JP3163065B2 - Imaging equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image photographing apparatus, which can perform good color reproduction even when a subject is illuminated by a fluorescent lamp, and can photograph without flicker even when the subject is illuminated by a fluorescent lamp. Is made possible.

[0002]

2. Description of the Related Art In an image photographing apparatus such as a video camera or a video still camera, a white balance is adjusted so that a white subject is reproduced white. The white balance is adjusted by controlling the gain of the red signal circuit and the gain of the blue signal circuit of the camera with reference to the green signal. To adjust the white balance, the color tone (color temperature) of the shooting environment
Need to be measured. As a method of white balance, there are an external photometric system and an internal photometric system which differ in color temperature measuring method.

In the external photometric method, a color temperature is directly detected by a color temperature sensor, and a white balance control signal for an R (red) signal and a white balance control signal for a B (blue) signal are generated based on the detected data, and the white light is output. I try to balance. The color temperature sensor is formed, for example, by integrally integrating a photosensor with a red filter, a photosensor with a green filter, and a photosensor with a blue filter, and calculates R, B from the output voltage of each photosensor. We are making white balance control signals for signals.

In the internal photometric system, the color temperature is detected indirectly, so to speak, if a predetermined range of the screen (for example, about 70% of the screen) is averaged when the white balance is matched, an achromatic color (gray) is obtained. Is controlled based on the knowledge that In other words, the average value of the color difference signals RY and BY, which become achromatic when the colors in a predetermined range of the screen are averaged under the reference color temperature condition, is set as a reference value and generated by a video camera at the time of shooting. The values of the R signal and the B signal are feedback-controlled so that the integrated average value of the actual color difference signals RY and BY becomes the reference value.

[0005]

By the way, when a subject illuminated by a fluorescent lamp is photographed by a video camera,
Simply adjusting the white balance may result in poor reproducibility of screen colors and unnatural human skin color.
This is because the light of the specific wavelength component in the light generated by the fluorescent lamp may be particularly intense than the light of the other wavelength components. This is because there may be an extreme peak in the distribution. At this time, even if the color temperature is corrected, the color phase and the saturation change and the color reproducibility deteriorates. On the other hand, in some conventional cameras, color reproducibility other than fluorescent lamp illumination is sacrificed to some extent in order to improve skin color reproducibility under fluorescent lamp illumination. FIG. 8 shows the spectrum distribution of various fluorescent lamps.

The color temperature is detected by a sensor or the like, the white balance is adjusted in accordance with the detected color temperature, and the hue (hue) and saturation (gain) of the color difference signal are determined in accordance with the detected color temperature. Correction techniques (for example, see
No. 318484 ”). However, this technique merely controls the color temperature and the correction amount of the hue and the saturation in correspondence with each other. When an object illuminated with various fluorescent lamps having different characteristics is photographed, the fluorescent lamp is controlled. The hue and saturation cannot be adjusted according to the type. Therefore, when photographing is performed in an environment illuminated by a fluorescent lamp, color reproducibility is not good.

[0007] In an area where the frequency of the commercial power supply is 50 Hz, flickering occurs when the subject is illuminated with a fluorescent lamp supplied with power from the commercial power supply and the subject is photographed.

As a method of eliminating the flicker and improving the image quality, an imaging apparatus shown in FIG. 9 has been considered. In FIG. 9, reference numeral 01 denotes an image sensor including a solid-state image sensor or the like;
Is a variable gain amplifier for amplifying the output, 03 is an optical sensor for detecting the light level of the illumination light, 04 is an integrator for integrating the output of the optical sensor 03, and 05 is a signal processing circuit for converting the signal to a television signal or the like. . FIG. 10 shows the configuration of the integrator 04, where 04a is an integrator with reset, and 04b
Is a hold circuit for sampling and holding in accordance with the accumulation and readout timing of the image sensor.

Since an image sensor 01 such as a CCD accumulates and reads out a video signal of one field at the same timing, an integrator with a reset may be used to determine the amount of change in the signal of the image sensor 01. The configuration of the actual integrator is shown in FIG.
As shown in (5), the reset timing of the integrator 04a is the same as the read timing of the image sensor 01, and the sample timing of the sample-and-hold circuit 04b is immediately before the reset timing. In this way, the timing of resetting and sampling of the integrator 04 is made the same as the timing of charge storage and reading of the image sensor. In this way, the amount of fluctuation such as flicker that occurs in the imaging signal in relation to the illumination light is obtained from the optical sensor 03 and the integrator 04. By calculating the reciprocal of the fluctuating component and multiplying (gain control) the signal captured by the variable gain amplifier 02, flicker can be reduced.

However, in the above configuration, the optical sensor 03 is required separately from the image pickup device 01, and the optical system is different. Therefore, a signal obtained by imaging an image within a certain viewing angle through the lens does not match the signal of the illumination light collected by the optical system of the optical sensor, and the flicker correction includes an error, and the correction is performed with sufficient accuracy. Absent. In addition, an optical sensor is required in addition to the image pickup device, which is disadvantageous because the cost is high.

An object of the present invention is to provide a video camera having a color compensation function capable of taking an image of a subject illuminated by a fluorescent lamp with good color reproducibility in view of the above prior art.

Another object of the present invention is to provide a video camera capable of taking an image of a subject illuminated by a fluorescent lamp without flickering, in view of the above prior art.

[0013]

According to the present invention for solving the above-mentioned problems, in white balance adjustment using an internal light measurement method, when a white balance is obtained under a certain temperature condition, a value of a white balance control signal is fixed. The type of the illumination light source is determined from the convergence value using the fact that the light source converges. Further, the hue control signal and the color difference gain control signal are adjusted so as to correct the phase and saturation of the color according to the illumination light.

In the present invention, the white balance adjustment using the internal photometry method utilizes the fact that the value of the white balance control signal converges to a constant value when the white balance is obtained under a certain temperature condition. It is determined whether the illumination light source is a fluorescent lamp. When the illumination light source is a fluorescent lamp, an electronic shutter operation with a shutter speed of 1/100 is performed.

[0015]

When the illumination light source is a fluorescent lamp, the color phase and saturation can be adjusted according to the characteristics of each fluorescent lamp, and the color reproducibility of human skin color and the like is improved.

Further, even if the illumination light source is a fluorescent lamp, it is possible to take a picture without flicker.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a video camera according to an embodiment of the present invention. As shown in FIG. 1, a subject image formed by a lens 1 is incident on an imaging surface of a charge-coupled device (CCD) 3 through an iris 2. The imaging surface of the CCD 3 is provided with a complementary color (cyan, magenta, yellow, green) filter. The charge signal E indicating the subject image is read through a readout circuit (CDS) 4 and an automatic gain control (AGC) circuit 5 , And is input to the signal separation circuit 6. The signal separation circuit 6 generates the charge signal E
, And outputs two types of image signals S1 and S2 and a luminance signal Y. The matrix circuit 7 processes the image signals S1 and S2 to output primary color signals R, G and B. The luminance signal Y is processed by the luminance signal processing unit 22. The primary color signal R,
G and B are γ-corrected by the γ correction circuit 9 after the white balance is adjusted by the white balance circuit 8, and then input to the matrix circuit 10. The matrix circuit 10 performs a matrix process on the primary color signals R, G, and B to generate a color difference signal R.
-Y and BY are output. In the encoder 11, a signal obtained by quadrature two-phase modulation of the color difference signals RY and BY and a luminance signal Y
And outputs an NTSC video signal.

The microcomputer 12 sends an AF (auto focus) control signal P1 to a lens driving unit for moving the lens 1, and sends an AE (auto iris) control signal P to the iris 2.
2 and sends an AGC control signal P3 to the AGC circuit 5.
Also, the microcomputer 12 sends the zoom information P from the lens drive unit.
4 is sent, iris data P5 indicating the iris opening is sent from the Hall element 13 that detects the iris opening, and C
Drive state information P6 indicating the CCD drive state is sent from the CD drive circuit 14. Note that the CCD drive circuit 14
When the movie mode or the electronic shutter mode is set, the CCD 3 is driven according to each mode. The gate array 15 obtains the iris state from the output signal of the CDS 4, obtains the AGC state from the output of the AGC 5, and sends the obtained state signal P 7 to the microcomputer 12.

The microcomputer 12 has an iris opening, a CCD,
The brightness of the subject is calculated in consideration of the driving state of A and the gain of the AGC. In other words, the higher the luminance, the narrower the iris, and the darker the AGC gain, the greater the AGC gain.
Since the result of calculating the gain of the GC corresponds to the luminance of the subject, the microcomputer 12 can process these conditions to detect the luminance of the subject. Microcomputer 1
The subject brightness data P8 calculated in 2 is serially transmitted to the microcomputer 20.

On the other hand, the color difference signals RY and BY output from the matrix circuit 10 are applied to low-pass filters 16 and 17 respectively.
, And is digitized by the A / D converters 18 and 19 before being sent to the microcomputer 20. Microcomputer 2
A value obtained by integrating and averaging the color difference signals RY and BY that become achromatic when the predetermined range of the subject screen is averaged under the reference color temperature condition is set to 0. Then, a white balance control signal R _CONT for a red signal for making the integrated average value of the color difference signal RY equal to the reference value for RY, and the integrated average value of the color difference signal BY and the reference value for BY green light for white balance control signal B _CONT so as to equal the door is output from the microcomputer 20 D / a converter 2
The signal is converted into an analog signal by 1 and sent to the white balance circuit 8. For this reason, the white balance circuit 8 adjusts the gain of the primary color red signal R and the primary color blue signal B according to the values of the white balance control signals R _CONT and B _CONT , and performs white balance feedback control. The area that the white balance control signals R _CONT and B _CONT can take will be described later.

Furthermore from the microcomputer 20, the color difference signals R-Y output from the matrix circuit 10, the gain signal R-Y _GAIN to control the gain of B-Y, B-Y _GAIN and color difference signals R-Y, hue control signal R-Y _hUE for controlling the phase of the B-Y, B-Y _hUE is output. In the matrix circuit 10, the color difference gain control signals RY _GAIN ,
The saturation is adjusted by changing the gain of the color difference signals RY and BY in accordance with the BY _GAIN , and the hue control signals RY _HUE and B are adjusted.
The hue is adjusted by changing the phase of the color difference signals RY and BY in accordance with −Y _HUE .

The microcomputer 20 has an outdoor mode and an indoor mode as shown in FIG. When the indoor mode is set, the white balance control signals R _CONT , B
The value of _CONT can take only the value in the area X surrounded by the solid line in FIG. In addition, light bulb, white normal type fluorescent lamp,
When shooting white paper illuminated by a white three-wavelength fluorescent lamp, a daylight white normal fluorescent lamp, a daylight three-wavelength fluorescent lamp, a daylight normal fluorescent lamp, or a daylight three-wavelength fluorescent lamp, R _CONT and B _CONT The value takes the value of the point indicated by the triangle in the figure. That is, the area X in the indoor mode
The various artificial light by R _CONT when the white balance adjustment by photographing a white paper illuminated, B _{CO NT} has become that narrowed and region width including a value to converge. On the other hand, when the outdoor mode is set, the values of the white balance control signals R _CONT and B _CONT can take only the values in the area Y surrounded by the dashed line in FIG. _Assuming that the values of R _CONT and B _CONT are the respective values of area Y, the color temperature characteristics at that time are on a normal color temperature change curve and, when displayed on a vectorscope, are within a limited area almost close to the I axis. enter.

The microcomputer 20 receives the subject brightness data P8 sent from the microcomputer 12, and determines that the subject mode is the outdoor mode if the subject brightness is above a certain set value, and determines the indoor mode if the subject brightness is lower than the set value. This utilizes the fact that the color temperature and the illuminance correspond to each other as shown in FIG.

The manner in which the microcomputer 20 adjusts the white balance is as follows. The microcomputer 20 sequentially changes the values of the white balance control signals R _CONT and B _CONT so that the integrated average value of the color difference signals RY and BY matches the reference value, and the color temperature at the time of this photographing. When the optimal white balance adjustment is performed, R _CONT and B
The value of _CONT becomes constant and converges. White balance control signal R _CONT, but B _CONT is gradually changed until it converges to a constant value, R _CONT if outdoor mode, B _CONT
Are limited to the values in the area Y. In the indoor mode, the possible values of R _CONT and B _CONT are limited to the values in the area X. When shooting a general scene in which each color is randomly mixed, good white balance adjustment can be performed if the values of R _CONT and B _CONT converge to a certain value in area X in indoor shooting, and R in outdoor shooting. _If the values of _CONT and B _CONT converge to a certain value in the area Y, good white balance adjustment can be performed.

Shooting a green grass outdoors full of the shooting screen
Even when shadowed, R_CONT, B_CONTThe value gradually changes
Try to change to a value outside the live area Y
Is R _CONT, B_CONTIs the boundary value of area Y
Roller R_CONT, B_CONTFix the value of. At this time, the area
The white balance can be adjusted if the width of the
No color feria is produced.

Assuming that the red wall is photographed indoors to cover the entire photographing screen, the values of R _CONT and B _CONT gradually change and try to change toward values outside the area X.
_When the values of _CONT and B _CONT become the boundary values of area X, the values of R _CONT and B _CONT are fixed. By doing so, the white balance does not significantly deviate, and color feria can be reduced.

The microcomputer 20 is set to the indoor mode and
White balance control signal R_CONT, B _CONTConverges to a constant value
Then, R_CONTIs any of the areas I to IV shown in FIG.
Determine whether you have entered the area. When you enter area I
Determined that it was lit by a light bulb and entered area II
Sometimes, it is determined that it is illuminated by a white fluorescent lamp,
When entering area III, illuminate with a neutral white fluorescent lamp.
Daylight when entering area IV
It is determined that it is illuminated with a color type fluorescent lamp.

When the microcomputer 20 determines the type of fluorescent lamp used for illumination in this manner, the color difference gain control signal R- so as to improve the color reproducibility of the reproduction screen according to the characteristics of each fluorescent lamp. Y _GAIN, B-Y _GAIN and the hue control signal R-Y _hUE, and corrects the value of the B-Y _hUE, to optimize state saturation and hue. FIG. 4 shows the characteristic tendency of the correction, and the color difference gain control signal R-
Y _GAIN , BY _GAIN and hue control signals RY _HUE , B-
Correct Y _HUE . For this reason, even when the fluorescent lamp is used as illumination, the human skin color can be reproduced as a natural color.
When the illumination light source is a light bulb, RY _GAIN , B-
Although the values of Y _GAIN , RY _HUE , and BY _HUE are normal values, there may be cases where it is better to add correction depending on the signal processing method.

In the above embodiment, the type of the fluorescent lamp is determined from the value of the white balance control signal R _CONT . However, a determination area corresponding to the white balance control signal B _CONT is set in advance, and the value of B _CONT is set. May be used to determine the type of the fluorescent lamp. Further, the type of the fluorescent lamp may be determined by comparing the convergence values of both R _CONT and B _{CONT with} the convergence characteristics of each fluorescent lamp in FIG.
In the above embodiment, the fluorescent lamp area is white, day white,
Although three types of daylight colors are used, each type may be further controlled into a normal type and a three-wavelength type.

FIG. 5 is a flowchart showing the operation of the embodiment. As shown in the figure, immediately after the power is turned on (step 1), the preset values of the white balance control signals R _CONT and B _CONT are output (step 2). After the power is turned on, the color difference signals RY and BY are fetched (step 3), and the white balance control signal R _CONT which makes the difference between the integrated value of the color difference signals RY and BY and the reference value zero is set. , B _CONT (step 4). When the camera is in the outdoor mode (step 5), R _CONT and B _CONT for the outdoor mode obtained in step 4 are output (step 6). If the outdoor mode is not set (step 5), step 4
The R _CONT and B _CONT for the indoor mode obtained in step (1) are output (step 7). When R _CONT and B _CONT for the indoor mode converge to constant values (step 8), and when the convergence position is the area of the fluorescent lamp (step 9), the type of the fluorescent lamp is determined from the convergence position (step 10). ), the color difference gain control signal in accordance with the type of fluorescent lamp _{R-Y gAIN, B-Y} gAIN and the hue control signal R-Y _hUE, controls the B-Y _hUE (step 1
1).

Next, an embodiment corresponding to the invention of claim 3 will be described.
The following description focuses on the operation of the microcomputer 20. Microcomputer 2
At 0, an outdoor mode Y and an indoor mode X are set as shown in FIG. Microcomputer 20
Is the subject brightness data P sent from the microcomputer 12.
8, when the subject brightness is equal to or more than the set value, the mode is determined to be the outdoor mode, and when the brightness is lower than the set value, the mode is determined to be the indoor mode. In the outdoor mode, the white balance control signals R _CONT and B _CONT having the values in the area Y are output, and in the indoor mode, the white balance control signals R _CONT and B _CONT having the values in the area X are output.

Further, in this embodiment, when the white balance control signals R _CONT and B _CONT converge in the areas II, III and IV during the indoor mode, it is determined that the illumination light is a fluorescent light. The microcomputer 20 sends the electronic shutter control signal P10 to the CCD drive circuit 14. Then, the CCD drive circuit 14 sets the shutter speed to 1 /
The electronic shutter operation of the CCD 3 is set to 100 seconds.

When the shutter speed is set to 1/100 second, flicker does not occur even when illuminating with a fluorescent lamp. This will be described with reference to FIGS. When the electronic shutter operates, the amplification in the AGC circuit 5 is increased.

FIG. 6 shows the brightness of the fluorescent lamp (indicated by a solid line in the figure) when the commercial power supply frequency is 50 Hz, and the amount of electric charge accumulated in the CCD of the video camera when the shutter speed is changed. (Corresponding to the hatched area in the figure). When the power supply frequency is 50 Hz, the brightness of the fluorescent lamp changes at a frequency of 100 Hz. In this case, the charge accumulated in the CCD is one field (1/1).
60 seconds).

As shown in FIGS. 6B, 6C and 6D, the electronic shutter speed is set to 1/800 second, 1/400 second, 1
At / 200 seconds, flicker occurs because the amount of charge stored in the preceding field and the subsequent field is different. However, as shown in FIG. 6E, when the electronic shutter speed is set to 1/100 second, the amount of charge accumulated in each field becomes equal, and no flicker occurs.

FIG. 7 shows the brightness of the fluorescent lamp and the amount of charge stored in the CCD of the video camera when the commercial power supply frequency is 60 Hz. In this case, no matter what value the electronic shutter speed is, the amount of charge accumulated in each field is equal, and no flicker occurs.

[0037]

According to the present invention, the color phase and the saturation are adjusted optimally even when illuminated by a fluorescent lamp as described above in detail with the embodiments. Is improved.

Further, according to the present invention, when illuminating with a fluorescent lamp, the electronic shutter speed is set to 1/100 second for photographing, so that flicker does not occur.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing a control area.

FIG. 3 is a characteristic diagram showing a relationship between luminance and color temperature.

FIG. 4 is an explanatory diagram showing a correction tendency of a color difference gain control signal and a hue control signal.

FIG. 5 is a flowchart showing an operation state of the embodiment.

FIG. 6 is an explanatory diagram showing a light emitting state and a charge accumulation state of a fluorescent lamp.

FIG. 7 is an explanatory diagram showing a light emitting state and a charge accumulation state of a fluorescent lamp.

FIG. 8 is a characteristic diagram showing a spectrum distribution of various fluorescent lamps.

FIG. 9 is a block diagram showing a conventional flicker prevention circuit.

FIG. 10 is a block diagram showing an integrator used in a conventional flicker prevention circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lens 2 Iris 3 CCD 4 Readout circuit 5 AGC circuit 6 Signal separation circuit 7 Matrix circuit 8 White balance circuit 9 γ correction circuit 10 Matrix circuit 11 Encoder 12, 20 Microcomputer 13 Hall element 14 CCD drive circuit 15 Gate array 16, 17 Low pass filter 18, 19 A / D converter 21 D / A converter 22 Luminance signal processing unit

Claims (3)

(57) [Claims] An imaging unit for photoelectrically converting a subject image formed by an optical system, and a primary color signal of red and blue among red, green, and blue primary color signals obtained by processing an output signal of the imaging unit. A white balance circuit that controls the amplification degree to perform white balance adjustment; and processes the white balance adjusted primary color signal to generate two types of color difference signals RY and BY, and the phase and color of the color difference signal. And a matrix circuit that adjusts and outputs the saturation of the respective color difference signals RY and BY that become an achromatic color when the predetermined range of the screen is averaged under the reference color temperature condition. A function of sending a white balance control signal for operating the white balance circuit to the white balance circuit so that the integrated average value of the color difference signals RY and BY at the time of photographing is equal to the reference value. And a function to send a hue control signal for controlling hue adjustment in the matrix circuit to the matrix circuit, and based on a value obtained by converging the value of the white balance control signal when white balance is obtained, the type of the illumination light source. And a signal adjustment processing unit for adjusting the state of the hue control signal according to the determined illumination light source. An image photographing apparatus having a color compensation function. 2. An imaging unit for photoelectrically converting a subject image formed by an optical system, and among red, green and blue primary color signals obtained by processing an output signal of the imaging unit, A white balance circuit for controlling the amplification degree to perform white balance adjustment; and processing the white balance adjusted primary color signals to generate two types of color difference signals RY and BY, and the phase and saturation of the color difference signals A matrix circuit that adjusts and outputs the degree, and an integrated average value of each of the color difference signals RY and BY that become an achromatic color when the predetermined range of the screen is averaged under the reference color temperature condition are set in advance as a reference value. And a function of sending a white balance control signal for operating the white balance circuit to the white balance circuit so that the integrated average value of the color difference signals RY and BY at the time of shooting is equal to the reference value. Has a function of transmitting a hue control signal for controlling hue adjustment in the matrix circuit and a color difference gain control signal for controlling saturation to the matrix circuit, and furthermore, when white balance is obtained, the value of the white balance control signal is A signal adjustment processing unit that determines the type of the illumination light source based on the converged value, and adjusts the state of the hue control signal and the color difference gain control signal according to the determined illumination light source. An image capturing device having a function. 3. An imaging unit having a function of an electronic shutter while photoelectrically converting a subject image formed by an optical system, and among red, green, and blue primary color signals obtained by processing output signals of the imaging unit. , A white balance circuit that controls the amplification of the red and blue primary color signals to perform white balance adjustment, and processes the white balance adjusted primary color signals to generate two types of color difference signals RY and BY. The matrix circuit and the integrated average value of each of the color difference signals RY and BY, which become achromatic when the predetermined range of the screen is averaged under the reference color temperature condition, are set in advance as reference values. Has a function of sending a white balance control signal for activating the white balance circuit to the white balance circuit so that the integrated average value of the color difference signals RY and BY becomes equal to the reference value. When the white balance is obtained, the type of the illumination light source is determined based on the converged value of the white balance control signal, and when the determined illumination light source is a fluorescent lamp, the electronic shutter speed is reduced by 1 / 100
An image photographing apparatus, comprising: a signal adjustment processing unit that operates according to the following.