JP2000341709A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pick up and output a highly accurate signal and to pickup and output sequentially scanned dynamic images suited to display on a liquid crystal display or the like by providing the image pickup device with a generation means for generating a high-definition video signal from an output signals of 1st to 3rd sold state image pickup elements and the output signals from 1st and 2nd signal processing parts or the like. SOLUTION: Beams of respective colors R, G and B decomposed by a prism 2 are photoelectrically converted by respective image pickup elements 3 to 5 and inputted to an analog processing part 6 as R, G and B signals. In the processing part 6, respective CDS circuits 301, 401, 501 improve the S/N ratios of the R, G and B signals by correlation double sampling processing, respective AGC circuits 302, 402, 502 adjust the levels of the R, G and B signals to prescribed levels and input the level adjusted signals to respective A/D converters 303, 403, 503, which convert the input signals into digital signals and input these digital signals to a digital signal processing part 7. Thus a highly accurate video signal is generated by a luminance signal processor part (Y processing part) 702, a color difference signal processing part 704 or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses three or four solid-state image pickup devices having a normal number of pixels corresponding to a conventional standard television system such as NTSC or PAL, or a computer video format such as VGA. Further, the present invention relates to an imaging device capable of outputting a high-definition image signal corresponding to four times the number of pixels of a solid-state imaging device.

[0002]

2. Description of the Related Art In recent years, 10 digital still cameras have been developed.
A digital still camera having an effective pixel number exceeding 10,000 pixels has been commercialized. Such high-definition image signals can be easily photographed, and their use is rapidly increasing. 3
In a plate-type image pickup device, red and blue solid-state image sensors arranged obliquely with respect to the spatial position of the solid-state image sensor for green are arranged, and based on signals obtained by interpolating output signals from these solid-state image sensors. By generating a low-frequency luminance signal and a high-frequency luminance signal, and synthesizing a luminance signal from the low-frequency luminance signal and the high-frequency luminance signal, an imaging device capable of doubling the resolution of the solid-state imaging device can be provided. Proposed.
(JP-A-6-217330, JP-A-6-3151)
No. 15) In such an imaging apparatus, a high-resolution video signal can be obtained by using a general-purpose solid-state imaging device.

[0003]

However, in particular,
In order to realize a high-definition progressive scan (sequential scanning) type imaging apparatus suitable for display on a high-definition display monitor for a personal computer (PC), the above-described 100 is used.
A solid-state image sensor having more than 10,000 pixels is for photographing a still image, and has a maximum output of 15 frames or less per second, and cannot output a moving image. Also, as a moving image photographing apparatus having an effective pixel number of 1,000,000 pixels or more, an HDTV (high definition) image pickup apparatus has been put into practical use. However, in the case of HDTV, an output signal is interlaced (interlaced scanning) and a vertical high frequency In the case of an image containing components, flicker due to line flicker can be seen, or a computer (P
C) has a problem that it is not suitable for display on a liquid crystal display monitor which has become widespread as a display monitor for C). Further, the imaging devices disclosed in JP-A-6-217330 and JP-A-6-315115 show that the passband characteristics of each pixel of the low-frequency luminance signal are significantly different and that Since a broadband luminance signal component is included, when a broadband luminance signal is generated from the lowband luminance signal and the highband luminance signal, the lowband luminance signal and the highband luminance signal are further divided as shown in FIG. A signal obtained by passing the low-pass signal through the LPF is subtracted from the high-pass luminance signal by subtracting a signal obtained by passing the high-pass luminance signal through the LPF from the high-pass luminance signal. Such complicated signal processing is required, which causes an increase in the cost of the circuit scale.

The present invention has been made in view of this point. By using three or four solid-state image pickup devices of general-purpose VGA compatible all-pixel readout type which are available at a low cost at present, the VGA is realized. It is an object of the present invention to provide an imaging apparatus capable of capturing a moving image suitable for display on a liquid crystal display for a personal computer (PC) of a high-definition progressive scan (sequential scanning) system corresponding to four times the number of pixels.

[0005]

In order to solve the above-mentioned problems, an image pickup apparatus according to the present invention separates incident light into color light of green (G), red (R), and blue (B). A first solid-state imaging device that receives the green (G) light of the all-pixel readout method, performs photoelectric conversion, and outputs a G signal;
A second solid-state imaging device that receives the red (R) light of the all-pixel readout method and photoelectrically converts the red (R) light to output an R signal;
A third solid-state imaging device for outputting a signal;
With respect to the spatial position of the solid-state imaging device, at least one or both of the second solid-state imaging device and the third solid-state imaging device are の of the pixel pitch of the solid-state imaging device in the horizontal and vertical directions. A low-frequency signal generated from a signal of each color output from each of the first solid-state imaging device, the second solid-state imaging device, and the third solid-state imaging device. And synthesizing an interpolated low-frequency signal generated by interpolating the signals of the respective colors to form an effective pixel of each of the first solid-state imaging device, the second solid-state imaging device, and the third solid-state imaging device. A first signal processing unit that generates a low-frequency signal of four times each color, and a first signal processing unit that generates a low-frequency signal of each color, and outputs the first solid-state imaging device, the second solid-state imaging device, and the third solid-state imaging device. The first solid-state image sensor, the second solid-state image sensor, and the third solid-state image sensor are combined by combining a high-frequency signal generated from a signal and an interpolated high-frequency signal generated by interpolating the high-frequency signal. A second signal processing unit for generating a high-frequency luminance signal four times higher than each effective pixel, and respective outputs of the first solid-state imaging device, the second solid-state imaging device, and the third solid-state imaging device It is characterized by comprising a generating means for generating a high definition video signal from a signal, an output signal of the first signal processing unit, and an output signal of the second signal processing unit.

[0006]

FIG. 1 is a diagram showing a first embodiment of an imaging apparatus according to the present invention. In FIG. 1, 1 is a lens, 2
Are prisms for separating the incident light into RGB colors, 3, 4,
5 is a solid-state image sensor for R, a solid-state image sensor for G, a solid-state image sensor for B, 6 is an analog signal processing circuit unit, 301, 401, 501 are correlated double sampling units (CDS), 302, 402. , 502 are the CDS 301,
AGC circuits for adjusting the levels of the output signals of 401 and 501, AD converters 303, 403 and 503, digital signal processing units 7, gamma (γ) 304, 404 and 504
Correction units 305, 405, and 505 are low-frequency signal generation units (RL generation unit, GL generation unit, and BL generation unit) for each color;
Denotes a high-frequency luminance signal generation unit (YH generation unit), 702 denotes a luminance signal processing unit (Y processing unit), and 306, 406, and 506 denote D.
A converter, 703 is a low frequency luminance signal generation unit (YL generation unit), 704 is a color difference signal processing unit, 8 is an output circuit unit, 30
7, 407 and 507 are low-pass filters (LPF), 3
08, 408 and 508 are 75Ω driver units, 509 is a luminance signal output terminal (Y), and 309 and 409 are component format color signal output terminals (PR, PB).

After passing through the lens 1, the incident light is separated into three colors of RGB by the prism 2 and enters the image pickup devices 3, 4 and 5. The solid-state imaging devices 3, 4, and 5, for example, read all pixels as they are by non-interlace scanning and can read all pixels independently. For example, VGA compatible (640 effective horizontal pixels, 480 vertical effective pixels) Things.

A VGA-compatible solid-state image pickup device is inexpensive but has a small number of pixels. Therefore, the three solid-state image pickup devices 3, 4, and 5 are arranged in a spatially oblique manner to improve the resolution. Specifically, as shown in FIGS. 2A and 2B, when the pixel pitch of the solid-state imaging device of each color is Px and the pixel pitch in the vertical direction is Py, each pixel of the solid-state imaging device 4 for G is used. R for
Each pixel of the solid-state imaging device 3 for B and each pixel of the solid-state imaging device 5 for B are １ ／ Px (FIG. 2A) in the horizontal direction,
It is displaced in the vertical direction by Ｐ Py (FIG. 2B).

For each pixel of the solid-state image sensor 4 for G, R
The pixels of the solid-state imaging device 3 for B and the pixels of the solid-state imaging device 5 for B are shifted from each other because the contribution ratio of the G signal when generating the luminance signal (for example, 0.59 in the NTSC system) R signal contribution ratio (eg, NTS
This is because the ratio of the contribution of the B signal (for example, 0.11 in the NTSC system) is substantially the same as the ratio of 0.30 in the C system, and the three solid-state imaging devices are shifted by pixels as described above. In addition, an interpolation process described later, that is, an interpolation process in which the number of pixels of the video signal of each color is enlarged twice in the horizontal direction and the vertical direction so that the number of pixels becomes four times as a whole , The resolution can be improved.

FIGS. 3 (a) and 3 (b) show the case where the number of pixels is four times the number of pixels of each of the above-mentioned solid-state image sensors, and pixels of each color of RGB actually exist. FIG. 3D shows a pixel obtained by synthesizing these in () and (c). As shown in FIG.
The actual pixel for B and the actual pixel for B exist separately at the same spatial position.

Hereinafter, interpolation using existing pixels will be described. The light beams of the respective colors RGB separated by the prism 2 are photoelectrically converted by the image pickup devices 3, 4, and 5, respectively.
The signals are input to the analog signal processing unit 6 as GB signals. In the analog signal processing unit 6, the S / N of the RGB signals is improved by the correlated double sampling processing in the CDSs 301, 401 and 501, respectively.
After being adjusted to a predetermined level in 2, 402 and 502 and subjected to white balance processing by a white balance processing unit (not shown), the AD converters 303, 403 and 5
03 and converted into digital signals respectively.
Each of the GB signals is input to the digital signal processing unit 7.

The above-described signal processing relating to white balance can be performed by a digital signal processing unit described later.

In the digital signal processing section 7, the gamma (γ) correction sections 304, 404, and 504 cause the solid-state imaging device 3,
After performing gamma correction for multiplying each color signal by a coefficient for improving non-linearity of gradation (color tone) due to photoelectric conversion characteristics of 4 and 5, 480 vertical effective pixels (the actual number of pixels is 494) (About pixels) are respectively input to the RL generation unit 305, the GL generation unit 405, and the BL generation unit 505, and according to the following equations (1) to (12), the R low-frequency signals RL, G , And the low-frequency signal BL of B are generated. GL (2,2) = (G (0,2) + 2G (2,2) + G (4,2) + G (2,0) + 2G (2,2) + G (2,4)) / 8 (1) GL (3,2) = (G (2,0) + 2G (2,2) + G (2,4) + G (4,0) + 2G (4,2) + G ( (4,4)) / 8 (2) GL (2,3) = (G (0,2) + 2G (2,2) + G (4,2) + G (0,4) + 2G (2, 4) + G (4,4)) / 8 (3) GL (3,3) = (G (2,2) + G (4,2) + G (2,4) + G (4,4) ) / 4 (4) RL (2,2) = (R (1,1) + R (3,1) + R (1,3) + R (3,3)) / 4 (5) RL (3 , 2) = (R (1,1) + 2R (3,1) + R (5,1) + R (1,3) + 2R (3,3) + R (5,3)) / 8 ( 6) RL (2,3) = (R (1,1) + 2R (1,3) + R (1,5) + R (3,1) + 2R (3,3) + R (3,5 )) / 8 (7) RL (3,3) = (R (1,3) + 2R (3,3) + R (5,3) + R (3,1) + 2R (3,3) + R (3,5)) / 8 (8) BL (2,2) = (B (1,1) + B (3,1) + B (1,3) + B (3,3)) / 4 (9) BL (3,2) = (B (1,1) + 2B (3,1) + B (5,1) + B (1,3) + 2B (3,3) + B (5, 3)) / 8 (10) BL (2,3) = (B (1,1) + 2B (1,3) + B (1,5) + B (3,1) + 2B (3,3) + B (3,5)) / 8 (11) BL (3,3) = (B (1,3) + 2B (3,3) + B (5,3) + B (3,1) + 2B (3,3) + B (3,5)) / 8 (12)

Equations (1), (8) and (12) show the generation of a low-frequency signal at a position where an image actually exists, and the remaining equations show the generation of a low-frequency signal at a position where no pixel exists. That is, generation by interpolation using existing surrounding pixels is shown. By generating a low-frequency signal according to Equations (1) to (12), a low-frequency signal having substantially the same frequency is generated at a position where a pixel actually exists and a position where a pixel does not actually exist.

Next, the color difference signal will be described. First,
RL generator 305, GL generator 405, BL generator 50
5 is a low-frequency luminance signal generator (YL).
The signal is input to a generating unit 703, and a low-luminance signal (YL) signal is generated according to Expression (13). Equation (13) is HD
This is a luminance / color difference signal equation shown in ITU-R recommendation 709 of the TV studio standard. YL = 0.7154GL + 0.0721BL + 0.2125RL (13)

The RGB signals that have been γ-corrected by the γ correction units 304, 404, and 504 are input to a high-frequency luminance signal generation unit (YH generation unit) 701, respectively, and the following equation (1) is used.
4) to (22), a high-frequency luminance signal YH is generated. YHH indicates a horizontal high-frequency luminance signal, YVH indicates a vertical high-frequency luminance signal, and the high-frequency luminance signal YH is expressed by the formula (1).
As shown in 4), it is obtained by adding YHH and YVH. Expressions (15) to (18) are high-frequency luminance signal generation expressions at positions where pixels actually exist.
Is a high-frequency luminance signal generation formula at a position where a pixel does not actually exist, and is generated by performing an interpolation process on the high-frequency luminance signal obtained by Expressions (15) to (18). YH (x, y) = (YHH (x, y) + YVH (x, y)) / 2 (14) YHH (2,2) = (2G (2,2) -G (0,2) -G (4,2)) / 4 (15) YVH (2,2) = (2G (2,2) -G (2,0) -G (2,4)) / 4 (16) YHH (3,3 ) = (2R (3,3) -R (1,3) -R (5,3) + 2B (3,3) -B (1,3) -B (5,3)) / 8 (17) YVH (3,3) = (2R (3,3) -R (3,1) -R (3,5) + 2B (3,3) -B (3,1) -B (3,5)) / 8 (18) YHH (3,2) = YHH (3,1) / 2 + YHH (3,3) / 2 (19) YVH (3,2) = YVH (2,2) / 2 + YVH ( 4,2) / 2 (20) YHH (2,3) = YHH (2,2) / 2 + YHH (2,4) / 2 (21) YVH (2,3) = YVH (1,3) / 2 + YVH (3,3) / 2 (22)

Next, a high-frequency luminance signal generator (YH generator)
The output signal of the low frequency luminance signal generation unit (YL generation unit) 703 and the output signal of the low frequency luminance signal generation unit (YL generation unit) 703 are a luminance signal processing unit (Y processing unit).
702, a luminance signal processing unit (Y processing unit) 702
In accordance with equation (23), the broadband (high definition) luminance signal YW
Generate An example of the Y processing unit 702 is shown in FIG. YW = YL + k1YH (23) The coefficient k1 in the equation (23) is usually a numerical value of 1 or more, and k1
The larger the value is, the more the high-frequency component is emphasized and a sharper image is obtained. However, if k1 is too large, high-frequency noise will also be emphasized, so that it is possible to make it variable according to the user's preference. In addition, since noise has a feature that becomes more noticeable as the signal level is smaller, k1 may be configured to be variable according to the signal level.

Next, the low frequency luminance signal YL output from the low frequency luminance signal generation unit (YL generation unit) 703 is RL
R low-frequency signal RL output from generation unit 305 and B low-frequency signal BL output from BL generation unit 505
Is also supplied to the color difference signal processing unit 704. The color difference signal processing unit 704 generates color difference signals BL-YL and RL-YL by calculating BL-YL and RL-YL.

The above-mentioned broadband (high definition) luminance signal (YW
Signal), color difference signal (BL-YL signal, RL-YL signal)
Are input to D / A converters 506, 406, and 306, respectively, and are converted into analog signals, respectively, and then supplied to the output circuit unit 8.

In the output circuit section 8, a low-pass filter (L
After removing high frequency noise outside the signal band by PF) 307, 407, 507, 75Ω drivers 308, 40
After the output impedances are matched and the levels are adjusted in steps 8 and 508, the signals are output from output terminals 309, 409 and 509 to a display device or a recording device (not shown).

Normally, BL-Y input to the output circuit 8
The L signal and the RL-YL signal are supplied to a PB signal and a PR signal in a level adjustment circuit (not shown) in accordance with equations (24) and (25).
Converted to a signal. PB = 0.5389 (BL-YL) (24) PR = 0.6349 (RL-YL) (25)

The conversion from the BL-YL signal and the RL-YL signal to the PB signal and the PR signal does not necessarily need to be performed by the output circuit section 8.
May perform the conversion process.

Normally, the output terminal 50 of the output circuit 8
9, 409, 309 output Y signal, PB signal,
A synchronization signal generated by a synchronization signal generation circuit (not shown) is added to the PR signal during the blanking period of the image signal and output. The synchronization signal added at this time corresponds to the sequential scanning.

As a result, the gamma correction units 304, 404, 50
The horizontal effective pixel number is 640 pixels, the vertical effective pixel number is 480 pixels. The horizontal effective pixel number is 1280 pixels, and the vertical effective pixel number is 480 pixels. A video signal of a signal of 960 pixels is output.

In the imaging apparatus shown in FIG. 1, an example has been described in which the wideband signals RW, GW, and BW of each color are output in the form of analog signals. It is also possible to convert the signal into a signal conforming to the above and output the converted signal.

FIG. 4 is a view showing another embodiment of the image pickup apparatus according to the present invention. The image pickup apparatus shown in FIG.
It is a block diagram in the case of outputting a B signal as an output signal. In FIG. 4, the configuration and operation up to the input to the digital signal processing unit 71 are the same as those in FIG. In FIG. 4, the same reference numerals are given to the same parts as in FIG. 1, and description thereof will be omitted.

In FIG. 4, the RGB signals input to the digital signal processing section 71 are converted into γ correction sections 304, 404, and 50.
The vertical effective pixel 480 gamma-corrected at 4 (usually 4
The signal of about 94 pixels) is input to the RL generator 305, the GL generator 405, the BL generator 505, and the high-frequency luminance signal generator (YH generator) 701, respectively. In this case, as in the case described with reference to FIG.
2) and a high-frequency luminance signal from the YH generator 701 and the GL generator 405 according to the equations (14) to (22).
The RL generation unit 305 and the BL generation unit 505 output an R low frequency signal RL, a G low frequency signal GL, and a B low frequency signal BL, respectively. As shown in FIG. 4, the high-frequency luminance signal and the low-frequency signal of each color are divided into an R wideband (high definition) signal generation unit (RW generation unit) 310 and a G wideband (high definition) signal generation unit (GW generation unit). ) 410, B are supplied to the wideband (high definition) signal generation unit (BW generation unit) 510, respectively, and the wideband (high definition) color signals GW, BW, RW of each color are generated according to the equations (26) to (28). You. GW = GL + k2YH (26) BW = BL + k2YH (27) RW = RL + k2YH (28) k2 in the above equation is determined in the same manner as k1 in equation (23).

The GW, RW, B thus generated
The W signal is subjected to digital-to-analog conversion in each of the D / A converters 306, 406, and 506, and then the output circuit unit 8
Are output to a not-shown display device or recording device (not shown) via the. In addition, synchronization signals (HD, VD) generated by a synchronization signal generation circuit (not shown) are output at the same time.

In the imaging apparatus shown in FIG. 4, an example has been described in which the wideband signals RW, GW, and BW of each color are output in the form of analog signals. It is also possible to convert the signal into a signal conforming to the above and output the converted signal.

In order to realize moving image output, a movie must be played at 2
Since there are four frames, the number of frames corresponding to 24 frames or more per second is usually required. On the other hand, as described above, the all-pixel readout solid-state image pickup device for moving image pickup which is currently available at a low cost has a horizontal effective pixel number of 640 and a vertical effective pixel number of 4
80 VGA-compatible solid-state imaging devices. The VGA-compatible solid-state imaging device is usually designed to have a margin, and has 659 horizontal pixels and 494 vertical pixels. Therefore, when the imaging apparatus according to the present invention is configured using a normal VGA-compatible solid-state imaging device, the maximum number of effective horizontal pixels is 1318 and the maximum number of effective vertical pixels is 988. When this number of pixels is compared with the video specification of a personal computer (PC), the closest pixel number is 1280 horizontal effective pixels.
There is an SXGA with 1024 vertical effective pixels.

Since there are several types of SXGA variations, an appropriate one is selected from these and an image signal is output based on the synchronization signal, so that an SXGA-compatible liquid crystal display monitor can be provided. It is possible to obtain the optimum moving image quality. If the number of pixels of the display signal is not enough for the number of effective vertical pixels of the SXGA, the date and time are displayed at the top or bottom of the screen. It is also possible to output and display various information such as comments.

[0032]

As described above in detail, the imaging apparatus according to the present invention uses three general-purpose all-pixel readout solid-state imaging elements which are available at a low cost at present and can be used for general-purpose solid-state imaging. It is possible to image and output a high-definition signal corresponding to four times the number of pixels of the element, and has the advantage of being able to image and output a progressive scanning moving image suitable for display on a liquid crystal display or the like.

[0033]

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an imaging apparatus according to the present invention.

FIG. 2 is a diagram illustrating an example of a pixel shift arrangement of a solid-state imaging device used in the imaging device illustrated in FIG. 1;

FIG. 3 is a diagram illustrating an example of a pixel arrangement of a solid-state imaging device used in the imaging device illustrated in FIG. 1;

FIG. 4 is a diagram showing another embodiment of the imaging apparatus of the present invention.

FIG. 5 is a diagram illustrating a luminance signal processing unit (Y) of the imaging apparatus according to the present invention.
FIG. 3 is a diagram illustrating an example of a (processing unit).

FIG. 6 is a diagram illustrating a luminance signal processing unit of a conventional imaging device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lens, 2 ... Prism, 3, 4, 5 ... Solid-state image sensor 6 ... Analog signal processing unit, 7, 71 ... Digital signal processing unit, 8 ... Output circuit unit 301, 401, 501 ... CDS (correlated double sampling) ), 302, 402, 502 AGC circuit, 303, 403, 503 AD converter, 304, 404, 504 γ correction unit, 305, 405, 505 Low frequency signal generation unit (RL generation unit, GL generation 306, 406, 506... DA converter, 307, 407, 507, 311, 411... Low-pass filter (LPF), 308, 408, 508... 75 ohm driver unit, 309, 409. Output terminal 509: luminance signal output terminal, 310, 410, 510: wide band (high definition) signal generation unit (RW generation unit, GW generation unit, BW generation unit) , 701 ... RF luminance signal generation unit (YH generator), 702 ... luminance signal processing unit (Y unit), 703 ... low-frequency luminance signal generation unit (YL generator), 704 ... color difference signal processing unit,

Claims (3)

[Claims] 1. An incident light is color-separated into green (G), red (R),
A color separation optical system that obtains each color light of blue (B), a first solid-state imaging device that receives the green (G) light of the all-pixel readout method, performs photoelectric conversion and outputs a G signal, and an all-pixel readout method A second solid-state imaging device that receives the red (R) light and photoelectrically converts the red (R) light to output an R signal; and receives and photoelectrically converts the blue (B) image of the all-pixel readout method and outputs a B signal. A third solid-state imaging device, and at least one or both of the second solid-state imaging device and the third solid-state imaging device with respect to a spatial position of the first solid-state imaging device with respect to a horizontal direction and a vertical direction. ,
Each of them is arranged at a position shifted by a distance of 倍 times the pixel pitch of the solid-state imaging device, and output from the first solid-state imaging device, the second solid-state imaging device, and the third solid-state imaging device, respectively. The low-frequency signal generated from the signals of the respective colors and the interpolated low-frequency signal generated by interpolating the signals of the respective colors are combined to form the first signal.
A first signal processing unit that generates a low-frequency signal of each color four times the effective pixel of each of the solid-state imaging device, the second solid-state imaging device, and the third solid-state imaging device; A high-frequency signal generated from a signal of each color output from each of the solid-state imaging device, the second solid-state imaging device, and the third solid-state imaging device is combined with an interpolated high-frequency signal generated by interpolating the high-frequency signal. And the first
Signal processing unit that generates a high-frequency luminance signal four times as large as an effective pixel of each of the solid-state imaging device, the second solid-state imaging device, and the third solid-state imaging device, and the first solid-state imaging device , The second solid-state imaging device, and the third
An image pickup apparatus comprising: a generating unit configured to generate a high-definition video signal from each output signal of the solid-state imaging device, the output signal of the first signal processing unit, and the output signal of the second signal processing unit. . 2. The method according to claim 1, wherein said generating means adds a low-frequency signal of each color output from said first signal generating unit at a predetermined ratio to generate a low-frequency luminance signal, and outputs said low-frequency luminance signal from said second signal generating unit. The imaging device according to claim 1, wherein the output high-frequency luminance signal and the low-frequency luminance signal are added to generate a broadband luminance signal. 3. The wide-band color signal is generated by adding the high-frequency luminance signal output from the second signal generation unit to the low-frequency signal of each color output from the first signal generation unit. The imaging device according to claim 1, wherein: