JP2011055336A - Imaging apparatus and signal processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus improving an image quality by matching black levels of fields when signals are read out in a plurality of fields. <P>SOLUTION: The imaging apparatus includes a solid-state image sensor 5 including: a valid pixel part 51 for receiving subject light to generate an electric charge; and an OB pixel part 53 which is light-shielded for output of a signal for black level determination. The imaging apparatus further includes: an imaging device drive unit 10 for performing driving to read signals from the solid-state image sensor 5 by separating the signals into a plurality of fields; a clamp circuit 82 for clamping an OB signal obtained from the OB pixel part 53 among imaging signals output from the solid-state image sensor 5 in the respective fields; and a black level difference correction unit 19 for performing correction to reduce a difference of black levels determined in accordance with the clamped OB signal in the respective fields based on at least a valid signal obtained from the valid pixel part 51 among imaging signals output form the solid-state image sensor 5 in the respective fields (S91, S92, S93). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and a signal processing method.

  FIG. 15 is a schematic plan view showing a schematic configuration of a general CCD (Charge Coupled Device) type solid-state imaging device. A pixel region 100 including an effective pixel unit 200, an OB unit 300, and an OB unit 400 is formed on a semiconductor substrate such as silicon.

  In the pixel region 100, a large number of lines in which a large number of photoelectric conversion elements such as photodiodes are arranged in the horizontal direction are arranged in the vertical direction orthogonal to the horizontal direction.

  The charge generated in each photoelectric conversion element in the pixel region 100 is read out to a vertical charge transfer path (not shown) in the pixel region 100 and is transferred here in the vertical direction. The charge for one line that has been transferred through the vertical charge transfer path is transferred in the horizontal direction by the horizontal charge transfer path 500. At the end of the horizontal charge transfer path 500, an output unit 600 such as a floating diffusion amplifier (FDA) that converts charges into a voltage signal (hereinafter also referred to as an imaging signal) proportional to the charge amount is provided. The charges transferred in the horizontal direction are converted into voltage signals by the output unit 600 and output to the outside.

  The OB portion 400 is a region where several lines at the end of the pixel region 100 on the horizontal charge transfer path 500 side are shielded from light. Each photoelectric conversion element formed in the OB unit 400 forms an OB pixel region for outputting a signal for determining a black level.

  The OB unit 300 is a region in which several photoelectric conversion elements at the end opposite to the output unit 600 side of each line except for several lines constituting the OB unit 400 are shielded from light. Each photoelectric conversion element formed in the OB unit 300 also forms an OB pixel region for outputting a signal for determining a black level.

  The effective pixel portion 200 is a region where photoelectric conversion elements other than the photoelectric conversion elements in the OB portion 300 and the OB portion 400 are formed. An opening is formed in the light-shielding film above each photoelectric conversion element of the effective pixel unit 200, from which subject light is incident. Each photoelectric conversion element formed in the effective pixel unit 200 forms an effective pixel region that is a region that receives light from the subject and generates charges. Hereinafter, an imaging signal output from the effective pixel area is also referred to as an effective signal, and an imaging signal output from the OB pixel area is also referred to as an OB signal.

  In an image pickup apparatus equipped with such an image pickup device, an OB signal obtained from the OB unit 300 among image pickup signals for one horizontal line output from the image pickup device is set to a predetermined target level (hereinafter referred to as a clamp level). Clamping is performed, and subsequent signal processing is performed based on the clamp level. In this signal processing, an average value of all the obtained OB signals is set as a black level, and offset correction is performed by subtracting the black level from the effective signal.

  When clamping with the OB signal obtained from the OB unit 300 as described above, the dark current in the vertical charge transfer path is greatly different between the center and the left and right of the pixel region 100 at high temperatures. The difference in the black level increases. In order to reduce the difference in black level, a technique is known in which clamping is performed using an OB signal obtained from the OB unit 400.

  However, in recent imaging devices, the number of OB signals that can be output in one field is reduced due to the increase in the number of pixels, so that the number of OB signals that can be output in one field is reduced. Even if it is clamped, the black level cannot be accurately determined. The number of photoelectric conversion elements included in the OB unit 400 may be increased. However, if the number of photoelectric conversion elements in the effective pixel unit 200 is increased in response to the increase in the number of pixels, the number of photoelectric conversion elements included in the OB unit 400 is not much. Many cannot be secured. For this reason, even if the black level is determined by the OB signal obtained from the OB unit 400, a new problem of black level variation due to the small number of OB signals per field occurs.

  Patent Documents 1 and 2 disclose an imaging device that determines a black level for each field based on a signal obtained from an OB pixel region or a signal obtained from an effective pixel region during light-shielding photographing. In the method of determining the black level based on the signal obtained from the effective pixel area, light-shielded photographing is required in addition to the main photographing, and power consumption and photographing time are excessive. In the method of determining the black level based on the signal obtained from the OB pixel region, if a plurality of fields are read out, the number of OB pixel regions from which signals are read out in one field is reduced, so that it is difficult to accurately determine the black level. .

Japanese Patent Laid-Open No. 11-196335 JP 11-220750 A

  The present invention has been made in view of the above circumstances, and provides an imaging apparatus and a signal processing method capable of improving image quality by aligning black levels between fields when signals are read out in a plurality of fields. With the goal.

  The imaging device of the present invention is an imaging device having a solid-state imaging device including an effective pixel region that receives a subject light and generates a charge, and a light-shielded OB pixel region for outputting a signal for determining a black level. A driving unit that performs driving to read signals from the solid-state imaging device in a plurality of fields, and an OB signal obtained from the OB pixel region among imaging signals output from the solid-state imaging device in each field; A clamping unit to be clamped and an effective signal obtained from at least the effective pixel region among imaging signals output from the solid-state imaging device in each field, and determined according to the OB signal clamped in each field A black level difference correction unit that performs correction to reduce the difference of the black level for each field.

  The signal processing method of the present invention is output from a solid-state imaging device including an effective pixel region that receives a subject light and generates an electric charge, and a shielded OB pixel region for outputting a signal for determining a black level. A signal processing method for processing a signal, comprising: a driving step for driving a signal to be read out in a plurality of fields from the solid-state imaging device; and an OB pixel among imaging signals output from the solid-state imaging device in each field A clamping step for clamping the OB signal obtained from the region, and at least a valid signal obtained from the effective pixel region among the imaging signals output from the solid-state imaging device in each field, And a black level difference correction step for performing correction for reducing the difference of each black level determined in accordance with the OB signal.

  According to the present invention, it is possible to provide an imaging apparatus and a signal processing method that can improve image quality by aligning black levels between fields when signals are read in a plurality of fields.

The figure which shows schematic structure of the imaging device for describing one Embodiment of this invention FIG. 1 is a schematic plan view showing a schematic configuration of a solid-state image sensor in the digital camera shown in FIG. The figure which showed the example of an arrangement | sequence of the photoelectric conversion element contained in the pixel area | region of the solid-state image sensor shown in FIG. The figure which showed the example of an arrangement | sequence of the photoelectric conversion element contained in the pixel area | region of the solid-state image sensor shown in FIG. The figure which shows the internal structure of the AD conversion part in the digital camera shown in FIG. The figure which showed the level of the dark signal obtained from one line of the pixel area of a solid-state image sensor at high temperature The figure which showed the operation state of the solid-state image sensor, and the state of a clamp pulse when the image sensor drive part in the digital camera shown in FIG. 1 divides into 3 fields and reads an image signal from a solid-state image sensor The flowchart explaining the operation until the digital camera shown in FIG. 1 performs offset correction. Flowchart for explaining the operation of the black level difference correction unit at the time of field-by-field offset correction The flowchart for demonstrating the modification of the process which the black level difference correction | amendment part in the digital camera shown in FIG. 1 implements. The flowchart for demonstrating the modification of the process (process which calculates | requires the integration average of an effective signal for every field) which the black level difference correction | amendment part in the digital camera shown in FIG. 1 implements. Diagram showing an example of pixel area division The flowchart for demonstrating the process (process which calculates | requires the integration average of an effective signal and an OB signal for every field) which the black level difference correction | amendment part in the digital camera shown in FIG. 1 implements. The flowchart for demonstrating the modification of the process which the black level difference correction | amendment part in the digital camera shown in FIG. 1 implements. A schematic plan view showing a schematic configuration of a general CCD (Charge Coupled Device) type solid-state imaging device.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an imaging apparatus for explaining an embodiment of the present invention. Examples of the imaging device include an imaging device such as a digital camera and a digital video camera, an imaging module mounted on an electronic endoscope, a camera-equipped mobile phone, and the like. Here, a digital camera will be described as an example.

  The imaging system of the digital camera shown in the figure includes a photographic lens 1, a CCD type solid-state imaging device 5, a diaphragm 2 provided therebetween, an infrared cut filter 3, and an optical low-pass filter 4.

  A system control unit 11 that performs overall control of the entire electric control system of the digital camera controls the lens driving unit 13 to adjust the position of the photographing lens 1 to a focus position or to perform zoom adjustment, and through the aperture driving unit 12. The amount of exposure is adjusted by controlling the aperture of the diaphragm 2.

  In addition, the system control unit 11 drives the solid-state imaging device 5 via the imaging device driving unit 10 and outputs a subject image captured through the photographing lens 1 as an imaging signal. An instruction signal from the user is input to the system control unit 11 through the operation unit 14.

  The electric control system of the digital camera further includes a CDS processing unit 6 that performs correlated double sampling processing connected to the output of the solid-state imaging device 5 and a VGA 7 that performs signal amplification connected to the output of the CDS processing unit 6. An A / D conversion unit 8 that converts an imaging signal output from the VGA 7 into a digital signal is provided, and these are controlled by the system control unit 11.

  Furthermore, the electric control system of this digital camera generates image data by performing main memory 16, memory control unit 15 connected to main memory 16, interpolation calculation, gamma correction calculation, RGB / YC conversion processing, and the like. A digital signal processing unit 17, a compression / decompression processing unit 18 that compresses image data generated by the digital signal processing unit 17 into a JPEG format or expands compressed image data, and a black that corrects a black level difference for each field. A level difference correction unit 19, an external memory control unit 20 to which a detachable recording medium 21 is connected, and a display control unit 22 to which a liquid crystal display unit 23 mounted on the back of the camera or the like is connected.

  The memory control unit 15, the digital signal processing unit 17, the compression / decompression processing unit 18, the black level difference correction unit 19, the external memory control unit 20, and the display control unit 22 are connected to each other by a control bus 24 and a data bus 25. It is controlled by a command from the system control unit 11.

  FIG. 2 is a schematic plan view illustrating a schematic configuration of the solid-state imaging element in the imaging apparatus illustrated in FIG. 1. A pixel region 50 including an effective pixel portion 51, an OB portion 52, and an OB portion 53 is formed on a semiconductor substrate such as silicon.

  In the pixel region 50, a plurality of lines in which a plurality of photoelectric conversion elements such as photodiodes are arranged in the horizontal direction are arranged in the vertical direction orthogonal to the horizontal direction.

  The charge generated in each photoelectric conversion element in the pixel region 50 is read out to a vertical charge transfer path (not shown) in the pixel region 50 and transferred here in the vertical direction. The charge for one line transferred through the vertical charge transfer path is transferred in the horizontal direction by the horizontal charge transfer path 54. At the end of the horizontal charge transfer path 54, an output unit 55 such as a floating diffusion amplifier (FDA) is provided that converts the charge into a voltage signal proportional to the amount of charge (hereinafter also referred to as an imaging signal) and outputs the voltage signal. The charges transferred in the horizontal direction are converted into voltage signals by the output unit 55 and output to the outside.

  The OB portion 53 is a region where several lines at the end of the pixel region 50 on the horizontal charge transfer path 54 side are shielded from light. Each photoelectric conversion element formed in the OB portion 53 forms an OB pixel region for outputting a signal for determining a black level.

  The OB part 52 is an area where several photoelectric conversion elements at the end opposite to the output part 55 side of each line except for several lines constituting the OB part 53 are shielded from light.

  The effective pixel portion 51 is a region where photoelectric conversion elements other than the photoelectric conversion elements in the OB portion 52 and the OB portion 53 are formed. An opening is formed in the light-shielding film above each photoelectric conversion element of the effective pixel portion 51, and subject light enters from here. Each photoelectric conversion element formed in the effective pixel portion 51 forms an effective pixel region that is a region that receives the subject light and generates charges. Hereinafter, an imaging signal output from the effective pixel area is also referred to as an effective signal, and an imaging signal output from the OB pixel area is also referred to as an OB signal.

  3 and 4 are diagrams illustrating an example of the arrangement of the photoelectric conversion elements included in the pixel region 50 of the solid-state imaging element illustrated in FIG. The blocks with “R” shown in FIGS. 3 and 4 indicate photoelectric conversion elements having a red color filter above the light receiving surface. A block with “G” indicates a photoelectric conversion element having a green color filter above the light receiving surface. The block with “B” indicates a photoelectric conversion element having a blue color filter above the light receiving surface. The block with “r” shown in FIG. 4 indicates a photoelectric conversion element having a red color filter above the light receiving surface. The block with “g” indicates a photoelectric conversion element having a green color filter above the light receiving surface. The block with “b” indicates a photoelectric conversion element having a blue color filter above the light receiving surface.

  In the example shown in FIG. 3, a Bayer array color filter is provided above the photoelectric conversion elements 51 a arranged in a square lattice pattern in the horizontal direction and the vertical direction. In the example shown in FIG. 4, the photoelectric conversion elements 51a arranged in a square lattice pattern in the horizontal direction and the vertical direction and the photoelectric conversion elements 51b arranged in a square lattice pattern are arranged at the arrangement pitch of each photoelectric conversion element. The arrangement is shifted in the horizontal and vertical directions by ½. The color filter array above the photoelectric conversion element 51a is a Bayer array, and the color filter array above the photoelectric conversion element 51b is also a Bayer array. In the configuration shown in FIG. 4, the photoelectric conversion element 51 a and the photoelectric conversion element 51 b provided with the color filters of the same color are adjacent to each other to form a pair, and a signal obtained from the pair is combined to process the dynamic range. And higher sensitivity can be achieved. Further, when the synthesis process is not performed, a high resolution image can be obtained.

  In the solid-state imaging device 5, readout electrodes are arranged so that imaging signals can be read out from the photoelectric conversion elements included in the pixel region 50 in a plurality of fields. In the digital camera, the image sensor driving unit 10 performs driving for reading the image signal from the solid-state image sensor 5 in a plurality of fields.

  FIG. 5 is a diagram showing an internal configuration of the AD conversion unit 8 in the digital camera shown in FIG. The AD conversion unit 8 includes an ADC 81 and a clamp circuit 82.

  The ADC 81 converts the imaging signal output from the VGA 7 into a digital signal.

  The clamp circuit 82 is a circuit that clamps the OB signal of the imaging signal output from the ADC 81 to a predetermined target level, and includes a correction amount calculation circuit 82a and an addition circuit 82b.

  The correction amount calculation circuit 82a compares the OB signal after digital conversion with the target level, calculates an error from the target level of the OB signal, and outputs a correction amount that eliminates this error to the addition circuit 82b. The addition circuit 82b adds the correction amount output from the correction amount calculation circuit 82a to the OB signal before digital conversion. The correction amount calculation circuit 82a operates in accordance with a clamp pulse that is at a high level during a period in which the OB signal is output from the solid-state imaging device 5, and performs a clamp process only on the OB signal.

  In this digital camera, the system control unit 11 supplies the clamp pulse to the correction amount calculation circuit 82a during the period when the OB signal is output from the OB unit 53. That is, the OB signal output from the OB unit 53 is clamped, and the subsequent offset correction processing is performed on the basis of the level of the OB signal after clamping. This offset correction processing includes uniform offset correction and field-specific offset correction, and these corrections are performed by the digital signal processing unit 17.

  The uniform offset correction is a correction in which an average value of all OB signals obtained by imaging is set as a black level, and this black level is subtracted from an effective signal obtained by imaging. The field-specific offset correction is a correction in which the average value of the OB signal obtained for each field is set as the black level of the field, and the black level is subtracted from the effective signal obtained in the field.

  FIG. 6 is a diagram showing the dark signal level obtained from one line of the pixel region 50 of the solid-state imaging device 5 at a high temperature. As shown in FIG. 6, at the time of high temperature, the dark signal obtained from the effective pixel unit 51 sinks at the center in the horizontal direction, and the difference from the level of the dark signal obtained from the OB unit 52 becomes large. .

  When clamping is performed with the OB signal obtained from the OB unit 52, the level indicated by “b” in FIG. 6 becomes the black level. For this reason, it is difficult to accurately perform offset correction. The dark signal obtained from the OB portion 53 has substantially the same waveform as the dark signal obtained from the effective pixel portion 51 shown in FIG. Therefore, when the OB signal obtained from the OB unit 53 is clamped, the black level becomes the level indicated by “a” in FIG. 6, and the offset correction is more accurate than when the OB signal obtained from the OB unit 52 is clamped. Can be done.

  For this reason, the digital camera shown in FIG. 1 clamps the OB signal obtained from the OB unit 53.

  FIG. 7 shows the operation state of the solid-state image sensor 5 and the state of the clamp pulse when the image sensor drive unit 10 reads the image signal from the solid-state image sensor 5 in a plurality of fields (three fields in the example of FIG. 7). FIG.

  When an imaging instruction is given, exposure of the solid-state imaging device 5 is started. When the exposure is completed, sweeping drive for sweeping out charges existing in the vertical charge transfer path is performed. When the sweeping drive is completed, idle transfer of the vertical charge transfer path and the horizontal charge transfer path is performed. When the empty transfer is completed, reading of the first field is started. Among the imaging signals read out in the first field, the clamp pulse becomes high level during the period in which the OB signal from the OB unit 53 is output, and the clamp process is performed. Thereafter, reading of the second field and reading of the third field are performed, and the OB signal from the OB unit 53 is similarly clamped. The imaging signal obtained in each field is stored in the main memory 16.

  Next, the operation at the time of offset correction performed by the digital signal processing unit 17 will be described.

  FIG. 8 is a flowchart for explaining operations until the digital camera shown in FIG. 1 performs offset correction.

  When the ISO sensitivity is manually set by the operation unit 14 or the ISO sensitivity is automatically set, the system control unit 11 determines whether or not the set ISO sensitivity is higher than a predetermined value (step S81). For example, when the ISO sensitivity can be set to 100, 200, 400, 800, 1600, it is determined whether or not the set ISO sensitivity is higher than 400.

  If the ISO sensitivity is higher than the predetermined value (step S81: YES), the system control unit 11 instructs the digital signal processing unit 17 to perform field-specific offset correction (step S82). When the ISO sensitivity is equal to or lower than the predetermined value (step S81: NO), the system control unit 11 instructs the digital signal processing unit 17 to perform uniform offset correction (step S83).

  As described above, in the digital camera shown in FIG. 1, under the imaging conditions where the set ISO sensitivity is low and the black level difference for each field becomes inconspicuous, uniform offset correction is performed, the set ISO sensitivity is high, Under imaging conditions where the black level difference is conspicuous, field-specific offset correction is performed. As will be described later, the field-by-field offset correction requires more computation than the uniform offset correction, so by determining which correction is performed according to the ISO sensitivity in this way, it is possible to perform corrections that suit the imaging conditions. It becomes. Note that the field-specific offset correction may always be performed regardless of the ISO sensitivity.

  Next, the operation of the black level difference correction unit 19 at the time of field-by-field offset correction will be described.

  FIG. 9 is a flowchart for explaining the operation of the black level difference correction unit 19 at the time of field-by-field offset correction. When an imaging signal is output from the solid-state imaging device 5 and this imaging signal is stored in the main memory 16, the black level difference correction unit 19 is an effective signal among the imaging signals of an arbitrary field stored in the main memory 16. Is divided by the number of effective signals to calculate an integrated average of effective signals in an arbitrary field (step S91). The black level difference correction unit 19 calculates an integrated average of effective signals in each field. In the following, it is assumed that the imaging signals are read out from the solid-state imaging device 5 in n (n = 1, 2, 3) fields, and the integrated average of effective signals in the n fields is Field_n.

  Next, the black level difference correcting unit 19 obtains the difference of the integrated average in each field (step S92). The difference between the integrated averages corresponds to the difference in black level for each field. For example, using a certain field as a reference, the difference between the integrated average in the reference field and the integrated average in other fields is obtained. When the first field is used as a reference, the black level difference correction unit 19 performs an operation of {(Field_2)-(Field_1)}, {(Field_3)-(Field_1)}.

  Alternatively, the black level difference correction unit 19 obtains an integrated average (equivalent to the average of Field_1, Field_2, and Field_3) of effective signals obtained in all fields, and sets the reference value (referred to as Field_ave). Find the difference from the cumulative average in the field. For example, the calculation of {(Field_1)-(Field_ave)}, {(Field_2)-(Field_ave)}, {(Field_3)-(Field_ave)} is performed.

  Next, the black level difference correction unit 19 corrects the imaging signal level of each field so that the black level determined by the OB signal obtained in each field has the same value (step S93). For example, correction is performed according to the following formula (1) or (2).

Field_n_pix ′ = (Field_n_pix) − {(Field_n) − (Field_1)} (1)
Field_n_pix is the level of each imaging signal obtained in the n field Field_n_pix ′ is the corrected level of each imaging signal obtained in the n field n is a natural number of 2 or more

Field_n_pix ′ = (Field_n_pix) − {(Field_n) − (Field_avg)} (2)
Field_n_pix is the level of each imaging signal obtained in the n field. Field_n_pix ′ is the corrected level of each imaging signal obtained in the n field. N is a natural number of 1 or more.

  When the calculation of Expression (1) is performed, the difference between the accumulated average of the effective signals in the n field and the accumulated average of the effective signals in the 1 field is subtracted from the Field_n_pix, so that the average of the OB signals obtained in the n field is 1 The value is close to the average of the OB signals obtained in the field. Since the average of the OB signal is the black level, the difference in the black level determined by the OB signal obtained in each field can be reduced (substantially eliminated) by Expression (1).

  When the calculation of Expression (2) is performed, the difference between the integrated average of the effective signals in the n field and the integrated average of the effective signals in all fields is subtracted from the Field_n_pix, so that the average of the OB signals obtained in each field is almost equal. Be the same. Since the average of the OB signal is the black level, the difference in the black level determined by the OB signal obtained in each field can be reduced (substantially eliminated) by the equation (2).

  When the correction of the imaging signal according to Expression (1) or Expression (2) is completed, the digital signal processing unit 17 performs field-specific offset correction.

  The digital signal processing unit 17 obtains an integrated average of the OB signals in Field_n_pix ′ and determines this as a black level in the n field. Next, the digital signal processing unit 17 subtracts the black level in the n field from the valid signal in Field_n_pix ′, and performs offset correction of the imaging signal obtained in the n field. The digital signal processing unit 17 performs offset correction for each field by changing n to 1, 2, and 3, and ends the field-specific offset correction. After the black level difference is corrected, the black level is aligned for each field. Therefore, the average of the OB signals obtained in all fields may be set to the black level and the offset correction may be uniformly performed in all fields.

  As described above, according to the digital camera shown in FIG. 1, the difference in black level determined for each field can be corrected based on the effective signal obtained from the effective pixel unit 51. Since the number of effective signals is larger than the number of OB signals obtained from the OB pixel unit 53, the difference in black level can be corrected with high accuracy. Since this effective signal can be obtained without performing shaded photography, it is possible to reduce the photographing time and power consumption.

  Next, a modification of the digital camera shown in FIG. 1 will be described.

(First modification)
FIG. 10 is a flowchart for explaining a modification of the processing performed by the black level difference correction unit 19 in the digital camera shown in FIG.

  When an imaging signal is output from the solid-state imaging device 5 and this imaging signal is stored in the main memory 16, the black level difference correction unit 19 outputs effective signals for all fields stored in the main memory 16 to a plurality of areas. Divide into Next, the black level difference correction unit 19 selects an arbitrary area, calculates an integrated average of effective signals in the area (hereinafter, referred to as an integrated average in the area) (step S101), and calculates the calculated integrated in the area. It is determined whether or not the average is equal to or less than a threshold value (step S102).

  When the integrated average within the area is equal to or less than the threshold (step S102: YES), the black level difference correction unit 19 sets an area where the average integrated within the area is equal to or less than the threshold as the integration target area (step S103).

  If the integrated average within the area exceeds the threshold value (step S102: NO), the black level difference correction unit 19 does not set the area as an integration target area, and selects one of the unselected areas (step S109). ) In step S101, the integrated average of the effective signals in the selected area is obtained.

  After setting the integration target area, the black level difference correction unit 19 determines whether all divided areas have been selected (step S104). If not all areas have been selected (step S104: NO), the black level difference correction unit 19 moves the process to step S109.

  If all areas have been selected (step S104: YES), the black level difference correction unit 19 determines whether or not the number of integration target areas set in step S103 is equal to or greater than a threshold (step S105).

  When the number of product difference target areas is equal to or greater than the threshold (step S105: YES), the black level difference correction unit 19 performs the same process as step S91 shown in FIG. However, when the black level difference correction unit 19 calculates the integrated average of the effective signals for each field, the black level difference correction unit 19 excludes the effective signals in areas other than the integration target area from the target of the integrated average, and calculates the integrated average. Do. In other words, the black level difference correction unit 19 calculates the average of the effective signals obtained in the first field and the average of the effective signals obtained in the second field among the effective signals obtained from all the areas to be integrated. , And the average of the effective signals obtained in the third field are obtained (step S106). These three integrated averages are referred to as Field_1, Field_2, and Field_3, respectively.

  Next, the black level difference correction unit 19 calculates {(Field_n)-(Field_1)} or {(Field_n)-(Field_avg)}, similarly to step S92 of FIG. 9 (step S107), and formula (1) ) Or (2), the imaging signal of each field is corrected (step S108).

  If the number of areas to be integrated is less than the threshold value in step S105 (step S105: NO), in this case, most of the image is bright and image quality deterioration due to the black level difference for each field is not noticeable. Therefore, the black level difference correction unit 19 ends the process without correcting the black level difference of each field. After the processing is completed, the digital signal processing unit 17 uniformly performs offset correction for each field or for all fields.

  As described above, in the first modification, only the effective signal of the area whose area average is less than the threshold is used (in other words, the effective signal of the area where the area average exceeds the threshold is excluded) The black level difference of the field is corrected. The effective signal in the area where the integrated average in the area exceeds the threshold value has a high signal level due to a high-luminance subject, a defect in the element, or the like, and there is a possibility that no level difference occurs between fields. Therefore, by excluding such an effective signal from the effective signals used for correction, the difference in black level can be corrected with high accuracy.

  Further, when the number of areas to be integrated is small, correction of the black level difference can be omitted, so that the photographing time can be shortened and the power consumption can be reduced by reducing the calculation amount.

(Second modification)
In this modification, when the black level difference correction unit 19 calculates the average of effective signals obtained in each field in step S91 of FIG. 9 and step S106 of FIG. The average signal is calculated by excluding the effective signal whose signal level exceeds the threshold from the signal.

  FIG. 11 is a flowchart for explaining a modification of the processing (processing for obtaining an integrated average of effective signals for each field) performed by the black level difference correction unit 19 in the digital camera shown in FIG. FIG. 11 exemplifies a flow for obtaining an integrated average of effective signals in the first field.

  First, the black level difference correction unit 19 is one of all effective signals obtained in one field from the main memory 16 or one of effective signals obtained in one field from the integration target area. Is read (step S110). Next, the black level difference correction unit 19 determines whether or not the level of the read effective signal is equal to or less than a threshold value (step S111).

  When the level of the read effective signal is equal to or lower than the threshold (step S111: YES), the black level difference correction unit 19 sets the effective signal as an integration target signal (step S112). When the level of the read effective signal exceeds the threshold (step S111: NO), the black level difference correction unit 19 shifts the processing to step S110 without setting the effective signal as the integration target signal, and transfers one field. One effective signal that has not yet been read out is read out from all the effective signals obtained in step 1 or the effective signal obtained in one field from the integration target area.

  After setting the integration target signal in step S112, the black level difference correction unit 19 has read all the valid signals obtained in one field and all the valid signals obtained in one field from the integration target area. If it has not been read out (step S113: NO), the process proceeds to step S110, and the valid signal that has not been read out is read out.

  If all the valid signals have been read (step S113: YES), the integrated average is calculated by dividing the value obtained by integrating the effective signals set in the integration target signal in step S112 by the total number of the effective signals. (Step S114).

  In this way, even if there are high-luminance subjects or pixel defects, effective signals that exceed a certain level are excluded from the calculation target of integration average, and this effect is eliminated and black level difference correction is performed with high accuracy. It can be carried out.

(Third modification)
In the above description, in order to obtain the black level difference in each field, the accumulated average of the effective signals obtained in each field is used. However, the accumulated average including the OB signal in addition to the effective signal is obtained. Also good. That is, in the flowchart shown in FIG. 9, instead of obtaining the integration average of effective signals for each field in step S91, for each field, a value obtained by integrating all the effective signals and OB signals obtained in that field, A value obtained by dividing the effective signal and the total number of OB signals may be calculated as an integrated average (Field_n) in the field.

  Further, with reference to the flowchart shown in FIG. 10, the imaging signal output from the solid-state imaging device 5 is divided into a plurality of areas as shown in FIG. 12 before step S101. In Steps S102 and S103, among the divided areas of the effective signal, the integrated average within the area is equal to or less than the first threshold, and among the divided areas of the OB signal, the integrated average within the area is the second threshold (<the first threshold). The area below (one threshold value) is set as the integration target area. In step S106, for each field, a value obtained by integrating all the valid signals and OB signals of the integration target area obtained in the field is divided by the total number of valid signals and OB signals. What is necessary is just to calculate as an average (Field_n).

  In this way, by calculating the integrated average including the OB signal, the accuracy of the integrated average is increased, and the correction accuracy of the black level difference can be improved.

  9 and 10, it is preferable to exclude OB signals having a certain level or higher from the integration target even when the integrated average is calculated using the OB signal in addition to the valid signal. In this case, the fixed level is smaller than the fixed level that is a threshold value when the effective signal is excluded.

  FIG. 13 is a flowchart for explaining a process (a process for obtaining an integrated average of the effective signal and the OB signal for each field) performed by the black level difference correction unit 19 in the digital camera shown in FIG. FIG. 13 exemplifies a flow for obtaining the integrated average of the effective signal and the OB signal in the first field.

  First, the black level difference correction unit 19 selects one of all the effective signals and OB signals obtained in one field from the main memory 16 or the effective signal and OB obtained in one field from the integration target area. One of the signals is read (step S131). Next, the black level difference correction unit 19 determines whether the read signal is a valid signal or an OB signal (step S132).

  When the read signal is a valid signal (step S132: YES), the black level difference correction unit 19 determines whether the level of the valid signal is equal to or less than the threshold A (step S133). When the level of the effective signal is equal to or lower than the threshold A (step S133: YES), the black level difference correction unit 19 sets the effective signal as an integration target signal (step S134).

  When the level of the valid signal exceeds the threshold A (step S133: NO), the black level difference correction unit 19 shifts the process to step S131 without setting the valid signal as the integration target signal, and in one field. One of the valid signals and OB signals obtained or one of the valid signals and OB signals obtained in one field from the integration target area is read out.

  In step S132, when the read signal is an OB signal (step S132: NO), the black level difference correction unit 19 determines whether the level of the OB signal is equal to or less than a threshold B (<threshold A) (step S132). S137). When the level of the OB signal is equal to or less than the threshold value B (step S137: YES), the black level difference correction unit 19 sets the OB signal as an integration target signal (step S134).

  When the level of the OB signal exceeds the threshold B (step S137: NO), the black level difference correction unit 19 shifts the process to step S131 without setting the OB signal as the integration target signal, and obtains it in one field. Of all the valid signals and OB signals that have been received, or one of the valid signals and OB signals obtained in one field from the integration target area, one signal that has not yet been read out is read out.

  After setting the integration target signal, the black level difference correction unit 19 outputs all the valid signals and OB signals obtained in one field, and all the valid signals and OB signals obtained in one field from the integration target area. It is determined whether or not the data has been read. If the data has not been read (step S135: NO), the process proceeds to step S131 to read a signal that has not been read.

  When all the signals have been read (step S135: YES), the value obtained by integrating the valid signal and the OB signal set as the integration target signal in step S134 is divided by the total number of the valid signal and the OB signal. Then, the integrated average is calculated (step S136).

  In this way, even if there is a high-luminance subject or a pixel defect, the black level difference is corrected by excluding the effective signal and OB signal exceeding a certain level from the calculation target of the integrated average, even if there is a high-luminance subject or pixel defect. Can be performed with high accuracy. In addition, the defect signal can be effectively excluded from the integration target by making the threshold value when determining whether or not to exclude from the integration target between the valid signal and the OB signal.

(Fourth modification)
In the operation example shown in FIG. 10, only the area whose area average is less than or equal to the threshold is set as the area to be integrated. However, since it is difficult to detect a difference in black level in an area that is too dark, the black level difference correction accuracy can be further improved by excluding the black level difference from the integration target area. In this modification, the correction accuracy of the black level difference is improved by setting an area where the integrated average within the area exceeds the threshold as the integration target area.

  FIG. 14 is a flowchart for explaining a modification of the process performed by the black level difference correction unit 19 in the digital camera shown in FIG. The flowchart shown in FIG. 14 is the same as that shown in FIG. 10 except that the process of step S102 is changed to step S142.

  In step S142, the black level difference correction unit 19 determines whether the in-area integrated average is in a range larger than the threshold D and smaller than the threshold C (> threshold D). Then, if the integrated average within the area falls within this range, the process proceeds to step S103, the area is set as the integration target area, and the integrated average within the area is outside this range. Then, without setting the area as an integration target area, the process proceeds to step S109 and the next area is selected.

  Thus, by excluding the bright area and the dark area from the integration target area, it is possible to further improve the correction accuracy of the black level difference for each field.

  If the area where the OB signal is divided is also included as the integration target area, if the selected area is a divided area of the effective signal in step S142, the black level difference correction unit 19 includes the area within that area. It is determined whether or not the integrated average is larger than the threshold value D and smaller than the threshold value C. If the integrated average within the area falls within this range, the process proceeds to step S103, and is outside this range. If there is an integrated average within the area, the process proceeds to step S109.

  In step S142, when the selected area is a divided area of the OB signal, the black level difference correction unit 19 makes the integrated average within the area larger than the threshold E and smaller than the threshold F (> threshold E). If it is determined whether there is an integrated average within the area within this range, the process proceeds to step S103, and if there is an integrated average within the area, the process proceeds to step S109. To do. The threshold relationship is threshold E <threshold D and threshold F <threshold C.

  It should be noted that the upper limit of the threshold when determining the integration target area is eliminated, and an area where the integrated average within the area is larger than the threshold D and an area where the integrated average within the area is larger than the threshold E are set as the integration target areas. Also good. Even in this case, since the dark area can be excluded from the integration target area, the correction accuracy of the black level difference for each field can be further improved.

  Also in the flowchart shown in FIG. 14, in step S142, the upper limit of the threshold for determining the integration target area may be eliminated, and all areas having an in-area average greater than the threshold D may be set as the integration target area.

  In the above description, the solid-state imaging device 5 is a CCD type, but it may be a MOS type.

  Further, although the clamp circuit 82 clamps the OB signal output from the OB unit 53, the OB signal output from the OB unit 52 may be clamped. When the OB signal output from the OB unit 53 is clamped, the number of OB signals output in each field is relatively small, so that the black level difference for each field tends to be remarkable. For this reason, it is effective to employ the above-described field-specific offset correction.

  For example, in the photoelectric conversion element array shown in FIG. 3, when reading the first line and the third line in one field and reading the second line and the fourth line in two fields, integration of effective signals in each field. Deviations in the average may occur. This shift is not caused by a difference in black level but is caused by a difference in sensitivity due to the color filter.

  For this reason, when there is a possibility that the accumulated average of the effective signals may be shifted in this way, that is, driving in which the ratio of the color signals constituting the imaging signal output from the solid-state imaging device 5 is different in all fields It is preferable that only the effective signal of the color component (G signal in the example of FIG. 3) included in common in each field is the target of integration averaging.

  In the photoelectric conversion element array shown in FIG. 4, when driving to read a signal from the photoelectric conversion element 51a in one field and read a signal from the photoelectric conversion element 51b in two fields, all effective signals are integrated and averaged. It should be the target.

  In the photoelectric conversion element array shown in FIG. 4, when driving is performed to read out signals from 1, 2, 5, 6 lines in one field, and read signals from 3, 4, 7, 8 lines in two fields. In this case, only the G signal may be targeted for integration averaging.

  As described above, the following items are disclosed in this specification.

  The disclosed imaging device is an imaging device having a solid-state imaging device including an effective pixel region that receives a subject light and generates a charge, and a light-shielded OB pixel region for outputting a signal for determining a black level. A driving unit that performs driving to read signals from the solid-state imaging device in a plurality of fields, and an OB signal obtained from the OB pixel region among imaging signals output from the solid-state imaging device in each field; A clamping unit to be clamped and an effective signal obtained from at least the effective pixel region among imaging signals output from the solid-state imaging device in each field, and determined according to the OB signal clamped in each field A black level difference correction unit that performs correction to reduce the difference of the black level for each field.

  With this configuration, it is possible to correct a difference in black level for each field using an effective signal obtained from the effective pixel region. Since the number of effective signals is larger than the number of OB signals obtained from the OB pixel area, variations due to noise can be absorbed, and the black level difference for each field can be accurately corrected. As a result, it is possible to obtain an image quality having a black level for each field. In addition, since the effective signal can be obtained without performing light-shielded shooting, it is possible to reduce the shooting time and power consumption.

  In the disclosed imaging device, an average value of the effective signals in the area among the areas when the effective level is divided as the effective signal used by the black level difference correction unit is a first threshold value. Exclude valid signals in areas that exceed.

  With this configuration, it is possible to perform correction to reduce the difference in black level by eliminating information on an area where a bright subject is imaged, and it is possible to improve correction accuracy.

  In the disclosed imaging apparatus, the black level difference correction unit excludes an effective signal exceeding a certain level as the effective signal used for correction.

  With this configuration, correction can be performed by removing the effective signal from the effective pixel area and the defective effective pixel area that received strong subject light, and the correction accuracy can be improved.

  In the disclosed imaging device, the black level difference correction unit uses signals obtained from each of the effective pixel region and the OB pixel region among imaging signals output from the solid-state imaging device in each field. Then, correction is performed to reduce the difference in black level for each field determined according to the OB signal clamped in each field.

  With this configuration, correction that reduces the difference in black level is also performed using a signal obtained from the OB pixel region, so that the correction accuracy can be improved.

  In the disclosed imaging apparatus, the average value of the effective signals in the area of the first area when the black level difference correction unit divides the effective signal as the imaging signal used for correction is the first. Of the effective signal of the area exceeding the threshold and the second area when the OB signal is divided, the average value of the OB signal in the area exceeds the second threshold smaller than the first threshold. The OB signal is excluded.

  With this configuration, it is possible to perform correction to reduce the difference in black level by eliminating the information of the first area in which a bright subject is imaged and the second area including the defect signal, thereby improving the correction accuracy. it can.

  In the disclosed imaging apparatus, the black level difference correction unit uses the effective signal exceeding a third threshold and the OB signal exceeding a fourth threshold smaller than the third threshold as the imaging signal used for correction. Is excluded.

  With this configuration, the effective signal and the OB signal can be integrated except for the signals from the effective pixel area and the defective effective pixel area that have received strong subject light, and the correction accuracy can be improved.

  In the disclosed imaging device, an average value of the effective signals in the area is a second threshold value among the areas when the effective level is divided by the black level difference correction unit as the effective signal used for correction. Exclude valid signals in the following areas:

  With this configuration, it is possible to perform correction for reducing the difference in black level by eliminating the information of the blacked area, and it is possible to improve the correction accuracy.

  In the disclosed imaging apparatus, the black level difference correction unit includes a first area when the effective signal is divided as the imaging signal used for correction, and a second area when the OB signal is divided. Among these, the effective signal of the first area in which the average value of the effective signals in the area is equal to or smaller than the fifth threshold value, and the sixth value in which the average value of the OB signals in the area is smaller than the fifth threshold value. The OB signal in the second area that falls below the threshold is excluded.

  With this configuration, it is possible to perform correction for reducing the difference in black level by eliminating the information of the blacked area, and it is possible to improve the correction accuracy.

  In the disclosed imaging apparatus, the black level difference correction unit corrects from an average value of integrated values of the effective signals obtained in an n (n is a natural number of 2 or more) field of the effective signals used for correction. The average value of the integrated values of the effective signals obtained in one field of the effective signals used for the correction or the average value of the integrated values of the effective signals obtained in all the fields of the effective signals used for correction Correction for reducing the difference in black level is performed by subtracting the value obtained by subtraction from the imaging signal of the n-th field.

  In the disclosed imaging device, the black level difference correction unit averages the integrated values of the effective signal and the OB signal obtained in the n (n is a natural number of 2 or more) field of the imaging signal used for correction. From the value, the effective signal obtained in one field of the imaging signal used for correction and the average value of the integrated values of the OB signals or the effective value obtained in all the fields of the imaging signal used for correction Correction for reducing the black level difference is performed by subtracting the value obtained by subtracting the average value of the integrated value of the signal and the OB signal from the n-th field image pickup signal.

  In the disclosed imaging device, when the drive unit drives the solid-state imaging device so that the ratio of the color component signals constituting the imaging signal output from the solid-state imaging device does not match in all fields, The level difference correction unit excludes effective signals other than effective signals of the same color component that are commonly included in the imaging signals obtained in each field, as the effective signals used for correction.

  With this configuration, the level difference for each field of the effective signal used for correction can be suppressed, and the correction accuracy can be improved.

  In the disclosed imaging device, the effective pixel region and the OB pixel region are arranged two-dimensionally in the horizontal and vertical directions, and the effective pixel region is arranged two-dimensionally in the horizontal and vertical directions. The OB pixel region is disposed at an end portion in the vertical direction of the effective pixel region, and the driving unit is arranged in the horizontal direction of the effective pixel region and the OB pixel region that are two-dimensionally disposed. Drive is performed to read out signals in units of lines composed of regions.

  With this configuration, a difference in black level for each field is likely to occur, so that correction by the black level difference correction unit is particularly effective.

  The disclosed signal processing method is output from a solid-state imaging device including an effective pixel region that receives a subject light and generates a charge, and a light-shielded OB pixel region for outputting a signal for determining a black level. A signal processing method for processing a signal, comprising: a driving step for driving a signal to be read out in a plurality of fields from the solid-state imaging device; and an OB pixel among imaging signals output from the solid-state imaging device in each field A clamping step for clamping the OB signal obtained from the region, and at least a valid signal obtained from the effective pixel region among the imaging signals output from the solid-state imaging device in each field, And a black level difference correcting step for performing correction for reducing the difference of each black level determined in accordance with the OB signal. .

  In the disclosed signal processing method, in the black level difference correction step, as the effective signal used for correction, an average value of the effective signals in the area is first among the areas when the effective signal is divided. Exclude valid signals in areas that exceed the threshold.

  In the disclosed signal processing method, in the black level difference correction step, an effective signal exceeding a certain level is excluded as the effective signal used for correction.

  In the disclosed signal processing method, in the black level difference correction step, signals obtained from each of the effective pixel region and the OB pixel region among image signals output from the solid-state image sensor in each field are used. Thus, correction is performed to reduce the difference of the black level for each field determined according to the OB signal clamped in each field.

  In the disclosed signal processing method, in the black level difference correction step, as the imaging signal used for correction, an average value of the effective signals in the first area when the effective signal is divided is first. Of the effective signal in the area exceeding the threshold value and the second area when the OB signal is divided, the area where the average value of the OB signal in the area exceeds the second threshold value which is smaller than the first threshold value Are excluded.

  In the disclosed signal processing method, in the black level difference correction step, the effective signal exceeding the third threshold and the OB exceeding the fourth threshold smaller than the third threshold are used as the imaging signal used for correction. Exclude the signal.

  In the disclosed signal processing method, in the black level difference correction step, among the areas when the effective signal is divided as the effective signal used for correction, an average value of the effective signals in the area is a second value. Exclude valid signals in areas below the threshold.

  In the disclosed signal processing method, in the black level difference correction step, as the imaging signal used for correction, a first area when the effective signal is divided and a second area when the OB signal is divided Among these, the effective signal of the first area in which the average value of the effective signals in the area is less than or equal to a fifth threshold value, and the sixth value in which the average value of the OB signals in the area is smaller than the fifth threshold value The OB signal in the second area that falls below the threshold value is excluded.

  According to the disclosed signal processing method, in the black level difference correction step, from an average value of integrated values of the effective signals obtained in an n (n is a natural number of 2 or more) field of the effective signals used for correction, The average value of the integrated values of the effective signals obtained in one field of the effective signals used for correction or the average value of the integrated values of the effective signals obtained in all the fields of the effective signals used for correction By subtracting the value obtained by subtracting from the imaging signal of the nth field, correction for reducing the black level difference is performed.

  In the disclosed signal processing method, in the black level difference correcting step, the integrated value of the effective signal and the OB signal obtained in the n field (n is a natural number of 2 or more) of the imaging signals used for correction. From the average value, the effective signal obtained in one field of the imaging signals used for correction and the average value of the integrated values of the OB signals or the fields obtained in all the fields of the imaging signal used for correction Correction for reducing the difference in black level is performed by subtracting the value obtained by subtracting the average value of the integration value of the valid signal and the OB signal from the imaging signal of the n-th field.

  In the disclosed signal processing method, when the drive unit drives the solid-state image sensor so that the ratio of the color component signals constituting the image signal output from the solid-state image sensor does not match in all fields, In the black level difference correction step, effective signals other than the effective signals of the same color component that are commonly included in the imaging signals obtained in each field are excluded as the effective signals used for correction.

  In the disclosed signal processing method, the effective pixel region and the OB pixel region are arranged two-dimensionally in the horizontal and vertical directions, and the effective pixel region is arranged two-dimensionally in the horizontal and vertical directions. The OB pixel area is disposed at a vertical end of the effective pixel area. In the driving step, the effective pixel area and the OB pixel area arranged in a two-dimensional manner are arranged in a horizontal direction. Drive is performed to read out signals in units of lines composed of the aligned regions.

DESCRIPTION OF SYMBOLS 5 Solid-state image sensor 10 Image sensor drive part 19 Black level difference correction part 51 Effective pixel part 53 OB part 82 Clamp circuit

Claims (24)

An imaging apparatus having a solid-state imaging device including an effective pixel region that receives an object light and generates a charge, and a shielded OB pixel region for outputting a signal for determining a black level,
A drive unit for driving to read out signals from the solid-state imaging device in a plurality of fields;
Among the imaging signals output from the solid-state imaging device in each field, a clamp unit that clamps an OB signal obtained from the OB pixel region;
A black level field determined in accordance with the OB signal clamped in each field using at least an effective signal obtained from the effective pixel region among imaging signals output from the solid-state imaging device in each field. An imaging apparatus comprising: a black level difference correction unit that performs correction to reduce a difference for each. The imaging apparatus according to claim 1,
The effective signal of the area where the average value of the effective signal in the area exceeds the first threshold among the areas when the effective signal is divided as the effective signal used by the black level difference correction unit. Imaging device to be excluded. The imaging apparatus according to claim 1 or 2,
An imaging apparatus in which the black level difference correction unit excludes an effective signal exceeding a certain level as the effective signal used for correction. The imaging apparatus according to claim 1,
The black level difference correction unit is clamped in each field using a signal obtained from each of the effective pixel region and the OB pixel region among imaging signals output from the solid-state imaging device in each field. An image pickup apparatus that performs correction to reduce a difference of each black level determined in accordance with the OB signal. The imaging apparatus according to claim 4,
Effective signal of an area where the average value of the effective signals in the area exceeds the first threshold among the first areas when the effective signal is divided as the imaging signal used for correction by the black level difference correction unit And an imaging device that excludes OB signals in areas where the average value of the OB signals in the area exceeds the second threshold value, which is smaller than the first threshold value, among the second areas when the OB signal is divided . The imaging apparatus according to claim 4 or 5, wherein
An imaging apparatus in which the black level difference correction unit excludes the effective signal exceeding a third threshold and the OB signal exceeding a fourth threshold smaller than the third threshold as the imaging signal used for correction. The imaging apparatus according to any one of claims 1 to 3,
As the effective signal used for correction by the black level difference correction unit, among the areas when the effective signal is divided, an effective signal in an area where the average value of the effective signals in the area is equal to or smaller than a second threshold value is used. Imaging device to be excluded. The imaging apparatus according to any one of claims 4 to 6,
Of the first area when the effective signal is divided and the second area when the OB signal is divided as the imaging signal used for correction by the black level difference correction unit, the effective within the area The effective signal of the first area where the average value of the signal is less than or equal to the fifth threshold value, and the second signal where the average value of the OB signal in the area is less than or equal to the sixth threshold value which is less than the fifth threshold value An imaging device that excludes OB signals in the area. The imaging device according to claim 1, 2, 3, or 7,
Of the effective signals used for correction, the black level difference correction unit calculates from the average value of the integrated values of the effective signals obtained in the n (n is a natural number of 2 or more) field of the effective signals used for correction. A value obtained by subtracting the average value of the integrated values of the effective signals obtained in one field or the average value of the integrated values of the effective signals obtained in all the fields of the effective signals used for correction. An imaging apparatus that performs correction to reduce the difference in black level by subtracting from the imaging signal of the n-th field. The imaging device according to claim 4, 5, 6, or 8,
The black level difference correction unit uses the average value of the integrated values of the effective signal and the OB signal obtained in the n (n is a natural number of 2 or more) field of the imaging signals used for correction. Integration of the effective signal and the OB signal obtained in all the fields of the imaging signal used for the average value or correction of the integration value of the effective signal and the OB signal obtained in one field of the imaging signal An imaging apparatus that performs correction to reduce the difference in black level by subtracting a value obtained by subtracting an average value from an imaging signal of an n-th field. The imaging apparatus according to any one of claims 1 to 10,
When the drive unit drives the solid-state imaging device so that the ratio of the color component signals constituting the imaging signal output from the solid-state imaging device does not match in all fields,
The black level difference correction unit is an imaging apparatus that excludes effective signals other than effective signals of the same color component that are commonly included in imaging signals obtained in each field as the effective signals used for correction. The imaging device according to any one of claims 1 to 11,
The effective pixel area and the OB pixel area are two-dimensionally arranged in the horizontal and vertical directions,
The effective pixel region is arranged two-dimensionally in the horizontal and vertical directions,
The OB pixel region is disposed at an end portion in the vertical direction of the effective pixel region,
The image pickup apparatus that drives to read out signals in units of lines that are formed by horizontally arranging the effective pixel region and the OB pixel region arranged in a two-dimensional manner. A signal processing method for processing a signal output from a solid-state imaging device including an effective pixel region that receives an object light and generates a charge, and a shielded OB pixel region for outputting a signal for determining a black level. There,
A driving step for driving to read out signals from the solid-state imaging device in a plurality of fields;
A clamping step of clamping an OB signal obtained from the OB pixel area among imaging signals output from the solid-state imaging device in each field;
A black level field determined in accordance with the OB signal clamped in each field using at least an effective signal obtained from the effective pixel region among imaging signals output from the solid-state imaging device in each field. A signal processing method comprising: a black level difference correction step for performing correction for reducing a difference for each. The signal processing method according to claim 13, comprising:
In the black level difference correction step, as the effective signal used for correction, an effective signal of an area where the average value of the effective signals in the area exceeds the first threshold among the areas when the effective signal is divided is used. Signal processing method to exclude. The signal processing method according to claim 13 or 14,
In the black level difference correction step, a signal processing method for excluding an effective signal exceeding a certain level as the effective signal used for correction. The signal processing method according to claim 13, comprising:
In the black level difference correction step, among the imaging signals output from the solid-state imaging device in each field, signals obtained from each of the effective pixel region and the OB pixel region are clamped in each field. A signal processing method for performing correction for reducing a difference of the black level for each field determined according to the OB signal. The signal processing method according to claim 16, comprising:
In the black level difference correction step, as the imaging signal used for correction, the effective signal of the area where the average value of the effective signals in the area exceeds the first threshold among the first areas when the effective signal is divided And signal processing for excluding OB signals in areas where the average value of the OB signals in the area exceeds the second threshold, which is smaller than the first threshold, among the second areas when the OB signal is divided Method. The signal processing method according to claim 16 or 17,
In the black level difference correction step, a signal processing method of excluding the effective signal exceeding a third threshold and the OB signal exceeding a fourth threshold smaller than the third threshold as the imaging signal used for correction. The signal processing method according to any one of claims 13 to 15, comprising:
In the black level difference correction step, as the effective signal used for correction, among the areas when the effective signal is divided, an effective signal in an area where the average value of the effective signals in the area is equal to or smaller than a second threshold value is used. Signal processing method to exclude. The signal processing method according to any one of claims 16 to 18, comprising:
In the black level difference correction step, as the imaging signal used for correction, the effective area in the area is selected from the first area when the effective signal is divided and the second area when the OB signal is divided. The effective signal of the first area where the average value of the signal is less than or equal to the fifth threshold value, and the second signal where the average value of the OB signal in the area is less than or equal to the sixth threshold value which is less than the fifth threshold value Signal processing method for excluding the OB signal of the area. The signal processing method according to claim 13, 14, 15, or 19,
In the black level difference correction step, from the average value of the integrated values of the effective signals obtained in the n (n is a natural number of 2 or more) field of the effective signals used for correction, A value obtained by subtracting the average value of the integrated values of the effective signals obtained in one field or the average value of the integrated values of the effective signals obtained in all the fields of the effective signals used for correction. , A signal processing method for performing correction to reduce the difference in black level by subtracting from the imaging signal of the n-th field. The signal processing method according to claim 16, 17, 18, or 20,
In the black level difference correction step, the average value of the integrated value of the effective signal and the OB signal obtained in the n (n is a natural number of 2 or more) field of the imaging signals used for correction is used for correction. Integration of the effective signal and the OB signal obtained in all the fields of the imaging signal used for the average value or correction of the integration value of the effective signal and the OB signal obtained in one field of the imaging signal A signal processing method for performing correction to reduce the difference in black level by subtracting a value obtained by subtracting an average value from an imaging signal of an n-th field. The signal processing method according to any one of claims 13 to 22,
When the drive unit drives the solid-state imaging device so that the ratio of the color component signals constituting the imaging signal output from the solid-state imaging device does not match in all fields,
In the black level difference correcting step, a signal processing method for excluding effective signals other than effective signals of the same color component that are commonly included in imaging signals obtained in each field as the effective signals used for correction. The signal processing method according to any one of claims 13 to 23, wherein:
The effective pixel area and the OB pixel area are two-dimensionally arranged in the horizontal and vertical directions,
The effective pixel region is arranged two-dimensionally in the horizontal and vertical directions,
The OB pixel region is disposed at an end portion in the vertical direction of the effective pixel region,
A signal processing method in which, in the driving step, driving is performed to read out signals in units of lines composed of regions that are arranged in the horizontal direction of the effective pixel region and the OB pixel region arranged in two dimensions.

Images