JP5999746B2 - Imaging apparatus, AF evaluation value calculation method, and program - Google Patents

Description

  The present invention relates to an imaging apparatus, an AF evaluation value calculation method, and a program, and more particularly to a technique for performing AF setting more accurately.

  In a conventional imaging device, when a subject is imaged through an optical lens, the captured image is distorted due to the influence of the optical lens, and thus correction for eliminating the distortion of the data of the captured image (hereinafter referred to as “correction”) , Called “distortion correction” (see Patent Document 1).

  Some conventional imaging apparatuses execute AF processing (Automatic Focus processing, autofocus processing) using a contrast AF method.

In AF processing using the contrast AF method, for example, the method described in Patent Document 2 is widely used. The technique described in Patent Document 2 uses the fact that the frequency component (excluding the DC component) included in the image signal is maximized at the in-focus position, and uses the amount of the frequency component included in the image signal as an evaluation value. A technique of detecting the in-focus state.
Such an AF processing method is hereinafter referred to as “AF detection”. The evaluation value detected by AF detection is detected from one area of the captured image. Such an evaluation value is hereinafter referred to as an “AF evaluation value”, and the one area where the AF evaluation value is detected is hereinafter referred to as an “AF detection area”. That is, the amount of the frequency component included in the image signal corresponding to each pixel in the AF detection area is integrated, and the integrated value obtained as a result is detected as the AF evaluation value.
Also, a frame for setting this AF detection area is set on the life view image. Hereinafter, such a frame is referred to as an “AF frame”. That is, the AF detection area is set based on the AF frame displayed together with such a live view image.

JP 2008-118387 A Japanese Patent Laid-Open No. 3-1668

However, the live view image in which the AF frame is set is an image after distortion correction. Accordingly, the AF detection area is set in the coordinate system of the live view image in which such an AF frame is set, that is, the coordinate system of the image after distortion correction (hereinafter referred to as “coordinate system after distortion correction”). .
On the other hand, AF detection is performed in a coordinate system of a captured image before distortion correction (hereinafter referred to as “coordinate system before distortion correction”).
Therefore, a deviation occurs between the actual AF detection area set corresponding to the AF frame of the coordinate system after distortion correction and the ideal AF detection area that should be originally set in the coordinate system before distortion correction. It will end up.

  Further, the deviation that occurs between the actual AF detection area set corresponding to the AF frame and the ideal AF detection area will be described in detail below.

  FIG. 6 is a functional block diagram showing a functional configuration for realizing an AF detection function among various functions of a general conventional imaging apparatus.

  A conventional imaging apparatus includes a complementary metal oxide semiconductor (CMOS) sensor 11, a preprocessing unit 12, an AF detection unit 13, a memory 14, a YUV generation unit 15, a distortion correction unit 16, and a CPU (Central Processing Unit). ) 17 and a display control unit 18.

  The CMOS sensor 11 captures an image that is distorted when it is imaged on its light receiving surface by an optical lens that generates a predetermined aberration (not shown), and the image signal of the captured image is displayed in the order of scanning in pixel units. Output sequentially.

  The preprocessing unit 12 supplies image signals in units of pixels sequentially output from the CMOS sensor 11 to the AF detection unit 13 and the memory 14 after performing preprocessing such as black level correction.

  The AF detection unit 13 includes a Y generation unit 31, an AF detection filter unit 32, a block integration unit 33, and a sensor coordinate supply unit 34.

The Y generation unit 31 generates a luminance component to be subjected to AF detection from an image signal in units of pixels output from the CMOS sensor 11 and supplied via the preprocessing unit 12.
The AF detection filter unit 32 extracts a frequency component (excluding a DC component) from the luminance component in units of pixels generated by the Y generation unit 31, and supplies the extracted frequency component to the block integration unit 33 as an AF detection value.
The block integration unit 33 calculates an AF evaluation value by integrating the AF detection values of the pixels in the AF detection region among the AF detection values supplied from the AF detection filter unit 32 in units of pixels.
The sensor coordinate supply unit 34 notifies the block integration unit 33 of the pixel position corresponding to the AF detection value supplied to the block integration unit 33 as the coordinates of the CMOS sensor 11, that is, the coordinates of the coordinate system before distortion correction. Then, the block integrator 33 notifies the distortion correction notified from the sensor coordinate supplier 34 whether or not the AF detection value supplied from the AF detection filter 32 corresponds to a pixel in the AF detection area. Judgment is based on the coordinates of the previous coordinate system.

  As described above, the AF detection unit 13 outputs an image signal of a captured image output from the CMOS sensor 11 and supplied via the preprocessing unit 12, that is, an image before distortion correction is performed by the distortion correction unit 16 described later. AF detection is performed on the signal.

The image signal of the captured image output from the CMOS sensor 11 is also supplied to the memory 14 as a digital image signal via the preprocessing unit 12.
Here, the digital image signal is hereinafter referred to as “data”. An aggregate of one-pixel data output from the CMOS sensor 11, that is, an aggregate of all pixel data within the input angle of view of the CMOS sensor 11 is hereinafter referred to as “frame image data”. . The unit of storage in the memory 14 is such frame image data.
That is, the memory 14 stores frame image data 51 output from the CMOS sensor 11 and supplied via the preprocessing unit 12. The frame image data 51 is image data of a RAW image in which distortion occurs as described above. Therefore, such frame image data 51 is hereinafter referred to as “distortion RAW 51”.

The YUV generation unit 15 reads out the distorted RAW 51 from the memory 14, and frame image data 52 including three elements of a luminance signal (Y), a blue component difference signal (U), and a red component difference signal (V). Is generated and stored in the memory 14.
Here, the frame image data 52 is still distorted. Therefore, such frame image data 52 is hereinafter referred to as “distorted YUV 52”.

  The distortion correction unit 16 reads the distortion YUV 52 from the memory 14, performs distortion correction, and stores the frame image data obtained as a result in the memory 14 as the correction YUV 53.

  FIG. 7 shows the relationship between the AF frame 55 and the distorted YUV 52 when the AF detection unit 13 performs AF detection.

AF detection is performed in the coordinate system of the distortion YUV 52 shown in FIG. 7, that is, the coordinate system before distortion correction.
However, as shown in FIG. 7, in the prior art, an actual AF detection area is set corresponding to the AF frame 55 of the coordinate system after distortion correction. That is, there is a problem that it is difficult to obtain an accurate AF evaluation value.

  The present invention has been made in view of such a situation, and an object thereof is to perform AF setting more accurately.

According to a first aspect of the invention,
In an imaging apparatus having an optical lens in which a predetermined aberration occurs,
An imaging unit that captures an image in which distortion is caused by the optical lens as an original image, and outputs the original image; a correction unit that corrects distortion for the original image output by the imaging unit;
Setting means for setting a range to be focused on a corrected image obtained as a result of distortion correction by the correcting means;
Generating means for generating an AF detection value of the original image output from the imaging means;
Conversion means for converting pre-Symbol the position of the AF detection value, the position of the second coordinate system the corrected image belongs from the position of the first coordinate system in which the original image belongs,
Using the original image whose coordinate system has been converted by the converting means and the corrected image, out of the AF detection values of the original image before distortion correction by the correcting means, the focus set by the setting means is focused. AF evaluation value calculating means for calculating an AF evaluation value within the range to be focused from the AF detection value at the position of the second coordinate system included within the power range;
An imaging apparatus comprising:

According to a fifth aspect of the present invention,
In an AF evaluation value calculation method for calculating an AF evaluation value,
An acquisition step of acquiring, as an original image, an image picked up by the image pickup means in a state where distortion is caused by the optical lens;
A correction step for correcting distortion of the original image;
A setting step for setting a range to be focused on a corrected image obtained as a result of distortion correction;
A generation step of generating an AF detection value of the original image output from the imaging means;
A conversion step of converting the position of the AF detection value from the position of the first coordinate system to which the original image belongs to the position of the second coordinate system to which the correction image belongs;
Using the original image obtained by converting the coordinate system by the converting means and the corrected image, the AF detection value of the original image before distortion correction is included in the set range to be focused . An AF evaluation value calculating step for calculating an AF evaluation value within the range to be focused from the AF detection value at the position of the coordinate system of 2 ;
An AF evaluation value calculation method including

According to a sixth aspect of the present invention,
Computer
An acquisition means for acquiring an image captured by the imaging means in a state where distortion is caused by the optical lens as an original image;
Correction means for performing distortion correction on the original image; setting means for setting a range to be focused on a corrected image obtained as a result of distortion correction by the correction means;
Generating means for generating an AF detection value of the original image output from the imaging means;
Conversion means which converts the position of the AF detection value, the position of the second coordinate system the corrected image belongs from the position of the first coordinate system in which the original image belongs,
Using the original image whose coordinate system has been converted by the converting means and the corrected image, out of the AF detection values of the original image before distortion correction by the correcting means, the focus set by the setting means is focused. An AF evaluation value calculating means for calculating an AF evaluation value within the range to be focused from the AF detection value at the position of the second coordinate system included within the power range;
Provide a program that functions as

  According to the present invention, AF can be set more accurately.

It is a block diagram which shows the structure of the hardware of the imaging device which concerns on one Embodiment of this invention. It is a functional block diagram which shows the functional structure for implement | achieving the function of AF detection among the various functions which the imaging device of FIG. 1 has. It is a figure which shows typically the relationship between the process of the coordinate correction by the coordinate deformation correction part of the imaging device of FIG. 2, and an AF frame. 3 is a flowchart illustrating an example of a flow of AF processing executed by the imaging apparatus of FIG. FIG. 3 is a diagram illustrating an example of a live view image and an AF frame displayed on a display unit of the imaging apparatus in FIG. 2. It is a functional block diagram which shows the functional structure for implement | achieving the function of AF detection among the various functions which the conventional imaging device has. It is a figure which shows the relationship between AF frame and distortion YUV when the conventional imaging device of FIG. 6 performs AF detection.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram illustrating a hardware configuration of an imaging apparatus 100 according to an embodiment of the present invention. The imaging apparatus 100 can be configured by a digital camera, for example.

  The imaging device 100 includes an optical lens device 111, an AF mechanism 112, a shutter device 113, an actuator 114, a CMOS sensor 115, a preprocessing unit 116, a TG (Timing Generator) 117, a signal processing unit 118, A DRAM (Dynamic Random Access Memory) 119, a CPU 120, a RAM (Random Access Memory) 121, a ROM (Read Only Memory) 122, a display control unit 123, a display unit 124, an operation unit 125, and a memory card 126. And comprising.

The optical lens device 111 is composed of, for example, a focus lens and a zoom lens.
The focus lens is an optical lens for forming a subject image on the light receiving surface of the CMOS sensor 115. The zoom lens is an optical lens that freely changes the focal length within a certain range.
When the subject image is formed on the light receiving surface of the CMOS sensor 115 by the optical lens in which such predetermined aberration occurs, the above-described distortion occurs.

  The AF mechanism 112 focuses the subject in the AF frame by moving the focus lens according to the control of the CPU 120 based on the AF evaluation value. Hereinafter, such control of the CPU 120 is referred to as “lens control”.

  The shutter device 113 includes, for example, shutter blades. The shutter device 113 functions as a mechanical shutter that blocks a light beam incident on the CMOS sensor 115. The shutter device 113 also functions as a diaphragm that adjusts the amount of light flux incident on the CMOS sensor 115.

  The actuator 114 opens and closes the shutter blades of the shutter device 113 according to the control of the CPU 120.

  A distorted subject image is incident on the CMOS sensor 115 from the optical lens device 111 via the shutter device 113. Therefore, the CMOS sensor 115 photoelectrically converts (captures) the subject image at regular intervals according to the clock pulse supplied from the TG 117, accumulates the image signal for each pixel, and outputs the accumulated image signal.

  The preprocessing unit 116 performs preprocessing such as correction of the black level on the image signal in units of pixels sequentially output from the CMOS sensor 115 according to the clock pulse supplied from the TG 117, and performs signal processing as a signal processing unit. 118 and DRAM 119, respectively.

  The TG 117 supplies a clock pulse to the CMOS sensor 115 and the preprocessing unit 116 at regular intervals according to the control of the CPU 120.

The signal processing unit 118 is constituted by, for example, a DSP (Digital Signal Processor). The signal processing unit 118 executes various types of signal processing on various digital signals such as image data supplied from the preprocessing unit 116 and image data stored in the DRAM 119 according to the control of the CPU 120.
For example, the signal processing unit 118 performs AF detection. Details of the AF detection will be described later with reference to FIGS.

  The DRAM 119 temporarily stores the image data supplied from the preprocessing unit 116 and the image data after the signal processing is executed by the signal processing unit 118. In this case, the recording unit of the DRAM 119 is frame image data.

The CPU 120 controls the overall operation of the imaging apparatus 100.
The RAM 121 functions as a working area when the CPU 120 executes each process.
The ROM 122 stores programs and data necessary for the imaging apparatus 100 to execute each process.
The CPU 120 executes various processes in cooperation with a program stored in the ROM 122 using the RAM 121 as a working area.

  For example, the CPU 120 continues the imaging operation of the CMOS sensor 115 at a predetermined timing such as before the captured image recording process, and the frame image data sequentially generated by the signal processing unit 118 during that time (correction in FIG. 2 described later) YUV 203) is temporarily stored in the DRAM 119. Hereinafter, a series of processes performed by the CPU 120 is referred to as “through imaging”.

  Further, the CPU 120 controls the display control unit 123 to sequentially read out each frame image data (such as correction YUV 203 in FIG. 2 described later) recorded in the DRAM 119 during through imaging, and display a corresponding frame image on the display unit. 124 is displayed. Hereinafter, a series of processing of the CPU 120 is referred to as “through display”. A frame image displayed through is called a “through image” or “live view image” as described above.

  In other words, the display control unit 123 reads frame image data (such as correction YUV 203 in FIG. 2 described later) stored in the DRAM 119 or the memory card 126 according to the control of the CPU 120 and displays the corresponding frame image on the display unit 124. Display.

Further, the CPU 120 can set an AF frame and control the display control unit 123 to display it on the live view image (see FIG. 5 described later). In this case, the CPU 120 sets an area surrounded by the AF frame of the coordinate system after distortion correction as an AF detection area.
Then, the CPU 120 controls the signal processing unit 118 to execute AF detection. Details of the AF detection will be described later with reference to FIGS.

The operation unit 125 receives operations of various buttons by the user. The operation unit 125 includes, for example, a power button, a cross button, a determination button, a menu button, a release button, and the like.
The operation unit 125 supplies the CPU 120 with signals corresponding to the operations of the received various buttons. The CPU 120 analyzes the user's operation content based on the signal from the operation unit 125 and executes processing according to the operation content.
For example, when a button to which an instruction operation for recording a captured image is assigned is pressed, the CPU 120 interprets that there is an instruction for recording, and records a correction YUV 203 described later on the memory card 126 or the like.

  In other words, the memory card 126 records the corrected YUV 203 and the like by such recording control of the CPU 120. The memory card 126 also records various data as necessary.

  FIG. 2 is a functional block diagram showing a functional configuration for realizing the AF detection function among various functions of the signal processing unit 118 of the imaging apparatus 100 having the above configuration.

  The signal processing unit 118 of the imaging apparatus 100 includes an AF detection unit 151, a YUV generation unit 152, and a distortion correction unit 153.

Here, the functional blocks excluding the AF detection unit 151, that is, each of the YUV generation unit 152 and the distortion correction unit 153, has basically the same configuration and function as each of the YUV generation unit 15 and the distortion correction unit 16 of FIG. have.
Therefore, each of the distorted RAW 201, the distorted YUV 202, and the corrected YUV 203 has basically the same structure as each of the distorted RAW 51, the distorted YUV 52, and the corrected YUV 53 shown in FIG.
Therefore, in the following, these descriptions will be omitted as appropriate, and mainly the AF detector 151 different from FIG. 6 will be described.

  The AF detection unit 151 includes a Y generation unit 161, an AF detection filter unit 162, a block integration unit 163, a sensor coordinate supply unit 164, and a coordinate deformation correction unit 165.

The Y generation unit 161 generates a luminance component to be subjected to AF detection from an image signal in units of pixels output from the CMOS sensor 115 and supplied via the preprocessing unit 116.
The AF detection filter unit 172 extracts a frequency component (excluding a DC component) from the luminance component generated in units of pixels by the Y generation unit 161 and supplies the frequency component to the block integration unit 163 as an AF detection value.
The block integration unit 163 calculates an AF evaluation value by integrating the AF detection values of the respective pixels in the AF detection area among the AF detection values supplied in units of pixels from the AF detection filter unit 162.

The sensor coordinate supply unit 164 acquires the pixel position of the pixel corresponding to the AF detection value supplied to the block integration unit 163 (hereinafter referred to as “target pixel position”) from the ROM 122 (FIG. 1) or the like via the CPU 120. Then, it is supplied to the coordinate deformation correction unit 165 as the coordinates of the CMOS sensor 115.
That is, the data of each pixel constituting the distorted RAW 201 is sequentially supplied from the CMOS sensor 115 to the signal processing unit 118 via the preprocessing unit 116 in the order of the scanning direction. As a result, luminance components are sequentially generated by the Y generation unit 161 in the order of the scanning direction in units of pixels and supplied to the AF detection filter unit 162.
Therefore, the sensor coordinate supply unit 164 acquires the coordinates on the CMOS sensor 115 of the luminance components sequentially supplied to the AF detection filter unit 162 in the order of the scanning direction in units of pixels from the ROM 122 or the like. Then, the sensor coordinate supply unit 164 supplies the acquired coordinates as the target pixel position to the coordinate deformation correction unit 165.

Here, the coordinate system of the CMOS sensor 115 is a coordinate system before distortion correction, whereas the coordinate system in which the AF frame is set is a coordinate system after distortion correction.
Therefore, the coordinate deformation correction unit 165 uses the coordinates of the target pixel position indicated in the coordinate system before distortion correction, the coordinates of the coordinate system after distortion correction, that is, the coordinates of the correction YUV 203 (hereinafter referred to as “coordinates after deformation correction”). Convert to
The coordinates after deformation correction of the target pixel position are supplied to the block integration unit 163. Then, the block integration unit 163 determines whether or not the AF detection value supplied from the AF detection filter unit 162 corresponds to a pixel in the AF detection region, and the pixel of interest supplied from the coordinate deformation correction unit 165. Judgment is made based on the coordinates after position deformation correction.

  Hereinafter, the coordinates after deformation correction of the target pixel position will be described in more detail.

  To the coordinate deformation correction unit 165, the coordinates of each pixel of the CMOS sensor 115 expressed in the coordinate system before distortion correction are sequentially supplied from the sensor coordinate supply unit 164 in the order of the scanning direction. The timing at which the coordinates in the coordinate system before distortion correction are supplied to the coordinate deformation correction unit 165 is synchronized with the timing at which the AF detection value for each pixel is supplied to the block integration unit 163. Accordingly, the coordinates supplied from the sensor coordinate supply unit 164 to the coordinate deformation correction unit 165 at a predetermined timing are the pixel positions corresponding to the AF detection values supplied to the block integration unit 163 at the predetermined timing, that is, the target pixel position. The coordinates of the coordinate system before distortion correction for are shown.

The coordinate deformation correction unit 165 converts the coordinates of the target pixel position in the coordinate system before distortion correction into coordinates after deformation correction according to a predetermined algorithm.
Specifically, in this embodiment, the coordinates of the target pixel position in the coordinate system before distortion correction are converted into coordinates after deformation correction according to the following algorithm.

  In the present embodiment, for example, it is assumed that a table that stores a ratio between an actual image height with distortion and an ideal image height is stored in advance in the ROM 122 or the like.

Here, the coordinate of the target pixel position in the CMOS sensor 115, that is, the coordinate of the target pixel position in the coordinate system before distortion correction is described as (xs, ys). The coordinates of the optical center in the coordinate system before distortion correction are described as (xcent, ycent).
A function for converting an actual image height ih to an ideal image height using a table stored in advance in the ROM 122 or the like is defined as Fdist (ih).
Here, the actual image height ih is expressed as in Expression (1).
ih = sqrt {(xs-xcent) ^ 2 + (ys-ysent) ^ 2}
... (1)
In this case, if the coordinate after deformation correction is described as (xi, yi) with respect to the coordinate (xs, ys) of the target pixel position in the coordinate system before distortion correction, the X coordinate xi of the coordinate after deformation correction is expressed by equation (2). ), And the Y coordinate yi of the coordinates after deformation correction is expressed as in Expression (3).
xi = (xs−xcent) × Fdist (ih) + xcent
... (2)
yi = (ys−ycent) × Fdist (ih) + ycent
... (3)

  Accordingly, the coordinate deformation correction unit 165 uses the table stored in advance in the ROM 122 or the like to execute the calculations of Expressions (2) and (3), thereby the coordinates of the pixel position of interest in the coordinate system before distortion correction ( xs, ys) can be easily converted into coordinates (xi, yi) after deformation correction.

  FIG. 3 is a diagram schematically showing the relationship between the coordinate correction processing by the coordinate deformation correction unit 165 and the AF frame.

  In FIG. 3, arrows 261 and 262 indicate the scanning order of the CMOS sensor 115, that is, the input order of AF detection values in pixel units to the block integration unit 163.

An arrow 261 indicates the scanning order in the coordinate system on the CMOS sensor 115 before coordinate correction by the coordinate deformation correction unit 165, that is, the coordinate system before distortion correction. Therefore, one arrow 261 indicates one line position in the coordinate system before distortion correction.
Here, for the sake of convenience, the arrow 261 is shown on the distortion YUV 202 represented in the coordinate system before distortion correction.

On the other hand, an arrow 262 indicates the scanning order in the coordinate system after coordinate correction by the coordinate deformation correction unit 165, that is, the coordinate system after distortion correction. Accordingly, one arrow 262 indicates one line position in the coordinate system after distortion correction.
That is, the coordinate deformation correction unit 165 converts the line position indicated by each arrow 261 in the coordinate system before distortion correction into the line position indicated by each arrow 262 in the coordinate system after distortion correction. .
Such conversion is processing equivalent to distortion correction by the distortion correction unit 153.
That is, the distortion correction unit 153 cuts out the data of the distorted area from the distorted YUV 202 having the same size as the input field angle of the CMOS sensor 115. The area cut out from the distorted YUV 202 in this way is hereinafter referred to as “YUV cut-out area”. Next, the distortion correction unit 153 generates correction YUV 203 having the same size as the input field angle of the CMOS sensor 115 by deforming and correcting the data of the YUV cut-out area.
For this reason, the arrow 262 is illustrated on the corrected YUV 203 represented in the coordinate system after distortion correction for convenience.

  In this way, the coordinate deformation correction unit 165 sequentially supplies the post-deformation correction coordinates (xi, yi) of the target pixel position to the block integration unit 163 along the arrow 262 represented by the coordinate system after distortion correction. It will be.

Here, as described above, the block integrator 163 determines whether or not the target pixel position exists in the AF detection area. The coordinates of the target pixel position in this case are coordinates after deformation correction (xi, yi) expressed in the coordinate system after distortion correction, and the actual AF detection area is also expressed in the same coordinate system after distortion correction. It is set from the passed AF frame 272.
That is, the post-deformation corrected coordinates (xi, yi) of the target pixel position on the arrow 262 drawn on the near side correction YUV 203 in FIG. 3 for convenience are set as the near side correction YUV 203 in FIG. It is determined whether or not an actual AF frame detection area in the rectangular AF frame 272 exists.
In this case, from the viewpoint of the pre-distortion correction coordinate system on the CMOS sensor 115, the arrangement position of the AF frame 271 for setting the actual AF detection area coincides with the ideal arrangement position of the AF detection area.
In other words, the processing of the block integration unit 163 described at the beginning of this paragraph is based on the AF frame (distorted AF frame 271 on the distortion YUV 202 on the back side in FIG. 3) existing at an ideal arrangement position in the coordinate system before distortion correction. Is set as the actual AF detection area, and the coordinates of the pixel position of interest in the coordinate system before distortion correction (coordinates on the arrow 261 drawn for convenience on the correction YUV 203 on the back side in FIG. 3) are set. The same effect as the process of using AF detection is obtained. In this way, AF detection can be performed after the AF detection area is set closer to the ideal position.

  Furthermore, there is the following difference between the processing of the block integration unit 163 and the processing described in Patent Document 1.

In other words, in the process described in Patent Document 1, an area in an AF frame (corresponding to the distorted AF frame 55 on the distorted YUV 202 on the back side in FIG. 3) present at an ideal arrangement position in the coordinate system before distortion correction. Are set as the actual AF detection area.
In this case, since the shape of the actual AF detection area is distorted, it is impossible to represent the actual AF detection area only by the coordinates of the upper left corner and the lower right corner.
Therefore, the process of determining whether or not the target pixel position is within the AF detection region becomes complicated, and it is difficult to obtain an accurate AF evaluation value accordingly. That is, accurate AF setting becomes difficult.

On the other hand, the actual AF detection area used in the processing of the block integration unit 163 is an area within the AF frame of the coordinate system after distortion correction. That is, the area within the rectangular AF frame 272 set to the correction YUV 203 on the near side in FIG. 3 is used as the actual AF detection area.
In this case, since the shape of the actual AF detection area remains rectangular, for example, as shown in step S21 of FIG. 4 described later, only the coordinates of the upper left end and the lower right end in the coordinate system after distortion correction are specified. An actual AF detection area can be expressed.
As a result, as shown in step S25 of FIG. 4 to be described later, the target pixel position is detected by AF detection only by comparing the post-deformation correction coordinates (xi, yi) of the target pixel position with the coordinates of the upper left corner and the lower right corner. It is possible to easily and accurately determine whether or not it is within the area.
Thereby, it is possible to obtain a more accurate AF evaluation value as compared with Patent Document 1, and thus it is possible to set a more accurate AF.

  Next, with reference to FIG. 4, an AF process among processes executed by the imaging apparatus 100 having the functional configuration of FIG. 2 will be described.

  FIG. 4 is a flowchart illustrating an example of the flow of AF processing.

In step S <b> 21, the CPU 120 sets an AF frame in the coordinate system after distortion correction, sets an area in the AF frame as an AF detection area, and notifies the block integration unit 163.
That is, the distortion RAW 201 output from the CMOS sensor 115 and stored in the DRAM 119 via the preprocessing unit 116 becomes the distortion YUV 202 by the YUV generation unit 152, and further, the distortion correction is performed by the distortion correction unit 153. Become. The AF frame is set on the corrected YUV 203 in the coordinate system after such distortion correction.
The set AF frame is displayed on the display unit 124 under the control of the display control unit 123 together with the correction YUV 203. Further, the area within the AF frame is set as the AF detection area and notified to the block integration unit 163.
In the present embodiment, the AF frame is a rectangular frame, the coordinates at the upper left corner of the coordinate system after distortion correction are (x0, y0), and the coordinates at the lower right corner of the coordinate system after distortion correction are (x1, y1). It shall be set to become. In this case, the AF detection area can be expressed only by coordinates (x0, y0) at the upper left corner of the coordinate system after distortion correction and coordinates (x1, y1) at the lower right corner of the coordinate system after distortion correction.

  In step S22, the block integrator 163 initializes the integrated value of the AF detection value. Here, when the integral value is described as Sum, initialization is performed so that Sum = 0.

In step S23, the block integration unit 163 acquires the AF detection value Flt and the coordinates (xi, yi) after deformation correction at the target pixel position.
Here, the target pixel position is updated in the process of step S27 described later, but when the process of step S23 is executed after the process of step S22, the pixel position of the upper left pixel of the CMOS sensor 115 is set. ing.
The AF detection filter unit 162 extracts a frequency component (excluding a DC component) from the luminance component at the target pixel position, and sends it to the block integration unit 163 as an AF detection value at the target pixel position (hereinafter referred to as “Flt”). Supply.
At this time, the coordinate deformation correction unit 165 performs the calculation of the above-described formulas (2) and (3), so that the target pixel position expressed in the post-distortion correction coordinate system, that is, the post-deformation correction coordinates of the target pixel position. (Xi, yi) is calculated and supplied to the block integrator 163.
Therefore, in step S23, the block integration unit 163 acquires the AF detection value Flt and the coordinates (xi, yi) after deformation correction at the target pixel position.

In step S24, the block integration unit 163 performs in-frame determination using the post-deformation corrected coordinates (xi, yi) of the target pixel position acquired in the process of step S23.
That is, the block integration unit 163 determines whether or not the post-deformation correction coordinates (xi, yi) of the target pixel position are included in the rectangular AF detection area set in the post-distortion correction coordinate system in the process of step S21. Determine.
Specifically, in the present embodiment, it is determined whether or not both the inequalities expressed by the following expressions (4) and (5) are satisfied.

x0 ≦ xi ≦ x1 (4)
y0 ≦ yi ≦ y1 (5)

The case where at least one of the inequalities of Expressions (4) and (5) is not satisfied means that the coordinates (xi, yi) after the deformation correction of the target pixel position are not included in the AF detection area.
In such a case, it is determined as NO in Step S24, and the process of Step S25 is not executed, that is, the AF detection value Flt acquired in the process of Step S23 is not accumulated, and the process is performed in Step S26. Proceed to

On the other hand, the case where both inequalities (4) and (5) are satisfied means that the coordinates (xi, yi) after the deformation correction of the target pixel position are included in the AF detection area. .
In such a case, it is determined as YES in Step S24, and the process proceeds to Step S25.
In step S25, the block integration unit 163 integrates the AF detection value Flt acquired in the process of step S23 with the previous integration value Sum, and sets the integration value as a new integration value Sum (Sum = Sum + Flt). ).

  In this way, when the process of step S25 ends or when it is determined NO in the process of step S24, the process proceeds to step S26. In step S26, the block integrator 163 determines whether or not the processing for one frame has been completed.

When the target pixel position is not the position of the pixel scanned last in the frame in the CMOS sensor 115, that is, when it is not the pixel at the lower right corner, it is determined as NO in Step S26, and the process proceeds to Step S27.
In step S27, the block integrator 163 shifts the target pixel position by one pixel in the scanning direction. Thereby, a process is returned to step S23 and the process after it is repeated.

That is, each luminance component of the distortion RAW 201 input from the CMOS sensor 115 via the preprocessing unit 116 is sequentially generated by the Y generation unit 161 as the luminance component at the target pixel position and sequentially output to the block integration unit 163. Each time, the loop process of steps S23 to S27 is repeated.
As a result, the AF detection values FLt corresponding to the respective luminance components in the AF detection region are sequentially integrated, and the integration value Sum is updated.
Then, when the position of the pixel scanned last in the frame in the CMOS sensor 115 becomes the target pixel position, it is determined NO in the process of step S24, or the process of step S25 is executed. Then, it is determined as YES in the next step S26, and the process proceeds to step S28.

  In step S28, the block integrator 163 detects the integration value Sum as an AF evaluation value.

When the AF evaluation value detected in this way is acquired by the CPU 120, the process proceeds to step S29.
In step S29, the CPU 120 executes lens control and AF frame display control using the AF evaluation value.
As a result, the AF process ends.

The AF process described above is repeatedly executed at predetermined intervals. As a result, the focus lens moves to a position where the AF evaluation value is highest. Of the AF frames on the live view image, the focused AF frame is displayed in a different display form from the unfocused AF frame.
FIG. 5 shows a display example of the AF frame on the live view image.
As shown in FIG. 5, the live view image 203 is configured by superimposing a plurality of AF frames 272 on the corrected YUV 203.
Of these AF frames 272, the AF frame 272F that is in focus is displayed in a different display form from the AF frame 272N that is not in focus.
The display form of the AF frame 272F that is in focus is sufficient as long as it is distinguishable from the AF frame 272N that is not in focus and can be viewed by the user. For example, the AF frame 272F is displayed with a thick line as shown in FIG. Alternatively, the line color may be changed for display.

In summary, the imaging apparatus 100 according to the present embodiment performs an AF process using the contrast AF method, as illustrated in FIG. 1, the optical lens apparatus 111, the CMOS sensor 115, and the signal processing. Unit 118 and CPU 120.
The CMOS sensor 115 captures, as an original image, an image that is distorted when the optical lens device 111 forms an image on the plane of the first coordinate system (the light receiving surface of the coordinate system before distortion correction), and the original image data. (Distortion RAW 201) is output.
The CPU 120 sets an AF detection area which is a range to be focused in the second coordinate system (post-distortion coordinate system) of the corrected image (corrected YUV 203) obtained as a result of performing distortion correction on the original image. To do.
The AF detection unit 151 calculates an AF evaluation value based on data of one or more pixels in which pixel positions expressed in the second coordinate system are included in the AF detection area in the original image data.

Such an imaging apparatus 100 according to the present embodiment can perform AF setting more accurately.
That is, when AF detection is performed in a state in which the AF detection area is represented by the second coordinate system while the pixel position of each pixel of the original image is represented by the first coordinate system, the problem to be solved by the invention is as follows. ], As described above, a deviation occurs between the actual AF detection area set corresponding to the AF frame and the ideal AF detection area. That is, the AF detection area cannot be set appropriately.
Therefore, in order to appropriately set the AF detection area, it is necessary to match the coordinate system of the AF detection area and the pixel position of each pixel of the original image.
However, as in Patent Document 1, when the AF detection area and the pixel position of each pixel of the original image are matched in the first coordinate system, the shape of the AF detection area is on the distortion YUV 202 on the back side in FIG. Similar to the shape of the distorted AF frame 271 drawn for convenience, it is distorted. Since it is complicated to determine whether or not a pixel is included in such a distorted AF detection area, it is difficult to obtain an accurate AF evaluation value. That is, accurate AF setting becomes difficult.
On the other hand, in the present embodiment, the AF detection area and the pixel position of each pixel of the original image are matched with each other in the second coordinate system. Therefore, the shape of the AF detection area is the corrected YUV 203 on the near side in FIG. Similar to the shape of the rectangular AF frame 272 drawn for convenience, the shape can be a simple shape such as a rectangle. It is very easy to determine whether or not a pixel is included in such a simple AF detection area. Specifically, in the present embodiment, a very easy determination process is executed, such as whether or not both the inequalities expressed by the above-described equations (4) and (5) are satisfied. As a result, a more accurate AF evaluation value can be obtained, and as a result, more accurate AF setting can be performed.

  In addition, this invention is not limited to the above-mentioned embodiment, The deformation | transformation in the range which can achieve the objective of this invention, improvement, etc. are included in this invention.

For example, in the above-described embodiment, the detection values used for AF detection are acquired for all the pixels constituting the captured image, and only the detection values of pixels belonging to the AF detection area among the acquired detection values for all the pixels. Was integrated to calculate an AF evaluation value. However, the AF evaluation value calculation method is not particularly limited to this.
For example, the AF evaluation value may be calculated by acquiring the detection values only for the pixels in the AF detection region and integrating them. The AF process in this case is, for example, as follows when compared with the AF process of FIG.
That is, after processing equivalent to steps S21 and S22 in FIG. 4 is executed, processing for obtaining the post-deformation correction coordinates (xi, yi) of the target pixel position is executed as processing corresponding to step S23. That is, at this time, the detection value Flt at the target pixel position is not acquired.
If it is determined as YES in the frame determination in step S24, that is, if the target pixel position exists in the AF detection area, the detection value Flt of the target pixel position is acquired. Then, integration of the acquired detection value Flt is executed by a process equivalent to step S25. Thereby, the process equivalent to the process after step S26 is performed.
On the other hand, when it is determined as NO in the determination in step S24, that is, when the target pixel position is outside the AF detection region, the detection value Flt of the target pixel position is not acquired, and as a result, The integration of the detection value Flt is not executed, and the processing is equivalent to the processing after step S26.
Note that a description of processing equivalent to the processing after step S26 is omitted.

Further, for example, in the above-described embodiment, the method of distortion of the image due to the influence of the optical lens is fixed for simplicity of explanation, but may be different depending on the situation of the optical lens. For example, there is a case where the method of distortion differs depending on the position of the zoom lens, that is, the zoom value.
In such a case, for example, the state of the optical lens such as a zoom value may be detected, and the distortion correction method and the correction amount may be changed based on the detection result.
Similarly, the conversion method and change amount when the coordinates of the target pixel position indicated in the coordinate system before distortion correction are converted to the coordinates after the distortion correction coordinate system, that is, the coordinates after deformation correction are also the same as those of the optical lens such as the zoom value. You may make it change based on the detection result of a condition.

  For example, in the above-described embodiment, the CMOS sensor 115 is employed as the image sensor. However, any image sensor can be adopted as the image sensor to which the present invention can be applied.

  For example, in the above-described embodiment, the imaging apparatus to which the present invention is applied has been described as an example configured as a digital camera. However, the present invention is not particularly limited to a digital camera, and can be applied to general electronic devices having an imaging function using an optical lens. Specifically, for example, the present invention is applicable to a video camera, a portable navigation device, a portable game machine, and the like.

  The series of processes described above can be executed by hardware or can be executed by software.

  When a series of processing is executed by software, a program constituting the software is installed on a computer or the like from a network or a recording medium. The computer may be a computer incorporated in dedicated hardware. The computer may be a computer capable of executing various functions by installing various programs, for example, a general-purpose personal computer.

  Although not shown, the recording medium including such a program is not only constituted by a removable medium distributed separately from the apparatus main body in order to provide a program to the user, but also in a state of being incorporated in the apparatus main body in advance. It is composed of a recording medium provided to the user. The removable medium is composed of, for example, a magnetic disk (including a floppy disk), an optical disk, a magneto-optical disk, or the like. The optical disk is composed of, for example, a CD-ROM (Compact Disk-Read Only Memory), a DVD (Digital Versatile Disk), or the like. The magneto-optical disk is configured by an MD (Mini-Disk) or the like. In addition, the recording medium provided to the user in a state of being preinstalled in the apparatus main body includes, for example, the ROM 122 of FIG. 1 in which a program is recorded, a hard disk (not shown), and the like.

  In the present specification, the step of describing the program recorded on the recording medium is not limited to the processing performed in time series along the order, but is not necessarily performed in time series, either in parallel or individually. The process to be executed is also included.

  DESCRIPTION OF SYMBOLS 100 ... Image processing apparatus, 111 ... Optical lens apparatus, 112 ... AF mechanism, 113 ... Shutter apparatus, 114 ... Actuator, 115 ... CMOS sensor, 116 ... Pre-processing part 117 ... TG, 118 ... Signal processing unit, 119 ... DRAM, 120 ... CPU, 121 ... RAM, 122 ... ROM, 123 ... Display control unit, 124 ... Display unit 125 ... Operation unit 126 ... Memory card 151 ... AF detection unit 152 ... YUV generation unit 153 ... Distortion correction unit 161 ... Y generation unit 162: AF detection filter unit, 163: Block integration unit, 164: Sensor coordinate supply unit, 165: Coordinate deformation correction unit

Claims (7)

In an imaging apparatus having an optical lens in which a predetermined aberration occurs,
An imaging unit that captures an image in which distortion is caused by the optical lens as an original image, and outputs the original image; a correction unit that corrects distortion for the original image output by the imaging unit;
Setting means for setting a range to be focused on a corrected image obtained as a result of distortion correction by the correcting means;
Generating means for generating an AF detection value of the original image output from the imaging means;
Conversion means for converting pre-Symbol the position of the AF detection value, the position of the second coordinate system the corrected image belongs from the position of the first coordinate system in which the original image belongs,
Using the original image whose coordinate system has been converted by the converting means and the corrected image, out of the AF detection values of the original image before distortion correction by the correcting means, the focus set by the setting means is focused. AF evaluation value calculating means for calculating an AF evaluation value within the range to be focused from the AF detection value at the position of the second coordinate system included within the power range;
An imaging apparatus comprising: Determination means for determining whether or not the position of the AF detection value in the second coordinate system is included in the range to be combined;
The AF evaluation value calculating means uses the AF detection value is determined to be included in the range to be the synthesis by the determination means, the image pickup according to claim 1, characterized in that to calculate the AF evaluation value apparatus. Display means for displaying an image;
Display control means for controlling the correction image so as to superimpose and display a rectangular frame indicating the range to be focused set by the setting means on the display means;
The imaging apparatus according to claim 1 or 2, further comprising a. Focusing control means for performing focusing control of the optical lens based on the AF evaluation value calculated by the AF evaluation value calculating means;
The imaging apparatus according to any one of claims 1 to 3, further comprising a.   The imaging apparatus according to claim 1, wherein the imaging apparatus performs focusing by a contrast AF method. In an AF evaluation value calculation method for calculating an AF evaluation value,
An acquisition step of acquiring, as an original image, an image picked up by the image pickup means in a state where distortion is caused by the optical lens;
A correction step for correcting distortion of the original image;
A setting step for setting a range to be focused on a corrected image obtained as a result of distortion correction;
A generation step of generating an AF detection value of the original image output from the imaging means;
A conversion step of converting the position of the AF detection value from the position of the first coordinate system to which the original image belongs to the position of the second coordinate system to which the correction image belongs;
Using the original image obtained by converting the coordinate system by the converting means and the corrected image, the AF detection value of the original image before distortion correction is included in the set range to be focused . An AF evaluation value calculating step for calculating an AF evaluation value within the range to be focused from the AF detection value at the position of the coordinate system of 2 ;
A method for calculating an AF evaluation value, comprising: Computer
An acquisition means for acquiring an image captured by the imaging means in a state where distortion is caused by the optical lens as an original image;
Correction means for performing distortion correction on the original image; setting means for setting a range to be focused on a corrected image obtained as a result of distortion correction by the correction means;
Generating means for generating an AF detection value of the original image output from the imaging means;
Converting means for converting the position of the AF detection value, the position of the second coordinate system the corrected image belongs from the position of the first coordinate system in which the original image belongs,
Using the original image whose coordinate system has been converted by the converting means and the corrected image, out of the AF detection values of the original image before distortion correction by the correcting means, the focus set by the setting means is focused. An AF evaluation value calculating means for calculating an AF evaluation value within the range to be focused from the AF detection value at the position of the second coordinate system included within the power range;
A program characterized by functioning as

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