JP2011130381A - Imaging apparatus and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To calculate correction amounts suited to each of motion picture imaging and still picture imaging, when calculating from discrete data, the correction amount for correcting image quality deterioration caused by any optical factor. <P>SOLUTION: An optical correction database discretely holds therein correction amounts for correcting image quality deterioration caused by an imaging optical system with respect to image heights, for a plurality of combinations of values of a plurality of optical parameters of an imaging optical system. When an imaging mode of an imaging apparatus is a motion picture mode, a plurality of correction amounts are selected more preferentially for the number of combinations of optical parameters than for the number of image heights, rather than during a still picture mode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and a control method thereof, and more particularly to an imaging apparatus having a function of correcting image quality degradation caused by characteristics of an optical system and a control method thereof.

  In recent years, small-sized and high-pixel imaging devices have become widespread, and it is possible to obtain high-pixel-number images even with small digital video cameras and digital cameras. On the other hand, due to factors such as pixel miniaturization and the difficulty in optical design of small lenses, image quality degradation that the optical system causes in principle, such as reduced light intensity around the image circle, lateral chromatic aberration, and axial chromatic aberration Is becoming apparent.

  To solve such a problem, a technique for correcting image quality deterioration from parameter information of an optical system is known. Patent Document 1 discloses correcting at least one of lateral chromatic aberration, distortion, peripheral light amount, and image blur from the characteristics of a lens that picks up an image and the positional information of the image. In Patent Document 2, distortion correction parameters are held for a plurality of discrete zoom positions, and correction parameters corresponding to the current zoom position information are generated by interpolating the held parameters for distortion. It is disclosed to make corrections.

  In addition, most current digital video cameras and digital cameras can capture both moving images and still images. However, if correction processing similar to still images is applied to each frame of moving images, Depending on the processing capacity, it is difficult to correct in real time. For this reason, in Patent Document 3, correction is performed using a precision calculation table that prioritizes correction accuracy over processing speed in the still image capturing mode, and approximate calculation table that prioritizes processing speed over correction accuracy is used in the moving image capturing mode. Correction is disclosed.

JP 11-225270 A JP 2005-057605 A JP 2004-128565 JP

  In particular, in the case of imaging where the optical parameters such as focal length, aperture, and focus position always change during imaging, such as moving image imaging, the magnitude of image quality degradation due to optical factors also changes sequentially due to changes in optical parameters. ing.

  If the relationship between the image height (distance from the optical axis) and the correction amount is obtained and stored in advance for all combinations of optical parameters, appropriate correction will be possible for any combination. However, since there are an enormous number of combinations of optical parameters, it is not realistic to store correction amounts for all combinations in the imaging apparatus.

Therefore, Patent Document 1 describes that the correction function is generated using an approximate function, and the order of the approximate function is determined according to the required correction accuracy, the processing capability required for the photo printer, and the like. Yes.
Further, in Patent Document 2, the parameters held for a plurality of discrete zoom positions are interpolated to generate a correction parameter corresponding to the current zoom position.

  If the change in image quality degradation for each parameter combination can be approximated by a simple model, it is relatively easy to obtain the correction amount for many parameter combinations with a small amount of data. However, since the correction characteristic for the image quality degradation due to optical factors varies in a nonlinear and complicated manner, it is difficult to approximate the change in the image quality degradation with a simple model. Therefore, the use of the approximation function as described in Patent Document 1 and the simple interpolation of discrete data as described in Patent Document 2 do not realize appropriate correction for various parameter combinations. Have difficulty.

  In the case of a moving image, since the optical parameter fluctuates during imaging, the correction accuracy related to the combination of optical parameters should be prioritized over the correction accuracy for fluctuations in image height. In the case of still images that are viewed one by one, priority should be given to correction accuracy with respect to fluctuations in image height in one image over correction accuracy relating to a combination of optical parameters. Accordingly, in order to effectively correct a moving image and a still image with a limited time and processing capability, it is desirable to use a correction amount calculation method suitable for each.

  However, Patent Documents 1 and 2 do not mention processing at the time of moving image capturing. Patent Document 3 discloses that different tables are used for calculating the correction amount in the moving image capturing mode and the still image capturing mode. However, in Patent Document 3, in order to realize real-time processing, the correction accuracy of moving images is merely lowered than the correction accuracy of still images, and correction suitable for moving images is not performed.

  The present invention has been made in view of the above-described problems of the prior art, and in an imaging apparatus for calculating a correction amount for correcting image quality degradation due to optical factors from discrete data, and a control method thereof, moving image imaging It is possible to calculate a correction amount suitable for each time and still image capturing.

  In order to solve the above-described problems, the present invention is an imaging apparatus having an imaging mode including a moving image mode and a still image mode, which captures a subject image formed by an imaging optical system and generates image data. Correction amount storage means for discretely holding correction amounts for correcting image quality degradation caused by the imaging optical system with respect to the image height, for a plurality of combinations of a plurality of optical parameter values of the imaging optical system, and imaging A selection unit that selects and outputs a plurality of correction amounts held in the correction amount storage unit according to whether the imaging mode of the apparatus is a moving image mode or a still image mode, and a plurality of correction amounts selected by the selection unit Correction amount generating means for obtaining a correction amount for each pixel of the image data with respect to a combination of values of a plurality of optical parameters of the imaging optical system at the time when the imaging means picks up the image. And a correction means for applying the correction amount is an amount generation means generates for each pixel of the image data. Furthermore, the selection unit of the imaging device is configured to select a combination of optical parameters rather than the number of image heights when the imaging mode of the imaging device is the moving image mode than when the imaging mode of the imaging device is the still image mode. A plurality of correction amounts are selected giving priority to the number.

  With such a configuration, according to the present invention, when calculating a correction amount for correcting image quality deterioration due to optical factors from discrete data, correction suitable for each of moving image capturing and still image capturing is performed. The amount can be calculated.

1 is a block diagram illustrating a configuration example of a digital video camera as an example of an imaging apparatus according to an embodiment of the present invention. (A) is a figure which shows the example of an optical correction characteristic, (b)-(d) is a figure explaining the selection method of the correction amount plot data in a moving image mode, and the calculation method of a correction amount. (A) The figure which shows the example of the horizontal synchronizing signal HD and the vertical synchronizing signal VD which TG11 produces | generates, (b) is a block diagram which shows the structural example of the pixel coordinate generation circuit 12, (c) is a figure explaining image height. is there. 5 is a flowchart showing an example of a read control processing operation of a correction amount plot data set Cm in the first embodiment of the present invention. The figure explaining the selection method of the correction amount plot data in still image mode, and the calculation method of correction amount. FIG. 3 is a block diagram illustrating a configuration example of a coefficient generation circuit 14. (A) is a block diagram showing a configuration example of a peripheral light amount drop correction circuit as an example of the optical correction circuit 6, and (b) is a configuration of a magnification chromatic aberration correction circuit or a distortion correction circuit as another example of the optical correction circuit 6. The block diagram which shows an example. The schematic diagram explaining the principle of lateral chromatic aberration correction or distortion aberration correction. 10 is a flowchart showing an example of a read control processing operation of a correction amount plot data set Cm in the second embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration example of a motion detection circuit 16. The figure for demonstrating operation | movement of a motion detection circuit. The flowchart which shows the example of the read-out control processing operation | movement of the correction amount plot data set Cm in the 3rd Embodiment of this invention.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.
(First embodiment)
FIG. 1A is a block diagram illustrating an example of a configuration related to the present embodiment in a digital video camera as an example of an imaging apparatus according to the first embodiment of the present invention. In this embodiment, the case where the present invention is applied to a three-plate type digital video camera will be described. Applicable to any device equipped with a possible camera.

  The digital video camera 100 includes an optical unit that includes a lens unit 1 including a zoom lens and a focus lens, an aperture 2, and actuators 8 to 10 for driving the zoom lens, the focus lens, and the aperture 2. . In the following description, the lens unit 1 and the diaphragm 2 are collectively referred to as an imaging optical system. The subject image formed by the optical unit is color-separated into a red (R) component, a green (G) component, and a blue (B) component by the color separation prism 3, and then an image sensor provided for each color component Images are taken at 41, 42 and 43. The imaging elements 41, 42, 43 are, for example, CCD image sensors or CMOS image sensors, and convert each color component image of the subject image into a video signal in pixel units. The video signal of each color component is analog front end (hereinafter abbreviated as AFE) 5 and performs correlated double sampling (CDS), automatic gain control (AGC), analog / digital conversion (ADC), etc., and digital video signals Sr, Sg , Sb is converted into image data.

  The optical correction circuit 6 sequentially applies the correction value Zt supplied from the coefficient generation circuit 14 to the digital video signals Sr, Sg, and Sb for each pixel, and the image quality generated by the optical characteristics of the lens unit 1 and the aperture stop 2. Compensate for deterioration. The optical correction circuit 6 outputs corrected image data composed of digital video signals Sr ′, Sg ′, and Sb ′.

  Next, the control unit 7, the timing generator (hereinafter abbreviated as TG) 11, the pixel coordinate generation circuit 12, the optical correction database 13, and the coefficient generation circuit 14 related to the generation of the correction value Zt will be described in detail. Note that the memory 15 is not used in this embodiment.

  The optical parameters of the digital video camera 100 vary depending on various factors such as zooming operation, movement of the subject, change of the imaging target, environmental change of ambient brightness, and imaging effect intended by the photographer. Here, the optical parameter is a parameter that affects image quality degradation caused by the imaging optical system. In this specification, the focal length (angle of view) and the focus position (the position at which focus is detected in the screen) will be referred to hereinafter. The aperture value is generically called an optical parameter. However, in the present invention, the type and number of optical parameters are not limited, and the focal length, the focus position, and the aperture value merely indicate exemplary combinations of optical parameters.

  Illustrative factors of image quality degradation caused by the imaging optical system include lateral chromatic aberration, distortion, and peripheral light loss, but the degree of image quality degradation varies depending on the image height (distance from the center of the optical axis). It is known. Therefore, the correction amount for correcting the image quality deterioration also varies according to the image height.

  FIG. 2A shows an example of the relationship between the image height and the correction amount (correction characteristics). FIG. 2A shows a plurality of correction characteristics, and each correction characteristic corresponds to one specific combination of optical parameter values. As described above, the correction characteristic (in other words, the relationship between the degree of image quality degradation and the image height) varies greatly depending on the image height depending on the combination of the parameter values.

  Returning to FIG. 1A, the control unit 7 is, for example, a microcomputer, and by executing a program stored in the memory 15, a memory (not shown) or a storage device, not only the correction method according to the present embodiment, but also exposure control and Focus detection is also performed. Note that automatic exposure control and focus detection methods are not directly related to the present invention, and any known method can be used, and therefore a description of specific methods and necessary configurations is omitted.

  For example, the control unit 7 outputs a drive pulse position CL in response to a zoom instruction given through an operation member (not shown), and drives the zoom lens actuator 8 of the lens unit 1. Thereby, the angle of view of the lens unit 1 changes.

  The control unit 7 outputs a drive pulse position CF for realizing a predetermined focal length, and drives the focus lens actuator 9 of the lens unit 1. Further, the control unit 7 outputs a drive pulse position Cf for realizing a predetermined aperture value, and drives the actuator 10 of the aperture 2.

  The TG 11 generates a horizontal synchronization signal HD and a vertical synchronization signal VD as shown in FIG. 3A in accordance with the drive specifications of the image sensors 41, 42, and 43 used by the digital video camera 100, and the AFE 5 has a drive waveform. Is input to the image sensors 41, 42, and 43.

The period of the horizontal synchronization signal HD is a period of one line of the video signal output from the image pickup devices 41, 42, and 43, and the period of the vertical synchronization signal VD is a period of one frame.
The horizontal synchronization signal HD and the vertical synchronization signal VD are input to the pixel coordinate generation circuit 12 together with the optical axis center position information Cx and Cy output from the control unit 7.

  A configuration example of the pixel coordinate generation circuit 12 is shown in FIG. In the pixel coordinate generation circuit 12, the H counter 121 reset at the falling edge of the horizontal synchronization signal HD outputs the horizontal counter value Xt, and the V counter 122 at the falling edge of the vertical synchronization signal VD outputs the vertical counter value Yt. To do.

  The horizontal counter value Xt and the vertical counter value Yt increase in the direction perpendicular to the scanning axis and the horizontal axis that increases in the scanning direction (right direction in the drawing) with the output pixel at the upper left corner of the image sensor 41, 42, 43 as the origin. Represents the coordinates of the two-dimensional orthogonal coordinate system (FIG. 3C) defined by the vertical axis.

  The optical axis center position information Cx and Cy input to the pixel coordinate generation circuit 12 corresponds to the orthogonal coordinate system of FIG. 3C corresponding to the optical axis center position c of the imaging optical system constituted by the lens unit 1 and the aperture stop 2. Coordinates.

と表すことができるので、像高算出回路１２３は、上記式の演算を行い、像高Ｒｔを出力する。像高を求める際の開平演算は、二分法、開平法などの既知の手法を有限語長精度で表現することにより、ハードウェアで実現可能である。もちろん、ＣＰＵがソフトウェアを実行して実現してもよい。 Here, if the coordinate of the pixel of interest t is (Xt, Yt), the image height Rt of the pixel of interest t is the distance from the optical axis center position c.

Therefore, the image height calculation circuit 123 calculates the above formula and outputs the image height Rt. The square root calculation for obtaining the image height can be realized by hardware by expressing known methods such as the bisection method and the square root method with finite word length accuracy. Of course, the CPU may execute the software.

  When the control unit 7 outputs the drive pulse positions CL, CF, and Cf to the actuators 8 to 10, for example, the control unit 7 accesses the optical correction database 13 stored in the nonvolatile memory and supplies the correction amount plot data set to the coefficient generation circuit 14. Cm is output. The optical correction database 13 as a correction amount storage means discretely holds correction amounts for correcting image quality degradation caused by the imaging optical system with respect to image height for a plurality of combinations of values of a plurality of optical parameters. Yes. Hereinafter, each discrete correction amount stored in the optical correction database 13 is referred to as correction amount plot data.

  In order to apply correction to each frame of a moving image in real time, it is necessary to finish the correction process within one cycle (one frame period) of the vertical synchronization signal VD. Therefore, the control unit 7 obtains a discrete correction amount stored in the optical correction database 13 that matches the current combination of optical parameter values of the digital video camera 100, or that corresponds to the closest combination. To the coefficient generation circuit 14.

  At this time, in the present embodiment, the coefficient generation circuit 14 selects at least a part of a different data set even if the combination of the optical parameter values is the same depending on whether the imaging mode of the digital video camera 100 is the moving image mode or the still image mode. To supply. In addition, the control unit 7 also supplies the coefficient generation circuit 14 with imaging mode information indicating the moving image mode or the still image mode.

  In the case of moving image capturing, a change in optical aberration or a decrease in peripheral light amount due to a change in optical parameters is continuously recorded. For this reason, in order to appropriately correct the image degradation caused by the imaging optical system, it is necessary to calculate the correction amount with high accuracy with respect to the optical parameter change (combination of different values) from the optical correction database 13. Accordingly, it is appropriate to provide the coefficient generation circuit 14 with a correction amount plot data set in which correction amount plot data is selected with priority given to the number of combinations of optical parameters over the number of image heights.

  On the other hand, in the case of still image capturing, the optical parameter does not change greatly during image capturing, but a small change in optical aberration or peripheral light loss due to the changing image height position is recorded. For this reason, in order to appropriately correct the image deterioration caused by the imaging optical system, it is necessary to calculate a correction amount with high accuracy in the image height changing direction from the optical correction database 13. Therefore, it is appropriate to provide the coefficient generation circuit 14 with a correction amount plot data set in which the correction amount plot data is selected with priority given to the number of image heights over the number of combinations of optical parameters.

An example of the read control processing operation of the correction amount plot data set Cm by the control unit 7 will be described with reference to the flowchart of FIG.
First, in S901, the control unit 7 determines whether the current imaging mode (at the time of imaging) is the moving image mode or the still image mode. If the moving image mode is selected, the control unit 7 proceeds to S902.

  The correction amount plot data set selects data corresponding to multiple image heights from a data series corresponding to multiple correction characteristics corresponding to the vicinity of the optical parameters at the time of imaging (including any that match). Configure by doing.

  In the moving image mode, in step S902, the control unit 7 selects correction amount plot data corresponding to n types of image heights (abbreviated as Dp in the figure) from each of m types of correction characteristics (abbreviated as Op in the figure). To do. In step S904, the control unit 7 reads out the selected m × n correction amount plot data from the optical correction database 13, and configures a correction amount plot data set Cm.

  FIG. 2B shows an example of correction amount plot data included in the correction amount plot data set Cm configured in the moving image mode. In this example, correction amount plot data sets Cm are selected by selecting correction amount plot data at four image heights at equal intervals from the optical axis from each of the correction characteristics corresponding to the eight types of optical parameters in the vicinity of the current optical parameter. It is composed.

  On the other hand, in the still image mode, in step S903, the control unit selects correction amount plot data corresponding to v types of image heights (abbreviated as Dp in the drawing) from each of the u types of correction characteristics. In step S904, the control unit 7 reads the selected u × v correction amount plot data from the optical correction database 13, and configures a correction amount plot data set Cm.

  FIG. 5A shows an example of correction amount plot data included in the correction amount plot data set Cm configured in the still image mode. In this example, the correction amount plot data set Cm is selected by selecting correction amount plot data at 16 image heights at equal intervals from the optical axis from each of the correction characteristics corresponding to two types of optical parameters in the vicinity of the current optical parameter. It is composed.

  As described above, the total number of correction amount plot data constituting the correction amount plot data set Cm read in the moving image mode and the still image mode is equal (m × n = u × v), but a relationship of m> u and n <v. Have

  In this way, the control unit 7 has a larger number of correction characteristics (optical parameters) than the number of image heights in the moving image mode, and a larger number of image heights than the number of correction characteristics (optical parameters) in the still image mode. A correction amount plot data set Cm is read from the optical correction database 13.

  Here, the case where the optical correction database 13 holds plot data directly indicating the optical correction amount has been described. However, the coefficient term of the function approximating the correction characteristic may be held, and in that case, the order of the approximate function may be similarly selected as the correction amount plot data.

FIG. 6 is a diagram illustrating a configuration example of the coefficient generation circuit 14 as a correction amount generation unit. The current image height Rt of the pixel of interest output from the pixel coordinate generation circuit 12 and the correction amount plot data set Cm (in this example, 32 correction amount plot data Cm0 to Cm31 output from the control unit 7). Is input to the function coefficient calculation circuit 141.
The function coefficient calculation circuit 141 changes the processing of the correction amount plot data set Cm according to the imaging mode information mode output from the control unit 7.

  When the imaging mode information mode indicates the moving image mode, the function coefficient calculation circuit 141 uses the 32 correction amount plot data (8 pieces / image height × 4) shown in FIG. 2B for each image height. Four correction plot data as shown in FIG. 2C are calculated by interpolation.

  Next, as shown in FIG. 2D, the function coefficient calculation circuit 141 obtains a plot section to which the image height Rt of the current pixel of interest belongs (black line section), and approximates the coefficient a of the approximate function corresponding to the plot section. , B, c are output.

  On the other hand, when the imaging mode information mode indicates the still image mode, the function coefficient calculation circuit 141 converts the 32 correction amount plot data (2 pieces / image height × 16) shown in FIG. By interpolating every height, 16 correction plot data as shown in FIG. 5B are calculated.

  Next, as shown in FIG. 5C, the function coefficient calculation circuit 141 obtains a plot section to which the image height Rt of the current pixel of interest belongs (black line section), and the coefficient a of the approximate function corresponding to the plot section. , B, c are output.

という２次関数であるが、１次関数（折れ線近似）や３次以上の高次関数で近似するように構成してもよい。 In this embodiment, the approximation function of the plot interval is

However, it may be configured to approximate with a linear function (polygonal line approximation) or a higher order function of 3 or more.

Then, the correction value calculation circuit 142 calculates the correction amount Zt from the current image height Rt of the target pixel based on the approximate function.
In the case of the peripheral light amount drop correction, the correction amount Zt is a gain common to the digital video signals Sr, Sg, Sb.
In the case of lateral chromatic aberration correction and distortion aberration correction, the correction amount Zt is a position shift amount ZtHr, ZtVr representing a position shift component in the horizontal and vertical directions, independent of each of the digital video signals Sr, Sg, Sb.

Next, the optical correction circuit 6 will be described in detail.
FIG. 7A shows a configuration example when the optical correction circuit 6 is a peripheral light amount drop correction circuit. In the case of the peripheral light amount drop, the correction amount Zt output from the coefficient generation circuit 14 is a gain value represented by the reciprocal of the light amount drop amount (decrease rate) at the target pixel position.

  The optical correction circuit 6 multiplies the digital video signals Sr, Sg, Sb by a correction amount Zt by multipliers 701, 702, 703, and corrects the digital video signals Sr ′, Sg ′, Sb ′ subjected to optical correction processing. The later image data is output.

FIG. 7B shows a configuration example when the optical correction circuit 6 is a magnification chromatic aberration correction circuit or a distortion aberration correction circuit.
In the case of lateral chromatic aberration correction and distortion aberration correction, the optical correction value is a positional deviation amount representing the distortion amount at the target pixel position as a horizontal and vertical positional deviation component.

The principle of correcting the aberration from this displacement amount will be described with reference to FIGS.
A black pixel in FIG. 8A indicates a position where the target pixel S should be originally, and a gray pixel indicates a position where the target pixel S is imaged with a positional shift due to the influence of lateral chromatic aberration or distortion. This is a virtual pixel S ′. In order to correct lateral chromatic aberration and distortion, a virtual pixel S ′ whose Hp is shifted in the horizontal direction and Vp is shifted in the vertical direction is obtained, and the target pixel S may be rearranged at the position where it should be.

  As shown in FIG. 8B, the virtual pixel S ′ is obtained from the values of the pixels S1, S2, S3, and S4 that are actually imaged in the vicinity and the pixels S1, S2, S3, and S4 and the virtual pixel S ′. It can be generated by a weighted interpolation calculation according to the inter-pixel distances c1, c2, c3, c4. For example, a larger weight can be added as the distance is shorter. As shown in FIG. 8C, the chromatic aberration of magnification and distortion are corrected by replacing the pixel of interest S with the generated virtual pixel S ′.

  The correction amounts ZtHr and ZtVr input to the optical correction circuit 6 are input to three interpolation control circuits 601, 608, and 615 provided for each of the R, G, and B components. The interpolation control circuits 601, 608, 615 output the respective color components Hrp, Hgp, Hbp and Vrp, Vgp, Vbp of the integer horizontal shift component Hp and vertical shift component Vp (see FIG. 8A) of the virtual pixel S ′. To do.

  Here, paying attention to the processing of the R component, the interpolation control circuit 601 obtains the virtual pixel Sr ′ from the reference pixels Sr1, Sr2, Sr3, Sr4 as the fractional displacement component of the virtual pixel S ′. , Cr2, cr3, cr4 are output. As described above, the weighting coefficient has a value corresponding to the distance between the reference pixel and the virtual pixel.

  The buffer memory 602 holds a digital video signal Sr (red component of image data), for example, for one frame. The buffer memory 602 sequentially outputs, as reference pixels sr1, sr2, sr3, and sr4 in the vicinity of the virtual pixel Sr ′, a plurality of pixels including the pixel held at the position designated for each pixel by Hrp and Vrp. .

で表され、参照画素ｓｒ１、ｓｒ２、ｓｒ３、ｓｒ４は、乗算器６０３、６０４、６０５、６０６で、補間係数ｃｒ１、ｃｒ２、ｃｒ３、ｃｒ４とそれぞれ乗じられ、平均値化回路６０７で平均されて補正後のデジタル映像信号Ｓｒ’として出力される。 The value of the virtual pixel Sr ′, that is, the corrected pixel value is

Reference pixels sr1, sr2, sr3, and sr4 are multiplied by interpolation coefficients cr1, cr2, cr3, and cr4 by multipliers 603, 604, 605, and 606, respectively, and averaged and corrected by an averaging circuit 607. It is output as a later digital video signal Sr ′.

  Similarly, the G component and the B component are processed by the buffer memories 609 and 616, the multipliers 610 to 613 and 617 to 620, and the averaging circuits 614 and 621, respectively, as corrected digital video signals Sg ′ and Sb ′. Is output.

  As described above, in this embodiment, correction data corresponding to a plurality of discrete image heights is stored for each combination of discrete optical parameter values, so that the storage capacity necessary for storing the correction amount is saved. be able to. Furthermore, in the moving image mode in which the optical parameters constantly change, the number of optical parameter combinations has priority over the number of image heights, and in the still image mode, the number of image heights has priority over the number of optical parameter combinations. Select the correction amount. Therefore, for example, even when the total number of correction values to be selected is equal, it is possible to calculate a correction amount appropriate for a moving image and a correction amount appropriate for a still image. In this way, a remarkable effect that it is possible to calculate a correction amount appropriate for a moving image and a correction amount appropriate for a still image with a small storage capacity can be realized.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. This embodiment is common to the first embodiment, except that the memory 7 as history storage means for holding the history of optical parameters is connected to the control unit 7. Therefore, only the memory 15 will be described, and a description overlapping with the first embodiment will be omitted.

The control unit 7 performs an optical parameter control unit time for each frame period.
A driving pulse position CL for driving the zoom lens actuator 8;
A drive pulse position CF for driving the focus lens actuator 9;
A drive pulse position Cf for driving the actuator 10 of the diaphragm 2;
Is output.

  In addition, when outputting the drive pulse positions CL, CF, and Cf to the optical unit 1 and the diaphragm 2, the control unit 7 accesses the optical correction database 13 and outputs a correction amount plot data set Cm to be given to the coefficient generation circuit 14. To do. In addition, the control unit 7 also outputs imaging mode information mode indicating the moving image mode or the still image mode.

  As described above, in the moving image mode, since the optical parameter constantly changes, it is possible to perform appropriate correction by selecting the correction amount plot data by giving priority to the number of combinations of optical parameters over the number of image heights. . However, when the optical parameters hardly change even during moving image capturing, correcting the optical aberration or the small change in the amount of peripheral light due to the image height position contributes to the improvement of the image quality.

  Therefore, in the present embodiment, the drive pulse positions output in the past are stored in the memory 15, and the correction control in the moving image mode is performed when the variation in the optical parameter is large, and the correction control in the still image mode is performed when the variation is small. I do.

An example of the read control processing operation of the correction amount plot data set Cm by the control unit 7 in this embodiment will be described with reference to the flowchart of FIG.
First, in step S1501, the control unit 7 determines whether the current shooting mode is the moving image mode or the still image mode. If the moving image mode is selected, the control unit 7 proceeds to step S1502. In the moving image mode, the memory 15 is accessed in S1502, and the values of the drive pulse positions CL, CF, and Cf that are held for each of the optical parameters and output in the most recent past frame period are read as history information. .

  In step S <b> 1504, the control unit 7 records the drive pulse position set in the current frame period in the memory 15 as a history for each optical parameter. In step S <b> 1505, the control unit 7 serving as a variation determination unit compares the drive pulse position history information read from the memory 15 with the current drive pulse position, and determines whether the magnitude of parameter variation is equal to or less than a predetermined threshold. To determine. Then, the control unit 7 advances the process to S903 if it is determined that the magnitude of the parameter fluctuation is equal to or less than the predetermined threshold, and advances to S902 if it is determined that the parameter exceeds the threshold.

As a comparison method with the history information, for example, the difference from the latest drive pulse position, the median value in a plurality of frames, or the integrated value of the differences in a plurality of frames may be observed. Further, when there are a plurality of types of optical parameters, if any one of the optical parameters fluctuates beyond the corresponding threshold value, the process proceeds to S902. Further, the predetermined threshold value may be set, for example, by appropriately setting the threshold value to a small value when the interval of the drive pulse of the optical parameter held in the optical correction database 13 is a rough guide and the interval is very rough.
Since the following processing is the same as that of the first embodiment, description thereof is omitted.

  Here, in order to facilitate explanation and understanding, it has been described that the same control as in the still image mode is performed when the parameter variation is equal to or less than a predetermined threshold. However, a plurality of threshold values are set stepwise, and as the parameter variation amount decreases, the combination of optical parameters is gradually decreased from m to u, and at the same time, the number of correction plot data is gradually increased from n to v. Control is also possible. By such stepwise control, it is possible to smoothly shift from correction control in the moving image mode to correction control in the still image mode.

  According to the present embodiment, in addition to the effects of the first embodiment, when the fluctuation of the optical parameter is small even in the moving image mode, the correction similar to that in the still image mode is applied to correct the moving image quality more appropriately. The effect that it becomes possible to do is realizable.

(Third embodiment)
Next, a third embodiment of the present invention will be described. FIG. 1B is a block diagram illustrating a configuration example of a digital video camera as an example of an imaging apparatus according to the present embodiment. The same reference numerals are given to the same configurations as those in the first embodiment. The digital video camera 100 ′ of the present embodiment includes a motion detection circuit 16 that performs motion detection inside an image before the optical correction circuit 6, and is the first except that the control unit 7 acquires the motion vector Mv. This is the same configuration as the embodiment.

  Therefore, in the following, only the relationship with the motion detection circuit 16 will be described, and the description overlapping with the first embodiment will be omitted. As in the second embodiment, the present embodiment performs correction control in the still image mode when a certain condition is satisfied even in the moving image mode. In the second embodiment, the amount of variation of the optical parameter is a condition, but in this embodiment, the size of the image motion is a condition. That is, even in the moving image mode, when the movement is small, correction control similar to that in the still image mode is performed. For this reason, in the present embodiment, the motion detection circuit 16 detects the motion of the image.

  FIG. 10 is a block diagram illustrating a configuration example of the motion detection circuit 16. The motion detection circuit 16 of the present embodiment has a general configuration for detecting motion by a matching operation using representative points.

The luminance signal generation circuit 161 outputs the digital video signals Sr, Sg, Sb, for example, y = 0.299Sr + 0.587Sg + 0.144Sb.
And the luminance signal Y is output.

  The frame memory 162 has a capacity for holding luminance representative point image data for at least two frames. The luminance representative point image data is image data composed of luminance signals of representative points obtained by re-sampling the luminance signal Y in the horizontal and vertical directions with a predetermined pixel interval. Similar luminance representative point image data is also stored in the buffer memory 163.

  The representative point matching circuit 164 shifts the position of the representative point pixel group Ys having a predetermined size from the upper left to the lower right of the frame memory 162 in units of a predetermined number of pixels as in the rectangular area shown in FIG. Read sequentially.

  On the other hand, the representative point matching circuit 164 partitions the luminance representative point frame image data from the buffer memory 163 by a predetermined size as shown in the rectangular area of FIG. The group Yt is sequentially read from the partition numbers 1 to 12.

  The representative point matching circuit 164 then reads the Ys read position from the frame memory 162 when the difference between the representative point pixel group Yt and the representative point pixel group Ys is the smallest, and the partition number 1 of the representative point pixel group Yt. From the position, the motion vector Mv of section number 1 is output.

When the matching operation for the partition number 1 is completed, the representative point matching circuit 164 reads the representative point pixel group Yt for the partition number 2 from the buffer memory 163. Further, the representative point matching circuit 164 reads the representative point pixel group Ys from the frame memory 162 while sequentially updating the representative point pixel group Ys from the upper left to the lower right of the frame memory 162 as in the case of the partition number 1.
Thereafter, by repeating the matching calculation, the motion detection circuit 16 outputs a motion vector Mv for each of the partition numbers 1 to 12.

  As mentioned above, in order to properly correct optical aberrations or peripheral light loss during general movie shooting, the correction amount plot data is selected with priority given to the number of combinations of optical parameters over the number of image heights. Can make appropriate corrections. However, if the image being picked up is hardly moving, it is better to correct small changes in optical aberration or peripheral light loss due to the image height position, even during moving image shooting. Contribute.

An example of the read control processing operation of the correction amount plot data set Cm by the control unit 7 in the present embodiment will be described with reference to the flowchart of FIG.
First, in step S1801, the control unit 7 determines whether the current shooting mode is the moving image mode or the still image mode. If the moving image mode is selected, the control unit 7 proceeds to step S1802.

  In the moving image mode, the control unit 7 acquires the motion vector Mv that is the output of the motion detection circuit 16 for all the sections in S1802. Next, in step S1804, the control unit 7 statistically processes the motion vectors Mv for all sections, and calculates a representative motion vector M in the current frame period.

  As an example of the statistical process for obtaining the representative motion vector M, there is a process in which the average value or median value of the motion vectors Mv of all sections is used as the representative vector M. Alternatively, a predetermined number of small and large motion vectors Mv may be deleted, and the average value or median value of the remaining motion vectors may be used as the representative vector M. Further, the average value or median value of the motion vectors detected in the section at the center of the screen (for example, sections 6 and 7 in the example of FIG. 11B) may be used as the representative vector M.

In step S1805, the control unit 7 serving as a motion determination unit determines whether or not the magnitude of the representative motion vector M is equal to or less than a predetermined threshold value. Then, the control unit 7 advances the process to S903 if it is determined that the magnitude of the representative motion vector M is equal to or less than the predetermined threshold, and advances to S902 if it is determined that the representative motion vector M exceeds the threshold. For example, the predetermined threshold value may be a value that allows the representative motion vector M to detect motion subjectively.
Since the following processing is the same as that of the first embodiment, description thereof is omitted.

  Here, in order to facilitate explanation and understanding, it has been described that the same control as in the still image mode is performed when the magnitude of the representative vector M is equal to or smaller than a predetermined threshold. However, a plurality of threshold values are set in stages, and as the representative vector M decreases, the combination of optical parameters is gradually decreased from m to u, and at the same time, the number of correction plot data is gradually increased from n to v. Stepwise control is also possible. By such stepwise control, it is possible to smoothly shift from correction control in the moving image mode to correction control in the still image mode.

  According to this embodiment, in addition to the effects of the first embodiment, when the image movement is small even in the moving image mode, the image quality of the moving image is corrected more appropriately by applying the same correction as in the still image mode. The effect that it becomes possible is realizable.

(Other embodiments)
In the above-described embodiment, in order to facilitate understanding of the characteristics of the present invention, the total number of correction amount plot data constituting the correction amount plot data set Cm read in the moving image mode and the still image mode is equal (m × n = u Xv), m> u and n <v. However, the total number of correction amount plot data may be different between the moving image mode and the still image mode. The essence of the present invention is that when selecting discrete correction amount plot data, the number of optical parameter combinations is greater than the number of image heights in the moving image mode, and the number of optical parameter combinations is greater than the number of image heights in the still image mode. Also has priority. Therefore, as a more general definition, the relationship of (m / n)> (u / v) may be satisfied.

  More generally, the priority between the number of image heights and the number of combinations of optical parameters may be relative between the moving image mode and the still image mode. Specifically, in the moving image mode, if the number of combinations of optical parameters is given priority over the number of image heights in the still image mode, the effect of the present invention can be realized. Similarly, the case where the priority of the number of image heights and the number of combinations of optical parameters is changed depending on the amount of variation in optical parameters or the amount of motion of an image may be a relative relationship between conditions. . That is, in the moving image mode, when the variation of the optical parameter is equal to or smaller than the threshold, the number of image heights is given priority over the number of optical parameters relative to the case where the variation is larger than the threshold. Also, in the moving image mode, when the magnitude of the image motion is equal to or smaller than the threshold, the number of image heights is given priority over the number of optical parameters relative to the case where the magnitude is larger than the threshold.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (6)

An imaging apparatus having an imaging mode including a moving image mode and a still image mode,
An imaging means for capturing a subject image formed by the imaging optical system and generating image data;
Correction amount storage means for discretely holding correction amounts for correcting image quality degradation caused by the imaging optical system with respect to image height for a plurality of combinations of values of a plurality of optical parameters of the imaging optical system;
Selection means for selecting and outputting a plurality of correction amounts held in the correction amount storage means according to whether the imaging mode of the imaging device is the moving image mode or the still image mode;
A plurality of correction amounts selected by the selection unit are interpolated to obtain a correction amount for each pixel of the image data for a combination of the values of the plurality of optical parameters of the imaging optical system at the time when the imaging unit picks up an image. Correction amount generating means;
Correction means for applying the correction amount generated by the correction amount generation means to each pixel of the image data,
When the imaging mode of the imaging device is the moving image mode, the selection unit prioritizes the number of combinations of optical parameters over the number of image heights than when the imaging mode of the imaging device is the still image mode. And selecting the plurality of correction amounts. History storage means for holding a history of values of the plurality of optical parameters of the imaging optical system;
Whether the magnitude of variation between the values of the plurality of optical parameters of the imaging optical system and the values of the plurality of optical parameters held by the history storage unit at the time when the imaging unit captures an image is equal to or less than a predetermined threshold value And a variation amount determination means for determining whether or not
When the imaging mode of the imaging apparatus is the moving image mode, the selection unit determines the magnitude of the variation when the variation amount determining unit determines that the magnitude of the variation is equal to or less than a predetermined threshold. 2. The plurality of correction amounts are selected by prioritizing the number of image heights over the number of combinations of optical parameters, rather than the case where it is determined that is larger than a predetermined threshold value. Imaging device. A motion vector of the image data corrected by the correction unit is calculated from the image data corrected by the correction unit and the image data captured by the imaging unit in the past, and the magnitude of the motion vector is equal to or less than a predetermined threshold value. A motion determination means for determining whether or not
The selection means, when the imaging mode of the imaging apparatus is the moving image mode, when the motion determination means determines that the magnitude of the motion vector is equal to or less than a predetermined threshold, 2. The plurality of correction amounts are selected by prioritizing the number of image heights over the number of combinations of optical parameters, rather than when the size is determined to be greater than a predetermined threshold. Imaging device.   4. The apparatus according to claim 1, wherein the selection unit selects an equal number of correction amounts regardless of whether the imaging mode of the imaging apparatus is the moving image mode or the still image mode. The imaging apparatus of Claim 1.   The plurality of optical parameters are an angle of view, a focus position, and an aperture value of the imaging optical system, and image quality degradation caused by the imaging optical system is any one of chromatic aberration of magnification, distortion, and loss of peripheral light amount. The imaging device according to any one of claims 1 to 4, wherein: It has an imaging mode that includes a video mode and a still image mode,
An imaging means for capturing a subject image formed by the imaging optical system and generating image data;
An imaging device comprising: a correction amount storage unit that discretely holds correction amounts for correcting image quality degradation caused by the imaging optical system with respect to image height for a plurality of combinations of a plurality of optical parameter values of the imaging optical system An apparatus control method comprising:
A selection step of selecting and outputting a plurality of correction amounts held in the correction amount storage means according to whether the imaging mode of the imaging device is the moving image mode or the still image mode;
A plurality of correction amounts selected in the selection step are interpolated, and a correction amount for each pixel of the image data is set for a combination of the values of the plurality of optical parameters of the imaging optical system at the time when the imaging unit captures an image. A correction amount generation step to be obtained;
A correction step of applying the correction amount generated in the correction amount generation step to each pixel of the image data,
In the selection step, when the imaging mode of the imaging device is a moving image mode, priority is given to the number of combinations of optical parameters over the number of image heights compared to the case where the imaging mode of the imaging device is a still image mode. And selecting the plurality of correction amounts.

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