JP3121055B2 - Imaging device - 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 pickup apparatus such as a video camera, and more particularly to an image pickup apparatus having a function of correcting a color balance by a difference in color rendering properties of a light source for illuminating a subject.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a configuration of a conventional image pickup apparatus having a color balance correction function. In the figure,
Reference numeral 11 denotes an image sensor including a solid-state image sensor, and reference numeral 12 denotes three primary colors R (red) output from the image sensor 11.
In a preamplifier circuit for amplifying a signal, a G (green) signal and a B (blue) signal, the gain of the R and B signal amplifiers can be adjusted for white balance control. Reference numeral 13 denotes a process circuit for performing a setup level adjustment, a blanking process, etc., from which a luminance signal Y and color difference signals RY, BY are obtained.
Is output. Reference numeral 14 denotes a color difference amplifier circuit for amplifying the color difference signals RY and BY, and each of the amplifiers is adjustable in gain. 15 is the luminance signal Y and the color difference signal R-
An encoder to which Y and BY are input, from which a composite video signal is output. Reference numeral 16 denotes a color temperature detecting means for detecting the color temperature of the light from the light source irradiating the subject, and 17 a system controller for controlling the preamplifier circuit 12 and the color difference amplifier circuit 14 based on the detected information.

[0003] In the image pickup apparatus constructed as described above, when photographing is started, first, the color temperature detecting means 16 operates to transmit the color temperature information of the light source to the system controller 17. The system controller 17 controls the preamplifier circuit 1 at the subsequent stage of the image sensor 11 according to the color temperature information.
The white balance is adjusted by changing the gain of the amplifiers of the R signal and B signal channels. At this time, the color temperature detecting means 16 is generally constituted by a light diffusing plate, R, G, and B optical sensors and an arithmetic circuit, and usually includes R / G and B / G.
Is input to the system controller 17 as the color temperature information.

An image signal captured by the image sensor 11 is output as R, G, and B color signals, and the white balance is adjusted by a preamplifier circuit 12, and then enters a process circuit 13, where blanking is performed. Processing and the like are performed and output as a luminance signal Y and color difference signals RY and BY. These signals are input to the encoder 15, where they are output as a composite video signal. The color difference signals RY and BY are amplified by the color difference amplifier circuit 14 and then input to the encoder 15. Is done. That is, the gain of the color difference signals RY and BY is controlled in accordance with the above-mentioned color temperature information. When the color temperature is low, the gain is increased to increase the saturation.
Thereby, the color balance is corrected by the difference in the color rendering of the light source, and the deterioration of the color reproducibility is prevented.

[0005]

However, in the above-described conventional imaging apparatus, the color balance due to the difference in the color rendering properties of the light source is corrected only by the color temperature information of the light source. Some light sources have high color rendering properties even at low color temperatures.On the other hand, some light sources have low color rendering properties even at high color temperatures. In the case of a light source having a low luminance, there is a problem that the saturation is lowered and compensation for effective color rendering cannot be made.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and can correct an appropriate color balance in accordance with a difference in the color rendering properties of a light source. It is an object of the present invention to obtain an imaging device capable of compensating for the above.

[0007]

An image pickup apparatus according to the present invention photoelectrically converts image pickup light from a subject and outputs an R (red) signal and a B signal.
(Blue) and an image sensor for generating a signal and G (green) signal, and the color rendering property detecting means for detecting the color rendering properties of a light source for irradiating the pre-Symbol subject, R output from the image sensor
(Red) signal and B (blue) signal.
Color rendering of the subject light detected by the color detection means
Multiplying a coefficient (G) signal according to the detection result of
Subtraction means for subtracting the signal obtained by
Provided at a stage subsequent to the means, and output from the image sensor.
G (green) signal and R output from the subtraction means
Based on the (red) signal and the B (blue) signal,
And a process means for generating a color difference signal .

[0008]

[0009]

FIG. 1 is a block diagram showing the configuration of an image pickup apparatus according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an image sensor that photoelectrically converts imaging light from a subject and outputs R, G, and B color signals, and is configured by a solid-state imaging device. Reference numeral 2 denotes a matrix circuit for performing a matrix operation on the color signal from the image sensor 1, and includes a subtractor 2a to which an R signal is input, a multiplier 2b to which a G signal is input, and a subtractor 2c to which a B signal is input. Have been. Reference numeral 3 denotes a preamplifier circuit for adjusting the white balance, which includes amplifiers 3a, 3b, and 3c for amplifying each color signal. The amplifiers 3a and 3c for the R signal and the B signal have variable gain adjustment for white balance control. . 4 performs blanking processing and the like,
From the G and B color signals, the luminance signal Y and the color difference signals RY, B-
A process circuit 5 for generating Y is an encoder for synthesizing the luminance signal Y output from the process circuit 4 and the color difference signals RY and BY, from which a composite video signal is output to the outside.

Reference numeral 6 denotes color temperature detecting means for detecting the color temperature of a light source for illuminating the subject, 7 denotes color rendering property detecting means for detecting the color rendering property of the light source, and 8 includes the matrix circuit 2 and preamplifier circuit 3. A system controller that controls the entire system controls the gain of each of the amplifiers 3a and 3c of the preamplifier circuit 3 based on the detection information of the color temperature detection unit 6, and controls the matrix circuit 2 based on the detection information of the color rendering property detection unit 7. Of the R and B color signals in the arithmetic processing by the subtractors 2a and 2c.

Next, the operation will be described. As before,
The color temperature information of the light source detected by the color temperature detecting means 6 is converted into R / G and B / G signals by the system controller 8.
The system controller 8 controls the gains of the amplifiers 3a and 3c of the preamplifier circuit 3 according to the signal, and adjusts the white balance. The color rendering information of the light source detected by the color rendering detecting means 7 is also input to the system controller 8, and the system controller 8 changes the addition ratio of the matrix circuit 2 according to the information.
At this time, when the system controller 8 determines that the color rendering property is low, the system controller 8 corrects the color balance by changing the addition ratio of the matrix circuit 2.

Here, in the matrix circuit 2, R '= R-αG, G' = G, B '= B-αG
Is performed. That is, the system controller 8
Controls the addition ratio of the color signals in each of the subtractors 2a and 2c by changing the value of a gain coefficient (gain control signal) α given to the multiplier 2b of the matrix circuit 2.
Correct the color balance. Then, the color signal whose color balance has been corrected is input to the preamplifier circuit 3, where the above-mentioned white balance is adjusted, and then enters the process circuit 4, where the luminance signal Y and the color difference signals RY and BY are output. And output as a video signal via the encoder 5.

FIG. 2 shows a detailed configuration of the color rendering property detecting means 7. In the figure, reference numeral 23 denotes an optical sensor including three sensors having R, G, and B color filters, respectively.
A light diffusing plate 21 and a color rendering filter 22 are arranged on the front side. The color rendering filter 22 is formed of a transmission type color filter having the spectral characteristics shown in FIG.
Are made different from each other.
FIG. 3 shows the relationship between the wavelength (nm) of light passing through the color rendering filter 22 and the transmittance.

The R, G,
B are connected to respective logarithmic (LOG) amplifiers 24a, 24a, 2b.
4b, 24c, and is led to subtractors 25a, 25b,
og (R / G) and log (B / G) signals. These signals are input to the subsequent subtractors 26a and 26b,
Here, the signals log (R / G) 'and log (B / G)' obtained by logarithmically amplifying the color temperature information of the above-mentioned color temperature detecting means 6 are subtracted, and the R correction signal and the B correction signal whose white balance has been adjusted are subtracted. Become. Then, this signal is input to the system controller 8 as the color rendering property information of the light source, and becomes the gain control signal of the matrix circuit 2 described above.

FIG. 4 is a diagram showing an example of a gain coefficient α to the matrix circuit 2 based on a combination of the values of the R correction signal and the B correction signal. The gain coefficient α is stored in a memory in the system controller 8. I have. In this example,
The gain α is 0.0 for both correction signals (20 to 100).
The figure shows a case where the value changes from 8 to 0.31. As shown in the figure, when both correction signals are low, it is determined that the color rendering properties are low, and the gain α is increased. As described above, appropriate color balance can be corrected in accordance with the difference in color rendering properties of the light source, and effective color rendering properties can be compensated with a simple circuit configuration.

Although the characteristics of the color rendering filter 22 shown in FIG. 2 are set as shown in FIG. 3 in the above embodiment, other characteristics may be used as long as they can show the difference in color rendering. Also,
Although the case where a pure color (three primary colors) color filter is used as the optical sensor 23 has been described, the present invention is also applicable to a case where a complementary color filter is used.

[0017]

As described above, according to the present invention, the color rendering property detecting means for detecting the color rendering property of the light source is provided, and the luminance signal and the color difference signal are generated based on the detection information. There is an effect that an appropriate color balance can be corrected according to a difference in color rendering properties, and effective color rendering properties can be compensated with a simple circuit configuration.

[Brief description of the drawings]

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

FIG. 2 is a detailed configuration diagram of a color rendering property detection unit in FIG. 1;

FIG. 3 is a characteristic diagram of the color rendering filter of FIG. 2;

FIG. 4 is an explanatory diagram showing an example of a gain coefficient for a matrix circuit.

FIG. 5 is a block diagram showing a configuration of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image sensor 2 Matrix circuit 3 Preamplifier circuit 4 Process circuit 5 Encoder 6 Color temperature detecting means 7 Color rendering property detecting means 8 System controller (control circuit)

Claims (1)

(57) [Claims] 1. An imaging light from a subject is photoelectrically converted to R
(Red) signal, B (blue) signal and G (green) signal
An image sensor for forming a color rendering detection means for detecting the color rendering properties of a light source for irradiating the pre-Symbol subject, R (red) signal output from the image sensor and
From each of the B (blue) signals, the color rendering
According to the result of the color rendering of the subject light detected
Multiplied by the G (green) signal
A subtraction means for subtracting a signal; and a subtraction means provided after the subtraction means, wherein the image sensor
(Green) signal output from the above and the output from the subtraction means
Based on the obtained R (red) signal and B (blue) signal.
Process means for generating a degree signal and a color difference signal.
Imaging device, characterized in that that.