JP4967432B2 - Imaging apparatus and camera system - Google Patents

Description

  The present invention relates to an imaging apparatus and a camera system including a solid-state imaging device such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor) sensor, and in particular, has a two-dimensional pixel array using a plurality of color filters. The present invention relates to an imaging apparatus and a camera system.

As a color filter arrangement of the image sensor, a Bayer arrangement using two green (G), one red (R), and one blue (B) of the three primary colors with good color reproducibility is known. It has been.
This Bayer array is an array in which luminance resolution is more important than color.

  By the way, in such a color filter array, an imaging apparatus having a pixel array in which a transparent filter is arranged so as to increase sensitivity while maintaining good color reproducibility has been proposed (for example, see Patent Document 1). ).

In addition, an image pickup apparatus has been proposed in which the signal charge amount and the color resolution are ensured even if the pixels are miniaturized by improving the transparent filter arrangement (see, for example, Patent Document 2).
JP-A-8-23542 JP 2004-304706 A

However, in the above-described imaging apparatus, there is a limit to improvement in resolution and color reproducibility.
Further, there is a disadvantage that the fineness of the image sensor pixel reduces the amount of light collected by the image sensor of the sensor and lowers the sensitivity.
In addition, in order to improve sensitivity, when a transparent filter is mounted on a solid-state image sensor mixed with primary / complementary colors, the level of the video signal output from the image sensor equipped with a filter with a different average transmittance varies, and the image There is a disadvantage of affecting the quality.

  It is an object of the present invention to provide an imaging apparatus and a camera system that can improve resolution, prevent variation in characteristics of imaging elements, and improve image quality.

An image pickup apparatus according to a first aspect of the present invention includes a pixel array unit in which a plurality of pixels having different spectral sensitivity characteristics are arranged in an array, and converts light transmitted through the pixels into an electrical signal, and reads from the pixel array unit. A signal processing unit that adjusts a signal level that is output, and the pixel array unit includes a first color filter pixel in which a peak of a spectral sensitivity characteristic including a color filter is in red, and a first in which a peak is in blue. Two color filter pixels, a third color filter pixel whose peak is green, is arranged in an array, and the first color filter pixel at any position in any row or column of the array pixel arrangement, A clear pixel having a high transmittance with respect to the second color filter pixel and the third color filter pixel is disposed, and the signal processing unit generates a luminance signal from a read signal of each color filter pixel, Chestnut Obtains the ratio of the signal level of a predetermined band removed low frequency component of the luminance signal generated and read signals of the pixels, based on the gain value ratio relative to the clear pixel signal or luminance signal as a gain value, or, The luminance signal and the low-frequency component of each color filter pixel are taken out to obtain a ratio between the signal levels in a predetermined band, and based on each gain value and clear pixel signal as a gain value, the luminance signal and each color filter pixel signal or The signal level of each color filter pixel signal other than the clear pixel signal or the luminance signal is adjusted.

The second aspect camera system of the present invention includes an imaging device, an optical system for guiding incident light to the imaging unit of the imaging device, a signal processing circuit for processing an output signal of the imaging device, the upper The imaging apparatus includes a plurality of pixels having different spectral sensitivity characteristics arranged in an array, a pixel array unit that converts light transmitted through the pixels into an electrical signal, and adjustment of a signal level read from the pixel array unit The pixel array unit includes a first color filter pixel in which a peak of spectral sensitivity characteristics including a color filter is red, a second color filter pixel in which a peak is blue, a peak Are arranged in an array, and the first color filter pixel and the second color filter pixel are located at any position in any row or column of the array pixel array. , And the third color frame High transmittance clear pixels are arranged with respect to filter pixel, the signal processing unit generates a luminance signal from the read signal of each color filter pixels, the low-frequency component of the luminance signal and the generated read signal of the clear pixels the calculated ratio of the signal level of a predetermined band removed, based on the gain value of the ratio based on the clear pixel signal or luminance signal as a gain value, or takes out the luminance signal and the low frequency component of each color filter pixels A ratio of signal levels in a predetermined band is obtained as a gain value based on each gain value and the clear pixel signal, and the brightness signal and each color filter pixel signal or the clear pixel signal, or the other than the brightness signal. The signal level of each color filter pixel signal is adjusted.

According to the present invention, Hakare the increased resolution, yet can prevent variations in characteristics of an imaging device, it is possible to image quality improvement.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram illustrating a configuration example of a main part of an imaging apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the imaging apparatus 10 includes a pixel array unit (ARY) 11, a clear pixel horizontal scan circuit (CHSCAN) 12, a color pixel horizontal scan circuit (CLRHSCAN) 13, and a vertical scan circuit (VSCAN) 14. -1, 14-2, timing control unit 15, power supply unit 16, clear pixel analog front end unit (CAFE) 17, color pixel analog front end unit (CLRAFE) 18, and signal processing unit (SPRC) 20. .

In the pixel array unit 11, for example, sensor unit pixels are arranged in an array with a predetermined arrangement form.
In the pixel array unit 11, a transfer selection line, a reset line, and a select line are wired to each row (row) of the pixel array, and a signal line is wired to each column (column) of the pixel array.

  FIG. 2 is a circuit diagram illustrating an example of a unit pixel according to the present embodiment. In FIG. 2, a CMOS sensor is shown as an example.

  The unit pixel 110 in FIG. 2 includes a photodiode 111, a transfer transistor 112, an amplification transistor 113, a select transistor 114, a reset transistor 115, and a floating node ND111.

The photodiode 111 photoelectrically converts incident light into signal charges (for example, electrons) having a charge amount corresponding to the amount of light, and stores the signal charges.
The transfer transistor 112 is connected between the cathode of the photodiode 111 and the floating node ND111, and the gate is connected to the transfer selection line TRFL. When the transfer transistor 112 is turned on, the signal stored in the photodiode 111 is transferred. It has a function of transferring charges to the floating node ND111.
The amplification transistor 113 and the select transistor 114 are connected in series between the power supply potential VDD and the signal line SGNL.
The amplifying transistor 113 has a gate connected to the floating node ND111, amplifies the potential of the floating node ND111, and outputs the amplified potential to the signal line SGNL via the select transistor 114.
The gate of the select transistor 114 is connected to the select line SELL.
The reset transistor 115 has a source connected to the floating node ND111, a drain connected to a predetermined potential line, a gate connected to the reset line RSTL, and a function of resetting the potential of the floating node ND111.

The transfer selection line TRFL, the select line SELL, and the reset line RSTL wired in each row of the pixel array are selectively driven by the vertical scan circuit 14 (-1, -2), and the signal line SGNL is a horizontal pixel scan circuit for clear pixels. 12. Selectively transfer the signal read from the pixel to the color pixel horizontal scan circuit 13.
The horizontal scanning circuits 12 and 13 and the vertical scanning circuit 14 are controlled in driving timing by the timing control unit 15.

  FIG. 3 is a diagram schematically illustrating an example of a pixel array of the pixel array unit 11 of the present embodiment.

As shown in FIG. 3, the pixel array unit 11 in FIG. 3 adopts an oblique pixel arrangement, and includes a color filter pixel R in which the peak of spectral sensitivity characteristics including the color filter is red, and a color filter in which the peak is green. A clear pixel C having a high transmittance is inserted evenly in the vertical and diagonal directions with respect to the pixel G and the color filter pixel B whose peak is blue, and is formed as a pixel array in which resolution bias is eliminated.
Note that the clear pixel C does not have to be white.
In the pixel array of FIG. 3, the even-numbered rows and even-numbered columns including the 0th row and the 0th column are formed by only the color filter pixels, and the odd-numbered rows and odd-numbered columns are formed by only the clear pixels C.

FIG. 4 is a diagram conceptually showing the spectral characteristics of the color filter pixels R, G, B and the clear pixel C.
In FIG. 4, the horizontal axis indicates the wavelength and the vertical axis indicates the relative output.
As can be seen from FIG. 4, the clear pixel C has sensitivity over substantially the entire visible light region (wavelength 360 nm to 700 nm).
That is, since the clear pixel C has a wide wavelength region component (all color signals are included), it is easy to reproduce the color at the boundary with the clear pixel.

  Hereinafter, the characteristic configuration of the pixel array unit 11 will be described in more detail with reference to FIGS.

  As shown in FIG. 5, the pixel array unit 11 according to the present embodiment is a so-called slant formed by rotating a so-called square unit pixel RGPXL by a predetermined angle θ (between θ = 0 and 90 degrees) about the column direction axis CAX. It arrange | positions as pixel OBLPXL.

The advantage of adopting such an array of oblique pixels OBLPXL will be described with reference to FIG. In FIG. 6, a Bayer array is taken as an example.
When 1 pixel pitch PTC square pixel RGPXL, pixel pitch in the diagonal pixel OBLPXL is, 1 / √2 next when the rotational angle θ is 45 degrees, the pixel pitch without changing the size of the pixel can be reduced.

In this embodiment, as shown in FIG. 7, a basic pixel is formed by inserting a clear pixel C in the middle of the four color filter pixels R, G, G, and B in the Bayer array of the diagonal pixel array. A pixel array unit is formed.
By leaving the Bayer array, it is possible to easily perform color interpolation processing in the signal processing system.

As a readout method for driving the pixel array unit 11 having the above configuration, the clear pixel C and the color filter pixels (color pixels) R, G, and B are read out by different channels.
In the present embodiment, for example, as shown in FIG. 8, the clear pixel dedicated read channel CH-A and the color filter pixel dedicated read channel CH-B are separated, and the clear pixel C and the color filter pixels R, G, B are separated. Reading is performed independently.
In the example of FIG. 8, the clear scan horizontal scan circuit 12 is arranged on the upper side in the figure as a channel CH-A readout processing system, and the color filter pixel (color pixel) horizontal scan circuit 13 is on the lower side in the figure. It is arranged as a readout system for channel CH-B.
In this embodiment, the signal line SGNL-O wired in the odd-numbered column is connected to the clear pixel horizontal scan circuit 12, and the signal line SGNL-E wired in the even-numbered column is connected to the color filter pixel (color Pixel) horizontal scan circuit 13.

  Further, in the present embodiment, in addition to adopting a method of reading the clear pixel C and the color filter pixels (color pixels) R, G, and B with different channels, the time and speed of the electronic shutter (rolling shutter) The gain in the subsequent processing is configured to be changed independently between the clear pixel C and the color filter pixels (color pixels) R, G, and B.

  FIG. 9 is a diagram schematically showing a driving method of the electronic shutter in the present embodiment.

In this embodiment, as shown in FIG. The rolling shutter time can be read by changing the accumulation time of clear pixels and color pixels.
Further, the shutter speed can be changed independently between the clear pixel C and the color filter pixels (color pixels) R, G, and B.
For example, the clear pixel shutter is quickly turned off in a bright place to prevent clear pixel saturation, and the clear pixel shutter is turned off late in a dark place to increase sensitivity.
With this configuration, it is possible to create a natural color by increasing the color information in a bright place and reducing the color information in a dark place.

The read signal of the clear pixel C read from the pixel array unit 11 having such a configuration is transferred to the clear pixel AFE 17 via the horizontal scan circuit 12.
The read signals of the color filter pixels (color pixels) R, G, B are transferred to the clear pixel AFE 18 via the horizontal scan circuit 13.
In the AFEs 17 and 18, analog processing such as amplification processing is performed on the read signal, converted into a digital signal, and transferred to the signal processing unit 20 in the subsequent stage.

  FIG. 10 is a block diagram illustrating a configuration example of the signal processing unit of the present embodiment.

  As shown in FIG. 10, the signal processing unit 20 includes a white balance adjustment unit 21, a color pixel unit interpolation processing unit 22, a luminance adjustment unit 23, and a clear pixel unit interpolation processing unit 24.

  The white balance adjustment unit 21 performs white balance adjustment based on the clear pixel signal C and the color filter pixel (color pixel) signals R, G, and B transferred from the AFEs 17 and 18.

FIG. 11 is a diagram for explaining white balance adjustment processing in a bright place in the present embodiment.
FIG. 12 is a diagram for explaining white balance adjustment processing in a dark place in the present embodiment.

The white balance adjustment unit 21 adjusts the signals of the clear pixel C and the other color filter pixels (color pixels) R and B on the basis of the signal of the color filter pixel (color pixel) G in a bright place.
On the other hand, the white balance adjustment unit 21 adjusts the signals of the color filter pixels (color pixels) R, G, and B on the basis of the signal of the clear pixel C in a dark place.

  The interpolation processing unit 22 performs interpolation processing only with the color filter pixel (color pixel) unit after white balance adjustment, and supplies the luminance signal Y to the luminance adjustment unit 23 by dividing into color information (RGB) and luminance information. , RGB signals are supplied to the interpolation processing unit 24.

  The luminance adjusting unit 23 adjusts the luminance signals of the color filter pixels (color pixels) R, G, and B and the luminance signal of the clear pixel C, and outputs a luminance signal Y.

  The interpolation processing unit 24 performs interpolation processing with white (clear) pixels based on the luminance signal Y, and outputs a color signal SC.

Hereinafter, specific configurations and functions of the luminance adjustment unit and the interpolation processing unit of the signal processing unit of the present embodiment will be described.
The luminance adjustment unit 23 and the interpolation processing unit 24 cooperate to perform luminance adjustment and interpolation processing, adjust the signal level, and generate the luminance signal Y and the color signal SC (color difference signals Cr, Cb).
Hereinafter, the luminance adjustment unit 23 and the interpolation processing unit 24 will be described as one signal level adjustment circuit.

The signal level adjustment circuit includes a circuit that absorbs the sensitivity difference between the image signals read from the pixel array unit 11 having the above-described configuration, and prevents the sensitivity difference or the variation in the characteristics of the image sensor, thereby improving the image quality. have.
The signal level adjustment circuit generates a luminance signal Y from the RGB signal, extracts a low-frequency component of the clear pixel C and the luminance signal Y in a low-pass filter (LPF) that is a filter that can absorb the phase difference of each color signal, It has a function of obtaining the ratio of the area signal levels and adjusting the gain with reference to the C or Y signal.
The signal level adjustment circuit adjusts the RGB signal levels other than the luminance signal Y when the signal of the clear pixel C is used as a reference.

  FIG. 13 is a circuit diagram showing a configuration example of a main part of the signal level adjustment circuit according to the present embodiment.

  The signal level adjustment circuit 30 of FIG. 13 includes LPFs 31 and 32, a divider 33, a gain adjustment unit 34, multipliers 35 to 39, and a luminance synthesis unit 40.

The LPF 31 extracts the low frequency component Ylpf of the luminance pixel Y and outputs it to the divider 33.
The LPF 32 extracts the low frequency component C (W) lpf of the clear pixel C signal and outputs it to the divider 33.

The divider 33 calculates the ratio of the low frequency components Clpf and Ylpf by the LPF 32 and the LPF 32, generates a gain value Ky for signal level adjustment, and outputs the gain value Ky to the gain adjustment unit 34.
There are two types of signal level adjustment: C (W) standard and Y standard.

When the signal level adjustment reference is the luminance signal Y, the gain adjustment unit 34 supplies the gain value Ky obtained by the divider 33 to the multiplier 35, and Y and RGB are supplied to the multipliers 36 to 39. Since there is no need to adjust the level, a constant “1” is supplied.
When the signal level adjustment reference is the signal of the clear pixel C, the gain adjustment unit 34 supplies a constant “1” to the multiplier 35, and uses the gain value Ky obtained by the divider 33 as the multiplier 36. ~ 39.

The multiplier 35 multiplies the signal of the clear pixel C by the gain value Ky or the constant “1” supplied from the gain adjustment unit 34, and outputs the result to the luminance synthesis unit 40 as C ′.
The multiplier 36 multiplies the luminance signal Y by the gain value Ky or constant “1” supplied from the gain adjusting unit 34 and outputs the result to the luminance combining unit 40 as Y ′.
The multiplier 37 multiplies the signal R by the gain value Ky or the constant “1” supplied from the gain adjustment unit 34, and outputs the result as R ′.
The multiplier 38 multiplies the signal G by the gain value Ky or constant “1” supplied from the gain adjustment unit 34, and outputs the result as G ′.
The multiplier 39 multiplies the signal B by the gain value Ky or the constant “1” supplied from the gain adjustment unit 34, and outputs the result as B ′.

  The luminance synthesis unit 40 performs a synthesis process based on the output signal C ′ of the multiplier 35 and the output signal Y ′ of the multiplier 36 to generate a final luminance signal Y ″.

  The operation when the signal level adjustment circuit 30 performs level adjustment will be described separately for the C (W) standard and the Y standard.

  When the signal level of the clear pixel C is adjusted based on the Y reference, the gain value Ky is calculated by the divider 33 in the following equation.

[Equation 1]
Ky = Ylpf / Wlpf

In this case, the gain value Ky is supplied to the multiplier 35. In the multiplier 35, the adjusted signal C ′ is obtained by the following equation and output to the luminance synthesis unit 40.

[Equation 2]
C '= C * Ky

  In this case, since it is not necessary to adjust the signals R, G, and B, the constant “1” is supplied to the multipliers 36 to 39. As a result, R ′ = R, G ′ = G, and B ′ = B are obtained, and a color signal is obtained.

  When adjusting Y, R, G, and B to the C reference, the gain value Ky is calculated by the following equation in the divider 33.

[Equation 3]
Ky = Wlpf / Ylpf

  Then, the gain value Ky is supplied to the multipliers 36 to 39. In the multipliers 35 to 39, the adjusted signals Y ′, R ′, G ′, and B ′ are calculated as follows. The signal Y ′ is output to the brightness synthesizer 40.

[Equation 4]
Y '= Y * Ky
R '= R * Ky
G '= G * Ky
B '= B * Ky

  Then, the final luminance signal Y ″ is generated from the signals C ′ and Y ′ in the luminance combining unit 40. Further, the color difference signal is generated from R ′, G ′, and B ′.

As described above, the signal level adjustment circuit 30 of FIG. 13 can select two types of reference, that is, the C reference and the Y reference for adjusting the signal level.
For example, as shown in FIG. 14, it is possible to obtain a more natural image by switching and selecting two types of reference according to the brightness according to the control signal CTL.
In the example of FIG. 14, for example, the output of the signal level adjustment circuit 30A adopting the Y reference is selected by the selector 41 in a bright place, and the output of the signal level adjustment circuit 30B adopting the C reference is selected by the selector 41 in a dark place. To do.

  FIG. 15 is a circuit diagram showing another configuration example of the main part of the signal level adjustment circuit according to the present embodiment.

The signal level adjustment circuit 50 of FIG. 15 includes LPFs 51 to 54, dividers 55 to 57, and multipliers 58 to 60.
In the signal level adjustment circuit 50 of FIG. 15, the luminance signal synthesis processing part is omitted.

The LPF 51 extracts the low frequency component Ylpf of the luminance signal Y and outputs it to the dividers 55 to 57.
The LPF 52 extracts the low frequency component Rlpf of the color filter pixel (color pixel) signal R and outputs it to the divider 55.
The LPF 53 extracts the low frequency component Glpf of the color filter pixel (color pixel) signal G and outputs it to the divider 56.
The LPF 54 extracts the low frequency component Blpf of the color filter pixel (color pixel) signal B and outputs it to the divider 57.

  The divider 55 calculates the ratio of the low frequency components Rlpf and Ylpf by the LPF 52 and the LPF 51, generates a gain value Kr for signal level adjustment based on the following equation, and outputs the gain value Kr to the multiplier 58.

[Equation 5]
Kr = Rlpf / Ylpf

  The divider 56 calculates the ratio of the low frequency components Glpf and Ylpf by the LPF 53 and the LPF 51, generates a gain value Kg for signal level adjustment based on the following equation, and outputs the gain value Kg to the multiplier 59.

[Equation 6]
Kg = Glpf / Ylpf

  The divider 57 calculates the ratio of the low frequency components Blpf and Ylpf by the LPF 54 and the LPF 51, generates a gain value Kb for signal level adjustment based on the following equation, and outputs the gain value Kb to the multiplier 60.

[Equation 7]
Kb = Blpf / Ylpf

The multiplier 58 multiplies the signal C by the gain value Kr supplied from the divider 55 and outputs the result as R ′.
The multiplier 59 multiplies the signal C by the gain value Kg supplied from the divider 56, and outputs the result as G ′.
The multiplier 60 multiplies the signal C by the gain value Kb supplied from the divider 57 and outputs the result as B ′.

Signal level adjustment circuit 50 of FIG. 15, in order to adjust the R / G / B signal, passed through a R / G / B in LPF52～54, to respectively eject the Rlpf / Glpf / Blpf as a low-frequency component.
When the R / G / B signal level adjustment gain values are Kr, Kg, and Kb, the dividers 55 to 57 calculate Kr = Rlpf / Ylpf, Kg = Glpf / Ylpf, and Kb = Blpf / Ylpf. .

  Next, in multipliers 58 to 60, R ′, G ′, and B ′ are obtained by the following equations.

[Equation 8]
R ′ = C * Kr
G '= C * Kg
B '= C * Kb

  FIG. 16 is a circuit diagram showing a modification of the signal level adjustment circuit of FIG.

The signal level adjustment circuit 50A in FIG. 16 is different from the signal level adjustment circuit 50 in FIG. 15 in that the low-frequency component Clpf is extracted by passing through the LPF 61 of the clear pixel signal C and supplied to the multipliers 58-60. It is to have done.
In this case, the multipliers 58 to 60 perform the following calculation.

[Equation 9]
R '= Wlpf * Kr
G '= Wlpf * Kg
B '= Wlpf * Kb

As described above, according to the present embodiment, the luminance signal Y is generated from the RGB signals, and the clear pixel C and the luminance signal Y of the luminance signal Y are obtained in the low-pass filter (LPF) that can absorb the phase difference of each color signal. The low-frequency component is extracted, the ratio of the low-frequency signal level is obtained, and the gain is adjusted based on the C or Y signal. When the clear pixel C signal is used as a reference, the RGB signal other than the luminance signal Y Since the signal level adjustment circuits 30, 50, and 50A having the function of adjusting the level are provided, it is possible to prevent the difference in sensitivity or the variation in the characteristics of the image sensor and improve the image quality.
That is, in the circuits of FIGS. 13 to 15, by adjusting the levels of the C and RGB signals by the above adjustment, the luminance signal is synthesized by C and Y, thereby obtaining a high luminance resolution.
Further, adjusting Y / R / G / B to the C standard has the effect of increasing sensitivity and improving S / N.
Further, as in the circuit of FIG. 16, when the R / G / B signal is passed through the LPF, the low frequency component is extracted and used together with Clpf to adjust R ′ / G ′ / B ′, the color difference noise is suppressed. Effect is obtained.

  In addition, according to the present embodiment, the pixel array unit 11 adopts an oblique pixel arrangement, and includes a color filter pixel R in which the peak of spectral sensitivity characteristics including the color filter is red, and a color filter pixel in which the peak is green. G, clear pixel C having a high transmittance with respect to the color filter pixel B whose peak is blue, is formed as a pixel array so as to eliminate the unevenness of resolution by evenly inserting the clear pixels C in the vertical direction, and the clear pixel dedicated read channel The CH-A and the color filter pixel dedicated readout channel CH-B are separated, and the clear pixel C and the color filter pixels R, G, and B are independently read out. The clear pixel C and the color filter pixel (color pixel) ) In addition to adopting a method of reading out R, G, and B on separate channels, electronic shutter (rolling shutter) time, speed, and gain in subsequent processing Since the clear pixel C and the color filter pixels (color pixels) R, G, and B are independently changed, the following effects can be obtained.

By rotating the pixel by 45 degrees, for example, the pixel pitch can be reduced to 1 / √2 and the resolution can be increased. In addition, the area can be doubled compared to the same pitch in a general pixel array, the sensitivity can be increased, and clear (transparent) pixels are included in the color coating of this diagonal pixel array. Further improvement in sensitivity becomes possible.
In addition, when the clear pixel is arranged in the middle of the Bayer array, color interpolation processing is facilitated.
In addition, the clear pixel C and color filter pixels (color pixels) R, B, and G can change the shutter time and gain independently, so the output of the clear pixel is conservative in bright places and the output is increased in dark places. And you can create a more natural picture similar to what you see with your eyes.
As described above, it is possible to improve the S / N ratio by improving the sensitivity, and it is possible to realize high-speed reading with low illuminance by improving the sensitivity.

In the above description, as shown in FIG. 3, the pixel array unit 11 employs an oblique pixel array, and the color filter pixel R in which the peak of the spectral sensitivity characteristic including the color filter is red, the peak is It is formed as a pixel array in which clear pixels C having a high transmittance are evenly inserted in the vertical and diagonal directions with respect to the color filter pixel G in green and the color filter pixel B in peak blue to eliminate the bias in resolution. Explained the example.
However, the present invention is not limited to the pixel array of FIG. 3, and various forms can be adopted as a pixel array into which clear pixels are inserted, and the same effects as those described above can be obtained.

As described above, the configuration example of the diagonal pixel array has been described. However, in the configuration in which the signal level adjustment circuit can be applied, and in the pixel array, the shutter can be released independently from the color pixel portion, and can be read out independently. Such a characteristic configuration can be applied not only to a diagonal pixel array but also to a square pixel array as shown in FIG. 17, for example, and the same effect as in the diagonal array can be obtained.
The example of FIG. 17 shows an example in which the diagonal pixel arrangement of FIG. 3 is a square arrangement.

  FIG. 18 is a block diagram showing an outline of the configuration of the camera system according to the embodiment of the present invention.

  The camera system 70 drives an imaging device 71, an optical system that guides incident light to the pixel region of the imaging device 71, for example, a lens 72 that forms incident light (image light) on an imaging surface, and the imaging device 71. And a signal processing circuit 74 that processes an output signal of the imaging device 71, and the like.

  In this camera system 70, the imaging apparatus according to the above embodiment is used as the imaging device 71.

The drive circuit 73 is a circuit corresponding to the timing control unit in FIG. 1 and drives the imaging device 71.
The signal processing circuit 74 performs various signal processing on the output signal Vout of the imaging device 71 and outputs it as a video signal.

  As described above, according to this camera system, since the high-speed operation can be secured by using the imaging apparatus according to the above-described embodiment as the imaging device 71, the image quality is small with a small circuit scale, low power consumption, and low noise. Can be obtained.

  The imaging device of the present invention may be an imaging device formed as a single chip or a module type imaging device formed as an aggregate of a plurality of chips. In the case of an imaging device formed as an assembly of a plurality of chips, the imaging device is divided into a sensor chip that performs imaging, a signal processing chip that performs digital signal processing, and the like, and may further include an optical system.

It is a block diagram which shows the structural example of the principal part of the imaging device which concerns on embodiment of this invention. It is a circuit diagram which shows an example of the unit pixel of this embodiment. It is a figure which shows typically an example of the pixel arrangement | sequence of the pixel array part of this embodiment. 3 is a diagram conceptually showing spectral characteristics of each color filter pixel R, G, B and clear pixel C. FIG. It is a figure for demonstrating a diagonal pixel arrangement | sequence. It is a figure for demonstrating the advantage by employ | adopting diagonal pixel arrangement | sequence. It is a figure which shows the basic diagonal pixel arrangement | sequence unit which inserted the clear pixel C in the middle of four color filter pixels R, G, G, B of a Bayer arrangement. It is a figure for demonstrating the read-out system at the time of the drive with respect to the pixel array part in this embodiment. It is a figure which shows typically the drive system of the electronic shutter in this embodiment. It is a block diagram which shows the structural example of the signal processing part of this embodiment. It is a figure for demonstrating the white balance adjustment process in the bright place in this embodiment. It is a figure for demonstrating the white balance adjustment process in the dark place in this embodiment. It is a circuit diagram which shows one structural example of the principal part of the signal level adjustment circuit which concerns on this embodiment. It is a figure which shows the suitable example of the signal level adjustment circuit which employ | adopted two kinds of references | standards. It is a circuit diagram which shows the other structural example of the principal part of the signal level adjustment circuit which concerns on this embodiment. FIG. 16 is a circuit diagram showing a modification of the signal level adjustment circuit of FIG. 15. It is a figure which shows the example which made the diagonal pixel arrangement | sequence of FIG. 3 square. It is a block diagram which shows the outline of a structure of the camera system which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Imaging device, 11 ... Pixel array part (ARY), 12 ... Horizontal scan circuit for clear pixels (CHSCAN), 13 ... Horizontal scan circuit for color pixels (CLRHSCAN), 14 ... Vertical scan circuit (VSCAN), 15... Timing control section, 16... Power supply section, 17... Analog front end section for clear pixels (CAFE), 18... Analog front end section for color pixels (CLRAFE) ), 20... Signal processing unit, 21... White balance adjustment unit, 22... Color pixel unit interpolation processing unit, 23 .. brightness adjustment unit, 24. , 30B, 50, 50A ... signal level adjustment circuit, 31, 32, 51-54, 61 ... LPF, 33, 55-57 ... divider, 34 ... gain Adjusting unit, 35-39, 58-60 ... multiplier, 40 ... luminance combining unit, 70 ... camera system, 71 ... imaging device, 72 ... lens, 73 ... driving circuit 74... Signal processing circuit.

Claims (8)

A plurality of pixels having different spectral sensitivity characteristics are arranged in an array, and a pixel array unit that converts light transmitted through the pixels into an electrical signal;
A signal processing unit that adjusts the signal level read from the pixel array unit,
The pixel array section is
A first color filter pixel having a spectral sensitivity characteristic peak including a color filter in red, a second color filter pixel having a peak in blue, and a third color filter pixel having a peak in green are arranged in an array, And,
A clear pixel having a high transmittance with respect to the first color filter pixel, the second color filter pixel, and the third color filter pixel is located at an arbitrary position of the row and column of the array pixel array. Arranged,
The signal processor is
Generate a luminance signal from the readout signal of each color filter pixel, extract the low-frequency component of the readout signal of the clear pixel and the generated luminance signal, obtain the ratio of the signal level of the predetermined band, and use the clear pixel signal or the luminance signal as a reference and the ratio based on the gain value as a gain value, or, the respective gain values and the gain value respectively determined the ratio of the signal level of a predetermined band removed the luminance signal and the low frequency component of each color filter pixels clear An image pickup apparatus that adjusts signal levels of the luminance signal and the color filter pixel signals or the clear pixel signal or the color filter pixel signals other than the luminance signal based on a pixel signal . The imaging apparatus according to claim 1, wherein when the luminance signal is used as a reference, the signal processing unit adjusts the level of the clear pixel signal with the gain value and holds the signal level of each color filter pixel as it is. The imaging apparatus according to claim 1, wherein the signal processing unit adjusts the level of the luminance signal and each color filter pixel signal with the gain value when the clear pixel signal is used as a reference. The imaging apparatus according to claim 1, wherein the signal processing unit is capable of selecting level adjustment based on a clear signal or level adjustment based on a luminance signal in accordance with a control signal. When the signal processing unit is based on the clear pixel signal, a ratio of the luminance signal and a signal level of a predetermined band of each color filter pixel is obtained as a gain value, and based on the gain value and the clear pixel signal, The imaging apparatus according to claim 1, wherein the level of each color filter pixel signal other than the luminance signal is adjusted. When the clear pixel signal is used as a reference, the signal processing unit obtains a ratio of the luminance signal and a signal level of a predetermined band of each color filter pixel to obtain a gain value, and the gain value and the low frequency component of the clear pixel signal The image pickup apparatus according to claim 1, wherein the level of each color filter pixel signal other than the luminance signal is adjusted based on the image signal. The imaging device according to any one of claims 1 to 6, wherein the pixel array unit includes the color filter pixels and the clear pixels arranged in an oblique pixel arrangement method. An imaging device;
An optical system for guiding incident light to the imaging unit of the imaging device;
A signal processing circuit for processing an output signal of the imaging device,
Above Symbol imaging device,
A plurality of pixels having different spectral sensitivity characteristics are arranged in an array, and a pixel array unit that converts light transmitted through the pixels into an electrical signal;
A signal processing unit that adjusts the signal level read from the pixel array unit,
The pixel array section is
A first color filter pixel having a spectral sensitivity characteristic peak including a color filter in red, a second color filter pixel having a peak in blue, and a third color filter pixel having a peak in green are arranged in an array, And,
A clear pixel having a high transmittance with respect to the first color filter pixel, the second color filter pixel, and the third color filter pixel is located at an arbitrary position of the row and column of the array pixel array. Arranged,
The signal processor is
Generate a luminance signal from the readout signal of each color filter pixel, extract the low-frequency component of the readout signal of the clear pixel and the generated luminance signal, obtain the ratio of the signal level of the predetermined band, and use the clear pixel signal or the luminance signal as a reference and the ratio based on the gain value as a gain value, or, the respective gain values and the gain value respectively determined the ratio of the signal level of a predetermined band removed the luminance signal and the low frequency component of each color filter pixels clear A camera system that adjusts signal levels of the luminance signal and the color filter pixel signals or the clear pixel signal or the color filter pixel signals other than the luminance signal based on a pixel signal .

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