V _R ) from the luminance data generated by the Y matrix circuit 94, a gain adjustment value of the preamplifier 5, and a γ of the γ correction circuit 91. An exposure control calculation circuit 95 that generates a correction table, a contour correction control circuit 96 that controls the contour correction of the enhancer 92, a light source determination circuit 97 that detects the color temperature of the light source from the image data and calculates the detection accuracy, and the amplifier described above. Color correction calculation circuit 98 for calculating a gain control value and this color correction calculation circuit 9
A D / A converter 99 for converting the amplifier gain control value output from 8 into analog data is provided.

The γ correction circuit 91 has three γ correction circuits corresponding to the image data of the R, G, and B color components.
Each of the γ correction circuits 91 (R), 91 (G), 91 (B) uses the look-up table for gradation correction created by the exposure control calculation circuit 95 to generate image data of R, G, B color components. .Gamma.-conversion is performed on each pixel data forming the. At this time, each pixel data is converted from 10-bit data to 8-bit data.

In this embodiment, since the input section is logarithmically converted and the range of the input image is wide, the level of the main subject is converted to an appropriate value by the input image at the time of image input, and the level after the conversion is changed. Therefore, it is necessary to provide optimum γ characteristics. The exposure level adjustment and γ adjustment for this output are performed by the γ correction circuits 91 (R), 91 (G), and 91 (B).

The enhancer 92 also has three enhancers for the image data of the R, G and B color components. Each of the enhancers 92 (R), 92 (G), 92 (B) adds an edge signal in the horizontal and vertical directions of the image data based on the edge control signal input from the edge correction control circuit 96 to add an edge of the image. The parts are emphasized to enhance the resolution.

The D / A converters 93 are also three D / A converters 93 for the image data of each of the R, G and B color components.
(R), 93 (G), 93 (B), which converts the image data after predetermined signal processing into an analog signal and outputs it.

The Y matrix circuit 94 synthesizes the image data of each of the R, G, and B color components at a predetermined ratio close to the relative luminous efficiency (for example, R: G: B: = 0.33: 0.59: 0.11) and luminance. Generate data. This brightness data is stored in the exposure control calculation circuit 95,
It is input to the light source determination circuit 97 and also to the contour correction control circuit 96 via the exposure control calculation circuit 95.

The exposure control calculation circuit 95 calculates the DC voltage V _R of the CCD image sensor 6 and the gain adjustment value of the preamplifier 5 from the brightness data generated by the Y matrix circuit 94 by using a preset table, and calculates the DC voltage. V _R
Is output to the timing generator 7, and the gain adjustment value is output to the preamplifier 5.

The contour correction control circuit 96 sets the contour emphasis level for the image data of each of the R, G, and B color components based on the luminance data, and enhancers 92 (R), 92 (G), and 92 as contour control signals, respectively. Output to (B).

The light source discriminating circuit 97 extracts the image data of the high brightness region of a predetermined level from the image data of the R, G and B color components, detects the color temperature of the light source from this image data, and the white balance adjustment data. WBD1 (R1
/ G1, B1 / G1) is calculated. In addition, the above R1, G
1 and B1 are average levels of image data of R, G, and B color components included in the high-luminance region.

Further, the light source discriminating circuit 97 discriminates the detection accuracy of the color temperature of the light source, and generates a control signal for generating the amplifier gain control values (AG _R , AG _B ) from the discrimination result.

The amplifier gain control value (AG _R ,
AG _B ) is a region excluding the white balance adjustment data WBD1 calculated from the image data in the high-brightness region and the high-brightness region as described later (hereinafter referred to as a low-brightness region).
Is generated by adding the white balance adjustment data WBD2 (R2 / G2, B2 / G2) calculated from the image data of 1 at a predetermined ratio α, and calculating the reciprocal of the addition result. This is a signal indicating the addition ratio α. Note that R2, G2, and B2 are average levels of image data of R, G, and B color components included in the low luminance area.

The color correction arithmetic circuit 98 extracts the image data of the low luminance area from the image data of the R, G and B color components, calculates the white balance adjustment data WBD2 from the image data, and determines the light source. based on the addition ratio α supplied from the circuit 97 adds the white balance adjustment data WBD2 and the white balance adjustment data WBD1, further amplifier gain control value by calculating the reciprocal of the addition result (AG _R, AG _B) To calculate. This amplifier gain control value (AG _R , AG _B ) is converted into an analog signal by the D / A converter, and then the WB circuit 83
Is input to the WB amplifiers 83 (R) and 83 (B).

FIG. 2 is a circuit configuration diagram of the light source discrimination circuit and the color correction arithmetic circuit. The light source discriminating circuit 97 includes a low light clipping circuit (region extracting means) 971, a highlight area calculating circuit 972, a weighting circuit 973,
It includes an integrating circuit 974, a color correction gain calculation circuit 975, a chromaticity data conversion circuit (detection means) 976, and a light source discrimination accuracy calculation circuit (discrimination means, accuracy calculation means, and data generation control means) 977.

On the other hand, the color correction calculation circuit 98 includes a highlight clip circuit 981 and a weighting circuit 98.
2, an integrating circuit 983, a color correction gain computing circuit 984, a color ferria clip circuit 985, a MIX circuit 986.
(Data generating means) and counter (cycle changing means) 98
It consists of 7.

The DC voltage V _R and the image data of each color component of R, G, B output from the timing generator 7 are input to the low light clip circuit 971 and the high light clip circuit 981.

The low light clipping circuit 971 is a circuit for clipping the low luminance portion of the image data at a predetermined clipping level and extracting only the image data of the high luminance portion.
The clipping level is variably set in accordance with the DC voltage V _R of the CCD image sensor 6, that is, the offset level of the dynamic range, whereby the region indicating the color temperature of the light source included in the image data (the light from the light source is directly incident Region) or a region reflecting the color temperature of the light source (region where light from the light source is specularly reflected and is incident) can be accurately extracted as an absolute value.

For example, in an outdoor shooting scene of clear or cloudy weather shown in FIG. 7, the photographed image reflects the color temperature of the light source in the region S1 indicating the sky (region shaded by diagonal lines), so that this region S1 is highlighted. It is extracted as a part.

In the backlight scene shown in FIG. 8, the area S2 indicating the sun (the area indicated by the dotted diagonal lines) indicates the color temperature of the light source, the area S3 indicating the white clouds and the area S4 indicating the white portion of the parasol (the oblique lines). (Region indicated by) reflects the color temperature of the light source, and these regions S2 to S4 are extracted as the highlight portion.

Further, in the night view scene shown in FIG. 9, since the area S5 indicating the moon (area indicated by diagonal lines) and the area S6 indicating building lights (area indicated by dotted diagonal lines) indicate the color temperature of the light source, These areas S5 and S6 are extracted as highlight portions, and in the illuminated backlight scene shown in FIG. 10, since the area S7 indicating illumination (the area indicated by the dotted diagonal lines) indicates the color temperature of the light source, this area S7 Is extracted as a highlight part.

The R color and B color image data of the highlight portion extracted by the low light clip circuit 971 are input to the weighting circuit 973, and the G color image data is input to the highlight portion area calculation circuit 982 and the weighting circuit 973. Entered in.

The highlight area calculation circuit 972 is a circuit for calculating the total area of the highlight area extracted by the low clip circuit 971 in the image pickup screen. The highlight area calculation circuit 972 calculates the total area from the number of pixels forming the highlight section, for example, and outputs the calculation result to the light source discrimination accuracy calculation circuit 976.

The weighting circuit 973 is a circuit for weighting the level by multiplying the image data of the highlight portion extracted by the low light clipping circuit 971 by a predetermined coefficient. The integrating circuit 974 is, for example, a CR integrating circuit, and is a circuit that integrates the image data of the highlight portion for a predetermined time τ in a predetermined cycle T and averages the level of the highlight portion.

The integration start timing of the integration circuit 978 and the integration time τ are controlled by a counter 987 described later. The integration time τ is set in advance as appropriate, and the integration start timing is determined according to the reliability of the color temperature of the light source detected from the image data of the highlight portion.

The integrating circuit 974 starts integration (averaging) of the level of the image data in the highlight portion at the integration start timing input from the counter 987, and a predetermined integration time τ
When only the integration is performed, this integration result is held until the next integration start timing. As a result, R of the highlight part,
The average levels R1, G1, and B1 of the G and B color components are updated at the predetermined cycle T.

The average levels R1 and B1 of the image data of the R and B color components output from the integration circuit 974 are input to the color correction gain calculation circuit 975 and the chromaticity data conversion circuit 976, and the image of the G color component is input. The average level G1 of the data is the color correction gain calculation circuit 975 and the chromaticity data conversion circuit 976.
And the light source discrimination accuracy calculation circuit 977.

The low light clip circuit 97 is used.
1, in the weighting circuit 973 and the integrating circuit 974, R,
Signal processing is performed on the image data of each of the G and B color components.

The color correction gain calculation circuit 985 outputs the average level R1 of the image data of each of the R, G and B color components.
White balance adjustment data WBD1 from G1 and B1
(R1 / G1, B1 / G1) is calculated. The calculation result is input to the MIX circuit 986.

The chromaticity data conversion circuit 976 uses the R,
Average levels R1 and G of image data of G and B color components
1, B1 is converted into chromaticity data (x coordinate value, y coordinate value) in a CIE (International Commission on Illumination) xy chromaticity diagram. This conversion into chromaticity data (x, y) is for calculating the accuracy (reliability) of the judgment when it is judged that the highlight part includes a light source.

That is, according to the CIExy chromaticity diagram, as shown in FIG. 11, the color temperature locus A due to the temperature change of the black body is shown.
(Hereinafter referred to as black body locus A) is shown, and the color of various light sources such as a tungsten white light bulb (point a in the figure), sunlight (point b in the figure), daylight (point c in the figure), etc. Since the temperature can be known, by comparing the chromaticity data (x, y) with the black body locus A, it can be estimated whether or not the highlight portion includes a light source.

If the chromaticity data (x, y) is located on or near the black body locus A, even if it is determined that the highlight portion indicates the color temperature of the light source, the accuracy of the determination is almost zero. 1
00% reliable, but chromaticity data (x, y)
As is away from the black body locus A, the reliability of the determination that the highlight portion includes the color temperature of the light source is reduced.

Therefore, in the present embodiment, the accuracy when it is determined from the chromaticity data (x, y) that the highlight portion includes the color temperature of the light source is empirically obtained in advance, The chromaticity data (x, y) converted by the chromaticity data conversion circuit 976 is used to calculate the accuracy when it is determined that the highlight portion includes a light source.

In FIG. 11, a region Q1 surrounded by three ellipses provided in the central portion (white region) of the xy chromaticity diagram.
Q2 and Q3 are areas showing the above-mentioned accuracy. The area Q1 is a near area including the black body locus A, and is a high accuracy area in which the accuracy of the determination that the light source is included in the highlight portion is approximately 100%. The area Q2 outside the area is a medium accuracy area where the accuracy of the above determination is medium, and the area Q3 outside is a low accuracy area where the accuracy of the above determination is low.

Further, α1 set in each area Q1, Q2, Q3 is a light source discrimination accuracy coefficient used for calculating the above-mentioned addition ratio α. The area outside the area Q3 is an area where the accuracy of the judgment is approximately 0%, and the light source discrimination accuracy coefficient α1 is “0”.

The above chromaticity data (x, y) is R, G, B
Average level of image data of each color component (R1, G1, B
1) is converted into tristimulus values (X, Y, Z) of the XYZ color system, and a predetermined calculation (x = X / (X + Y +) is applied to these tristimulus values.
Z), y = Y / (X + Y + Z)).
The result of this calculation, together with the average level G1 of the G color image data, together with the light source discrimination accuracy calculation circuit 977 and M
It is input to the IX circuit 986.

The light source discrimination accuracy calculation circuit 977 calculates the light source discrimination accuracy coefficient α1 from the chromaticity data (x, y), and from the luminance level of the highlight portion (average level G1 of G color image data). An addition coefficient α2, which will be described later, is calculated based on a preset table, and is preset from the light source discrimination accuracy coefficient α1, the addition coefficient α2, and the total area data of the highlight part input from the highlight part area calculation circuit 972. The addition ratio α is calculated based on the table.

FIG. 12 is a diagram showing an example of a calculation table for the addition coefficient α2. In the figure, the horizontal axis is the brightness level of the highlight part (that is, the average level G1 of the G color image data of the highlight part), and the vertical axis is the addition coefficient α2.
It is. “Max” on the horizontal axis is the CCD image sensor 6
Corresponding to the upper limit value of the dynamic range (see FIG. 6, upper limit value of the dynamic range), and the low light clip level is a level set in the low light clip circuit 971 based on the DC voltage V _R of the CCD image sensor 6. .

The table shown in the figure shows that if the luminance level (G1) of the highlight portion is equal to or higher than a predetermined high level threshold value G _H based on the photoelectric conversion characteristic of the CCD image sensor 6 (see FIG. 6), the highlight portion Is assumed to include a light source almost certainly, the addition coefficient α2 is set to “1”, and when the brightness level of the highlight portion is smaller than the high level threshold G _H , the light source is placed in the highlight portion. Since the reliability of the determination that it is included is not sufficient, the predetermined addition coefficient α2 is set according to the brightness level of the highlight part according to a predetermined diagram obtained by an experiment or the like.

FIG. 13 is a diagram showing an example of WB control based on the discrimination result of the color temperature of the highlight portion.

The table for calculating the addition ratio α is preset based on the WB control shown in FIG. 13, and the addition ratio α is "addition ratio" according to each case in FIG.
It is set as shown in the column.

In the figure, "highlight portion area" is the total area of the highlight portion extracted by the lowlight clip circuit 971 and is the output content of the highlight portion area calculation circuit 972.

"Black body locus discrimination" is chromaticity data (x, y).
According to the light source discrimination of the highlight portion by, the “black body locus” may include the light source in the highlight portion (in FIG. 11, the chromaticity data (x, y) is in the areas Q1 to Q3). “Outside the black body locus” indicates that there is no possibility that a light source is included in the highlight portion (in FIG. 11, the chromaticity data (x, y) is outside the area Q3).

The "highlight brightness level" is the average level G1 of the G color image data of the highlight part, and substantially indicates the brightness level of the highlight part, and the "assumed scene" is the "highlight part area". , "Black body locus discrimination" and "highlight luminance level" discrimination results are shown, showing a shooting scene of a subject assumed.

"WB control content" indicates qualitative white balance adjustment content, and "addition ratio" is MIX.
The content of the addition control in the circuit 986 is shown, and the “light source” is the addition ratio (α × 100 [%]) of the white balance adjustment data WBD1 (R1 / G1, B1 / G1) calculated from the image data in the high luminance area, “Normal” means the addition ratio of the white balance adjustment data WBD2 (R2 / G2, B2 / G2) calculated from the image data in the low luminance area ((1
-Α) × 100 [%]).

The cases (1) to (3) in the figure are cases in which the area of the extracted highlight portion is large and it is estimated that the color temperature of the light source is included in this highlight portion.

Case (1) is a case where the brightness level of the highlight portion is high and it is estimated that a light source exists in the highlight portion, and is a backlight scene shown in FIG. 8, for example. Also,
In case (2), the highlight brightness level is medium,
In the case where it is estimated that the reflected light from the light source exists in the highlight part, for example, a normal light scene as shown in FIG.

In cases (1) and (2), the average level G1 of G color in the highlight portion exceeds the high level threshold G _H ,
Since accurate color temperature information can be obtained from the highlight part, the addition coefficient α is set to “1”. That is, the amplifier gain control values (AG _R , AG _B ) are generated based on the white balance adjustment data WBD1 (R1 / G1, B1 / G1).

Case (3) is a case where the brightness of the highlight portion is low and it is estimated that there is a white reflective object in the highlight portion although there is no object reflecting the color temperature of the light source. In case (3), the average level G1 of G color in the highlight portion becomes lower than the high level threshold G _H , and therefore the addition coefficient α2 is set according to the average level G1 from a predetermined diagram.

Therefore, in case (3), the average value of the light source discrimination accuracy coefficient α1 calculated from the chromaticity data (x, y) and the addition coefficient α2 calculated from the average level G1 of the G color of the highlight portion. Therefore, the addition ratio α (= (α1 + α2)
/ 2) is set and the amplifier gain control value (AG _R , A
G _B ) is white balance adjustment data WBD1 (R1 / G1, B1 / G1) obtained from the high luminance area and white balance adjustment data WBD2 obtained from the low luminance area.
(R2 / G2, B2 / G2) is added based on the value obtained by adding the addition ratio α.

In addition, cases (4) and (5) in the figure are cases where the area of the extracted highlight portion is small and it is estimated that a point light source is included in the screen. in this case,
Even if the color temperature information of the light source is obtained from the highlight part, since it is a point light source and has little influence on the subject, the color temperature information of the light source of the highlight part is not considered.

Therefore, in cases (4) and (5), the addition ratio α is set to "0" and the amplifier gain control value (AG
_R, AG _B) is generated on the basis of the white balance adjustment data obtained from the low luminance region WBD2 (R2 / G2, B2 / G2).

Further, in the cases (6) and (7) in the figure, the highlight part is large and the brightness level of that part is also above the middle level, but the brightness level of the highlight part does not reflect the white light source. In the case that it is judged that there is not, the shooting scene,
For example, it is a case where a color light bulb is used as a light source or a case where it is estimated to be a color feria scene such as a sunset.

In the cases (6) and (7), considering the color temperature of the light source of the highlight part, the WB adjustment may be deteriorated, so the addition ratio α is set to the case (4),
Similar to (5), it is set to "0", and the amplifier gain control values (AG _R , AG _B ) are the white balance adjustment data WBD2 (R2 / G2, B2 / G) obtained from the low luminance area.
It is generated based on 2).

Since the white balance adjustment data WBD2 generated from the image data in the low luminance area is corrected by the color ferria clipping circuit 985 so as to suppress the color ferria as described later, the photographed scene is the color ferria scene. In the case of (case (7)), W
At the same time, the color adjustment is performed by adjusting B.

Further, the case (8) in the figure is a case where the highlight portion is not extracted. In this case, since the color temperature information of the light source cannot be obtained from the subject, the WB control similar to the case (8) is performed. Be seen.

Returning to FIG. 2, the highlight clipping circuit 981 is a circuit for clipping the highlight portion of the image data and extracting the image data in the low luminance area. The same level as the low light clip circuit 981 is set as the clip level. This highlight clip circuit 98
1, the areas excluding the areas S1 to S7 are extracted as the low-brightness areas in the example of the shooting scenes of FIGS.

The weighting circuit 983 and the integrating circuit 98
4 is a weighting circuit 971 in the light source discrimination circuit 97.
And an integrating circuit 972 corresponding to R,
Average levels R2 and G of image data of G and B color components
2, B2 is calculated.

The integration start timing of the integration circuit 984 and the integration constant τ are also controlled by the counter 987, and the average levels R2, G2, B2 of the image data of each color component of R, G, B in the low luminance area are also the above-mentioned predetermined values. Cycle T
Will be updated with.

The color correction gain calculation circuit 984 corresponds to the color correction gain calculation circuit 975, and corresponds to R, G, and
Average level R2, G2, B of image data of each color component of B
2 to white balance adjustment data WBD1 (R1 / G
1, B1 / G1) is calculated. The calculation result is input to the color ferria clip circuit 985.

The color ferria clip circuit 985 has a W
The color balance is suppressed by overcorrection of the B adjustment, and the white balance adjustment data WBD2 (R2 /
G2, B2 / G2) exceeds a predetermined high level,
The high level is clipped and output to the MIX circuit 986.

The MIX circuit 986 receives the white balance adjustment data WBD1 (R1 / G1, B1 / G1) input from the color correction gain calculation circuit 975 and the white balance adjustment data WBD2 (R2 input from the color rear clipping circuit 985. / G2, B2 / G2),
The addition is performed with the addition ratio α input from the light source discrimination accuracy calculation circuit 977, and the reciprocal of the addition result is calculated to generate the amplifier gain control values (AG _R , AG _B ).

The amplifier gain control value (AG _R , A
G _B ) is calculated by the following equation.

[0122]

(Equation 5)

The counter 987 is an integrating circuit 974, 9
The integration time of 83 is controlled, and the integration start timing of the integration circuits 974, 983 is controlled based on the light source discrimination accuracy coefficient α1 input from the light source discrimination accuracy calculation circuit 987. The counter 987 operates the integrator circuits 974 and 983 for a predetermined time τ, holds the integration result for a predetermined time T _HLD , and alternately repeats the integration operation and the hold operation to obtain amplifier gain control values (AG _R , AG _B ) is updated at the cycle T (= _THLD + τ). In the normal state, T _HLD = 0 and T = τ are set.

The integration time τ is set to an appropriate time of about several seconds so that the image data is averaged for several screens. If the average level of the image data can be calculated for at least one screen, the above-mentioned amplifier gain control value can be calculated. However, for example, when shooting a moving object or changing the angle of view by panning or zooming for the same subject. In such a case, if the amplifier gain control value is calculated according to the change of the frame image and the WB adjustment is performed, the above-mentioned amplifier gain control value may change and the color balance may fluctuate. The integration time τ is set relatively long as described above.

The hold time T _{HLD of the} integration result is also
Is changed and set so as to become longer as the light source discrimination accuracy coefficient α1 becomes larger. If the light source is stable in the moving object shooting, the panning or zooming shooting, the color temperature of the light source is substantially constant even if the shooting screen changes. Therefore, the WB adjustment cycle is longer than the integration time τ. It is desirable to carry out a longer and more suitable cycle.

In this embodiment, the color temperature of the light source is detected from the photographed image and the detection accuracy is calculated. Therefore, the hold time T _HLD of the integration result is changed according to the calculation result. The WB adjustment cycle T is adjusted more finely.

That is, when the light source discrimination accuracy coefficient α1 is large, it is estimated that the accuracy of the color temperature of the light source detected from the photographing screen is high and the light source of the subject is stable.
The hold time T _HLD of the integration result is lengthened to update the amplifier gain control value (AG _R , AG _B ) update cycle (T _HLD + τ).
I try to make it longer.

Next, the image pickup operation of the image pickup apparatus 1 will be briefly described by taking as an example the case of shooting the shooting scene shown in FIG. The subject light image incident through the lens system 2 is separated by the dichroic prism 5 into light images of R, G, and B color components, and the CCD image sensor 6 (R),
An image is formed on the 6 (G) and 6 (B) imaging planes.

CCD image sensor 6 (R), 6 (G), 6
When the control pulse φ _D is input from the timing generator 7 to (B), the exposure is started, and when the predetermined exposure time Tv set by the exposure control calculation circuit 95 has elapsed, the CCD image sensor 6 from the timing generator 7 is started.
The shift pulse φ _S is input to (R), 6 (G), and 6 (B) to stop the exposure.

CCD image sensor 6 (R), 6 (G), 6
An electric charge amount logarithmically compressed with respect to the incident light amount is accumulated in the electric charge accumulating portion 62 of (B) within the exposure time Tv, and the image signal composed of the accumulated electric charges is supplied to the first and the first It is output to the CDS circuit 81 in synchronization with the two transfer pulses φ1 and φ2. After the noise is suppressed by the CDS circuit 81, the image signals of the R, G, and B color components are amplified to a predetermined prescribed level by the preamplifier 82, and further, from the color correction arithmetic circuit 98 to the D / A converter 99. Amplifier gain control value (A
G _R, the white balance is adjusted by the WB circuit 83 based on the AG _B).

R, G, B whose white balance has been adjusted
The image signal of each color component of is converted into digital image data by the A / D converter 91, and the exposure control arithmetic circuit 9
Γ correction data and contour correction control circuit 96 input from
Γ correction circuit 9 based on the contour correction data input from
After the .gamma. Correction and the contour correction are performed by 1 and the enhancer 92, the D / A converter 93 converts the .gamma.-correction and the contour correction again into an analog image signal and outputs the analog image signal to a circuit at a subsequent stage (not shown).

The image data of each of the R, G, and B color components is also input to the Y matrix circuit 94, and from the brightness data generated by the Y matrix circuit 94, the DC voltage V _R , The γ correction data is calculated, and the contour correction control circuit 96 generates the contour correction data.

The image data of the R, G, and B color components are input to the light source discriminating circuit 97, and the light source discriminating circuit 97 extracts a high-luminance region (empty region S1). From the image data of the R, G, and B color components that make up the white balance adjustment data WBD1 (R1
/ G1, B1 / G1) is calculated. Also, the empty area S
The color temperature of the light source is calculated from the total area of 1, the average luminance level and the chromaticity data, and the color temperature of the light source of the sky region S1 is estimated from these three elements, and the accuracy of this estimation (light source discrimination accuracy coefficient α1, addition The addition ratio α is set based on the coefficient α2).

The image data of each of the R, G, and B color components is input to the color correction calculation circuit 98, and the color correction calculation circuit 98 causes a low luminance area (areas other than the empty area S1).
Is extracted, and white balance adjustment data W is obtained from the image data of each of the R, G, and B color components forming this low-luminance region.
BD2 (R2 / G2, B2 / G2) is calculated.

Then, based on the addition ratio α, the white balance adjustment data WBD1 (R1 / G1, B1 /
G1) and white balance adjustment data WBD2 (R2 /
G2, B2 / G2), and the reciprocal of the addition result is calculated to generate the amplifier gain control value (AG _R , AG _B ).

This amplifier gain control value (AG _R , AG _B )
Is converted into an analog signal by the D / A converter 99 and then fed back to the WB circuit 83.

In the first image pickup operation at the time of startup, the DC voltage V _R , the exposure time Tv and the amplifier gain control values (AG _R , AG _B ) are set to preset initial values, and the image pickup and image signal are obtained. Although signal processing is performed, then the set DC voltage V _R and the amplifier gain control value by the exposure control calculation circuit 95 and the light source discrimination circuit 97 and the color correction operation circuit 98 (AG _R, AG _B) is a predetermined timing Alternatively, it is updated and set in a predetermined cycle.

As described above, according to the present embodiment, the CCD image sensor 6 having a logarithmic photoelectric conversion characteristic is used to capture an image signal in a high-luminance region without overflowing, and an image in the high-luminance region is captured. The color temperature of the light source of the subject is estimated from the signal, and the accuracy of the estimation is calculated. Based on this accuracy, the color temperature of the light source is added to the amplifier gain control value (AG _R ,
Since so as to set the AG _B), it is possible to perform white balance adjustment with high accuracy.

Especially, since the estimation accuracy of the color temperature of the light source in the high brightness region is set from the three elements of the area of the high brightness region, the average brightness level and the chromaticity data, the color temperature of the light source in various shooting scenes is set. Can be estimated with relatively high accuracy, and a suitable white balance adjustment can be performed according to the shooting scene.

Further, the higher the above-mentioned estimation accuracy is, the integration 97
The hold time T _HLD of the integration result of 5,983 is changed to be long, and when the light source of the subject is stable, the update cycle of the white balance adjustment is set to be long. It is possible to prevent unpleasant color balance fluctuation due to adjustment.

[0141]

As described above, according to the present invention,
An image of an object is picked up by an image pickup unit including a plurality of photoelectric conversion elements having a logarithmic characteristic, and white balance adjustment data is generated at a predetermined cycle based on the color temperature of a light source included in a predetermined high brightness region in the captured image. At the same time, the generation cycle of the white balance adjustment data is changed according to the accuracy of determining the color temperature of the light source. Therefore, even when the screen configuration is changed under the same light source, it occurs according to the change in the screen configuration. Unpleasant color balance fluctuation can be prevented.

When the screen configuration is changed under the same light source by, for example, panning or zooming, the white balance adjustment cycle is lengthened to make the white balance adjustment data constant regardless of the change in the screen configuration. Can be suppressed, and stable color correction control can be performed.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an image pickup apparatus according to the present invention.

FIG. 2 is a circuit configuration diagram of a light source determination circuit and a color correction calculation circuit.

FIG. 3 is an equivalent circuit diagram of each pixel of the image sensor.

FIG. 4 is a time chart of drive control of the image sensor.

5A and 5B show potential states of the charge storage portion at each timing during exposure, and FIGS. 5A to 5F respectively show potential states at timings t1 to t6 in the time chart of FIG. It is a figure.

FIG. 6 is a diagram showing photoelectric conversion characteristics of an image sensor.

FIG. 7 is a diagram showing an example of a high-luminance region in a clear or cloudy shooting scene.

FIG. 8 is a diagram showing an example of a high-luminance region in a backlight scene.

FIG. 9 is a diagram showing an example of a high-luminance region in a night scene.

FIG. 10 is a diagram showing an example of a high-luminance region in an illuminated backlit scene.

FIG. 11 is a diagram for explaining a method of discriminating the detection accuracy of the color temperature of the high luminance region from the CIE chromaticity diagram.

FIG. 12 is a diagram showing a calculation table of an addition coefficient α2.

FIG. 13 shows W based on the determination result of the color temperature of the highlight portion.
It is a figure which shows an example of B control.

FIG. 14 is a diagram showing photoelectric conversion characteristics of a conventional CCD image sensor.

[Explanation of symbols]

 1 Imaging Device 2 Lens System 3 Iris 4 Iris Driver 5 Dichroic Prism 6 CCD Image Sensor 61 Photosensitive Section 62 Charge Storage Section 7 Timing Generator 8 Analog Signal Processing Circuit 81 Correlated Double Sampling Circuit 82 Preamplifier 83 White Balance Circuit 84 A / D Converter 9 Digital Signal Processing Circuit 91 γ Correction Circuit 92 Enhancer 93 D / A Converter 94 Y Matrix Circuit 95 Exposure Control Calculation Circuit 96 Contour Correction Control Circuit 97 Light Source Information Detection Circuit 971 Low Light Clip Circuit 972 Highlight Area Calculation Circuit 973 Weighting Circuit 974 Integration circuit 975 Color correction gain calculation circuit 976 Light source color temperature calculation circuit 977 Light source discrimination accuracy calculation circuit 98 Color correction calculation circuit 981 Highlight clip circuit 982 Weight Only circuit 983 integrating circuit 984 color correction gain calculating circuit 985 color failure clipping circuit 986 MIX circuit 987 Counter 99 D / A converter

Claims (1)

[Claims] 1. An image pickup means comprising a plurality of photoelectric conversion elements having a logarithmic characteristic for converting incident light into an electric signal logarithmically compressed with respect to the light quantity and outputting the electric signal, and an image picked up by the image pickup means. Area extraction means for extracting a predetermined high-brightness area, determination means for determining the presence or absence of a light source in the extracted high-brightness area, accuracy calculation means for calculating the accuracy of the determination result of the determination means, and the high-brightness area Detecting means for detecting the color temperature of the light source, data generating means for generating the white balance adjustment data of the captured image based on the detected color temperature of the light source, and the white balance adjustment data at a predetermined cycle. And a cycle changing means for changing the generation cycle of the white balance adjusting data according to the calculation result of the accuracy calculating means. Imaging device.