JP5404346B2 - Imaging apparatus, electronic scope, and electronic endoscope system - Google Patents

Description

  The present invention relates to an imaging device having a function of removing fixed pattern noise of a solid-state imaging device, an electronic scope having the imaging device, and an electronic endoscope system having the electronic scope.

In recent years, imaging devices equipped with solid-state imaging elements have become widespread. As a representative solid-state imaging device, for example, CMOS (Complementary Metal) that is inexpensive, has low power consumption, and is excellent in mass productivity.
Oxide Semiconductor) image sensors are known. However, the CMOS image sensor has a problem that the image quality deteriorates due to a large fixed pattern noise. The fixed pattern noise here is noise that is unavoidably generated by each pixel. Causes of the occurrence of fixed pattern noise include, for example, variations in transistor characteristics for each pixel, dark current generated regardless of the amount of incident light, and the like.

  A general image processing circuit that processes output charges of a CMOS image sensor holds in advance fixed pattern noise data of an on-board CMOS evaluated at the manufacturing stage in order to improve image quality degradation due to this type of noise. . The image processing circuit subtracts the corresponding fixed pattern noise data from the imaging data of each pixel output from the CMOS image sensor, and removes noise that differs for each pixel. In the following description, the fixed pattern noise data held by the image processing circuit is referred to as “noise removal data” in order to avoid confusion with the fixed pattern noise potentially possessed by the CMOS image sensor.

  In this type of imaging apparatus, the fixed pattern noise to be removed changes according to the gain of the signal amplifier arranged at the subsequent stage of the CMOS image sensor. When the noise removal data is a fixed value, the fixed pattern noise after the change cannot be completely removed, so that the image quality deterioration due to the remaining noise is unavoidable. Therefore, for example, Patent Document 1 proposes an imaging apparatus that corrects noise removal data according to the gain of a signal amplifier.

JP 2003-18475 A

  By the way, in an analog circuit configuration such as a signal amplifier, individual component differences, changes with time, use environment (temperature), and the like are also cited as causes for changing fixed pattern noise. The change of the fixed pattern noise due to this kind of cause and the change of the fixed pattern noise at the time of gain adjustment appear in combination. Therefore, for example, in order to satisfactorily remove fixed pattern noise that changes in accordance with the gain, the gain change rate is simply reflected in the noise removal data (for example, when the gain is set to 2 times, the noise removal data is also 2). However, it is necessary to correct the noise removal data in consideration of individual differences in signal amplifier components, changes with time, temperature dependence, and the like. However, it is difficult to predict the cause of these changes, and it is virtually impossible to prepare correction data in advance. That is, in the imaging device described in Patent Document 1, since the noise removal data cannot be corrected appropriately, image quality deterioration due to remaining noise is inevitable.

  Further, Patent Document 1 describes a configuration in which a temperature sensor is mounted in an imaging device in order to correct noise removal data in consideration of the temperature dependence of components. However, for example, in a small-sized imaging device such as an electronic scope, it is difficult to place components such as a temperature sensor near the CMOS image sensor due to restrictions on mounting space. As described above, the imaging device described in Patent Document 1 has a drawback that it is not suitable for downsizing design.

  Further, in order to satisfactorily remove fixed pattern noise that changes due to multiple causes, a mechanical shutter that temporarily shields the CMOS image sensor is required. However, if the mechanical shutter is disposed in the vicinity of the CMOS image sensor, the electronic scope becomes large and cannot be easily adopted.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an imaging apparatus suitable for correcting noise removal data in accordance with changes in fixed pattern noise. Another object of the present invention is to provide an electronic scope that is one form of equipment suitable for mounting the imaging apparatus, and an electronic endoscope system having the electronic scope.

  An imaging apparatus according to an aspect of the present invention that solves the above problems includes a solid-state imaging device, noise removal data holding means that holds noise removal data corresponding to the fixed pattern noise, and a part of the solid-state imaging device. It has pixel light shielding means for shielding the pixels. In this imaging apparatus, the noise removal data correction unit corrects the noise removal data based on the signal ratio between the imaging signal value of the light-shielded pixel and the signal value of the light-shielded pixel expressed by the noise removal data. This signal ratio is a value based on an actual measurement value via a peripheral circuit (for example, an analog amplifier) of the solid-state imaging device. For this reason, the corrected noise removal data reflects individual differences in components of the peripheral circuit such as an analog amplifier, changes with time, temperature dependency, and the like. Therefore, the fixed pattern noise included in the imaging signal output from the solid-state imaging device is, for example, the noise removal data corrected by the fixed pattern noise removing unit regardless of the gain of the analog amplifier, individual component differences, aging, temperature dependency, etc. It is removed favorably by the removal process using.

  The pixel shading means includes a low-brightness image pick-up means that operates a solid-state imaging device to pick up a low-brightness image so that some pixels are substantially light-shielding pixels, and the picked-up low-brightness image is divided into a plurality of regions. A low-luminance image dividing means for dividing; a low-luminance area selecting means for selecting a predetermined number of low-luminance areas having a low luminance from a plurality of divided areas; and a predetermined condition for the predetermined number of low-luminance areas selected It may be configured to include a condition determination unit that determines whether or not the condition is satisfied and a light-shielding pixel considering unit that regards a predetermined number of pixels in the low luminance region as light-shielding pixels when it is determined that the predetermined condition is satisfied.

  When a low-brightness image is picked up by the low-brightness image pickup unit, the solid-state image sensor may be operated at the highest electronic shutter speed in order to minimize the exposure amount.

  The low-brightness image capture means captures multiple low-brightness images and generates a single low-brightness image by averaging multiple low-brightness images in order to satisfactorily remove random noise that may be included in the low-brightness image. May be. In this case, the low luminance image dividing means divides the generated low luminance image into a plurality of regions.

  In order to determine whether or not the signal values of all the selected low-luminance areas are distributed at a low value, the imaging apparatus according to the present invention calculates standard deviation calculation means for calculating the standard deviation of the signal values of these low-luminance areas It is good also as a structure which further has. In this case, the predetermined condition means that the standard deviation of the signal value in the low luminance region is not more than a predetermined threshold.

  According to another aspect, the imaging apparatus according to the present invention determines whether or not the signal values of all the selected low-luminance regions are distributed at a low value, so that the standard deviation of the signal values of these low-luminance regions is determined. And a calculation means for calculating an average value of the signal values. In this case, the predetermined condition means that the standard deviation and average value of the signal value in the low luminance region are equal to or less than the first and second threshold values, respectively.

  The pixel light shielding means may be a light shielding film that coats a part of the pixels in the solid-state imaging device. The light-shielding film may be formed by coating pixels outside the effective pixel area of the solid-state imaging device so that black dots do not appear in the captured image.

  The solid-state imaging device assumed in the imaging device according to the present invention is, for example, a CMOS image sensor.

  An electronic scope according to an embodiment of the present invention that solves the above-described problems is a device in which the imaging device according to any one of the above is mounted at the distal end of the insertion portion.

  An electronic endoscope system according to an aspect of the present invention that solves the above problems includes the electronic scope, and a signal processing device that performs predetermined signal processing on an imaging signal that is output from the electronic scope and after removal of fixed pattern noise. It is a system with In order to avoid a dark image being suddenly presented to the surgeon during the low-brightness image pick-up by the low-brightness image pick-up means, this signal processing device outputs the image to the external monitor immediately before picking up the low-brightness image. To fix.

  According to the present invention, an imaging apparatus suitable for correcting noise removal data in accordance with a change in fixed pattern noise is provided.

1 is an external view of an electronic endoscope system according to an embodiment of the present invention. It is a block diagram which shows the structure of the electronic endoscope system of embodiment of this invention. It is a block diagram which shows the structure of the driver signal processing circuit which the electronic scope of embodiment of this invention has, and its peripheral circuit. It is a flowchart which shows the noise removal data correction process for removing the fixed pattern noise performed in embodiment of this invention. It is a flowchart which shows the noise removal data correction process for removing the fixed pattern noise performed in another embodiment.

  Hereinafter, an electronic endoscope system having an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an external view of an electronic endoscope system 1 according to the present embodiment. As shown in FIG. 1, the electronic endoscope system 1 includes an electronic scope 100 for photographing a subject. The electronic scope 100 includes a flexible tube 11 covered with a flexible sheath (outer skin) 11a. Connected to the distal end of the flexible tube 11 is a distal end portion 12 that is sheathed by a rigid resin casing. The bending portion 14 at the connecting portion between the flexible tube 11 and the distal end portion 12 is remotely operated from the hand operating portion 13 connected to the proximal end of the flexible tube 11 (specifically, the rotation of the bending operation knob 13a). The operation is flexible. This bending mechanism is a well-known mechanism incorporated in a general electronic scope, and is configured to bend the bending portion 14 by pulling the operation wire in conjunction with the rotation operation of the bending operation knob 13a. When the direction of the distal end portion 12 changes according to the bending operation by the above operation, the imaging region by the electronic scope 100 moves.

  As shown in FIG. 1, the electronic endoscope system 1 has a processor 200. The processor 200 is an apparatus that integrally includes a signal processing device that processes a signal from the electronic scope 100 and a light source device that illuminates a body cavity that does not reach natural light via the electronic scope 100. In another embodiment, the signal processing device and the light source device may be configured separately.

  The processor 200 is provided with a connector portion 20 corresponding to the connector portion 10 provided at the proximal end of the electronic scope 100. The connector unit 20 has a coupling structure corresponding to the connector unit 10 and is configured to electrically and optically connect the electronic scope 100 and the processor 200.

  FIG. 2 is a block diagram showing a configuration of the electronic endoscope system 1. As shown in FIG. 2, the electronic endoscope system 1 includes a monitor 300 connected to the processor 200 via a predetermined cable. In FIG. 1, the monitor 300 is not shown in order to simplify the drawing.

  As illustrated in FIG. 2, the processor 200 includes a system controller 202 and a timing controller 204. The system controller 202 controls each element constituting the electronic endoscope system 1. The timing controller 204 outputs a clock pulse for adjusting the signal processing timing to various circuits in the electronic endoscope system 1.

  The lamp 208 emits white light after being started by the lamp power igniter 206. As the lamp 208, a high-intensity lamp such as a xenon lamp, a halogen lamp, a mercury lamp, or a metal halide lamp is suitable. Illumination light emitted from the lamp 208 is collected by the condenser lens 210, is limited to an appropriate amount of light through the diaphragm 212, and enters an incident end of an LCB (light carrying bundle) 102.

  A motor 214 is mechanically connected to the diaphragm 212 via a transmission mechanism such as an arm or a gear (not shown). The motor 214 is a DC motor, for example, and is driven under the drive control of the driver 216. The diaphragm 212 is operated by the motor 214 to change the opening degree so that the image displayed on the monitor 300 has an appropriate brightness, and the amount of illumination light emitted from the lamp 208 is limited according to the opening degree. To do. The appropriate reference for the brightness of the image is changed according to the brightness adjustment operation of the front panel 218 by the operator. Note that the dimming circuit that controls the brightness by controlling the driver 216 is a well-known circuit and is omitted in this specification.

  Illumination light incident on the incident end of the LCB 102 propagates by repeating total reflection inside the LCB 102. The illumination light that has propagated through the LCB 102 is emitted from the exit end of the LCB 102 disposed at the tip of the electronic scope 100. The illumination light emitted from the exit end of the LCB 102 illuminates the subject via the light distribution lens 104. The reflected light from the subject forms an optical image on the light receiving surface of the solid-state image sensor 108 via the objective lens 106.

  The solid-state image sensor 108 is, for example, a single-plate color CMOS image sensor having a Bayer-type pixel arrangement, accumulates an optical image formed by each pixel on the light receiving surface as charges corresponding to the amount of light, and R, G, B Are converted into imaging signals corresponding to the respective colors. The converted image signal is amplified by an analog amplifier AP in an AFE (Analog Front End) 110, is AD-converted, and is input to the driver signal processing circuit 112.

  Here, the brightness of the image is normally adjusted by dimming control on the light source side. Therefore, the electronic shutter speed of the solid-state image sensor 108 and the gain of the analog amplifier AP are basically fixed values. However, the electronic shutter speed or gain is changed under certain conditions, for example, when camera shake correction is performed or when the brightness of the subject changes abruptly. For example, when camera shake correction is performed, the electronic shutter speed of the solid-state image sensor 108 is increased. At this time, the mechanical elements such as the diaphragm 212 or the motor 214 are delayed in following a sudden change. As a result, the brightness of the video sharply decreases due to insufficient exposure. In order to avoid this, the gain of the analog amplifier AP is increased only for a temporary period until the aperture 212 reaches the target opening, and the brightness of the image is increased to an appropriate level.

  FIG. 3 is a block diagram showing the configuration of the driver signal processing circuit 112 and its peripheral circuits. In FIG. 3, the driver signal processing circuit 112 is connected to the solid-state imaging device 108 or the AFE 110, but the connection to other circuits is omitted to simplify the drawing.

  As shown in FIG. 3, the driver signal processing circuit 112 includes a scope control unit 30, an image processing engine 32, a flash ROM (Read Only Memory) 34, an SDRAM (Synchronous Dynamic Random Access Memory) 36, and a DA converter 38. doing.

  The scope control unit 30 accesses the memory 114 and reads unique information of the electronic scope 100. The unique information of the electronic scope 100 includes, for example, the number of pixels and sensitivity of the solid-state image sensor 108, a compatible rate, a model number and the like. The scope control unit 30 outputs the unique information read from the memory 114 to the system controller 202.

  The system controller 202 performs various calculations based on the unique information output from the scope control unit 30 and generates a control signal. The system controller 202 uses the generated control signal to control the operation and timing of various circuits in the processor 200 so that processing suitable for the electronic scope (here, the electronic scope 100) connected to the processor 200 is performed. To do. The system controller 202 may be configured to have a table in which a model number of the electronic scope is associated with control information suitable for the electronic scope of this model number. In this case, the system controller 202 refers to the control information in the correspondence table, and controls the operation and timing of various circuits in the processor 200 so that processing suitable for the electronic scope connected to the processor 200 is performed.

  The timing controller 204 supplies clock pulses to the scope control unit 30 according to the timing control by the system controller 202.

  The scope control unit 30 drives and controls the solid-state imaging device 108 at a timing synchronized with the frame rate of the video processed on the processor 200 side in accordance with the clock pulse supplied from the timing controller 204. The scope control unit 30 also controls the operation of the image processing engine 32 according to the clock pulse of the timing controller 204. The image processing engine 32 executes the noise removal data correction process shown in the flowchart of FIG. 4 to correct the noise removal data in order to satisfactorily remove the fixed pattern noise of the solid-state imaging device 108 that changes due to various causes. . In the following description and drawings in this specification, the processing step is abbreviated as “S”.

  The noise removal data correction process shown in FIG. 4 is periodically executed, for example, during system startup. However, in order to save resources, the execution timing of the noise removal data correction process may be limited to immediately after the system is started or to a specific timing. As the specific timing here, for example, the above-described timing for performing camera shake correction, the timing at which the brightness of the subject rapidly changes, and the like are assumed.

  The image processing engine 32 has a noise removal data correction circuit 32a. In the processing of S1, the noise removal data correction circuit 32a reads the noise removal data by accessing the flash ROM 34 periodically, immediately after system startup, or at a specific timing for changing the gain of the analog amplifier AP. In the flash ROM 34, default noise removal data corresponding to the fixed pattern noise of the solid-state imaging device 108 evaluated in the manufacturing stage is stored in advance.

  In the noise removal data correction processing of FIG. 4, in order to remove fixed pattern noise satisfactorily, it is necessary to temporarily shield the pixels of the solid-state image sensor 108. However, because of the characteristics of the CMOS image sensor, it is difficult to completely block the pixels during operation. According to another expression, in the CMOS image sensor, it is difficult to set the exposure time by the electronic shutter to 0 hours. Therefore, a configuration equipped with a mechanical shutter can be considered. When a mechanical shutter is used, the pixels can be completely shielded from light. However, a general electronic scope, which is a small imaging device, does not have a space for mounting a mechanical shutter. Therefore, the scope control unit 30 operates the solid-state imaging device 108 at the highest electronic shutter speed when the execution of the noise removal data correction process in FIG. 4 starts. The maximum speed of the electronic shutter of the solid-state image sensor 108 is, for example, 1/12000 (unit: s).

  In the process of S2, a predetermined number (for example, a plurality) of low-luminance image data captured at the highest electronic shutter speed is input to the noise removal data correction circuit 32a. At this time, since the low-brightness image passes through the analog amplifier AP, the fixed pattern noise increases in accordance with the gain together with the imaging signal of the subject and is input to the noise removal data correction circuit 32a. Note that during acquisition of a low-luminance image, in order to avoid suddenly presenting a dark image to the surgeon, an output image to the monitor 300 is displayed immediately before the start of the noise removal data correction processing in FIG. It may be fixed to the image immediately before imaging.

  In the process of S3, the noise removal data correction circuit 32a generates a single low-brightness image by averaging the obtained predetermined number of low-brightness images. By this averaging process, random noise is satisfactorily removed. The larger the number of low-luminance images used in the averaging process, the higher the effect of removing random noise. On the other hand, the processing load on the image processing engine 32 is reduced as the number of low-luminance images used for the averaging process is smaller. If priority is given to reducing the latter processing burden, the low-luminance image acquired in the processing of S2 may be one. In the processing after S3, the defective pixel (the pixel address is stored in advance in, for example, the flash ROM 34) may be excluded from the calculation target and the processing may proceed.

  In the process of S4, the noise removal data correction circuit 32a selects a light shielding area candidate that can be regarded as being substantially in a light shielding state from the low-brightness image (effective pixel area) after the averaging process. This process is executed by the following procedure, for example.

The noise removal data correction circuit 32a divides the low-brightness image after the averaging process into a total of 256 areas of 16 × 16. Denoising the data correction circuit 32a, for all of the divided regions, computing the average value S _AV of the image signal values of the pixels constituting the region. Denoising the data correction circuit 32a selects the divided region of an average image signal value S _AV low 16 as a candidate of the light shielding area from 256 divided regions.

In the process of S5, the noise removal data correction circuit 32a calculates an average value AV and standard deviation σ of the average image signal value S _AV shading region candidates has been selected 16. The noise removal data correction circuit 32a determines whether or not the calculated standard deviation σ and average value AV are both equal to or less than a predetermined threshold (each threshold is an independent value). When the standard deviation σ and the average value AV are both equal to or smaller than the predetermined threshold value (S5: YES), the 16 light shielding area candidates are regarded as light shielding areas, and the process proceeds to S6. If at least one of the standard deviation σ or the average value AV exceeds a predetermined threshold (S5: NO), it is determined that there is no light-shielding area, the low-luminance image is discarded, and the process returns to S2. The average image signal value S _AV shading region candidate, no problem even branded mostly distributed in an absolute low. Therefore, whether or not the light shielding area candidate is a light shielding area may be determined based only on the standard deviation σ. In this case, the calculation processing of the average value AV and the like can be omitted, which contributes to reducing the processing load on the image processing engine 32. Further, the determination of the light shielding area using the standard deviation σ and the average value AV has higher determination accuracy than the determination of the light shielding area using only the standard deviation σ. Therefore, the threshold for the standard deviation σ in the former determination may be larger than the threshold for the standard deviation σ in the latter determination.

In the process of S6, the noise removal data correction circuit 32a calculates a predetermined signal ratio R for each constituent pixel of all the light shielding regions. The signal ratio R is defined as, for example, a value obtained by dividing the imaging signal value of the target pixel by the signal value of the target pixel expressed by default noise removal data. The noise removal data correction circuit 32a then calculates an average value R _AV of the calculated signal ratio R. Denoising the data correction circuit 32a multiplies the default noise removal data by the average signal ratio R _AV, corrects the noise removal data. The signal ratios R which are away from the mean signal ratio R _AV than the predetermined value is excluded from the calculation target, it may be calculated again average signal ratio R _AV.

  In the process of S7, the noise removal data correction circuit 32a stores (or overwrites) the corrected noise removal data (hereinafter referred to as “corrected noise removal data”) in the SDRAM 36, and the noise removal data of FIG. The correction process is terminated.

The image processing engine 32 has a fixed pattern noise removal circuit 32b. The fixed pattern noise removal circuit 32b accesses the SDRAM 36 and reads the corrected noise removal data. The fixed pattern noise removal circuit 32b subtracts the signal value expressed by the corrected noise removal data from the imaging signal value output from the AFE 110. Here, the average signal ratio R _AV is generated based on the actually measured value via the analog amplifier AP. For this reason, the average signal ratio R _AV is not an ideal gain of the analog amplifier AP, but is an actual measurement that incorporates various causes of changes in fixed pattern noise such as individual differences in the analog amplifier AP, changes over time, temperature dependency, and the like. The value corresponds to a large gain. Therefore, even corrected noise removal data corrected by using the average signal ratio R _AV, these changes cause is woven. Therefore, in the subtraction process by the fixed pattern noise removing circuit 32b, the fixed pattern noise changed from the default is satisfactorily removed.

  The image processing engine 32 has an image processing circuit 32c. The imaging signal after removal of the fixed pattern noise is input to the image processing circuit 32c. The image processing circuit 32 c performs predetermined signal processing such as clamping, knee, γ correction, interpolation processing, and AGC (Auto Gain Control) on the imaging signal, and outputs the processed signal to the DA converter 38. The imaging signal is output to the signal processing circuit 220 of the processor 200 after DA conversion by the DA converter 38.

  The signal processing circuit 220 performs predetermined processing on the imaging signal output from the DA converter 38 and buffers the image signal in a frame memory (not shown) in units of frames. The buffered signal is swept from the frame memory at a timing controlled by the timing controller 204, and converted into a video signal conforming to a predetermined standard such as NTSC (National Television System Committee) or PAL (Phase Alternating Line). Is done. As the converted video signals are sequentially input to the monitor 300, a color image of the subject is displayed on the monitor 300. The color image displayed on the monitor 300 has no deterioration in image quality because the fixed pattern noise of the solid-state image sensor 108 is satisfactorily removed by the image processing engine 32.

  As described above, according to the present embodiment, fixed pattern noise that changes due to various causes is satisfactorily removed with a simple circuit configuration. Moreover, it is not necessary to mount components such as a temperature sensor and a mechanical shutter for removing fixed pattern noise. That is, according to the present embodiment, the peripheral circuit of the solid-state image sensor 108 is not complicated, and the number of parts around the solid-state image sensor 108 can be reduced, which is advantageous for downsizing of the image pickup apparatus.

  The above is the description of the embodiment of the present invention. The present invention is not limited to the above-described configuration, and various modifications can be made within the scope of the technical idea of the present invention. For example, fixed pattern noise also exists in a CCD (Charge Coupled Device). Therefore, the present invention can also be applied to an image pickup apparatus equipped with a CCD.

  FIG. 5 is a flowchart showing a noise removal data correction process executed in another embodiment. The electronic endoscope system 1 according to another embodiment is an optical black pixel in which a part of pixels (at least one pixel) of the solid-state imaging device 108 are completely shielded from light by a light shielding film (for example, an aluminum light shielding film). The configuration is substantially the same as that of the above-described embodiment. The optical black pixels are preferably arranged outside the effective pixel region so that they do not appear as black spots in the captured image.

As shown in FIG. 5, in the process of S11, the default noise removal data is read in the same manner as the process of S1 of FIG. In another embodiment, the flash ROM 34 stores default noise removal data corresponding to fixed pattern noise of the solid-state image sensor 108 including optical black pixels. In the process of S12, as in the process of S2 of FIG. 4, a predetermined number (at least one) of image data is input to the noise removal data correction circuit 32a. In the process of S13, the input image data is averaged as in the process of S3 of FIG. In the process of S14, a predetermined signal ratio R is calculated for each optical black pixel, as in the process of S6 of FIG. The signal ratio R in this case is defined as a value obtained by dividing the imaging signal value of the optical black pixel after the averaging process by the signal value expressed by the default noise removal data of the optical black pixel. Next, an average value R _AV of the signal ratio R is calculated. Denoising the data correction circuit 32a multiplies the default noise removal data by the average signal ratio R _AV, corrects the noise removal data. In the process of S15, the corrected noise removal data is written to the SDRAM 36 as in the process of S7 of FIG.

In another embodiment, it is not necessary to execute a process for specifying a light shielding area, which is advantageous in terms of the processing burden of the image processing engine 32. In another embodiment, the average signal ratio R _AV is generated based on the actually measured value via the analog amplifier AP as in the above-described embodiment. Therefore, in the subtraction process by the fixed pattern noise removing circuit 32b, the fixed pattern noise changed from the default is satisfactorily removed.

DESCRIPTION OF SYMBOLS 1 Electronic endoscope system 32 Image processing engine 100 Electronic scope 108 Solid-state image sensor 110 AFE
200 processor AP analog amplifier

Claims (8)

A solid-state image sensor;
Noise removal data holding means holding noise removal data corresponding to the fixed pattern noise of the solid-state imaging device;
Pixel shading means for shielding a part of the pixels in the solid-state imaging device;
Noise removal data correction means for correcting the noise removal data based on a signal ratio between the image signal value of the light-shielded light-shielded pixel and the signal value of the light-shielded pixel represented by the noise removal data;
Fixed pattern noise removing means for removing fixed pattern noise included in an imaging signal output from the solid-state imaging device, using the noise removal data after correction;
I have a,
The pixel shading means is
A low-brightness image pickup means for picking up a low-brightness image by operating the solid-state image sensor;
Low luminance image dividing means for dividing the captured low luminance image into a plurality of regions;
Low-luminance area selection means for selecting a predetermined number of low-luminance areas having low luminance from the plurality of divided areas;
Condition determination means for determining whether or not the selected predetermined number of low-luminance regions satisfy a predetermined condition;
When it is determined that the predetermined condition is satisfied, a light-shielded pixel considering unit that regards the pixels of the predetermined number of low-luminance regions as the light-shielded pixels;
To have a,
Imaging device. The low luminance image capturing means includes
Operating the solid-state imaging device at the highest electronic shutter speed ;
The imaging device according to claim 1 . The low luminance image capturing means includes
Taking a plurality of the low brightness images,
Average the plurality of low-brightness images to generate a single low-brightness image,
The low luminance image dividing means includes
Dividing the generated single low-luminance image into the plurality of regions ;
The imaging device according to claim 1 or 2 . A standard deviation calculating means for calculating a standard deviation of signal values of the predetermined number of low-luminance regions;
The predetermined condition is
The calculated standard deviation is less than or equal to a predetermined threshold ;
The imaging apparatus according to any one of claims 1 to 3. A calculation means for calculating a standard deviation of signal values of the predetermined number of low-luminance regions and an average value of the signal values;
The predetermined condition is
The calculated standard deviation and the average value are equal to or less than the first and second threshold values, respectively .
The imaging apparatus according to any one of claims 1 to 3. The solid-state imaging device is
A CMOS image sensor ,
The imaging device according to any one of claims 1 to 5 . The imaging device according to any one of claims 1 to 6 is mounted at a distal end of an insertion portion .
Electronic scope. An electronic scope according to claim 7 ;
A signal processing device that performs predetermined signal processing on the imaging signal after removal of fixed pattern noise output by the electronic scope;
Have
The signal processing device includes:
During the low-brightness image capturing by the low-brightness image capturing means, the output to the external monitor is fixed to the image immediately before capturing the low-brightness image .
Electronic endoscope system.

Images