JP2008263314A - Imaging device and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To capture an image of high picture quality at a low frame rate, using a simple configuration. <P>SOLUTION: A camera process section 14 makes nonlinear correction of imaging signals output from image sensors 13B, 13G, and 13R converting imaging light into the imaging signals, and a synchronous adding circuit 15 adds a predetermined number of frames of nonlinearly corrected imaging signals, frame by frame. Then a correcting circuit 17 corrects deviations in the correction characteristics of the nonlinear correction, caused by the addition by the synchronous adding circuit 15 for the imaging signal added by the predetermined number of frames, so that the corrected imaging signal is output or recorded. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging apparatus applied to a video camera capable of imaging at a low frame rate, and an imaging method applied to the imaging apparatus.

In the case of a video camera that obtains a video signal compliant with a format for television broadcasting or the like, the frame period for imaging with an imager is determined to be 1/60 seconds or 1/50 seconds. For example, in a video camera having a frame period of 1/60 seconds, the maximum period (so-called shutter period) in which the imager receives and accumulates imaging light of each frame is 1/60 seconds.
If a process called a so-called electronic shutter, which shortens the light receiving period of imaging light within one frame period, imaging with a high-speed shutter such as 1/100 second or 1/1000 second is possible. So-called low speed shutters longer than the frame period are usually not possible.

  In order to realize a shutter at a speed lower than 1/60 seconds, the imager receives long-term imaging light over a plurality of frame periods, and the signals received over the plurality of frame periods are received from the imager. It is possible by reading. For example, when a CCD (Charge Coupled Devices) type image sensor is used as an imager, it is possible to lengthen the period in which charges are accumulated in each pixel by receiving light. For example, a period in which charges are accumulated in each pixel is 1/30 second of a two-frame period, and a signal accumulated in 1/30 seconds is read, so that low-speed imaging can be performed with the accumulation period doubled. The imaging signal thus obtained is an intermittently changing video signal that changes every 1/30 second, which is twice the normal frame period. However, since the charge accumulation period is long, the sensitivity of the image signal is increased. High imaging is possible. For example, it is possible to capture an image in a dark situation such as at night. Here, an example of performing the process of accumulating twice the period has been described, but by adjusting the period for accumulating charges in the imager, imaging for a long time such as several tens of frame periods can be performed.

Patent Document 1 describes an example of an imaging apparatus that performs a process of adding frames and adding a frame rate.
JP 2005-39710 A

  However, as described above, when the period for accumulating charges in the light receiving element of the image sensor becomes long, the dynamic range of the correction function of the image sensor is insufficient, and the fixed pattern noise of the image sensor becomes an exposed image, or Since it is an intermittent image, an automatic control system such as white balance cannot be put into practical use, and the image quality is greatly deteriorated.

  In order to solve this problem, for example, a configuration in which the output of the image sensor is digitally added at the stage where the imaging signal output by the image sensor is a linear signal can be considered. The stage in which the imaging signal is linear is a stage in which the output of the image sensor is reflected as it is before various imaging signal processing such as white balance adjustment and gamma correction is performed.

  In order to add the output of the image sensor as it is, a frame memory that adds the output of the image sensor as it is is necessary. However, since the image signal output from the image sensor has a very high signal rate, In addition, an expensive memory is required.

When the signal of each frame is added after performing nonlinear conversion such as gamma correction, if the addition is simply performed, the nonlinear processing parameters will be shifted in each frame to be added, and as a video signal There is a problem that there is a high possibility of deterioration.
The process described in Patent Document 1 is configured to add the signals of each frame after performing non-linear conversion such as gamma correction. However, in Patent Document 1, the characteristics deteriorate when the signals are added after gamma correction. The issue is not mentioned.

  The present invention has been made in view of the above points, and an object of the present invention is to enable imaging at a low frame rate to achieve high image quality with a simple configuration.

  In the present invention, nonlinear correction is performed on an imaging signal extracted from an image sensor that converts imaging light into an imaging signal, and the imaging signal that has been subjected to the nonlinear correction is added a predetermined number of frames in units of frames. Then, the deviation of the correction characteristic of the nonlinear correction caused by the addition is corrected to the imaging signal added with the predetermined number of frames, and the corrected imaging signal is output or recorded.

  By performing such processing, the low-frame-rate imaging signal that has been corrected after the frame addition for the nonlinear correction such as gamma correction performed before the imaging signal is added to the frame and that has been subjected to the correct nonlinear correction is added. Can be obtained.

  According to the present invention, the non-linear correction such as gamma correction performed before adding the imaging signal to the frame is corrected after the frame addition. Therefore, the gamma correction before the frame addition is performed at the time of imaging without frame addition (that is, Non-linear correction can be performed with the same characteristics as during normal imaging without a low frame rate, and a signal subjected to correct non-linear correction can be obtained simply by adding a subsequent processing circuit after frame addition. Therefore, an image signal with a high image quality and a low frame rate that has been correctly subjected to gamma correction or the like can be obtained with a simple configuration in which only a few circuits are added to the conventional image pickup apparatus.

Hereinafter, an example of an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram illustrating a configuration example of an imaging apparatus according to an example of the present embodiment. The configuration will be described with reference to FIG. 1. The imaging light obtained through the lens 11 is separated into three primary colors by the prism 12, and the separated color imaging light is converted into blue, green, and red image sensors 13 </ b> B, The light is incident on the imaging surfaces of 13G and 13R. The imaging light imaged on the imaging surface of each color image sensor 13B, 13G, 13R is converted into an electrical signal by each image sensor 13B, 13G, 13R, and the converted electrical signal is read out. The electrical signals read from the image sensors 13B, 13G, and 13R are referred to as imaging signals.

  In FIG. 1, only one lens is shown in FIG. 1 for ease of explanation, but the lens 11 is actually composed of a plurality of (a plurality of groups) lenses and may be configured as a zoom lens. Although not shown, the iris, which is a diaphragm mechanism, is also arranged in the optical path of the lens 11. As the image sensors 13B, 13G, and 13R, for example, a CCD type image sensor or a CMOS type image sensor is used.

The imaging signals read from the image sensors 13B, 13G, and 13R are supplied to the camera process unit 14. In the camera process unit 14, various correction processes of the imaging signal are performed. The correction processing includes correction by linear signal processing and correction by non-linear signal processing. As linear signal processing, for example, there is white balance adjustment correction processing for adjusting the balance of blue, green, and red imaging signals. Examples of correction by nonlinear signal processing include gamma (γ) correction and knee correction. Gamma correction is a correction process that converts the luminance value of each color with a nonlinear input / output characteristic based on a gamma correction curve, and knee correction is a nonlinear correction process that adjusts the brightness of a bright part in an image. The correction by the nonlinear signal processing in the camera process unit 14 is a correction characteristic on the premise that no frame addition is performed.
The camera process unit 14 converts the primary color signals (hereinafter referred to as RGB signals) of blue, green, and red into imaging signals of luminance signals (hereinafter referred to as Y signals) and chroma signals (hereinafter referred to as C signals). And output from the camera process unit 14. These processes in the camera process unit 14 are executed under the control of the control unit 25.

  The imaging signals (Y signal and C signal) output from the camera process unit 14 are supplied to the changeover switch 27. The changeover switch 27 is a switch that switches according to the presence / absence of low frame rate imaging in conjunction with a changeover switch 28 described later. When the low frame rate imaging is not performed (that is, in the case of normal imaging), the output of the camera process unit 14 Is supplied to the codec section 19 via the changeover switches 27 and 28. The codec unit 19 performs codec processing for converting the supplied imaging signal into a video signal of a predetermined format, supplies the converted video signal to the recording system circuit 20, and records it on a recording medium (storage medium). . As a recording medium, various media such as a memory card, an optical disk, and a magnetic tape are applicable.

  When performing low frame rate imaging, the imaging signal output from the camera process unit 14 is supplied to the synchronous adder circuit 15 via the changeover switch 27. A frame buffer 24 composed of a frame memory is connected to the synchronous adder circuit 15, and processing for adding the supplied imaging signals in units of frames is performed. The number of added frames and the like are controlled by the control unit 25. The added imaging signal is read from the synchronous addition circuit 15 and supplied to the RGB conversion circuit 16. While the synchronous addition circuit 15 adds the image pickup signal for each frame to the frame buffer 24, the image pickup signal at the timing immediately before the image pickup signal being added is read out at a period of one frame, and RGB It is configured to supply to the conversion circuit 16. Details of this addition and reading state will be described later with reference to the timing chart of FIG.

The RGB conversion circuit 16 converts the supplied Y signal and C signal imaging signals into RGB signals. The converted RGB signal is supplied to the correction circuit 17. In the correction circuit 17, correction for correcting disturbance due to addition of nonlinear correction such as gamma correction and knee correction is performed for each primary color signal. Although the correction characteristics will be described later, the non-linear correction disturbance caused by the frame addition process is corrected. The characteristics to be modified vary according to the number of frames added in the synchronous adder circuit 15.
The RGB signal corrected by the correction circuit 17 is supplied to the YC conversion circuit 18 to be converted into a Y signal and a C signal, and the converted imaging signal is supplied to the codec unit 19 via the changeover switch 28. In the configuration of FIG. 1, the system from the synchronous addition circuit 15 to the YC conversion circuit 18 is not passed during imaging at a normal frame rate. For example, this system is also used during imaging at a normal frame rate. The passing configuration may be a configuration in which frame addition is not performed by the synchronous addition circuit 15.

  The imaging signal output from the camera process unit 14 and the imaging signal supplied to the changeover switch 28 are configured to be sent to the selector 21. Based on the control of the control unit 25, the imaging signal to be monitored by the selector 21 is selected. select. For example, when imaging at a low frame rate, the selector 21 selects an imaging signal obtained by the changeover switch 28 when monitoring an imaging signal captured at the low frame rate, and adds during imaging at the low frame rate. When monitoring an imaging signal of each frame that is not performed, the output of the camera process unit 14 is selected. During normal imaging, it is the same regardless of which imaging signal is selected.

  The imaging signal selected by the selector 21 is displayed on the display unit 23 after the frame rate conversion unit 22 performs frame rate conversion processing for monitoring or external output. Alternatively, the video signal converted by the frame rate conversion unit 22 is output from an output terminal (not shown). The conversion at the frame rate conversion unit 22 and the display at the display unit 23 are also executed under the control of the control unit 25. When the frame rate conversion unit 22 converts the frame rate, the frame buffer 24 is used as a temporary storage unit to perform conversion processing.

  The control unit 25 that controls the operation of each unit of the imaging apparatus is supplied with an operation command from an operation unit 26 including an operation switch and the like, and the imaging operation such as start and stop of imaging is controlled. A mode setting or the like is also set based on an operation on the operation unit 26. The image signal accumulation operation in the frame buffer 24 is also controlled by the control unit 24. The frame buffer 24 is a memory that stores the imaging signal in the form of a Y signal and a C signal.

  Here, with reference to FIG. 2, a configuration in the case where the frame buffer 24 is used as a storage circuit for synchronous addition is shown. The imaging signal obtained at the input terminal 24a is supplied to the adder 24c via the changeover switch 24b. The changeover switch 24b selects the side from which 0 data can be obtained instead of the input terminal 24a side during a period when the imaging signal is not added. The adder 24c adds outputs from the storage unit 24d. Then, the output of the adder 24c is supplied to and stored in the storage unit 24d. Then, the imaging signal stored in the storage unit 24d is output from the output terminal 24e. In the configuration shown in FIG. 2, the storage unit 24d stores one frame of the imaging signal, and the adder 24c adds the stored imaging signal to the input signal in synchronization with each frame. Thus, the signals imaged in each frame are added in order. Then, the imaging signal with the required number of frames added is output from the output terminal 24e. When the addition is performed in the frame buffer 24, the pixel positions to be added in each frame are set to be equal.

  FIG. 3 is a timing diagram illustrating an imaging operation when the addition processing is performed in the synchronous addition circuit 15 of the imaging apparatus of this example. The example of FIG. 3 is an example of adding three frames of imaging signals. FIG. 3A shows the frame period of the image pickup signal. As shown in FIG. 3B, the image pickup signals of the exposure period of 3 frames are added to form a signal of 1 frame. That is, the image sensor outputs of the three frame periods of the exposure periods 1.1, 1.2, and 1.3 are added, and the image pickup signal of frame number 1 obtained by adding three frames by the synchronous adder circuit 15 is obtained. The imaging signal of frame number 1 is output from the synchronous adder circuit 15 continuously for three frame periods. The image sensor outputs of the next three exposure periods 2.1, 2.2, and 2.3 are added to obtain an imaging signal of frame number 2 added with three frames by the synchronous addition circuit 15. The imaging signal of frame number 2 is also output from the synchronous adder circuit 15 continuously for three frame periods.

  In this way, the image signal that has been subjected to the addition of 3 frames has an exposure time of about three times that of the image signal at the time of normal imaging, and the image capture frame rate is as follows. The frame rate is 1/3, and good imaging can be performed even in a dark situation. However, the cycle of changing the image is also reduced to 1/3. In the example of FIG. 3, an example of adding three frames is shown, but the number of added frames can be any number of two or more frames. For example, when one frame is 1/60 second, if 60 frames are added, imaging can be performed at a low frame rate every second.

Next, gamma correction processing performed in the imaging apparatus of this example will be described with reference to FIG. 4A shows an ideal gamma correction state in the low frame rate mode, and FIG. 4B shows a gamma correction state in the low frame rate mode performed in this example. It is.
First, when an ideal gamma correction state is shown in FIG. 4A, the output of the imaging signal from the image sensor 1 is added k frames by the adder circuit 3 (k is the number of frames to be added), and then the gamma correction circuit. In 2a, by correctly performing gamma correction on the signal added with k frames, it is possible to obtain the image signal Ya that has been correctly gamma corrected.

  In order to obtain the same characteristics as the gamma correction shown in FIG. 4A, in this example, the processing shown in FIG. 4B is performed. That is, the output of the imaging signal from the image sensor 1 is gamma-corrected by the gamma correction circuit 2b with the same characteristics as those at the time of imaging at the normal frame rate, and the gamma-corrected imaging signal is Frame addition is performed (k is the number of frames to be added). After that, the output of the addition circuit 3 is supplied to the correction circuit 4 and corrected with the correction characteristic H (x) of the gamma characteristic to obtain an imaging signal with the corrected gamma characteristic, and finally k frames are added. To obtain an image signal Yb that has been correctly gamma-corrected. The correction circuit 4 corresponds to the correction circuit 17 in FIG.

Next, an actual gamma characteristic will be described with reference to a characteristic diagram. A gamma characteristic G11 in FIG. 5A indicates an optimum gamma characteristic of an imaging signal obtained by adding four frames. In FIG. 5, the horizontal axis represents the luminance level of each color of the imaging signal output from the image sensor, and the vertical axis represents an output example after gamma correction. In FIG. 5A, when the gamma gain of the characteristic G11 is 1, the gamma characteristics G12, G13, and G14 are characteristics of an example in which the gamma gain is limited to 2/3, 1/3, and 0, respectively. In the case of the characteristic G14 in which no gamma correction is performed, the conversion characteristic is a straight line, and the characteristic curve is curved as the appropriate gamma characteristic G11 is reached.
FIG. 5B is an enlarged view showing the vicinity of the rising portion of the characteristic curve of FIG. As can be seen from FIG. 5B, the characteristic G11 intersects the other characteristics G12, G13, G14 at one point. The gamma characteristic shown in FIG. 5 is a gamma characteristic defined by the SMPTE standard.

FIG. 6 is a diagram illustrating a gamma characteristic correction example (correction characteristic example) performed by the correction circuit 17 when imaging is performed in the low frame rate mode. The example of FIG. 6 is an example in the case of performing 4-frame addition. The correction characteristics G11, G12, G13, and G14 shown in FIG. 6A are the appropriate conversion characteristics shown in FIG. 5 when four frames of imaging signals that have been appropriately gamma corrected for each frame are added. The correction characteristics for obtaining G11, G12, G13, and G14 are shown. FIG. 6B is an enlarged view showing the vicinity of the rising portion of FIG.
In any of the gamma gains, the correction characteristic is almost in a straight line state and can be represented by a straight line approximation. As shown in the enlarged view of FIG. 6B, the correction characteristic also has a fold point near the rising edge because the gamma curve itself is composed of two segments. In particular, it appears remarkably in the correction characteristic G11 in the case of gamma gain 1. As described above, since the shape of the curve is greatly changed by the gamma gain, it is necessary to change the setting of the correction characteristic in accordance with the change of the gamma gain.
5 and 6 are examples in the case of 4-frame addition, and the correction characteristics change depending on the number of additions.

Here, for example, it is assumed that an imaging signal Ya in which a frame-added signal is correctly gamma corrected by gamma correction in one gamma correction circuit 2a shown in FIG. Assume that an image signal Yb that has been correctly gamma-corrected finally is obtained by performing correction by the correction circuit 4 with the configuration of FIG. 4B. If the correction characteristic is correct, Ya = Yb, and the correction characteristic H (x) in the correction circuit 4 at this time is expressed by the following equation. K is the number of frame additions.
Ya = Gamma1 (KX) (1)
Zb = K · Gamma1 (X) (2)
Considering that X is deleted in order to obtain H (Zb), X = Gamma1 ⁻¹ (Zb / K) (3) from equation (2).
Therefore, H (Zb) is expressed as the following equation.
H (Zb) = Gamma1 {K · Gamma1 ⁻¹ (Zb / K)} (4)
In the equation (4), when the frame addition is not performed, since the addition number is 1, K in the equation (4) is 1, and the correction characteristic is 1.

In order to analytically obtain the gamma correction function of equation (4), an inverse function is required. Here, in the case of the gamma characteristic defined by the SMPTE standard as shown in FIG. 5, since an inverse function can be derived, the correction characteristic in a relatively simple form as shown in FIG. Obtainable.
When the second curve of the gamma characteristic defined by the SMPTE standard is generalized, the following equation is obtained.
γ (L) = aL ^d + e (5)
a, d, and e are constants determined by the standards. For example, in a standard called SMPTE274M, a = 1.99, d = 0.45, and e = 0.099.
When the inverse function of equation (5) is obtained,
γ ⁻¹ (L) = {(L−e) / a} ^−d (6)
It becomes. When these are applied to the equation (4) as a gamma correction function and its inverse function, the following correction characteristics can be obtained.
H (x) = Kd ⁻¹ x + (1−K ^d ) e (7)
This equation (7) is a straight line, and the slope and intercept can be understood. Thus, it can be seen that by applying the gamma characteristic defined in the SMPTE standard, a very simple correction characteristic (correction characteristic) can be obtained, and that the correction circuit can be realized by an amplitude transfer characteristic conversion circuit.

  Next, an example of processing at the time of imaging at a low frame rate performed under the control of the control unit 25 will be described with reference to the flowchart of FIG. First, the control unit 25 determines whether the current imaging mode is imaging at a normal frame rate or imaging at a low frame rate (step S11). Here, at the time of imaging at a normal frame rate, the changeover switches 27 and 28 are switched so that processing is not performed by the synchronous addition circuit 15 and the correction circuit 17 (or what is performed by the synchronous addition circuit 15 and the correction circuit 17). Also, recording and display are performed (step S12).

  On the other hand, when imaging at a low frame rate, the synchronous addition circuit 15 obtains an imaging signal added by the frame addition number K (step S13). The correction circuit 17 corrects the gamma characteristic corresponding to the addition number for the added image pickup signal (step S14), and an image pickup signal that is correctly gamma corrected with the frame addition number is obtained.

Also, it is selected whether the video to be displayed on the display unit 23 is a video with a normal frame period or a video with a low frame rate added with frames (step S15). When an image having a normal frame period is selected, the output of the camera process unit 14 is selected by the selector 21, and the image based on the selected imaging signal is displayed on the display unit 23 (step S16). When an image picked up in this normal frame period is displayed, it is an image that changes in a normal frame period (that is, a period of 1/60 seconds, etc.), and the actual image pickup state is known. Lens focus adjustment and zoom lens angle of view adjustment can be performed quickly and accurately. However, since the video is not frame-added, the brightness is dark.
Further, when it is selected to display a frame-added low frame rate video, the selector 21 selects the output of the YC conversion circuit 18 and causes the display unit 23 to display the video based on the selected imaging signal. (Step S17). When displaying an image captured at the low frame rate, the brightness of the image obtained by actually capturing the image at the low frame rate can be confirmed. However, since the frame rate is low, the followability of moving objects in the video deteriorates.

As described above, according to the imaging apparatus according to the present embodiment, when the configuration is such that an imaging signal captured at a low frame rate is obtained, the configuration in which gamma correction is corrected after frame addition is simplified. Thus, an image signal that has been correctly gamma corrected can be obtained. That is, the camera process unit 14 may perform gamma correction with exactly the same characteristics during normal imaging without frame addition and when frame addition is performed, and after the synchronous addition circuit 15 that performs frame addition, It is only necessary to provide a correction circuit, which can be realized with a simple configuration.
Further, since the synchronous adder circuit 15 is configured to process and add with the luminance signal and the chroma signal, it can be shared with other frame memories for various image processing in the image pickup apparatus, and can be configured simply. be able to. In the configuration of FIG. 1, the frame rate conversion frame memory is shared, and the configuration of the imaging apparatus can be simplified accordingly.

  Further, the selector 21 selects a case where an image signal of a normal frame rate is displayed and a case where an image signal of a low frame rate is displayed as a display image on the display unit 23 at the time of image pickup at a low frame rate. Because it is configured to be able to check the image captured at the normal frame rate even when imaging at a low frame rate, for example, it is possible to quickly determine the focus state, etc., and the frame is added By displaying the image, it is possible to easily confirm how much brightness the image has become from the frame addition.

  In the case of the present embodiment, a normal frame rate imaging signal is displayed as a display image on the display unit 23 during imaging at a low frame rate, and a low frame rate imaging signal is displayed. In any case, the image with the correct gamma correction can be displayed. That is, the image pickup signal before frame addition is an image pickup signal that has been correctly gamma-corrected frame by frame by the camera process unit 14, and a good image can be displayed on the display unit 23. Further, the imaging signal subjected to frame addition is also an imaging signal in which gamma correction is corrected according to the number of frame additions, and can be displayed favorably on the display unit 23.

In the above-described embodiment, the gamma correction processing in the case of performing image addition at a low frame rate by performing frame addition has been described. However, for other nonlinear correction performed by the imaging apparatus, the correction amount is similarly set after frame addition. You may make it correct. For example, the knee correction performed by the camera process unit 14 of FIG. 1 may be corrected by the correction circuit 17 of FIG. 1 when adding frames.
In the above description, an example in which processing is performed in units of frames has been described. However, similar processing can be performed in units of fields, and similar effects can be obtained.

It is a block diagram which shows the structural example of the imaging device by the example of one embodiment of this invention. It is a block diagram which shows the example of synchronous addition by the example of one embodiment of this invention. It is a timing chart showing an example of imaging timing (example of 3 frame addition) according to an example of an embodiment of the present invention. It is explanatory drawing which shows the outline | summary of the process by one embodiment of this invention, (a) shows the process example in an ideal state, (b) shows the process example by this Embodiment. FIG. 6 is a characteristic diagram illustrating an example of gamma characteristics when four frames are added in the imaging apparatus, where (a) illustrates overall characteristics and (b) is an enlarged view thereof. FIG. 4 is a characteristic diagram showing an example of correction of gamma characteristics required according to an embodiment of the present invention, where (a) shows the overall characteristics and (b) is an enlarged view thereof. It is a flowchart which shows the process example by the example of one embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Lens, 12 ... Prism, 13B, 13G, 13R ... Image sensor, 14 ... Camera process part, 15 ... Synchronous addition circuit, 16 ... RGB conversion circuit, 17 ... Correction circuit, 18 ... YC conversion circuit, 19 ... Codec part 20 ... recording circuit, 21 ... selector, 22 ... frame rate conversion unit, 23 ... display unit, 24 ... frame buffer, 25 ... control unit, 26 ... operation unit

Claims (6)

An image sensor for converting imaging light obtained through the optical system into an imaging signal;
An imaging signal processing unit that performs nonlinear correction on the imaging signal extracted from the image sensor;
A frame addition unit for adding a predetermined number of frames for each imaging signal processed by the imaging signal processing unit;
A correction unit that corrects a shift in the correction characteristic of the nonlinear correction caused by the addition in the frame addition unit to the imaging signal that has been added a predetermined number of frames in the frame addition unit;
An image pickup apparatus that outputs or records an image pickup signal in which the correction characteristic of the nonlinear correction is corrected by the correction unit. The imaging device according to claim 1,
The non-linear correction is a gamma correction. The imaging device according to claim 1,
The imaging signal processing unit outputs the imaging signal as a luminance signal and a chroma signal,
The frame addition unit stores the output luminance signal and chroma signal in a frame memory and performs addition in units of frames.
The correction unit corrects the imaging signal as the luminance signal and the chroma signal added by a predetermined number of frames by the frame addition unit after converting the imaging signal as a primary color signal, and the corrected imaging signal of the primary color signal is corrected. An imaging device characterized by converting into a luminance signal and a chroma signal for output. The imaging device according to claim 3.
A frame memory provided in the frame addition unit is shared with a frame memory provided in a conversion processing unit that handles luminance signals and chroma signals in the imaging device. The imaging device according to claim 1,
A selection unit that selects one of an imaging signal output from the imaging signal processing unit and an imaging signal added by a predetermined number of frames corrected by the correction unit as an imaging signal to be supplied to a display unit that displays a captured image An imaging apparatus comprising: Apply non-linear correction to the imaging signal taken from the image sensor that converts the imaging light into the imaging signal,
The imaging signal subjected to the nonlinear correction is added a predetermined number of frames per frame,
Correcting the deviation of the correction characteristic of the nonlinear correction caused by the addition to the imaging signal added with the predetermined number of frames,
An imaging method comprising outputting or recording the corrected imaging signal.

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