JP2624646B2 - Color video camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color video camera, and more particularly, to a color video camera that generates a color signal by adding and subtracting a plurality of signals output from an image sensor having a color separation optical filter. Regarding suppression of moiré in video cameras.

[Conventional technology]

In recent years, home-use VTRs have become widespread,
Color video camera that can be used with
The need for an integrated color video camera integrated with the R is increasing. Such a color video camera is required to satisfy not only basic performance such as high sensitivity and high image quality but also to be small and inexpensive. For this reason, an image pickup unit or a solid-state image sensor is used in the image pickup unit in comparison with a three-tube camera having three image pickup tubes corresponding to red, green, and blue signal components conventionally used in a broadcast camera or the like. A single tube type or a single plate type using only one is predominant.

In such a single tube type or single plate type color video camera, color separation optical filters that transmit different color lights are regularly arranged on a light receiving surface of an image pickup tube or a solid state image pickup device (hereinafter collectively referred to as an image pickup device). Then, each signal corresponding to these color separation optical filters is calculated, and a luminance signal and a color signal are generated according to the television system. In this case, the color separation optical filter is configured to transmit yellow, cyan, and transparent light having a large light transmission amount instead of primary color light having a small light transmission amount (that is, primary color light of each of red, green, and blue). The so-called complementary color system is advantageous for increasing the sensitivity.

FIG. 3 is a schematic diagram showing an example of an arrangement of color separation optical filters (color filter arrangement) in a solid-state imaging device having such a color separation optical filter on a light receiving surface, where W is a transparent light (that is, all light). Light) a light receiving element, Cy is a cyan light receiving element, G is a green light receiving element, and Ye is a yellow light receiving element.

However, in a color video camera having an image pickup device provided with such a color separation optical filter, when an image of a subject having a fine picture is taken, a false signal called moiré is generated, and the image quality is remarkably deteriorated. Moiré is a beat disturbance caused by sampling a video signal by a pixel array corresponding to each color separation optical filter.

Techniques for suppressing such moiré are described in “Review of Moiré in High-Resolution Degree MOS Single-Chip Color Camera”, Proceedings of the Institute of Television Engineers of Japan (July 1984), pp. 89-90. There is known a method of suppressing moiré (luminance moiré) generated in a luminance signal by a luminance matrix.

Further, in the color filter arrangement shown in FIG. 3, color moire occurs in the color signal, and the input spatial frequency at which the color moire occurs is shown in FIG. In the figure, the coordinates of the color moiré 10 indicated by a circle indicate the input spatial frequency generated, and s and l are the sampling frequencies in the horizontal and vertical directions, respectively. A technique for suppressing such color moiré is disclosed in, for example, JP-A-58-198978. In this method, the response of an input spatial frequency band in which moire occurs is reduced using an optical low-pass filter using two quartz crystals and a λ / 4 plate or the like.

[Problems to be solved by the invention]

In the above-described moiré suppressing means using the luminance matrix,
Although luminance moiré can be suppressed, color moiré cannot be suppressed. Color moire is a particularly serious obstacle in a system using a color separation filter of a complementary color system used for improving sensitivity. Therefore, when the two crystal filters are used to suppress the color moiré, the response to a required signal is also reduced at the same time, and the resolution is reduced, and it is difficult to secure high image quality as a basic performance. . Further, since the crystal filter is expensive, there is a problem that it is not suitable for the purpose of providing a camera at low cost for home use.

An object of the present invention is to solve such a problem and to provide a color video camera capable of sufficiently suppressing occurrence of color moiré and obtaining good image quality.

[Means for solving the problem]

In order to achieve the above object, the present invention has an image pickup section provided with four types of color separation optical filters having different spectral sensitivities, and calculates four signals corresponding to each of the color separation optical filters at a predetermined operation ratio. To generate two color signals,
A means for setting the operation ratio is provided to set a predetermined condition.

[Action]

In the present invention, color moiré is reduced by correcting the sensitivity difference of each color separation optical filter when generating a color signal by the means for setting the operation ratio. For example, two color signals C1 and C2 are calculated from the outputs S1 to S4 from the four types of separation filters in a relationship of C1 = αS1−βS2 + γS3−δS4 C2 = α′S1 + β′S2−γ′S3−δ′S4. Along with each of the operation ratios α, α ', β,
β ′, γ, γ′δ, δ ′ are set so as to almost satisfy the relationship α × S1 + β × S2 = γ × S3 + δ × S4 or α ′ × S1 + γ ′ × S2 = β ′ × S3 + δ ′ × S4 Accordingly, color moiré can be reduced.

〔Example〕

 Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a block diagram showing an embodiment of a solid-state color camera according to the present invention, wherein 1 is an image pickup device, 2 ₁ , 2 ₂ , 2 ₃ , 2 ₄
Denotes an amplification circuit, 3 denotes a color signal generation circuit, 4 denotes a luminance signal generation circuit, 5 denotes a process circuit, and 6 denotes a color encoder.

In FIG. 3, the image sensor 1 includes the above-described color separation optical filter, has a light receiving surface on which each light receiving element is arranged as shown in FIG. 3, and has a W signal (colorless) and a Cy signal. (Cyan), Ye signal (yellow) and G signal (green). These signals are amplified by respective amplifier circuits 2 _1, 2 _2, 2 _3, 2 _4, are supplied to the color signal generation circuit 3 and a luminance signal generation circuit 4.

The color signal generation circuit 3 calculates the W signal, the Cy signal, the Ye signal, and the G signal at a calculation ratio described later, and obtains two color signals, that is, a red signal (hereinafter, referred to as an R signal) and a blue signal (hereinafter, referred to as a B signal).
A signal).

On the other hand, the luminance signal generating circuit 4 sets the addition ratio of the W signal, the Cy signal, the Ye signal, and the G signal, for example, so that the respective signal amounts are substantially equal to each other, and thereby generates a broadband luminance signal Y with little moire. Generates ₁ . Also, W signal, Cy signal,
Ye signal, and summed with a addition ratio so as to obtain a good color reproduction G signal, and generates a luminance signal Y ₂ narrowband for generating color difference signals. The generated Y ₁ signal, Y ₂ signal, R signal,
And B signals, the gamma correction in the process circuit 5, a clamp, and Y ₁ signal known signal processing is performed is process processing such as white balance, (Y ₂ -R) signals and (Y ₂ -B)
Two color difference signals of the signal are generated. These signals are supplied to a color encoder 6 to form, for example, an NTSC color video signal, which is supplied to an output terminal 7 as a camera output signal.

Figure 2 is a block diagram showing the configuration of a color signal generation circuit 3 of FIG. 1, 7 _{1-7 7} amplifier circuit, 8 _{1-8 4} adder circuit, 9 ₁ and 9 ₂ a subtraction circuit is there.

W signal from the amplifier 2 ₁ (FIG. 1) in the figure is amplified by the amplifier circuit 7 ₁ and 7 _5, also amplifying circuit 2 ₂ (first
Cy signal from the drawing) is amplified by the amplifier circuit 7 ₂ and 7 _6, also Ye signal from the amplifier circuit 2 ₃ (FIG. 1) is amplified by 7 ₃ and 7 _7, further amplifying circuit 2 ₄ (first G signal from the drawing) is amplified by the amplifier circuit 7 ₄ and 7 _8. Further Ye signal from W signal amplifying circuit 7 ₃ from the amplifier circuit ₇₁ are summed in summing circuit 8 _1, G signals from Cy signal amplifying circuit 7 ₄ from the amplifier 7 ₂ in the adder circuit ₈₂ are added, by further subtracting the output from the adder circuit _81, 82 in the subtraction circuit 9 _1, it generates the R signal.

Similarly amplifier circuit 7 _5, 7 W from ₆ adds the Cy signal by the addition circuit 8 _3, also Ye from the amplifier 7 ₇ 7 _8, adds the G signal circuit 8
Was added in _4, by subtracting the output from the adding circuit _{83, 84} in the subtracting circuit 9 _2, it generates the B signal.

The arithmetic expressions for the R signal and the B signal are as follows.
Equations (1) and (2) are obtained.

R = W−αCy + βYe−γG (1) B = W + α′Cy−β′Ye−γ′G (2) where W, Cy, Ye, and G are light receiving elements corresponding to the respective color separation filters. , And is proportional to the sensitivity ratio of each light receiving element. Α, β, γ indicate the operation ratio when calculating the R signal, and α ′, β ′, γ ′ indicate the operation ratio when calculating the B signal. However, the operation ratio of the W signal is 1.

By the way, the intensity Mr of the R moire generated in the R signal when expressed by the equations (1) and (2) is expressed as follows.

Mr (0, fl / 2) = W + αCy−βYe−γG (3) Mr (s / 2,0) = W−αCy−βYe + γG (4) Mr (s / 2, l / 2) = W + αCy + βYe + γG (( 5) In Equations (3), (4), and (5), the values in parentheses indicate the center coordinates of the spatial frequency at which moiré occurs.
The figure shows the positions on the two-dimensional spatial frequency where these moirés occur.

Among these R moire, moire shown in the equations (3) and (4) are moire caused by the sensitivity difference of the light receiving element corresponding to each color separation optical filter, and by setting the operation ratio to cancel the sensitivity difference. These moire can be suppressed almost completely. This condition can be obtained as follows by setting the right side of Expressions (3) and (4) = 0.

β = W / Ye (6) γ = α × Cy / G (7) Although β and γ can be determined as in equations (6) and (7), α is an arbitrary real number. α may be set so as to obtain good color reproducibility, but is generally α1. Therefore, β and γ may be set as β = W / YeCy / Gγ.

Therefore amplifier 7 _{1-7 4} arithmetic ratio as described above alpha, beta, gamma
The amplification degree is set so that is obtained.

Similarly to the R moire, the intensity Mb of the B moire is expressed as follows.

Mb (0, fl / 2) = W−α′Cy + β′Ye−γ′G (8) Mb (s / 2,0) = W + α′Cy + β′Ye + γ′G (9) Mb (s / 2, l / 2) = W-α'Cy-β'Ye + γ'G (10) Among these B moire, the moire shown in the equations (8) and (10) is the sensitivity difference of the light receiving element corresponding to each color separation optical filter. And moire can be almost completely suppressed in the same manner as R moire. The condition for suppressing the B moiré is set to 0 on the right side of equations (8) and (10).
Α ′ = W / Cy (11) γ ′ = β ′ × Ye / G (12) Since β′1 here, α ′ = W / CyYe / Gγ ′
It can be seen that the operation ratio should be set as follows. In addition,
In the expressions (3), (4), and (5), fs represents the repetition frequency of the pixel in the horizontal direction. Assuming that the width between one pixel is H and the height is V, if spatial sampling is performed by a pixel array such that the relationship of H = 1 / fs and V = 1 / fl is satisfied, a shift in spatial frequency occurs. What happens (aliasing) reads this as moiré. Equations (3)-(5) indicate that the shift amount on the spatial frequency of the R signal is (0, fl / 2), (fs
/ 2,0) and (fs / 2, fl / 2).
Equations (3)-(5) and (8)-(10) are obtained by Fourier transforming the spatial description of W, G, Cy, Ye in the filter array of FIG. , R signal can be obtained by substituting into equation (1), and B signal can be obtained by substituting into equation (2). Since the pixel positions of W, G, Cy, and Ye are different from each other, a phase term occurs in the frequency component of each signal. If the phase of W is used as a reference, the moire (the component of the shift amount (0, fs / 2)) generated with (0, fl / 2) as the center frequency is C
y and Ye become minus (the phase shift is 180 degrees). Similarly, for (fs / 2,0), G, Ye, for (fs / 2, fl / 2)
G and Cy are negative, and the above equation is derived from these relationships.

Therefore amplifier 7 _{5-7 9} operational ratio as mentioned above alpha ',
The amplification degree is set so as to obtain β ′ and γ ′.

By setting the operation ratio of the R and B signals as described above, it is possible to almost completely suppress color moiré caused by the difference in sensitivity of the light receiving elements corresponding to the color separation optical filters, and obtain good image quality. . This suppression effect is shown in FIG.

FIG. 5 shows the location of the occurrence of moire on the two-dimensional input spatial frequency axis as in FIG. According to the effect of the present invention, R moiré and B moiré of (0, l / 2) can be completely suppressed, and residual color moiré occurs in principle (s / 2, l /
2) R moire 11 and B moire 12 occurring in (s / 2,0)
It can only be.

FIG. 6 is a block diagram showing another embodiment of the present invention. The embodiment shown in FIG. 1 is different from that shown in FIG. This is exactly the same configuration. FIG. 7 shows the spatial frequency characteristics of this optical low-pass filter. Such characteristics can be realized by a single crystal whose thickness is determined such that the spectral distance due to the birefringence of the crystal corresponds to the distance of one picture element pitch in the horizontal direction of the image sensor light receiving unit. With this quartz filter, the remaining R moire 11 and B moire 12 shown in FIG. 5 can be completely suppressed.

As shown in the present embodiment, according to the present invention, moire caused by the difference in sensitivity of the light receiving element corresponding to the color separation optical filter of the image pickup element can be sufficiently suppressed, so that as shown in FIG. l / 2), no color moiré is generated, and expensive two-sheet alignment or λ
A complete moiré suppression effect can be obtained only by using one crystal together without deteriorating the resolution by using a crystal using a / 4 plate.

By the way, W light receiving element, Cy light receiving element, Ye
Since the sensitivity ratio between the light receiving element and the G light receiving element changes according to the color temperature, the moire intensity also changes according to the color temperature.

FIG. 8 is a graph showing the R moiré intensity with respect to the color temperature. The abscissa represents the reciprocal of the color temperature, and the ordinate represents (0, l /
The moire intensity generated at the frequency 2) is taken. FIG. 9 is a graph showing the B moire with respect to the color temperature similarly to FIG. 8, and shows the B moire generated at the frequency of (0, l / 2).

In FIGS. 8 and 9, when the R signal and the B signal are generated at a 1: 1 operation ratio of the output signal from the image sensor as in the prior art, the moire intensity is very large as shown by the curve a. Amplifier 7 of FIG. 2 _{1-7 4} and 7 _{5-7 8} by the color temperature 5000 ° K
When the operation ratio is set so as to suppress the _R moiré and the B moiré, the moire becomes as shown by a curve b. Similarly, when the operation ratio is set at a color temperature of 3000 ° K, it becomes as shown by a curve c.

Thus by the amplifier 7 _{1-7 4,} 7 _{5-7 8,} equation (6) at a color temperature in the manner described above, (7) and (11), (1
Even if the amplification degree is set under the conditions shown in 2), W, Cy, Ye, G
Since the sensitivity ratio of the light receiving element changes depending on the color temperature, moire can be almost completely suppressed only in the vicinity of a specific color temperature at which the operation ratio is set. However, in curves b and c, the color temperature range 30 in the general use of video cameras
From 00 ° K to 7000 ° K, it can be seen that there is an extremely large moiré suppression effect compared to the conventional case shown by the curve a.

FIG. 8 shows that R moire increases at high color temperatures,
FIG. 9 shows that B moiré has the property of increasing at low color temperatures. Therefore, the operation ratio of the R signal condition at a high color temperature (e.g., 5000 ° K) (6), sets the amplification circuit 7 _{1-7 4} amplification degree to satisfy (7), B signal operation ratio conditional expression at low color temperature (e.g., 3000 ° K) (11), the amplifier circuit 7 ₅ so as to satisfy the (12)
It is very effective to set a _7-8 amplification of.

FIG. 10 is a block diagram showing another embodiment of the color video camera according to the present invention, wherein 15 is a color temperature detection sensor, 16 is a control signal generation circuit, 18 ₁ and 18 ₂ are control signals, Parts corresponding to FIG. 1 or FIG.

This embodiment amplifying circuits 2 ₁ to the color signal generation circuit 17
W signal from the 2 _4, Cy signal, Ye signal, by changing the operation ratio was calculated in accordance with the G signal is the color temperature, and generates a R signal and B signal. The color temperature detection sensor 15 detects the color temperature, and outputs a control signal 18 ₁ for controlling the operation ratio of the R signal and a control signal 18 ₂ for controlling the operation ratio of the B signal in accordance with the detected color temperature. Occurs. These control signals 18 ₁ and 18 ₂ are supplied to the color signal generation circuit 17, and the above-mentioned operation ratio is changed according to the color temperature.

FIG. 11 is a block diagram showing a specific structure of the color signal generation circuit 17 of FIG. 10, 19 ₁ to 19 ₈ amplification factor variable amplifier circuit, 20 ₁ to 20 ₄ are the adding circuit, 21 ₁ 21 ₂ is the subtraction circuit.

The In FIG. 11, W signal, Cy signal, Ye signal, respectively G signal amplification degree variable amplifying circuit 19 ₁ and 19 _5, 19 ₂ and 19 _6, 19 ₃
Is supplied to the 19 _7, 19 ₄ and 19 _8. Variable amplification type amplifier 1
9 _{1-19 4} degree of amplification is controlled by the control signal 18 _1, also the amplification degree variable amplifier circuit 19 _{5-19 8} amplification degree is controlled by a control signal 18 _2. Amplified W signal amplification degree variable amplifying circuit 19 ₁ ~ 19 _4, Cy signal, Ye signal and G signal is predetermined calculation by the adder circuit 20 _1, 20 ₂ and the subtraction circuit 21 ₁ made, R signal is generated Is done. Amplified W signal amplification degree variable amplifying circuit 19 _{5-19 8} In the same manner, Cy signal, Ye signal,
G signal predetermined operation is performed by the adder circuit 20 _3, 20 ₄ and a subtraction circuit 21 _2, B signals are generated.

Amplification factor variable amplifier circuit 19 ₁ to 19 ₄ of the amplification factor varies depending on the color temperature detected by the color temperature sensor 15, W in a range of a predetermined color temperature (e.g. 3000 ° K~5000 ° K) The arithmetic ratio of the signal, the Cy signal, the Ye signal, and the G signal is controlled so as to satisfy the R moiré suppression conditional expressions (6) and (7). The same applies to the B signal as well.
19 _{5-19 8} amplification of varying in accordance with the color temperature.

FIG. 12 is a graph showing the relationship between the amplification factor and the color temperature of the variable amplification factor amplification circuit in FIG. However, the amplification of the variable amplifier circuit 19 ₁ and 19 ₂ of the amplification degree for amplifying the W signal is 1, and shall all amplification factor of the amplifier 21 _{to 24} (FIG. 10) equal. In this case, the amplification degree of the amplification degree variable amplifier circuit is equal to the operation ratio of the R signal and the B signal.

In FIG. 12, a is an amplification degree variable amplification circuit 19 ₃ , 19
₄ (Figure 11)
This is the degree of amplification of the e signal and the G signal. And b is an amplification factor of the variable amplifier circuit 19 _7, 19 ₈ (FIG. 11), the amplification degree of the Cy signal and G signal when generating the B signal.

This embodiment corresponds to the curve b in FIGS.
Alternatively, c is continuously shifted in accordance with the color temperature, and the minimum point of the curve (ie, the minimum point of moiré) is obtained. Even if the color temperature changes, moiré does not increase, and always A good moiré suppression effect can be ensured.

In this embodiment, it is not always necessary to automatically detect the color temperature. For example, the relationship shown in FIG. You may do it.

FIG. 13 is a block diagram showing another embodiment of the video camera according to the present invention, in which 22 is an aperture control device, 3 'is a color signal generation circuit, and portions corresponding to those in FIG. And the explanation is omitted.

In this embodiment, the operation ratio of the above-described color signal is switched between low illumination and high illumination by a control signal indicating the degree of aperture of the lens (that is, the level of illumination) supplied from the aperture control device 22. Conditional expressions (6), (7), (10), and (11) are set to minimize moiré at the time of illuminance, and the operation ratio of each signal of W, Cy, Ye, and G is set to 1: 1 at the time of low illuminance. Should be approximately equal.

Hereinafter, the effect of switching the operation ratio at the time of high illuminance and low illuminance will be described. Each signal of W, Cy, Ye, and G includes random noise such as thermal noise generated by the amplifier circuit up to the color signal generation circuit and thermal noise generated by the image sensor. Is W, Cy, Ye,
G equals. On the other hand, the signal amounts of the W, Cy, Ye, and G signals obtained from the imaging device are the largest for W and the smallest for G according to the sensitivity difference when a white subject is imaged. Therefore, the S / N of the signal is best in W and poor in G in proportion to the sensitivity. In the condition that minimizes moiré, the calculation is performed to correct the sensitivity difference, so the ratio of G signal with poor S / N increases compared to the case where W, Cy, Ye, and G are calculated 1: 1 each. And
Therefore, the S / N ratio of the R and B signals also deteriorates. In this way, with moire
The S / N is in a conflicting relationship: if one is better, the other is worse.

However, the occurrence of moire is a problem in most cases at high illuminance where the contrast of the subject is high and the focus is well adjusted, and almost no moiré occurs at low illuminance. On the other hand, S / N becomes a problem in low illumination. From this, it is possible to suppress the moire and to reduce the S / N by switching to the arithmetic ratio for suppressing the moiré at the time of high illuminance and the arithmetic ratio (for example, 1: 1) for improving the S / N at the time of low illuminance as in the present embodiment. Degradation can also be prevented.

In each of the embodiments described above, the color filter array of the image pickup device is shown in FIG. 3, but as shown in FIG. As shown in FIG.
The present invention can be applied to the case where the repetition period is a pixel unit.

〔The invention's effect〕

As described above, according to the present invention, strong color moiré which cannot be avoided in a color video camera including a complementary color separation optical filter in an imaging unit according to the present invention, without deteriorating resolution or color reproducibility, It is possible to sufficiently suppress the color temperature regardless of the color temperature, and it is also possible to omit an expensive optical filter. Thus, it is possible to provide a color video camera with excellent image quality by eliminating the above-mentioned disadvantages of the prior art.

[Brief description of the drawings]

FIG. 1 is a block diagram of a video camera according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a specific configuration of a color signal generation circuit, and FIG. FIGS. 4 and 5 are schematic diagrams showing moire occurrence frequencies, FIG. 6 is a block diagram showing another embodiment,
FIG. 7 is a characteristic diagram of a quartz filter, FIGS. 8 and 9 are graph diagrams showing color temperature dependency of color moiré, FIGS. 10 and 11 are block diagrams showing still another embodiment of the present invention, and FIGS. FIG. 13 is a graph showing the degree of amplification, FIG. 13 is a block diagram showing still another embodiment of the present invention, and FIG. 14 is a schematic diagram showing another example of a color filter array. 1 ...... the imaging element, ₂₁ to ₂₄ ...... amplifier 3,3 ', 17 ...... color signal generating circuit 4 ...... luminance signal generating circuit, 5 ...... process circuit 6 ...... encoder 7 _{1-7 8} ...... amplifying circuit 8 _{1-8 4,} 20 ₁ to 20 ₄ ...... adder circuit 9 _1, 9 _2, 21 _1, 21 ₂ ...... subtraction circuit 10-12 ...... moire, 22 ...... aperture control device

Claims (3)

(57) [Claims] 1. A first color separation optical filter having different spectral sensitivities and transmitting at least red and blue color light, and being adjacent to the first color separation optical filter in a horizontal direction and transmitting at least green color light. A third color separation optical filter that is vertically adjacent to the first or second color separation optical filter and transmits at least red and green color light; and the third color separation optical filter A fourth color separation optical filter that is adjacent to the color separation optical filter in the horizontal direction and transmits at least green and blue color light; A first signal S1 corresponding to the color separation optical filter; a second signal S2 corresponding to the second color separation optical filter; a third signal S3 corresponding to the third color separation optical filter; Of the fourth signal S4 corresponding to the color separation optical filter, calculating ratio alpha, alpha ', beta,
The following operation is performed using β ′, γ, γ ′, δ, δ ′, C1 = α × S1−β × S2 + γ × S3−δ × S4 C2 = α ′ × S1 + β ′ × S2−γ ′ × S3−δ ′ × S4, a color signal generating circuit for generating a first color signal C1 representing at least a red component and substantially free of a blue component and a second color signal C2 representing at least a blue component and substantially free of a red component; Calculation ratios α, α ', β, β', γ, γ ', δ,
δ 'is defined as α × S1 ′ + β × S2 ′ = γ × S3 ′ + δ × S4 ′ or α ′ × S1 ′ + γ ′ × S3 ′ = β ′ × S2 ′ + δ × S4 ′ (where S1 ′ , S2 ', S3', and S4 'are respectively calculated so as to substantially satisfy the sensitivity ratios of the light receiving elements corresponding to the first to fourth color separation optical filters when white light is photographed. , Α ', β, β', γ, γ ', δ,
A color video camera comprising means for setting δ '. 2. A color video camera according to claim 1, wherein said first color separation optical filter is a white filter transmitting all of red, green and blue, and said color signal C1 is red. The primary color signal and the color signal C2 are blue primary color signals. For each primary color signal, the above-mentioned arithmetic ratio is set at a predetermined color temperature, and the color temperature for setting the arithmetic ratio of the red signal is set to the arithmetic ratio of the blue signal. A color video camera, wherein the color temperature is set higher than the color temperature set. 3. A color video camera according to claim 1, wherein said means comprises a variable gain amplifier whose gain changes in accordance with a color temperature.