JP4103741B2 - Imaging device - Google Patents

Description

  The present invention provides a photoelectric conversion between a linear conversion operation that outputs an electric signal linearly changing with respect to an incident light amount and a logarithmic conversion operation that outputs an electric signal that naturally changes logarithmically with respect to the incident light amount. The present invention relates to an imaging device capable of switching a conversion operation.

  Conventionally, in a solid-state imaging device that performs a linear conversion operation that linearly converts the amount of incident light, its dynamic range is as narrow as two orders of magnitude, so when imaging a subject that constitutes a luminance distribution in a wide luminance range, other than the dynamic range The luminance information in the range is not output. Further, as a conventional solid-state imaging device, there is one that performs a logarithmic conversion operation for logarithmically converting the amount of incident light (see Patent Document 1). In this solid-state imaging device, the dynamic range is as wide as 5 to 6 digits. Therefore, even if an image of a subject constituting a luminance distribution in a slightly wide luminance range is captured, all luminance information in the luminance distribution is converted into an electrical signal. Can be output. However, since the imageable area becomes wider with respect to the luminance distribution of the subject, an area without luminance data is formed in the low luminance area or the high luminance area in the imageable area. On the other hand, the present applicant has proposed what can switch between the above-described linear conversion operation and logarithmic conversion operation (Patent Document 2).

In addition, when a color image is picked up by providing a color filter in an image pickup apparatus including these solid-state image pickup devices, the spectral distribution of the light source at the time of image pickup and the transmittance of the color filter differ, so that the photoelectric conversion of each color signal The characteristics will be different. Therefore, in an imaging apparatus that captures such a color image, white balance processing is performed to match the photoelectric conversion characteristics of the color signals. Therefore, the present applicant has proposed an imaging apparatus that performs white balance processing in a white balance processing circuit based on a color temperature detected by a color temperature detection circuit in an imaging apparatus including a solid-state imaging device that performs a logarithmic conversion operation. (Patent Document 3). In addition, the present applicant has proposed an imaging apparatus that performs white balance processing by switching an offset voltage when performing AD conversion in an AD converter in an imaging apparatus including a solid-state imaging element that performs a logarithmic conversion operation ( Patent Document 4).

JP-A-11-313257 JP 2002-77733 A JP 2002-10275 A JP 2002-290980 A

  However, the imaging devices in Patent Literature 3 and Patent Literature 4 are effective for white balance correction of an image signal output from a solid-state imaging device that performs a photoelectric conversion operation using only logarithmic conversion characteristics. A white balance cannot be achieved for a solid-state imaging device that performs a photoelectric conversion operation based on characteristics. Therefore, when using a solid-state imaging device capable of automatically switching between logarithmic conversion characteristics and linear conversion characteristics as in Patent Document 2, in white balance processing only for multiplication / division or addition / subtraction like conventional white balance processing, Cannot get enough white balance. In addition, when such a solid-state imaging device is used, when white balance processing is performed in a luminance range in which photoelectric conversion characteristics different depending on each color signal overlap, the calculation processing becomes complicated.

  In view of such a problem, the present invention is simple for any signal output by any of the characteristics when the solid-state imaging device in which the linear conversion characteristic and the logarithmic conversion characteristic are automatically switched in the photoelectric conversion characteristic is provided. An object of the present invention is to provide an image pickup apparatus capable of performing white balance processing with simple calculation processing.

  In order to achieve the above object, an imaging apparatus according to the present invention outputs a first state in which an electric signal that linearly changes with respect to an incident light quantity and an electric signal that changes in a natural logarithm with respect to the incident light quantity. A solid-state imaging device including a pixel that can be switched between the second state and a plurality of types of color filters, and a white balance for the color signals for each type of the color filter output from the solid-state imaging device In an imaging apparatus including a white balance circuit that performs processing, when one of the plurality of types of color signals is used as a reference first color signal and a color signal other than the reference color signal is used as a second color signal, In the solid-state imaging device, the pixel that outputs the first color signal and the pixel that outputs the second color signal have the same luminance value at the switching point between the first state and the second state, and Balance times In this case, for each type of the second color signal, a signal level with respect to a luminance value serving as a switching point between the first state and the second state of the second color signal is set as a threshold level, and based on the threshold level. The photoelectric conversion characteristic of the second color signal is identified as a linear conversion characteristic according to the first state or a logarithmic conversion characteristic according to the second state, and the second color signal is determined according to the identified photoelectric conversion characteristic. A white balance process is applied to the above.

  In such an imaging device, the color signal is converted into the linear conversion characteristic in the first state in the luminance region lower than the luminance value serving as a switching point between the first state and the second state, and the first In the luminance region higher than the luminance value serving as a switching point between the first state and the second state, the logarithmic conversion characteristic obtained by converting the color signal in the second state is used. At this time, if the signal level is smaller than the threshold level, the photoelectric conversion characteristic of the second color signal is identified as the linear conversion characteristic. If the signal level is higher than the threshold level, the photoelectric conversion characteristic of the second color signal is identified as the logarithmic conversion characteristic.

  The “luminance” in the present specification and claims may be a single value correlated with the intensity of the radiant energy of the light source, and does not mean photometric luminance. For example, solid-state imaging This includes the case where the intensity of the light source is expressed by the output value of the G channel from the element (signal level of the G signal) or the like.

In addition, the white balance circuit compares the signal level of the second color signal with the threshold level for the second color signal to confirm the photoelectric conversion characteristics of the second color signal, and the linear said second color signal conversion characteristics, the a first operation unit that converts, based on a linear conversion characteristic of the first signal, said second color signal of the logarithmic conversion characteristics, the logarithmic conversion characteristic of the first signal a second arithmetic unit that converts, based on, when the photoelectric conversion characteristic of the second color signal by the comparator, it was confirmed the a linear conversion characteristic, selects a signal from the first processor And a selection unit that selects and outputs a signal from the second arithmetic unit when the comparator confirms that the photoelectric conversion characteristic of the second color signal is the logarithmic conversion characteristic. Prepare.

  Further, the first arithmetic expression used for white balance processing in the white balance circuit for each of the second color signals, the parameter to the second arithmetic expression, and the photoelectric conversion characteristics of the second color signal are identified. A control unit is provided for setting a threshold level and sending the parameter and the threshold level to the white balance circuit.

  At this time, the white balance circuit provides a color signal detection unit for confirming the type of the color signal, the parameter given to the first and second arithmetic units for each type of the second color signal, and the comparator. A parameter setting unit that switches the threshold level to be applied, and the second color detected by the color signal detection unit with the parameter and the threshold level given for each type of the second color signal from the control unit. The white balance processing may be performed for each type of the second color signal by switching the parameter setting unit for each signal type and supplying the signal to the first and second arithmetic units and the comparator.

  The white balance circuit includes the comparison unit, the first and second calculation units, and the selection unit for each type of the second color signal, and the control unit sets the second color signal for each type of the second color signal. The given parameter and the threshold level may be given to the first and second arithmetic units and the comparator provided for each type of the second color signal.

  In these imaging apparatuses, the first calculation unit is a multiplier that multiplies the first calculation value set by the parameter, and the second calculation unit is a second calculation value set by the parameter. Is an adder.

  In addition, an evaluation value representing a relationship between the photoelectric conversion characteristics of the first color signal and the photoelectric conversion characteristics of the second color signal is input from the solid-state imaging device for each type of the second color signal. An evaluation value detection circuit that detects the relationship between the color signal and the signal level of the second color signal is provided, and the parameter, the threshold level, and the luminance value serving as a switching point between the first state and the second state are It may be set based on the evaluation value and the photoelectric conversion characteristic of the first color signal. At this time, the evaluation value detection circuit may be operated by being instructed from the outside, and the parameter, the threshold level, and the luminance value serving as a switching point between the first state and the second state may be obtained. Alternatively, the evaluation value detection circuit may be operated for each predetermined frame, and the parameter, the threshold level, and the luminance value serving as a switching point between the first state and the second state may be obtained.

  In the evaluation value detection circuit, for each type of the second color signal, the evaluation is performed based on the relationship between the average values of the first color signal and the second color signal given from the solid-state imaging device. It does not matter if the value is required.

  In the evaluation value detection circuit, for each type of the second color signal, each of the first color signal and the second color signal linearly changed with respect to the incident light amount given from the solid-state imaging device. Based on the relationship with the average value, the first evaluation value is obtained, and the average of each of the first color signal and the second color signal logarithmically changed with respect to the incident light amount given from the solid-state imaging device. A second evaluation value is obtained based on the relationship with the value, and the first evaluation value and the second evaluation value are weighted and added, whereby the photoelectric conversion characteristic of the first color signal and the second color signal An evaluation value representing the relationship between photoelectric conversion characteristics may be obtained. At this time, based on the relationship between the number of pixels that output a signal that linearly changes with respect to the incident light amount and the number of pixels that output a signal that changes logarithmically with respect to the incident light amount, the weighting coefficient in the weighted addition Set.

  Further, the photoelectric conversion characteristic of the first color signal is determined based on the dynamic range of the solid-state imaging device, and the photoelectric conversion characteristic of the second color signal is determined from the photoelectric conversion characteristic of the first color signal and the evaluation. Determine based on the value.

  In addition, when the evaluation value is obtained by the evaluation value detection circuit, the linear conversion characteristic and the logarithmic conversion characteristic are obtained at the same signal level in the photoelectric conversion characteristic in each type of color signal output from the solid-state imaging device. The solid-state imaging device is driven so as to switch between them.

  The solid-state image sensor may be a single-plate solid-state image sensor provided with a plurality of types of color filters for each pixel, and is formed by a plurality of plates of solid-state image sensors for each of a plurality of different color filters. It does not matter if it is.

  Further, in the above-described imaging apparatus, the parameter, the threshold level, and the luminance value serving as a switching point between the first state and the second state are preliminarily set according to a shooting environment such as sunlight, tungsten light, or a fluorescent lamp. It is possible to store the parameter, the threshold level, and the luminance value to be a switching point between the first state and the second state by specifying the shooting environment from the outside.

  According to the present invention, by setting the switching point between the linear conversion characteristic and the logarithmic conversion characteristic in the photoelectric conversion characteristic of each color signal to the same luminance value, the luminance range having the linear conversion characteristic and the luminance range having the logarithmic conversion characteristic are obtained. The same luminance range can be set for different types of color signals. Therefore, the luminance range having the linear conversion characteristic and the luminance range having the logarithmic conversion characteristic do not overlap between different types of color signals. Therefore, the second color signal having the linear conversion characteristic is converted based on the linear conversion characteristic of the first color signal, and the second color signal having the logarithmic conversion characteristic is converted based on the logarithmic conversion characteristic of the first color signal. By performing the calculation, white balance processing can be performed by simple calculation processing.

  Further, by providing the evaluation value detection circuit, it is possible to detect the evaluation value for each color signal that can confirm the relationship between the color signals. Therefore, the calculation parameter can be easily obtained from the photoelectric conversion characteristics of the evaluation value and the reference color signal. In addition, after obtaining an evaluation value for each of the color signal linearly changing with respect to the incident light amount and the color signal changing logarithmically with respect to the incident light amount, these evaluation values are weighted and added to each color. By setting the evaluation value of the signal, a more accurate evaluation value can be obtained. Furthermore, since the weight coefficient in the weighted addition is set based on the relationship between the number of pixels that output a linearly changed signal and the number of pixels that output a logarithmically changed signal with respect to the incident light quantity, The parameter can be set according to the luminance distribution of the imaged subject. Therefore, it is possible to perform white balance processing according to the luminance distribution of the imaged subject.

<Configuration of imaging device>
A configuration of an imaging apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating an internal configuration of the imaging apparatus.

  1 is output from an optical system 1 composed of a plurality of lenses, a solid-state image sensor 2 that converts an incident light amount of light incident through the optical system 1 into an electrical signal, and the solid-state image sensor 2. An amplifier 3 for amplifying the electric signal, an AD conversion circuit 4 for converting the electric signal amplified by the amplifier 3 into a digital signal, a black reference correction circuit 5 for setting a minimum level of the digital signal from the AD conversion circuit 4, An FPN correction circuit 6 that removes FPN (Fixed Pattern Noise) due to the sensitivity of each pixel of the solid-state imaging device 2 from the digital signal corrected by the black reference value in the black reference correction circuit 5, and the FPN correction circuit 6 An AE / WB evaluation value detection circuit 7 for detecting respective evaluation values for performing automatic exposure control (AE) and white balance (WB) from the digital signal from which FPN has been removed at Based on the WB control circuit 8 that performs correction for each color signal so that the color balance of the digital signal from which FPN is removed by the FPN correction circuit 6 is obtained, and the color signals of a plurality of adjacent pixels output from the WB control circuit 8. The color interpolation circuit 9 that interpolates each color signal, the color correction circuit 10 that corrects the hue of each color signal output from the color interpolation circuit 9 for each pixel by another color signal, and the color correction circuit 10 output the color signal. A gradation conversion circuit 11 that performs gradation conversion of a digital signal, a coring circuit 12 that performs processing such as edge enhancement on the digital signal output from the gradation conversion circuit 11, and an overall control unit 13 that controls each block An aperture control unit 14 for controlling the exposure amount by the aperture 1 a provided in the optical system 1, and a clock for supplying a clock for operation timing to the solid-state imaging device 2 and the AD conversion circuit 4. It includes a timing generating circuit 15, a.

  In the imaging apparatus configured as described above, when light is incident on the solid-state imaging device 2 having a different color filter for each pixel through the optical system 1, a photoelectric conversion operation is performed in each pixel. An analog signal that is a different color signal for each pixel is output. That is, as shown in FIG. 2, when a color filter having a Bayer array with RGB is provided in the solid-state imaging device 2, an R signal representing red is a color that becomes G from a pixel provided with an R color filter. A G signal representing green is outputted from the pixel provided with the filter, and a B signal representing blue is outputted from the pixel provided with the color filter B. As will be described later, in the solid-state imaging device 2, the luminance position at which the linear conversion operation and the logarithmic conversion operation are switched is changed by changing the driving condition by the overall control unit 13. As a result, the dynamic range of the solid-state imaging device 2 changes. The dynamic range becomes wider as the switching point becomes the higher luminance side.

  The R signal, the G signal, and the B signal that are serially output from the solid-state imaging device 2 are amplified by the amplifier 3 and then converted into a digital signal by the AD conversion circuit 4. When the R signal, the G signal, and the B signal thus converted into digital signals are given to the black reference correction circuit 5, the black level that becomes the minimum luminance value is based on the dynamic range data given from the overall control unit 13. It is corrected to the reference value (0). That is, since the black level varies depending on the dynamic range of the solid-state imaging device 2, the signal level that becomes the black level is subtracted from the signal levels of the R signal, the G signal, and the B signal output from the AD conversion circuit 4. Thus, the reference value correction is performed.

  The FPN component is removed from the R signal, the G signal, and the B signal subjected to the black reference correction by subtracting the FPN component stored in the FPN correction circuit 6. This FPN component is an offset variation caused by a threshold variation of MOS transistors constituting each pixel in the solid-state imaging device 2. When extracting the FPN component, for each of the RGB signals, an offset based on the difference in transmittance of the color filter is subtracted from the image signal for each pixel output from the solid-state imaging device 2 during uniform light irradiation. At this time, the offset based on the transmittance of each color filter is determined by the average value of each RGB signal at the time of uniform light irradiation, and each average value is subtracted from the RGB signal at the time of uniform light irradiation. The FPN component of the pixel may be extracted. The R signal, G signal, and B signal from which the FPN component has been removed in this way are supplied to the AE / WB evaluation value detection circuit 7 and the WB control circuit 8.

  The AE / WB evaluation value detection circuit 7 calculates the average value distribution range of the luminance representing the luminance range of the subject by confirming the luminance value of the image signal composed of the given R signal, G signal, and B signal, It is sent to the overall control unit 13 as an AE evaluation value for setting the exposure amount. Based on this AE evaluation value, the overall control unit 13 controls the aperture of the diaphragm 1a, whereby the exposure amount is controlled. The AE / WB evaluation value detection circuit 7 confirms the respective luminance ratios and luminance differences from the given R, G, and B signals, and calculates a WB evaluation value that is a reference value for white balance. And sent to the overall control unit 13. The WB control circuit 8 performs white balance processing based on the WB evaluation value and dynamic range data given from the overall control unit 13 so that the R signal, the G signal, and the B signal have the same photoelectric conversion characteristics. Is done. Details of the AE / WB evaluation value detection circuit 7 and the WB control circuit 8 will be described later.

  The R, G, and B signals that have been subjected to white balance processing by the WB control circuit 8 are subjected to color interpolation processing by the color interpolation circuit 9. When a color filter having a Bayer-type arrangement using RGB as shown in FIG. 2 is provided in the solid-state imaging device 2, the color signal output from each pixel is only the color signal from the color filter provided with the pixel. Therefore, the color interpolation circuit 9 performs color interpolation processing by generating other color signals from the color signals of adjacent pixels.

  When the RGB color filters are arranged in the pixels G11 to G44 as shown in FIG. 2, the R signals r11, r31, r13, and r33 are converted from the pixels G11, G31, G13, and G33 to the pixels G21, G41, and G33, respectively. G12, G32, G23, G43, G14, G34 to G signals g21, g41, g12, g32, g23, g43, g14, g34, and pixels G22, G42, G24, G44 to B signals b22, b42, b24, b44 Is output. At this time, RGB signals of the pixels G22, G23, G32, and G33 are expressed by the following equations.

R signal r22, G signal g22, B signal b22 of pixel G22
r22 = (r11 + r31 + r13 + r33) / 4
g22 = (g21 + g12 + g32 + g23) / 4
b22 = b22
R signal r32, G signal g32, B signal b32 of the pixel G32
r32 = (r31 + r33) / 2
g32 = g32
b32 = (b22 + b42) / 2
R signal r23, G signal g23, B signal b23 of pixel G23
r23 = (r13 + r33) / 2
g23 = g23
b23 = (b22 + b24) / 2
R signal r33, G signal g33, B signal b33 of pixel G33
r33 = r33
g33 = (g32 + g23 + g43 + g34) / 4
b33 = (b22 + b42 + b24 + b44) / 4

  By performing pixel interpolation processing in this way, when RGB signals are obtained for each pixel, the RGB signals of each pixel are given to the color correction circuit 10 and color correction processing for emphasizing the color of each pixel is performed. Is done. At this time, each of the RGB signals is subjected to color correction by the values of other color signals. That is, by substituting the RGB signals rkl, gkl, bkl of the pixel Gkl into the following expression, the RGB signals rxkl, gxkl, bxkl of the pixel Gkl subjected to the hue correction are generated. At this time, the matrix coefficients of a1 to a3, b1 to b3, and c1 to c3 are switched based on the dynamic range control signal input from the overall control unit 13, and the hue of the RGB signals of each pixel is emphasized.

rxkl = a1 * rkl + a2 * gkl + a3 * bkl
gxkl = b1 * rkl + b2 * gkl + b3 * bkl
bxkl = c1 * rkl + c2 * gkl + c3 * bkl

  The RGB signal subjected to the color correction by the color correction circuit 10 is given to the gradation conversion circuit 11 so that the dynamic range control signal and the AE evaluation value are input from the overall control unit 13 so as to obtain an appropriate output level. Based on the above, the gradation characteristics are changed by a change based on the γ curve or a change in digital gain. Then, as shown in FIG. 3, the edge component is superimposed on each of the RGB signals in the coring circuit 12 having level conversion characteristics for converting all the outputs within a predetermined range to the reference signal level as seen from the reference signal level. The noise component is removed, and the edge component is extracted and subjected to edge enhancement processing.

<Configuration example of solid-state imaging device>
The configuration of the solid-state imaging device 2 in the imaging apparatus configured as shown in FIG. 1 will be described with reference to the drawings. FIG. 4 is a block diagram schematically showing a part of the configuration of the solid-state imaging device of this example, and FIG. 5 is a circuit diagram showing the configuration of each pixel.

  As shown in FIG. 4, in the solid-state imaging device 2, G11 to Gmn represent pixels arranged in a matrix (matrix arrangement). Reference numeral 21 denotes a vertical scanning circuit, which sequentially scans rows (lines) 23-1, 23-2,..., 23-n that apply a signal φV to each pixel and lines 24-1 and 24-2. ,..., 24-n, a signal φVD is given to each pixel, and a signal φVPS is given to each pixel via lines 25r, 25g, and 25b. A horizontal scanning circuit 22 sequentially reads out photoelectric conversion signals derived from the pixels to the output signal lines 26-1, 26-2, ..., 26-m in the horizontal direction for each pixel. Reference numeral 20 denotes a power supply line. For each pixel, not only the lines 23-1 to 23-n, 24-1 to 24-n, 25r, 25g, and 25b, the output signal lines 26-1 to 26-m, and the power supply line 20, but also other lines. (For example, a clock line and a bias supply line) are also connected, but these are omitted in FIG.

  The lines 25r, 25g, and 25b are connected to pixels provided with RGB filters, respectively. Therefore, the signal φVPS from the line 25r is input to the pixel provided with the R filter, the signal φVPS from the line 25g is input to the pixel provided with the G filter, and the pixel provided with the B filter is supplied. The photoelectric conversion characteristics can be switched for each color signal by inputting the signal φVPS from the line 25b.

  Also, constant current sources 27-1 to 27-m are connected to the output signal lines 26-1 to 26-m, and pixels are provided via the signal lines 26-1 to 26-m, respectively. Selection circuits 28-1 to 28-m for sample-holding image signals and noise signals supplied from G11 to Gmn are provided. Then, when the image signal and the noise signal are sequentially transmitted from the selection circuits 28-1 to 28-m to the correction circuit 29, the correction circuit 29 performs correction processing and outputs the image signal from which noise has been removed to the outside. Is done. The DC voltage VPS is applied to one end of the constant current sources 27-1 to 27-m.

  In such a solid-state imaging device, an image signal and a noise signal output from the pixel Gab (a natural number of a: 1 ≦ a ≦ m, b: 1 ≦ b ≦ n) are respectively output signal lines 26- The signal is output via a and amplified by a constant current source 27-a connected to the output signal line 26-a. The image signal and noise signal output from the pixel Gab are sequentially sent to the selection circuit 28-a, and the sent image signal and noise signal are sampled and held in the selection circuit 28-a. Thereafter, after the sampled and held image signal is sent to the correction circuit 29 from the selection circuit 28-a, the same sampled and held noise signal is sent to the correction circuit 29. The correction circuit 29 corrects the image signal given from the selection circuit 28-a based on the noise signal similarly given from the selection circuit 28-a, and outputs the noise-removed image signal to the amplifier 3.

  In the solid-state imaging device 2 having such a configuration, as shown in FIG. 5, the pixels G11 to Gmn have the drain of the MOS transistor T1 connected to the anode of the photodiode PD to which the DC voltage VPD is applied to the cathode. The gate and drain of the MOS transistor T2 and the gate of the MOS transistor T3 are connected to the source of T1. The gate of the MOS transistor T4 and the drain of the MOS transistor T5 are connected to the source of the MOS transistor T3, and the drain of the MOS transistor T6 is connected to the source of the MOS transistor T4. The drain of the MOS transistor T6 is connected to the output signal line 26 (corresponding to the output signal lines 26-1 to 26-m in FIG. 4). The MOS transistors T1 to T6 are P-channel MOS transistors.

  The signal φVPS is input to the source of the MOS transistor T2 via the line 25 (corresponding to the lines 25r, 25g, and 25b in FIG. 4), and the DC voltage VPD is applied to the drains of the MOS transistors T3 and T4. Further, the other end of the capacitor C to which the signal φVD is applied via the line 24 (corresponding to the lines 24-1 to 24-n in FIG. 4) is connected to the source of the MOS transistor T3. The DC voltage VRG is input to the source of the MOS transistor T5, and the signal φRS is input to the gate thereof. Further, signals φS and φV are input to the gates of the MOS transistors T1 and T6, respectively.

  The signal φVPS is a binary voltage signal. When the amount of incident light exceeds a predetermined value, the voltage for operating the MOS transistor T2 in the subthreshold region is VL, and the voltage higher than this voltage is used for the MOS transistor T2. The voltage for making the conductive state is VH. The signal φVD is a ternary voltage signal, the voltage value when integrating the capacitor C is set to the highest Vh, the voltage value when reading the image signal is set to Vm lower than Vh, and the noise signal is read The voltage value is set to Vl lower than Vm.

  The operation of the pixels G11 to Gmn in the solid-state imaging device 2 configured as described above will be described with reference to the time chart of FIG. First, when a pulse signal φVD having a voltage value Vm and a pulse signal φV are supplied and an image signal is output, the signal φVD is set to Vh, then the signal φS is set high to turn off the MOS transistor T1, and the reset operation is performed. Begins. Next, the signal φVPS applied to the source of the MOS transistor T2 is set to VH, and the source voltage of the MOS transistor T2 is increased, so that the negative charge accumulated in the gate and drain of the MOS transistor T2 and the gate of the MOS transistor T3. Are quickly recombined. At this time, the signal φRS is set to low, the MOS transistor T5 is turned on, and the voltage at the connection node between the capacitor C and the gate of the MOS transistor T4 is initialized.

  Then, the signal φVPS applied to the source of the MOS transistor T2 is set to VL to return the potential state of the MOS transistor T2 to the original state, and then the signal φRS is set to high to turn off the MOS transistor T5. Thereafter, the capacitor C performs an integration operation, and the voltage at the connection node between the capacitor C and the gate of the MOS transistor T4 becomes in accordance with the reset gate voltage of the MOS transistor T2. Then, the pulse signal φV is applied to the gate of the MOS transistor T6 to turn on the MOS transistor T6 and set the voltage value of the signal φVD to Vl. At this time, since the MOS transistor T4 operates as a source follower type MOS transistor, a noise signal appears on the output signal line 26 as a voltage signal. Thereafter, the pulse signal φRS is again applied to the MOS transistor T5 to reset the voltage at the connection node between the capacitor C and the gate of the MOS transistor T4, and then the signal φS is set low to turn on the MOS transistor T1 to perform the imaging operation. Make it ready.

  After the noise signal is output in this way, the imaging operation is started when the MOS transistor T1 is turned on. At this time, the signal φRS is set high and the MOS transistor T5 is turned off. Further, the signal φVPS applied to the source of the MOS transistor T2 is set to VL, and the voltage value of the signal φVD applied to the capacitor C is set to Vh to perform the integration operation. When photocharge corresponding to the amount of incident light flows from the photodiode PD into the MOS transistor T2, the MOS transistor T2 is in a cut-off state, so that the photocharge is accumulated at the gate of the MOS transistor T2.

  Therefore, when the brightness of the subject to be imaged is low and the amount of incident light entering the photodiode PD is small, a voltage corresponding to the amount of photocharge accumulated at the gate of the MOS transistor T2 appears at the gate of the MOS transistor T2, A voltage that changes linearly with respect to the integrated value of the amount of light appears at the gate of the MOS transistor T3. Also, when the luminance of the subject to be imaged is high and the amount of incident light entering the photodiode PD is large, and the voltage according to the amount of photocharge accumulated at the gate of the MOS transistor T2 increases, the MOS transistor T2 operates in the subthreshold region. Therefore, a voltage that changes logarithmically with respect to the amount of incident light appears at the gate of the MOS transistor T3.

  Since a drain current that is linearly or naturally logarithmically changed with respect to the incident light amount flows from the capacitor C, the gate voltage of the MOS transistor T4 is set to the integrated value of the incident light amount. Thus, the voltage changes linearly or in a natural logarithm. Then, by setting the voltage value of the signal φVD to Vm and applying the pulse signal φV to the MOS transistor T6, a source current corresponding to the gate voltage of the MOS transistor T4 flows to the output signal line 6 via the MOS transistor T6. . At this time, since the MOS transistor T4 operates as a source follower type MOS transistor, an image signal appears as a voltage signal on the output signal line 6. Thereafter, the signal φV is set high to turn off the MOS transistor T6, and the voltage value of the signal φVD is set to Vh.

  When operating in this way, the voltage value VL of the signal φVPS at the time of imaging decreases, and the potential difference between the gate and the source of the MOS transistor T2 increases as the difference from the voltage value VH of the signal φVPS at the time of reset increases. The ratio of subject luminance at which the MOS transistor T2 operates in the cutoff state increases. Therefore, as shown in FIG. 7, the lower the voltage value VL, the larger the ratio of subject luminance to be linearly converted. Therefore, for example, the luminance range of the subject is detected, and if the luminance range of the subject is narrow, the voltage value VL is lowered to widen the luminance range for linear conversion, and if the luminance range of the subject is wide, the voltage value VL is increased. By widening the luminance range for logarithmic conversion, photoelectric conversion characteristics that match the characteristics of the subject can be obtained. It should be noted that when the voltage value VL is minimized, it is possible to always perform linear conversion. When the voltage value VL is maximized, it is possible to always perform logarithmic conversion.

  The solid-state image pickup device in which the dynamic range can be switched according to the luminance range of the subject by the overall control unit 13 switching the voltage value VL of the signal φVPS given to the pixels G11 to Gmn of the solid-state image pickup device 2 operating in this way. 2 can be used. That is, the inflection point (luminance value) for switching from the linear conversion operation to the logarithmic conversion operation in the pixels G11 to Gmn of the solid-state imaging device 2 can be set by switching the voltage value VL of the signal φVPS. it can. Note that the amount of photoelectric charge flowing into the MOS transistor T2 until reaching the gate voltage of the MOS transistor T2 when changing to the logarithmic conversion operation at the time of imaging is the same in all the pixels.

  In this configuration example, a solid-state imaging device including pixels configured as shown in FIG. 5 is used. However, the present invention is not limited to this configuration, and linear conversion operation and logarithmic conversion operation are automatically performed in each pixel. As long as it can be switched to the above, it may be composed of a pixel having another configuration such as a pixel having a configuration as shown in Patent Document 2. In addition, the inflection point between the linear conversion operation and the logarithmic conversion operation is changed by changing the voltage value VL of the signal φVPS at the time of imaging. However, the linear value can be changed by changing the voltage value VH of the signal φVPS at the time of resetting. The inflection point between the conversion operation and the logarithmic conversion operation may be changed. The inflection point may be changed by changing the reset time. Further, although each pixel is provided with an RGB filter, other color filters such as cyan, magenta, and yellow may be provided.

<First Example of AE / WB Evaluation Value Detection Circuit>
A first example of the AE / WB evaluation value detection circuit in the imaging apparatus configured as shown in FIG. 1 will be described in detail below with reference to the drawings. FIG. 8 is a block diagram showing the internal configuration of the AE / WB evaluation value detection circuit of this example.

  As shown in FIG. 8, the AE / WB evaluation value detection circuit 7 of this example is provided with each of the RGB signals from which the FPN component has been removed by the FPN correction circuit 6 and is subjected to either linear conversion or logarithmic conversion. Photoelectric conversion characteristic discriminating units 71r, 71g, 71b for confirming whether or not, and average value calculation units 72r, 72g for obtaining average values r1av, g1av, b1av of the RGB signals subjected to linear conversion (with linear conversion characteristics) , 72b, and average value calculation units 73r, 73g, 73b for obtaining the average values r2av, g2av, b2av of the logarithmically converted RGB signals (having logarithmic conversion characteristics), and average value calculation units 72r, 72g, respectively. A WB evaluation value calculation unit 74r for obtaining a WB evaluation value wr1 for the R signal from the average values r1av and g1av of the RG signals, and an average value calculation unit 72g , 72b, a WB evaluation value calculation unit 74b for obtaining a WB evaluation value wb1 for the B signal from the average values g1av, b1av of the GB signals respectively received from the respective GB signals, and average values of the RG signals supplied from the average value calculation units 73r, 73g, respectively. The WB evaluation value calculation unit 75r for obtaining the WB evaluation value wr2 for the R signal from r2av and g2av, and the WB evaluation value wb2 for the B signal from the average values g2av and b2av of the GB signals given from the average value calculation units 73g and 73b, respectively. The WB evaluation value wr for the R signal is generated by weighted addition of the WB evaluation value calculation unit 75b to be obtained and the WB evaluation values wr1 and wr2 from the WB evaluation value calculation units 74r and 75r, respectively, and output to the overall control unit 13. WB evaluations from the weighted addition unit 76r and the WB evaluation value calculation units 74b and 75b, respectively. And a weighted addition unit 76b outputs the total control unit 13 generates a WB evaluation value wb for the B signal by weighted addition value wb1, wb2.

  Further, as shown in FIG. 9, the overall control unit 13 adjusts the dynamic range of the solid-state imaging device 2 and controls the timing of the clock output from the timing generation circuit 15, and AE / WB evaluation. In other words, the microcomputer 132 controls the sensor driving unit 131 according to the AE evaluation value and the WB evaluation value detected by the value detection circuit 7 and generates data to be given to the WB control circuit 8, in other words, according to the dynamic range of the solid-state imaging device 2. For example, a memory 133 that stores data that provides photoelectric conversion characteristics according to the position of the switching point between the linear conversion characteristic and the logarithmic conversion characteristic. For example, the microcomputer 132 provides the sensor driving unit 131 with a dynamic range control signal for changing the dynamic range of the solid-state imaging device 2 so that an appropriate dynamic range can be obtained according to the luminance range of the subject. The sensor driving unit 131 changes the driving condition based on the dynamic range control signal, and changes the dynamic range of the solid-state imaging device 2.

  The operation of the AE / WB evaluation value detection circuit 7 configured as shown in FIG. 8 will be described below with reference to the drawings. When the WB evaluation values wr and wb are obtained in the AE / WB evaluation value detection circuit 7, the value of the signal φVPS given from the lines 25r, 25g and 25b is equal to each pixel provided with the RGB filter. Is set. First, an RGB signal from which the FPN component has been removed by the FPN correction circuit 6 is given to each of the photoelectric conversion characteristic discriminating units 71r, 71g, 71b. A typical example of the RGB signal input in this way is shown in FIG. FIG. 10 is a graph showing the relationship of the signal level of the RGB signal with respect to the luminance value, and the luminance value is represented by a logarithmic value. That is, when the voltage VL of the signal φVPS given from the sensor driving unit 131 to the solid-state imaging device 2 is set by the dynamic range control signal from the microcomputer 132 of the overall control unit 13, the black reference correction circuit 5 and the FPN correction circuit 6 are set. In order to eliminate the offset, the potential positions at which the operation of the MOS transistor T2 of each pixel determined by the voltage VL of the signal φVPS is switched can be made substantially equal. Therefore, as shown in FIG. 10, in each of the RGB signals, the signal level that becomes an inflection point at which the linear conversion characteristic is switched to the logarithmic conversion characteristic becomes equal.

  A signal level serving as an inflection point at which the linear conversion characteristic in the RGB signal is switched to the logarithmic conversion characteristic is defined as a threshold level Vth. When the voltage VL of the signal φVPS to be given to the solid-state imaging device 2 is set by the sensor driving unit 131 of the overall control unit 13, this threshold level Vth is obtained as dynamic range data from the microcomputer 132 of the overall control unit 13. It is given to each of the photoelectric conversion characteristic discriminating units 71r, 71g, 71b. Therefore, the photoelectric conversion characteristic discriminating units 71r, 71g, 71b determine that the signal level is logarithmically converted if the signal level is higher than the threshold level Vth, and if the signal level is equal to or lower than the threshold level Vth, the signal is linearly converted. Judge that there is. The signal level may be determined to be a logarithmically converted signal when it is equal to or higher than the threshold level Vth, and may be determined to be a linearly converted signal when the signal level is lower than the threshold level Vth. The same applies to the following description.

  Then, the R signal determined by the photoelectric conversion characteristic determination unit 71r to be a signal linearly converted with the signal level equal to or lower than the threshold level Vth is given to the average value calculation unit 72r, and also in the photoelectric conversion characteristic determination unit 71r. The R signal determined to be a logarithmically converted signal having a signal level higher than the threshold level Vth is provided to the average value calculator 73r. Similarly, the G signal determined by the photoelectric conversion characteristic determination unit 71g to be a signal linearly converted with the signal level equal to or lower than the threshold level Vth is given to the average value calculation unit 72g, and the photoelectric conversion characteristic determination unit 71g. The G signal determined to be a logarithmically converted signal having a signal level higher than the threshold level Vth is provided to the average value calculation unit 73g. In addition, the B signal determined by the photoelectric conversion characteristic determination unit 71b as a signal linearly converted with the signal level equal to or lower than the threshold level Vth is given to the average value calculation unit 72b, and the photoelectric conversion characteristic determination unit 71b The B signal determined to be a logarithmically converted signal having a signal level higher than the threshold level Vth is provided to the average value calculation unit 73b.

  The average value calculators 72r, 72g, and 72b add the signal levels of the linearly converted RGB signals given from the photoelectric conversion characteristic discriminators 71r, 71g, and 71b, respectively, and each of the given RGB signals. Count the total number. Similarly, the average value calculation units 73r, 73g, and 73b add the respective signal levels of the logarithmically converted RGB signals provided from the photoelectric conversion characteristic determination units 71r, 71g, and 71b, respectively. Count the total number of In this way, when all the RGB signals are output from the photoelectric conversion characteristic determination units 71r, 71g, 71b, a signal indicating that all the RGB signals have been output is sent from the photoelectric conversion characteristic determination unit 71r to the average value calculation units 72r, 73r. The photoelectric conversion characteristic discriminating part 71g is sent to the average value calculating parts 72g and 73g, and the photoelectric conversion characteristic discriminating part 71b is sent to the average value calculating parts 72b and 73b, respectively.

  Thereafter, in each of the average value calculation units 72r, 72g, 72b, 73r, 73g, and 73b, the average value calculation is performed by dividing the summed signal level by the total number of given signals. In this way, the average value r1av of the linearly converted R signal is changed from the average value calculation unit 72r to the WB evaluation value calculation unit 74r, and the average value g1av of the linearly converted G signal is changed from the average value calculation unit 72g to WB. The average value b1av of the linearly converted B signal is sent from the average value calculation unit 72b to the WB evaluation value calculation unit 74b to the evaluation value calculation units 74r and 74b. Similarly, the average value r2av of the logarithmically converted R signal is converted from the average value calculator 73r to the WB evaluation value calculator 75r, and the average value g2av of the logarithmically converted G signal is converted from the average value calculator 73g to the WB evaluation value calculator. The average value b2av of the B signal logarithmically converted is sent to 75r and 75b from the average value calculation unit 73b to the WB evaluation value calculation unit 75b, respectively.

  Then, in the WB evaluation value calculation unit 74r to which the average values r1av and g1av of the linearly converted RG signal are given, photoelectric conversion of the average values r1av and g1av of the RG signal and the G signal given from the microcomputer 132 of the overall control unit 13 is performed. From the characteristics, the WB evaluation value wr1 for the linearly converted R signal is obtained, and the average value g1av of the GB signal is obtained in the WB evaluation value calculation unit 74b to which the average value g1av and b1av of the linearly converted GB signal is given. The WB evaluation value wb1 for the linearly converted B signal is obtained from b1av and the photoelectric conversion characteristics of the G signal given from the microcomputer 132 of the overall control unit 13.

  Similarly, in the WB evaluation value calculator 75r to which the logarithmically converted RG signal average values r2av and g2av are given, the RG signal average values r2av and g2av and the G signal photoelectricity given from the microcomputer 132 of the overall control unit 13 are used. From the conversion characteristics, the WB evaluation value wr2 for the logarithmically converted R signal is obtained, and the average value g2av of the GB signal is obtained in the WB evaluation value calculation unit 75b to which the average values g2av and b2av of the logarithmically converted GB signal are given. , B2av and the photoelectric conversion characteristic of the G signal given from the microcomputer 132 of the overall control unit 13, the WB evaluation value wb2 for the logarithmically converted B signal is obtained. The WB evaluation value calculators 74r, 74b, 75r, and 75b are each given a G signal photoelectric conversion characteristic according to the dynamic range of the solid-state imaging device 2 from the microcomputer 132 of the overall controller 13.

  Processing operations in the WB evaluation value calculation units 74r, 74b, 75r, and 75b will be described by taking the WB evaluation value calculation units 74r and 75r as an example. It is assumed that the photoelectric conversion characteristics of the G signal as shown in FIG. 11 are given to the WB evaluation value calculation units 74r, 74b, 75r, and 75b from the microcomputer 132 of the overall control unit 13. At this time, the WB evaluation value calculation unit 74r first obtains the luminance value Lav in the average value g1av of the G signal based on the photoelectric conversion characteristics of the G signal as shown in FIG. That is, when the linear conversion characteristic region of the G signal is expressed by the equation (1), the luminance value Lav (= (g1av−C) is calculated by substituting the average value g1av of the G signal into the equation (1). ) / Ag).

V = Ag × L + C (1)
(V: signal level, L: luminance, Ag: photoelectric conversion coefficient for G signal, C: offset)

  Then, assuming that the average value r1av of the R signal is obtained for this luminance value Lav, the photoelectric conversion coefficient Ar (= (r1av−C) / Lav) for the R signal is obtained, and FIG. Thus, the photoelectric conversion characteristic of the R signal in the linear conversion characteristic region is obtained. It should be noted that the expression representing the linear conversion characteristic region of the R signal is expressed as Expression (2), and the offset C is equal to Expression (1).

  V = Ar × L + C (2)

  When the photoelectric conversion characteristic of the R signal in the linear conversion characteristic region is obtained in this way, the luminances Lrth and Lgth for the RG signals having the threshold level Vth are obtained from the photoelectric conversion characteristics of the RG signals as shown in FIG. It is done. That is, the luminance levels Lgth (= (Vth−C) / Ag) and Lrth (= (Vth−C) / Ar) are calculated by substituting the threshold level Vth into each of the expressions (1) and (2). Is required. The WB evaluation value wr1 for the linearly converted R signal is obtained as the difference value Lgth-Lrth based on the luminances Lrth and Lgth of the RG signals having the threshold level Vth thus obtained.

  Further, in the WB evaluation value calculation unit 75r, first, as shown in FIG. 12A, the logarithm value ln (Lav) of the luminance value in the average value g2av of the G signal is obtained based on the photoelectric conversion characteristics of the G signal. That is, when the logarithmic conversion characteristic region of the G signal is expressed by the expression (3), the logarithmic value ln (Lav) of the luminance value is calculated by substituting the average value g2av of the G signal into the expression (3) and performing the reverse calculation. (= (G2av−βg) / α) can be obtained. Note that the photoelectric conversion characteristic of the G signal in FIG. 12 is equal to the photoelectric conversion characteristic of the G signal in FIG.

V = α × ln (L) + βg (3)
(Α: predetermined amplification factor, βg: logarithmic conversion value of photoelectric conversion coefficient for G signal)

  Then, by assuming that the average value r2av of the R signal is obtained for the logarithmic value ln (Lav) of this luminance value, the logarithmic conversion value βr (= r2av−α × ln (Lav) of the photoelectric conversion coefficient for the R signal is obtained. ) = R2av−g2av + βg), and the photoelectric conversion characteristic of the R signal in the logarithmic conversion characteristic region is obtained as shown in FIG. The expression representing the logarithmic conversion characteristic region of the R signal is expressed as the following expression (4), and the amplification factor α is equal to the expression (3).

  V = α × ln (L) + βr (4)

  When the photoelectric conversion characteristic of the R signal in the logarithmic conversion characteristic region is obtained in this way, the logarithmic values ln (Lrth) and ln (Lgth) of the luminance for each RG signal having the threshold level Vth are as shown in FIG. It is obtained from the photoelectric conversion characteristics of each RG signal. That is, by substituting the threshold level Vth into each of the equations (3) and (4) and calculating backward, the logarithmic value of luminance ln (Lgth) (= (Vth−βg) / α), ln (Lrth) ( = (Vth−βr) / α). Therefore, the luminance Lrth (= exp ((Vth−βr) / α)) and Lgth (= exp ((Vth−βg) / α)) for each RG signal having the threshold level Vth is finally obtained. The WB evaluation value wr2 for the logarithmically converted R signal is obtained as the difference value Lgth-Lrth based on the luminances Lrth and Lgth of the RG signals having the threshold level Vth thus obtained.

  When the WB evaluation values wr1, wb1, wr2, and wb2 are output by performing such processing operations in the WB evaluation value calculation units 74r, 74b, 75r, and 75b, the WB evaluation values wr1 and wr2 are weighted and added. The WB evaluation values wb1 and wb2 are given to the weighted addition unit 76b. A weighting coefficient corresponding to the set dynamic range of the solid-state imaging device 2 is given to each of the weighted addition units 76r and 76b from the microcomputer 132 of the overall control unit 13. Therefore, when the weighting coefficients 76r and yr for the WB evaluation values wr1 and wr2 are given in the weighted addition unit 76r, the WB evaluation value wr is obtained as shown in Equation (5). In addition, when weighting factors xb and yb for the WB evaluation values wb1 and wb2 are given in the weighted addition unit 76r, the WB evaluation value wb is obtained as shown in Equation (6).

wr = xr * wr1 + yr * wr2 (5)
wb = xb × wb1 + yb × wb2 (6)

  The WB evaluation values wr and wb obtained by the weighted addition units 76r and 76b in this way are given to the microcomputer 132 of the overall control unit 13. The microcomputer 132 determines a set value to be given to the WB control unit 8 based on the WB evaluation values wr and wb and the dynamic range data. In this example, the weighting factors xr, yr, xb, and yb given to the weighted addition units 76r and 76b are set according to the set dynamic range of the solid-state imaging device 2. The microcomputer 132 may be set according to the distribution range or the luminance value and given to the weighted addition units 76r and 76b. Further, the weight coefficients xr, yr, xb, yb may be set from the outside.

<Second Example of AE / WB Evaluation Value Detection Circuit>
A second example of the AE / WB evaluation value detection circuit 7 in the imaging apparatus configured as shown in FIG. 1 will be described in detail below with reference to the drawings. FIG. 13 is a block diagram showing the internal configuration of the AE / WB evaluation value detection circuit of this example. In the AE / WB evaluation value detection circuit shown in FIG. 13, the detailed description of the parts used for the same purpose as the AE / WB evaluation value detection circuit of FIG. 8 is omitted, and the same reference numerals are given.

  As shown in FIG. 13, the AE / WB evaluation value detection circuit 7 of this example includes photoelectric conversion characteristic determination units 71r, 71g, 71b, average value calculation units 72r, 72g, 72b, 73r, 73g, 73b, and WB. The total number of each of the linearly converted signal and the logarithmically converted signal confirmed by the evaluation value calculating units 74r, 74b, 75r, and 75b, the weighted adding units 76r and 76b, and the photoelectric conversion characteristic discriminating units 71r, 71g, and 71b. And a weighting factor setting unit 77 that counts and sets the weighting factors xr, yr, xb, and yb based on these count values. When the WB evaluation values wr and wb are obtained in the AE / WB evaluation value detection circuit 7, the value of the signal φVPS given from the lines 25r, 25g and 25b is equal to each pixel provided with the RGB filter. Is set.

  When configured in this manner, the photoelectric conversion characteristic discriminating units 71r, 71g, 71b, the average value calculating units 72r, 72g, 72b, 73r, 73g, 73b, the WB evaluation value calculating units 74r, 74b, 75r, 75b, and The weighted addition units 76r and 76b perform the same operation as the AE / WB evaluation value detection circuit (FIG. 8) in the first example. That is, in the photoelectric conversion characteristic discriminating units 71r, 71g, 71b, the signal level of the input RGB signal is compared with the threshold level Vth, and it is a logarithmically converted signal or a linearly converted signal. Is determined. Then, RGB signals confirmed to be linearly converted by the photoelectric conversion characteristic discriminating units 71r, 71g, 71b are given to the average value calculating units 72r, 72g, 72b, and the average values r1av, g1av, b1av are given. The RGB signals obtained and confirmed to be logarithmically converted by the photoelectric conversion characteristic discriminating units 71r, 71g, 71b are given to the average value calculating units 73r, 73g, 73b, and the average values r2av, g2av , B2av.

  Thereafter, the WB evaluation value calculation unit 74r obtains the WB evaluation value wr1 for the linearly converted R signal based on the average values r1av and g1av and the photoelectric conversion characteristics of the G signal, and the WB evaluation value calculation unit 75r Based on the average values r2av, g2av and the photoelectric conversion characteristics of the G signal, a WB evaluation value wr2 for the logarithmically converted R signal is obtained. Further, in the WB evaluation value calculation unit 74b, the WB evaluation value wb1 for the linearly converted B signal is obtained based on the average values g1av, b1av and the photoelectric conversion characteristics of the G signal, and in the WB evaluation value calculation unit 75b, Based on the average values g2av, b2av and the photoelectric conversion characteristics of the G signal, a WB evaluation value wb2 for the logarithmically converted B signal is obtained. Then, the weighted addition unit 76r performs weighted addition of the WB evaluation values wr1 and wr2 using the weighting factors xr and yr given from the weighting factor setting unit 77, thereby obtaining the WB evaluation value wr and performing the weighted addition. The unit 76b performs weighted addition of the WB evaluation values wb1 and wb2 using the weighting factors xb and yb given from the weighting factor setting unit 77, thereby obtaining the WB evaluation value wb.

  Thus, when obtaining the WB evaluation values wr and wb, unlike the first example, the weighting factor setting unit 77 sets weighting factors xr, yr, xb and yb to be given to the weighting addition units 76r and 76b. Therefore, hereinafter, the operation of the weighting coefficient setting unit 77 will be described. First, when the discrimination results for the RGB signals are given to the weighting coefficient setting unit 77 by the photoelectric conversion characteristic discriminating units 71r, 71g, 71b, the total number or logarithmically converted signals are linearly converted according to the given discrimination result. Count the total number of signals. Therefore, the total number of R signals transmitted from the photoelectric conversion characteristic determination unit 71r to the average value calculation units 72r and 73r is n1r and n2r, respectively, and is output from the photoelectric conversion characteristic determination unit 71g to the average value calculation units 72g and 73g, respectively. When the total number of G signals is n1g and n2g, and the total number of B signals sent from the photoelectric conversion characteristic determination unit 71b to the average value calculation units 72b and 73b is n1b and n2b, the total number of linearly converted signals Is n1 (= n1r + n1g + n1b), and the total number of logarithmically converted signals is n2 (= n2r + n2g + n2b).

  Then, the weighting coefficients xr, yr, xb, yb are set according to the ratio of the total number n1 of linearly converted signals and the total number n2 of logarithmically converted signals. At this time, for example, xr = xb = n1 / (n1 + n2) and yr = yb = n2 / (n1 + n2) are set so that the weighting coefficient for a signal whose total number increases is increased. When the weighting coefficients xr, yr, xb, yb are set in this way, the weighting coefficients xr, yr are given to the weighted addition unit 76r, and the weighting coefficients xb, yb are given to the weighted addition unit 76b.

  In the AE / WB evaluation value setting unit 7 of this example, the weighting coefficient setting unit 77 uses the total number n1 of linearly converted signals and the total number n2 of logarithmically converted signals for all RGB signals. The weighting coefficients xr, yr, xb, and yb are obtained, but the total number n1r, n1g, and n1b of the linearly converted signals for each of the RGB signals and the total number n2r, n2g, and n2b of the logarithmically converted signals. And the weighting coefficients xr, yr, xb, and yb may be obtained. At this time, the weighting coefficients xr and yr are obtained from the relationship between the total number n1r of the R signals subjected to linear transformation and the total number n2r of the logarithmically transformed R signals, and the weighting factors xb and yb are obtained from the linearly transformed B signal. May be obtained from the relationship between the total number n1b of the B signals and the total number n2b of the logarithmically converted B signals. Further, the weighting coefficients xr and yr are obtained from the relationship between the total number n1r and n1g of each of the linearly converted RG signals and the total number n2r and n2g of the logarithmically converted RG signals, and the weighting coefficients xb and yb are linearly converted. The total number n1g and n1b of the GB signals thus obtained and the total number n2g and n2b of the logarithmically converted GB signals may be obtained.

  In addition, when an autofocus (AF) function for detecting the main subject is provided, the pixels in the region centered on the main subject detected by the AF function are logarithmically converted with the number of pixels that output a linearly converted signal. The weighting coefficient may be set according to the relationship with the number of pixels that output a signal.

  In the AE / WB evaluation value setting unit 7 of the first and second examples described above, the photoelectric conversion characteristics of the G signal are given to the WB evaluation value calculation units 74r, 74b, 75r, and 75b, and the WB evaluation value wr1. , Wb1, wr2, and wb2 are obtained, the luminance value L1av in the average value of the linearly converted signal is given to the WB evaluation value calculation units 74r and 74b, and the luminance in the average value of the logarithmically converted signal The value L2av may be given to the WB evaluation value calculators 75r and 75b to obtain the WB evaluation values wr1, wb1, wr2, and wb2.

  At this time, the WB evaluation value calculation unit 74r confirms the photoelectric conversion characteristics of each of the RG signals based on the relationship between the average values r1av and g1av of each of the linearly converted RG signals and the luminance value L1av, and the threshold level of each of the RG signals. A WB evaluation value wr1 that is a difference in luminance value corresponding to Vth is obtained. Similarly, the WB evaluation value calculation unit 75r confirms the photoelectric conversion characteristics of each RG signal from the relationship between the average values r2av and g2av of each logarithmically converted RG signal and the luminance value L2av, and obtains the WB evaluation value wr2. . Similarly, the WB evaluation value calculation unit 74b confirms the photoelectric conversion characteristics of each GB signal from the relationship between the average values g1av and b1av and the luminance value L1av of each linearly converted GB signal, and obtains the WB evaluation value wb1. In addition, the WB evaluation value calculation unit 75b confirms the photoelectric conversion characteristics of each GB signal from the relationship between the average values g2av and b2av of each logarithmically converted GB signal and the luminance value L2av, and obtains the WB evaluation value wb2. .

<Photoelectric conversion characteristic detection operation by the overall control unit>
Below, the photoelectric conversion characteristic detection operation | movement of the RGB signal by the whole control part is demonstrated. When the AE / WB evaluation value setting unit 7 operates as in the first example or the second example of the AE / WB evaluation value setting unit and the WB evaluation values wr and wb are set in the AE / WB evaluation value setting unit 7, the configuration shown in FIG. This is given to the microcomputer 132 of the overall control unit 13. When the microcomputer 132 confirms the WB evaluation values wr and wb, the photoelectric conversion characteristic for each of the RGB signals is obtained from the memory 133 based on the WB evaluation values wr and wb and the size of the dynamic range set for the solid-state imaging device 2. read out. Then, the microcomputer 132 generates a data table for performing white balance processing in the WB control circuit 8 and gives it to the WB control circuit 8.

  At this time, the photoelectric conversion characteristics of the G signal are discretely stored in the memory 133 according to the dynamic range of the solid-state imaging device 2, for example, as shown in the graph of FIG. The photoelectric conversion characteristics are stored discretely as shown in the graph of FIG. 14 according to the WB evaluation value for each dynamic range. Further, as shown in the graph of FIG. 7, four types of photoelectric conversion characteristics a1 to a4 are stored as the photoelectric conversion characteristics of the G signal, and as shown in the graph of FIG. 14, the photoelectric conversion characteristics of the RB signal with respect to the size of the dynamic range. When six types of photoelectric conversion characteristics b1 to b6 are stored, 4 × 6 types of photoelectric conversion characteristics are stored in the memory 133.

  At this time, the parameters A and C in the equation (7) representing the linear conversion characteristic region of the photoelectric conversion property and the parameters α and β in the equation (8) representing the logarithmic conversion property region of the photoelectric conversion property are stored in the memory 133. 24 types are stored. FIG. 14 is based on the photoelectric conversion characteristics of the G signal when the dynamic range corresponding to the photoelectric conversion characteristics a2 in FIG. 7 is selected.

V = A × L + C (7)
V = α × ln (L) + β (8)

  Then, when the solid-state imaging device 2 is set to have a predetermined dynamic range, the photoelectric conversion characteristic of the G signal corresponding to the selected dynamic range is read from the memory 133. Further, when the WB evaluation values wr and wb are given from the AE / WB evaluation value detection circuit 7, the selected dynamic range, the photoelectric conversion characteristic of the R signal according to the WB evaluation value wr, the selected dynamic range, The photoelectric conversion characteristics of the B signal corresponding to the WB evaluation value wb are read from the memory 133. That is, when the sensor driving unit 131 drives and controls the solid-state imaging device 2 so that the dynamic range according to the photoelectric conversion characteristic a2 in FIG. 7 is obtained, first, the photoelectric conversion characteristic a2 is obtained as the G signal photoelectric conversion characteristic from the memory 133. Read out. When a WB evaluation value wr that is ΔL1 and a WB evaluation value wb that is −ΔL2 are given, the photoelectric conversion characteristic b4 is the photoelectric conversion characteristic of the R signal, and the photoelectric conversion characteristic b2 is the photoelectric conversion characteristic of the B signal. Are read from the memory 133.

  When the photoelectric conversion characteristics of each of the RGB signals are confirmed in this way, the luminance value that switches from the linear conversion characteristic to the logarithmic conversion characteristic in the photoelectric conversion characteristics of the RB signal is set to the luminance value Lgth that switches in the G signal. The signal levels Vrth and Vbth of the RB signals with respect to Lgth are obtained as threshold levels. That is, when the equation (9) holds in the linear conversion characteristic region of the photoelectric conversion characteristic of the R signal and the equation (10) holds in the linear conversion characteristic region of the photoelectric conversion property of the B signal, the threshold level Vrth (= Ar × Lgth + C) and the threshold level Vbth (= Ab × Lgth + C) of the B signal are obtained. Further, the threshold level Vgth of the G signal is set to the threshold level Vth of the photoelectric conversion characteristic confirmed from the dynamic range control signal.

V = Ar × L + C (9)
V = Ab × L + C (10)

  Thus, when the threshold levels Vrth and Vbth of the RB signal are obtained, the logarithmic conversion characteristic region of the photoelectric conversion characteristic of the RB signal is obtained. When it is confirmed that the logarithmic conversion characteristic of the photoelectric conversion characteristic of the R signal has a relationship as shown in the equation (11) from the photoelectric conversion characteristic of the WB evaluation value wr and the G signal, the threshold level Vrth of the R signal is obtained. , The logarithmic conversion characteristic of the photoelectric conversion characteristic of the R signal has a relationship as shown in the equation (12). Further, when it is confirmed that the logarithmic conversion characteristic of the photoelectric conversion characteristic of the B signal is as shown in the equation (13) from the photoelectric conversion characteristic of the WB evaluation value wb and the G signal, the threshold level Vbth of the B signal is obtained. Then, the logarithmic conversion characteristic of the photoelectric conversion characteristic of the B signal has a relationship as shown in the equation (14).

V = α × ln (L) + βr (11)
V = α × ln (L) + βr + Vrth−Vth (12)
V = α × ln (L) + βb (13)
V = α × ln (L) + βb + Vbth−Vth (14)

  In this way, photoelectric conversion characteristics are obtained with respect to the R signal so that the linear conversion characteristic region has a relationship as expressed by equation (9) and the logarithmic conversion characteristic region has a relationship as expressed by equation (12). As described above, the voltage value VL or the voltage value VH of the signal φVPS for the pixel having the R filter of the solid-state imaging device 2 is set. Further, a solid conversion characteristic region can be obtained for the B signal so that the linear conversion characteristic region has a relationship as expressed by equation (10) and the logarithmic conversion characteristic region has a relationship as expressed by equation (14). A voltage value VL or a voltage value VH of the signal φVPS for a pixel having a B filter of the image sensor 2 is set. Further, a solid state is obtained so that a photoelectric conversion characteristic can be obtained with respect to the G signal so that the linear conversion characteristic region has a relationship as expressed by equation (15) and the logarithmic conversion characteristic region has a relationship as expressed by equation (16). A voltage value VL or a voltage value VH of the signal φVPS for a pixel having a G filter of the image sensor 2 is set.

V = Ag × L + C (15)
V = α × ln (L) + βg (16)

  Further, based on the photoelectric conversion characteristic of the R signal according to the equation (9) set as described above and the photoelectric conversion characteristic of the G signal according to the equation (15), white balance processing is performed on the linear conversion portion of the R signal. Parameter Sr1 (= Ag / Ar) of the R signal based on the photoelectric conversion characteristic of the R signal according to the equation (12) and the photoelectric conversion characteristic of the G signal according to the equation (16) set as described above. The parameter Sr2 (= βg−βr−Vrth + Vth) for performing the white balance processing on the logarithmic conversion portion is obtained. Similarly, the white balance processing is performed on the linear conversion portion of the B signal based on the photoelectric conversion characteristic of the B signal according to the equation (10) set as described above and the photoelectric conversion characteristic of the G signal according to the equation (15). Parameter Sb1 (= Ag / Ab) for the B signal based on the photoelectric conversion characteristic of the B signal according to the equation (14) set as described above and the photoelectric conversion characteristic of the G signal according to the equation (16). Parameters Sb2 (= βg−βb−Vbth + Vth) for performing white balance processing on the logarithmic conversion portion of the signal are respectively obtained. The parameters Sr1, Sr2, Sb1, Sb2 obtained in this way are given to the WB control circuit 8 together with the threshold levels Vrth, Vbth of the RB signal.

  At this time, for example, as described above, when it is confirmed from the dynamic range control signal and the WB evaluation values wr and wb that the photoelectric conversion characteristics of the RGB signals are the photoelectric conversion characteristics b4, a2 and b2, respectively. As shown in FIG. 15, the relationship between the luminance values Lrth, Lgth, and Lbth of the RGB signals at the threshold level Vth is Lrth> Lgth> Lbth. Then, when the luminance value at which the photoelectric conversion characteristic of the RB signal switches is Lgth and the photoelectric conversion characteristic of the RB signal is changed, as shown in FIG. 16, the relationship among the threshold levels Vrth, Vgth, and Vbth of the RGB signal is Vrth <Vgth < Vbth. In this way, since the signal φVPS to be given to the pixels each including the RGB filter of the solid-state imaging device 2 is set so that the photoelectric conversion characteristics of the RGB signal are switched with the same luminance value, the linear conversion characteristic area of each RGB signal is set. And the logarithmic conversion characteristic area becomes the same luminance range, and there is no luminance range where the linear conversion characteristic area and the logarithmic conversion characteristic area overlap between different color signals.

  In addition, although it demonstrated as above as what switches the dynamic range of the solid-state image sensor 2 discretely, when switching the dynamic range of the solid-state image sensor 2 continuously, the following operation processing is performed. It doesn't matter. First, the memory 133 stores a plurality of stages of photoelectric conversion characteristics as in the case where the dynamic range of the solid-state imaging device 2 is discretely switched. Then, when the set dynamic range value of the solid-state imaging device 2 (for example, the voltage value VL of the signal φVPS) becomes a value between two discretely set dynamic ranges, it is set discretely. Two photoelectric conversion characteristics for two dynamic ranges are read from the memory 133.

  Then, the dynamic range value set for the solid-state imaging device 2 (for example, the voltage value VL of the signal φVPS) is read from the memory 133 based on the relationship between the two dynamic range values set discretely and 2 A new photoelectric conversion characteristic is generated by interpolating each coefficient (A in equation (7) and α, β in equation (8)) of the two photoelectric conversion characteristics. The photoelectric conversion characteristics generated in this way are used as the G signal photoelectric conversion characteristics for the dynamic range currently set for the solid-state imaging device 2.

  That is, for example, as in the graph of FIG. 7, four types of data tables for the photoelectric conversion characteristics a1 to a4 of the solid-state imaging device 2 are stored in the memory 133, and the photoelectric conversion between the photoelectric conversion characteristics a2 and a3 is performed. It is assumed that a dynamic range serving as conversion characteristics is set for the solid-state imaging device 2. At this time, the photoelectric conversion characteristics a2 and a3 are interpolated to obtain the photoelectric conversion characteristics ax for the dynamic range currently set for the solid-state imaging device 2 as shown in FIG. Used as a characteristic. Each of the photoelectric conversion characteristics of the RB signal is obtained using the photoelectric conversion characteristics of the G signal thus obtained and the WB evaluation values wr and wb. At this time, the photoelectric conversion characteristic of the RB signal may be calculated backward using the photoelectric conversion characteristic of the G signal and the luminance difference at the threshold level Vth obtained from the WB evaluation values wr and wb.

  In the above description, the photoelectric conversion characteristics of each of the RGB signals are stored in the memory 133, but only the photoelectric conversion characteristics of the G signal are stored in the memory 133, and the photoelectric conversion characteristics of the RB signal are the above-described WB evaluation value wr. , Wb may be obtained by calculation. For example, the parameter A (Ar) in the equation (7) representing the linear characteristic region of the photoelectric conversion characteristic with respect to the R signal can be calculated from the following equations (17) to (19).

Vth = Ag × Lg + C (17)
Vth = Ar × (Lg + wr) + C (18)
From the equations (17) and (18) Ar = (Ag × Lg) / (Lg + wr) (19)
However, Ag shows the photoelectric conversion coefficient with respect to G signal, Lg shows the brightness | luminance of G signal.

  Similarly, the logarithmic characteristic region of the R signal can be obtained by calculation. Further, the photoelectric conversion characteristic regarding the B signal can be obtained by calculation similarly to the R signal. As described above, when the photoelectric conversion characteristics are obtained by calculation, high-accuracy white balance processing can be performed.

<First Example of WB Control Circuit>
A first example of the WB control circuit in the imaging apparatus configured as shown in FIG. 1 will be described in detail below with reference to the drawings. FIG. 18 is a block diagram showing the internal configuration of the WB control circuit of this example. The WB control circuit 8 of this example is given parameters Sr1, Sr2, Sb1, Sb2 and threshold levels Vrth, Vbth by the overall control unit 13.

  As shown in FIG. 18, the WB control circuit 8 of this example compares the R signal from which the FPN component has been removed by the FPN correction circuit 6 to determine whether the photoelectric conversion characteristic is a linear conversion characteristic or a logarithmic conversion characteristic. 81r, a comparator 81b for identifying whether the photoelectric conversion characteristic of the B signal from which the FPN component has been removed by the FPN correction circuit 6 is a linear conversion characteristic or a logarithmic conversion characteristic, and an RB signal that is a linear conversion characteristic, respectively Multipliers 82r and 82b for multiplying parameters Sr1 and Sb1, and adders 83r and 83b for adding the parameters Sr2 and Sb2 to the RB signals having logarithmic conversion characteristics, the R signal from the multiplier 82r, and the adder 83r, respectively. A selection unit 84r that selects and outputs one of the R signals, and a selection unit that selects and outputs either the B signal from the multiplier 82b or the B signal from the adder 83b. It comprises a section 84b, selection unit 84r, and the timing adjusting unit 85 that adjusts the output timing of the RB signal and the G signal FPN component is removed by the FPN correction circuit 6 which is output from 84b respectively, the.

  In the WB control circuit 8 configured in this way, when the parameters Sr1, Sr2, Sb1, Sb2 and threshold levels Vrth, Vbth are set by the overall control unit 13, the threshold levels Vrth, Vbth are respectively input to the comparators 81r, 81b. The parameters Sr1 and Sb1 are supplied to the multipliers 82r and 82b, respectively, and the parameters Sr2 and Sb2 are supplied to the adders 83r and 83b, respectively. Thereafter, when an R signal is given from the FPN correction circuit 6, this R signal is inputted to the comparator 81r, the multiplier 82r, and the adder 83r.

  The comparator 81r compares the signal level Vr of the input R signal with the threshold level Vrth. The multiplier 82r multiplies the signal level Vr of the R signal by the parameter Sr1, and the adder 83r adds the parameter Sr2 to the signal level Vr of the R signal. At this time, when the signal level Vr of the signal R is equal to or lower than the threshold level Vrth, the comparator 81r confirms that the photoelectric conversion characteristic of the R signal is a linear conversion characteristic. The R signal is selected. When the signal level Vr of the signal R is greater than the threshold level Vrth, the comparator 81r confirms that the photoelectric conversion characteristic of the R signal is a logarithmic conversion characteristic. Therefore, the selector 84r causes the R signal from the adder 83r to be output. Is selected.

  Similarly, when a B signal is provided from the FPN correction circuit 6, this B signal is input to the comparator 81b, the multiplier 82b, and the adder 83b. The comparator 81b compares the signal level Vb of the input B signal with the threshold level Vbth. The multiplier 82b multiplies the signal level Vb of the B signal by the parameter Sb1, and the adder 83b adds the parameter Sb2 to the signal level Vb of the B signal. At this time, when the signal level Vb of the signal B is equal to or lower than the threshold level Vbth, the comparator 81b confirms that the photoelectric conversion characteristic of the B signal is a linear conversion characteristic. The B signal is selected. When the signal level Vb of the signal B is greater than the threshold level Vbth, the comparator 81b confirms that the photoelectric conversion characteristic of the B signal is a logarithmic conversion characteristic. Therefore, the selector 84b causes the B signal from the adder 83b to be detected. Is selected.

  By operating in this way, the photoelectric conversion characteristics of each RB signal representing a luminance range in which the luminance value is equal to or less than Lgth are switched to the same as the linear conversion characteristic of the G signal, and the luminance value is higher than Lgth. The photoelectric conversion characteristics of each RB signal representing the range are switched to those equivalent to the logarithmic conversion characteristics of the G signal, and each RB signal is subjected to white balance processing. Then, the RB signal converted to the signal level after white balance processing and the G signal subjected to FPN correction by the FPN correction circuit 6 are input to the timing adjustment unit 85 from each of the selection units 84 r and 84 b. The timing adjustment unit 85 adjusts the timing for outputting the RB signal output from the selection units 84r and 84b and subjected to the conversion process, and the G signal that is not subjected to the conversion process. The RGB signal whose output timing is adjusted in this way is output to the color interpolation circuit 9 in the subsequent stage, and signal processing corresponding to each pixel can be performed in each circuit in the subsequent stage.

<Second Example of WB Control Circuit>
A second example of the WB control circuit in the imaging apparatus configured as shown in FIG. 1 will be described in detail below with reference to the drawings. FIG. 19 is a block diagram showing the internal configuration of the WB control circuit of this example. The WB control circuit 8 of this example is given parameters Sr1, Sr2, Sb1, Sb2 and threshold levels Vrth, Vbth by the overall control unit 13.

  As shown in FIG. 19, the WB control circuit 8 of this example determines whether the photoelectric conversion characteristic of the RB signal from which the FPN component has been removed by the FPN correction circuit 6 is a linear conversion characteristic or a logarithmic conversion characteristic, as a threshold level Vxth. A comparator 81 for identifying each of the RB signals having a linear conversion characteristic, a multiplier 82 for multiplying each of the RB signals having a linear conversion characteristic, an adder 83 for adding the parameter S2 to each of the RB signals having a logarithmic conversion characteristic, and a multiplier A selection unit 84 that selects and outputs one of the RB signal from 82, the RB signal from the adder 83, and the G signal from the FPN correction circuit 6, and the RGB signal from which the FPN component has been removed by the FPN correction circuit 6 RGB detection unit 86 to detect, parameter setting unit 87 for setting threshold level Vxth and parameters S1 and S2 based on the detection result in RGB detection unit, and RGB detection unit 86 And a selection control unit 88 that controls the selection operation of the selection unit 84 based on the detection result of the comparator 81 and the comparison result of the comparator 81.

  When the parameters Sr1, Sr2, Sb1, Sb2 and threshold levels Vrth, Vbth are set by the overall control unit 13, the WB control circuit 8 configured in this way is given to the parameter setting unit 87 and stores it. When the RGB signal detector 86 detects that the signal input from the FPN correction circuit 6 is an R signal, the threshold level Vxth is set to Vrth, the parameters S1 and S2 are set to Sr1 and Sr2, and the FPN When the RGB signal detector 86 detects that the signal input from the correction circuit 6 is a B signal, the threshold level Vxth is set to Vbth and the parameters S1 and S2 are set to Sb1 and Sb2.

  Therefore, when the R signal is detected by the RGB detector 86, the signal level Vr of the R signal input in the comparator 81 is compared with the threshold level Vrth, and the signal level Vr of the R signal is compared in the multiplier 82. The adder 83 adds the parameter Sr2 to the signal level Vr of the R signal. Further, the selection control unit 88 controls the selection unit 84 to select the output from the multiplier 82 or the adder 83. That is, when the comparison result of the comparator 81 is Vr ≦ Vrth, the selector 84 selects the R signal from the multiplier 82, and when the comparison result of the comparator 81 is Vr> Vrth. The selection control unit 88 controls the selection unit 84 so that the selection unit 84 selects the R signal from the adder 83.

  Similarly, when the RGB signal is detected by the RGB detector 86, the signal level Vb of the B signal input in the comparator 81 is compared with the threshold level Vbth, and the signal level Vb of the B signal is compared in the multiplier 82. On the other hand, the parameter Sb1 is multiplied, and the adder 83 adds the parameter Sb2 to the signal level Vb of the B signal. Further, the selection control unit 88 controls the selection unit 84 to select the output from the multiplier 82 or the adder 83. That is, when the comparison result of the comparator 81 is Vb ≦ Vbth, the selector 84 selects the B signal from the multiplier 82, and when the comparison result of the comparator 81 is Vb> Vbth. The selection control unit 88 controls the selection unit 84 so that the selection unit 84 selects the B signal from the adder 83. Further, when the G signal is detected by the RGB detection unit 86, the selection control unit 88 controls the selection unit 84 to select the G signal from the FPN correction circuit 6.

  By operating in this way, the photoelectric conversion characteristics of each RB signal representing a luminance range in which the luminance value is equal to or less than Lgth are switched to the same as the linear conversion characteristic of the G signal, and the luminance value is higher than Lgth. The photoelectric conversion characteristics of each RB signal representing the range are switched to those equivalent to the logarithmic conversion characteristics of the G signal, and each RB signal is subjected to white balance processing. Then, the selection unit 84 selects and outputs the RB signal that has been subjected to the white balance process and the G signal that has been FPN corrected by the FPN correction circuit 6.

  As described above, the AE / WB evaluation value detection circuit 7, the WB control circuit 8, and the overall control unit 13 are operated, so that when the white balance process is performed, only one AE for every predetermined number of frames. The WB evaluation value detection circuit 7 and the overall control unit 13 may set parameters and threshold levels used in white balance processing, and photoelectric conversion characteristics of a pixel including each of the RGB filters of the solid-state imaging device 2. That is, the signal φVPS given to each pixel of the solid-state imaging device 2 is made the same so that the threshold levels of the RGB signals are equal as shown in FIG. 15 only when there is one frame for every predetermined number of frames. In other frames, the lines 25r and 25g are applied to each pixel provided with the RGB filter of the solid-state imaging device 2 so that the luminance values at which the photoelectric conversion characteristics of the RGB signals are switched are equal as shown in FIG. , 25b is different from the signal φVPS.

  Each of the solid-state imaging devices 2 is set so that the RGB signal threshold levels are equal as shown in FIG. 15 when input from the outside by the user of the imaging apparatus so as to set parameters and threshold levels used in white balance processing. The signal φVPS given to the pixels may be the same, and the parameter and threshold level and the value of the signal φVPS given via the lines 25r, 25g, 25b may be set. Also, parameters and threshold levels according to the shooting environment such as sunlight, tungsten light, and fluorescent light, and the value of the signal φVPS given through the lines 25r, 25g, and 25b are set in advance, and the shooting environment is externally set by the user of the imaging apparatus. May be used to set the input parameter and threshold level and the value of the signal φVPS given through the lines 25r, 25g, and 25b.

  In this embodiment, the solid-state imaging device is operated so as to remove pixel variation in the device by subtracting the noise signal from the image signal, and the FPN component further remaining in the image signal in the FPN correction circuit. However, the FPN correction circuit may be configured to remove all FPN components generated by pixel variation or the like without reading the noise signal in the solid-state imaging device.

  In the present embodiment, a single-plate solid-state image sensor having a plurality of types of color filters provided in one solid-state image sensor is used. For example, a three-plate solid-state image sensor having a solid-state image sensor for each RGB color filter As described above, a solid-state imaging device having the same color filter may be provided for each type of color filter. At this time, as shown in FIG. 20, instead of the solid-state imaging device 2 of FIG. 1, a solid-state imaging device 2r in which R pixels are provided in all pixels, a solid-state imaging device 2g in which G pixels are provided in all pixels, A solid-state imaging device 2b in which all pixels are provided with a B filter is provided. Therefore, the line 25r is connected to all the pixels of the solid-state imaging device 2r, the line 25g is connected to all the pixels of the solid-state imaging device 2g, and the line 25b is connected to all the pixels of the solid-state imaging device 2b. Is connected.

These are block diagrams which show the structure of the imaging device which is embodiment of this invention. These are figures which show the arrangement | sequence of the color filter provided in a solid-state image sensor. These are graphs showing level conversion characteristics for edge components in a coring circuit. FIG. 3 is a circuit block diagram for explaining the overall configuration of the solid-state imaging device. These are circuit diagrams which show one structural example of the pixel which comprises the solid-state image sensor of FIG. These are timing charts showing the operation of the pixel of FIG. These are graphs showing the relationship between the luminance of a subject and the output of a pixel. These are block diagrams which show an example of an internal structure of an AE / WB evaluation value detection circuit. These are block diagrams which show the internal structure of a whole control part. These are graphs showing the relationship between luminance values of RGB signals and signal levels. These are figures for showing operation of a WB evaluation value operation part. These are figures for showing operation of a WB evaluation value operation part. These are block diagrams which show the other example of an internal structure of an AE * WB evaluation value detection circuit. These are figures which show an example of the photoelectric conversion characteristic of the RB signal stored in the memory of a whole control part. These are figures which show the relationship of the photoelectric conversion characteristic of the detected RGB signal. These are the figures which show the relationship of the photoelectric conversion characteristic of the RGB signal converted after photoelectric conversion characteristic detection. FIG. 5 is a diagram for explaining an operation of generating photoelectric conversion characteristics. These are block diagrams showing an example of the internal configuration of the WB control circuit. These are block diagrams which show the other example of the internal structure of a WB control circuit. These are block diagrams which show another structure of the imaging device which is embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical system 2 Solid-state image sensor 3 Amplifier 4 AD conversion circuit 5 Black reference correction circuit 6 FPN correction circuit 7 AE / WB evaluation value detection circuit 8 WB control circuit 9 Color interpolation circuit 10 Color correction circuit 11 Gradation conversion circuit 12 Coring Circuit 13 Overall control unit 14 Aperture control unit 15 Timing generation circuit

Claims (14)

Provided with a plurality of pixels that can be switched between a first state that outputs an electrical signal that changes linearly with respect to the amount of incident light and a second state that outputs an electrical signal that changes logarithmically with respect to the amount of incident light. In an imaging apparatus comprising: a solid-state imaging device provided with a type of color filter; and a white balance circuit that performs white balance processing on a color signal for each type of the color filter output from the solid-state imaging device.
When one of the plurality of types of color signals is used as a reference first color signal and a color signal other than the reference color signal is used as a second color signal,
In the solid-state imaging device,
The pixel that outputs the first color signal and the pixel that outputs the second color signal have the same luminance value at the switching point between the first state and the second state,
In the white balance circuit,
For each type of the second color signal, a signal level with respect to a luminance value serving as a switching point between the first state and the second state of the second color signal is set as a threshold level,
Identifying whether the photoelectric conversion characteristic of the second color signal is a linear conversion characteristic according to the first state or a logarithmic conversion characteristic according to the second state based on the threshold level;
An image pickup apparatus that performs white balance processing on the second color signal in accordance with the identified photoelectric conversion characteristics. The white balance circuit is
A comparator that compares the signal level of the second color signal with the threshold level for the second color signal to confirm the photoelectric conversion characteristics of the second color signal;
It said second color signal of the linear conversion characteristic, a first operation unit that converts, based on a linear conversion characteristic of said first signal,
A second operation unit of the second color signal of the logarithmic conversion characteristics, that converts, based on the logarithmic conversion characteristic of the first signal,
When the photoelectric conversion characteristic of the second color signal is confirmed to be the linear conversion characteristic by the comparator, the signal from the first arithmetic unit is selected and output, and the second color signal is output by the comparator. When it is confirmed that the photoelectric conversion characteristic of the color signal is the logarithmic conversion characteristic, a selection unit that selects and outputs a signal from the second calculation unit;
The imaging apparatus according to claim 1, further comprising:   The first arithmetic expression used for white balance processing in the white balance circuit for each of the second color signals, the parameter to the second arithmetic expression, and the threshold level for identifying the photoelectric conversion characteristics of the second color signal The imaging apparatus according to claim 2, further comprising: a control unit configured to send the parameter and the threshold level to the white balance circuit. The white balance circuit is
A color signal detector for confirming the type of the color signal;
A parameter setting unit that switches between the parameter given to the first and second computing units and the threshold level given to the comparator for each type of the second color signal;
With
The parameter given by the control unit for each type of the second color signal and the threshold level are switched by the parameter setting unit for each type of the second color signal detected by the color signal detection unit. The image pickup apparatus according to claim 3, wherein white balance processing is performed for each type of the second color signal by giving the first and second arithmetic units and the comparator. The white balance circuit includes the comparison unit, the first and second calculation units, and the selection unit for each type of the second color signal,
The parameter and the threshold level given for each type of the second color signal from the control unit are the first and second arithmetic units and the comparator provided for each type of the second color signal. The imaging apparatus according to claim 3, wherein the imaging apparatus is provided. The first calculation unit is a multiplier for multiplying a first calculation value set by the parameter;
The imaging apparatus according to claim 2, wherein the second calculation unit is an adder that adds a second calculation value set by the parameter. The first color signal input from the solid-state image sensor for each type of the second color signal, with an evaluation value representing the relationship between the photoelectric conversion characteristic of the first color signal and the photoelectric conversion property of the second color signal. And an evaluation value detection circuit for detecting from the relationship of the signal level of the second color signal,
The parameter, the threshold level, and a luminance value serving as a switching point between the first state and the second state are set based on the evaluation value and a photoelectric conversion characteristic of the first color signal. The imaging device according to any one of claims 1 to 6.   In the evaluation value detection circuit, for each type of the second color signal, the evaluation value is calculated based on the relationship between the average values of the first color signal and the second color signal given from the solid-state imaging device. The imaging apparatus according to claim 7, wherein the imaging apparatus is obtained. In the evaluation value detection circuit,
For each type of the second color signal,
A first evaluation value is obtained based on the relationship between the average value of each of the first color signal and the second color signal that linearly changes with respect to the amount of incident light applied from the solid-state imaging device,
Based on the relationship between the average value of each of the first color signal and the second color signal logarithmically changed with respect to the amount of incident light applied from the solid-state imaging device, a second evaluation value is obtained.
An evaluation value representing a relationship between a photoelectric conversion characteristic of the first color signal and a photoelectric conversion characteristic of the second color signal is obtained by weighted addition of the first evaluation value and the second evaluation value. The imaging device according to claim 7.   The weighting coefficient in the weighted addition is set based on the relationship between the number of pixels that output a signal that linearly changes with respect to the incident light amount and the number of pixels that output a signal that changes logarithmically with respect to the incident light amount. The imaging apparatus according to claim 9. While determining the photoelectric conversion characteristics of the first color signal based on the dynamic range of the solid-state imaging device,
The imaging apparatus according to claim 7, wherein the photoelectric conversion characteristic of the second color signal is determined based on the photoelectric conversion characteristic of the first color signal and the evaluation value.   When the evaluation value is obtained by the evaluation value detection circuit, the photoelectric conversion characteristics in the respective types of color signals output from the solid-state imaging device are the same signal level between the linear conversion characteristics and the logarithmic conversion characteristics. The imaging device according to claim 7, wherein the solid-state imaging device is driven so as to be switched.   The imaging device according to claim 1, wherein the solid-state imaging device is a single-plate solid-state imaging device in which a plurality of types of color filters are provided for each pixel.   The imaging device according to claim 1, wherein the solid-state imaging device is formed of a plurality of plates of solid-state imaging devices for each of a plurality of different types of color filters.

Images