JP6464553B2 - Lens drive control device, electronic camera, and lens drive control program - Google Patents

Description

  The present invention relates to a lens drive control device, an electronic camera, and a lens drive control program.

  2. Description of the Related Art Conventionally, there is known an autofocus device that obtains a contrast value of an image at each position while moving a focus lens in the optical axis direction, and detects a lens position having the highest contrast value as a focus position (for example, Patent Document 1). reference).

JP-A-4-274405

  However, the conventional autofocus device has a problem that it takes a long time to detect the focus position because the focus lens is driven in the optical axis direction over a wide range.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a lens drive control device, an electronic camera, and a lens drive control program capable of quickly focusing an image.

The lens drive control device that solves the above problems includes a region extraction unit that extracts a specific region from an image, and an in-focus state of the specific region based on a color component amount of an edge of the specific region extracted by the region extraction unit. A focus detection unit that detects a focus, a lens drive control unit that controls driving of a lens that performs focus adjustment based on a focus state of the specific region detected by the focus detection unit, and a plurality of the specific regions of divided into divided regions, based on the ratio of the number of the divided region including the edge of the specific area to the number of the divided region including the specific region, the focus state of the specific region by the focus detection unit And a calculation unit for calculating the reliability of the detection result.

  The lens drive control device further includes an edge detection unit that detects, for each color component, the edge of the specific region extracted by the region extraction unit, and the focus detection unit includes a color component that is detected by the edge detection unit. It is preferable to detect the in-focus state of the specific area based on the color component amount of the edge of the specific area detected every time.

  Further, in the lens drive control device, the in-focus state includes a direction indicator indicating that the image is focused on the near point side or the far point side with respect to the specific region, and the lens drive control unit includes: It is preferable that the driving direction of the lens is set based on the direction indicator detected by the focus detection unit.

Further, in the lens drive control device, before Kigoase state further includes a defocus amount of the specific region, the lens driving control unit, if the value the calculation unit has calculated is not less than a predetermined threshold value, based on the defocus amount detected by the focus detection unit, it is preferable to set the drive amount of the lens.

In the lens drive control device, the value calculated by the calculation unit is further set to a second threshold value that is larger than the first threshold value when the predetermined threshold value is the first threshold value. And when the value calculated by the calculation unit is equal to or greater than the second threshold value , the lens drive control unit displays an image in the specific region based on the defocus amount detected by the focus detection unit. calculates a target drive amount of the lens focusing, it is preferable the calculated target driving amount to be set as the driving amount of said lens.

Further, in the lens drive control device, the lens drive control unit has a value greater than the target drive amount when the value calculated by the calculation unit is equal to or greater than the first threshold and less than the second threshold. it is preferable to set a smaller value as the drive amount of the lens.

In the lens drive control device, it is preferable that the region extraction unit extracts the specific region by performing a labeling process on the image.
In the lens drive control device, it is preferable that the region extraction unit extracts the specific region by performing a pattern recognition process on the image.

  Further, in the lens drive control device, the focus detection unit is positioned on the closest side in the depth direction of the image among the plurality of specific regions when the region extraction unit extracts the plurality of specific regions from the image. It is preferable that the in-focus state of the specific area is detected based on the color component amount of the specific area.

  In addition, an electronic camera that solves the above problems includes an imaging unit that captures an image of a subject, and a lens drive control device configured as described above that controls driving of a lens that performs focus adjustment of an image corresponding to the subject imaged by the imaging unit. It is characterized by having.

Further, a lens drive control program for solving the above-described problem is obtained by performing, on a computer, an area extraction step for extracting a specific area from an image, and the color component amount of an edge of the specific area extracted in the area extraction step. A focus detection step for detecting a focus state of the specific area; and a lens drive control step for controlling the driving of the lens that performs focus adjustment based on the detection result of the focus state of the specific area in the focus detection step; The specific area is divided into a plurality of divided areas, and is detected in the focus detection step based on a ratio of the number of the divided areas including the edge of the specific area to the number of divided areas including the specific area. And a calculation step of calculating the reliability of the detection result of the in- focus state of the specific area.

  According to the present invention, an image can be focused quickly.

1 is a block diagram of a digital camera according to an embodiment. (A) is a schematic diagram showing the positional relationship between the imaging element and the focus lens in a state where the image is in focus on the near point side of the subject position, and (b) is a schematic diagram showing that the image is farther from the subject position. The schematic diagram which shows the positional relationship of an image pick-up element and a focus lens in the state which has focused on the point side. The schematic diagram which shows the positional relationship in the optical axis direction of the focus for every color component of the incident light which injected into the focus lens. FIG. 6 is a schematic diagram illustrating a positional relationship for each color component of incident light incident on an image sensor from a subject through a focus lens, in which (a) is a schematic diagram when an image is in a front pin state with respect to the subject; FIG. 6B is a schematic diagram when the image is in a rear pin state with respect to the subject. The schematic diagram which shows an example of an image. FIG. 7A is a graph showing the amount of color components for each color component in the vicinity of an edge, where FIG. Graph when in a pin state. 7 is a graph showing the amount of color components for each color component in the vicinity of an edge, wherein (a) is a color component of red light and green light when an image is in a front pin state or a back pin state with respect to a subject. The graph which shows quantity, (b) is a graph which shows the amount of color components of blue light and green light when the image is in the front pin state or the back pin state with respect to the subject. 6 is a flowchart of a lens drive control processing routine executed by the image processing engine. The schematic diagram which shows an example of a to-be-photographed mask. FIG. 5 is a schematic diagram showing a scan range of contrast scanning set according to the reliability of a defocus feature amount of a subject mask. FIG. 5 is a schematic diagram illustrating a scan range of contrast scanning set according to a defocus amount of a defocus feature amount of a subject mask.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, a digital camera (hereinafter referred to as “camera 10”), which is a kind of electronic camera, includes a lens unit 12 (in FIG. 1, a focus lens 11 that is a lens for performing focus adjustment). Only the focus lens 11 is shown), and an imaging element 13 as an example of an imaging unit that images the light that has passed through the lens unit 12 on the image space side of the lens unit 12 for imaging. The imaging device 13 is a CMOS (Complementary Metal Oxide Semiconductor) type or a CCD (Charge Coupled Device) type color image sensor.

  An image processing engine 14 is connected to the output side of the image sensor 13 via an A / D conversion circuit 15. The pixel signal output as an analog signal from the image sensor 13 is converted into a digital signal by the A / D conversion circuit 15 and then input to the image processing engine 14.

  The image processing engine 14 includes an MPU 16 (Micro Processing Unit) that comprehensively controls various operations of the camera 10. The MPU 16 generates a predetermined image by performing image processing such as color interpolation processing, gradation correction, white balance processing, and contour compensation on the pixel signal input from the image sensor 13.

  A focus drive circuit 17 is connected to the image processing engine 14. Then, the image processing engine 14 drives and controls the AF motor 18 through the focus drive circuit 17 to move the focus lens 11 in the optical axis direction. As a result, the light emitted from the subject passes through the focus lens 11. The image is formed on the image sensor 13.

  In addition, a non-volatile memory 21, a buffer memory 22, an interface unit (hereinafter referred to as “I / F unit 23”) and a monitor 24 are connected to the image processing engine 14 via a data bus 20.

  The nonvolatile memory 21 stores a program executed by the MPU 16 to operate the image processing engine 14. In the present embodiment, the nonvolatile memory 21 stores a lens drive control program shown in the flowchart of FIG. The MPU 16 functions as the main control unit 25, the image processing unit 26, and the focusing control unit 27 by executing a lens drive control program stored in the nonvolatile memory 21. Further, the MPU 16 executes the lens drive control program, so that the image processing engine 14 functions as a lens drive control device that controls the drive of the focus lens 11. The image processing unit 26 includes a face recognition unit 29 that recognizes a human face in the image by pattern recognition processing. The focus control unit 27 includes an area extraction unit 31, an edge detection unit 32, a feature amount calculation unit 33, a reliability calculation unit 34, and a lens drive control unit 35.

For example, the buffer memory 22 temporarily stores captured images, images in the image processing process, images after image processing, images after image compression, and the like.
The I / F unit 23 has a card slot (not shown) in which the memory card 38 is detachably mounted. Then, the I / F unit 23 outputs the image generated by the image processing engine 14 to the memory card 38 attached to the I / F unit 23, or the image stored in the memory card 38 is output to the image processing engine 14. Or has a function to output to

  On the monitor 24, an image temporarily stored in the buffer memory 22 and an image stored in the memory card 38 attached to the I / F unit 23 are output and displayed by the image processing engine 14.

  Further, a release button 39 and an operation unit 40 are connected to the image processing engine 14. The release button 39 inputs an operation signal to the image processing engine 14 when a half-press operation or a full-press operation is performed. The operation unit 40 includes a menu button, a select button, a determination button, a power button, and the like, and inputs an operation signal to the image processing engine 14 when a pressing operation is performed.

  Next, an outline of the principle by which the image processing engine 14 detects the in-focus state of the object edge by analyzing the color shift of the longitudinal chromatic aberration at the object edge detected from the image will be described.

  In FIG. 2A, the state in which the image is in focus at the position of the subject S is indicated by a solid line, and the state in which the image is in focus on the near point side from the position of the subject S (hereinafter, “ The “front pin state” is indicated by a dashed line. As shown in FIG. 2A, in the front pin state, the position where the light emitted from the subject passes through the focus lens 11 and is in focus is closer to the photographer side than the image sensor 13 (in FIG. 2A). Located on the right).

  On the other hand, in FIG. 2B, the state in which the image is in focus at the position of the subject S is indicated by a solid line, and the state in which the image is in focus on the far point side from the position of the subject S (hereinafter referred to as “the subject S”) , Referred to as “rear pin state”). As shown in FIG. 2B, in the rear pin state, the position where the light emitted from the subject passes through the focus lens 11 and is in focus is closer to the focus lens 11 than the image sensor 13 (FIG. 2B). It is located on the left side.

  FIG. 3 shows the state of axial chromatic aberration that occurs when the light emitted from the subject passes through the focus lens 11. As shown in FIG. 3, since axial chromatic aberration occurs due to the difference in wavelength in the light that has passed through the focus lens 11, the focal position is shifted for each wavelength component of the light. Specifically, since the refractive index of light increases as the wavelength of light is shorter, the focus lens 11 is in the order of blue (B) light, green (B) light, and red (R) light. The refractive index when passing through the lens gradually decreases, and the focal position through which the focus lens 11 is focused is gradually distant from the focus lens 11. Then, by analyzing the color shift due to such axial chromatic aberration, the defocus feature amount of the subject is calculated (detected) as the focused state of the subject.

  Here, the defocus feature amount includes a direction index and a defocus amount. The direction index is an index indicating that the image is in the front pin state or the rear pin state with respect to the subject. An example of an evaluation value for calculating the direction index and the defocus amount is Edge Difference (hereinafter referred to as “Ed”).

Next, an outline of the principle of calculating the direction index and the defocus amount in the subject using Ed will be described.
As shown in FIG. 4A, when the image is in the front pin state with respect to the subject, the light emitted from the subject is outside due to the longitudinal chromatic aberration generated when passing through the focus lens 11. To red (R) light, green (G) light, and blue (B) light are guided to the image sensor 13 in a state of being dispersed so as to be positioned in this order. In this case, the defocus amount of the subject that the light passing through the focus lens 11 captures on the image sensor 13 for each color component is in the order of blue (B) light, green (G) light, and red (R) light. It grows gradually.

  On the other hand, as shown in FIG. 4B, when the image is in the rear pin state with respect to the subject, the light emitted from the subject is caused by the axial chromatic aberration generated when passing through the focus lens 11. Then, the light is guided from the outside to the image sensor 13 in a state of being dispersed so as to be positioned in the order of red (R) light, green (G) light, and blue (B) light. In this case, the defocus amount of the subject that the light passing through the focus lens 11 images on the image sensor 13 for each color component is in the order of red (R) light, green (G) light, and blue (B) light. It grows gradually.

  In other words, depending on whether the image is in the front pin state or the rear pin state with respect to the subject, the defocus amount of the subject that the light passing through the focus lens 11 captures on the image sensor 13 for each color component The magnitude relationship of is different.

  FIG. 5 shows a black and white chart S1 as an example of the subject in the image. In FIG. 5, the X coordinate is set in the horizontal direction and the Y coordinate is set in the vertical direction, and the edge E1 of the black and white chart S1 located at the position of X = q is set as the defocus feature amount calculation target. .

  In this case, first, pixel values for each RGB are acquired in the direction crossing the edge E1 (X direction in FIG. 5). At this time, if a pixel value of only one pixel row is acquired, an erroneous pixel value may be acquired if the one pixel row includes noise. Therefore, in this embodiment, as shown in the following formulas (1) to (3), n pixel values in one pixel row are integrated over the width of n pixels in the Y direction, and the integrated value is divided by n. The average value thus obtained is acquired as a pixel value for each RGB crossed by the edge E1 located at x = q.

ここで、ｒ（ｘ，ｋ）、ｇ（ｘ，ｋ）、ｂ（ｘ，ｋ）は、ｙ方向のｎピクセル幅におけるｎ本（ｋ＝１，２，…，ｎ）の１ピクセル行のＲ画素値、Ｇ画素値、Ｂ画素値をそれぞれ示している。ただし、ｘは、図５に示す例ではＸ＝ｑを含む所定範囲（例えば、ｑ−Ｑ／２≦ｘ≦ｑ＋Ｑ／２）を変域とする値を示している。

Here, r (x, k), g (x, k), and b (x, k) are n (k = 1, 2,..., N) one pixel row in the n pixel width in the y direction. R pixel value, G pixel value, and B pixel value are shown. In the example shown in FIG. 5, x represents a value having a predetermined range including X = q (for example, q−Q / 2 ≦ x ≦ q + Q / 2) as a domain.

  Subsequently, by normalizing r_ave (x), g_ave (x), and b_ave (x) using respective maximum values and minimum values as shown in the following equations (4) to (6), Each normalized output is calculated.

ここで、ｘｍｉｎは、エッジＥ１の検出対象領域ＥＡ内で画素値が最小（図５に示す例では黒領域）となるＸ座標値を示し、ｘｍａｘは、エッジＥ１の検出対象領域ＥＡ内で画素値が最大（図５に示す例では白領域）となるＸ座標値を示している。

Here, xmin represents an X coordinate value at which the pixel value is minimum (black area in the example shown in FIG. 5) in the detection target area EA of the edge E1, and xmax is a pixel in the detection target area EA of the edge E1. An X coordinate value having a maximum value (white area in the example shown in FIG. 5) is shown.

  FIG. 6A shows the normalized output of each color component in the vicinity of the edge E1 of the black and white chart S1 when the image is in the front pin state with respect to the edge E1 of the black and white chart S1. As shown in FIG. 6A, when the image is in the front pin state with respect to the edge E1 of the black and white chart S1, the black and white chart S1 in the order of blue (B), green (G), and red (R). The gradient of the color component amount at the edge E1 becomes gradually gentler. This is because, when the image is in the front pin state with respect to the edge E1 of the black and white chart S1, the light that has passed through the focus lens 11 is defocused on the edge E1 of the black and white chart S1 that is captured by the image sensor 13 for each color component This is because the amount gradually increases in the order of blue (B) light, green (G) light, and red (R) light.

  On the other hand, FIG. 6B shows the normalized output of each color component in the vicinity of the edge E1 of the black and white chart S1 when the image is in the back pinned state with respect to the edge E1 of the black and white chart S1. As shown in FIG. 6B, when the image is in the rear pin state with respect to the edge E1 of the black and white chart S1, the black and white chart S1 in the order of red (R), green (G), and blue (B). The gradient of the color component amount at the edge E1 becomes gradually gentler. This is because, when the image is in a back-pin state with respect to the edge E1 of the black and white chart S1, defocusing of the edge E1 of the black and white chart S1 in which the light that has passed through the focus lens 11 is captured by the image sensor 13 for each color component. This is because the amount gradually increases in the order of red (R) light, green (G) light, and blue (B) light.

  That is, as shown in FIG. 7A, the gradient of each color component amount in the vicinity of the edge E1 of the black and white chart S1 is as follows. When the image is in the front pin state with respect to the edge E1 of the black and white chart S1, the gradient of the red (R) color component amount is smaller than the gradient of the green (G) color component amount. On the other hand, when the image is in the rear pin state with respect to the edge E1 of the black and white chart S1, the gradient of the red (R) color component amount is larger than the gradient of the green (G) color component amount. Therefore, the gradient of the red (R) color component amount at the edge E1 of the black and white chart S1 depends on whether the image is in the front pin state or the rear pin state with respect to the edge E1 of the black and white chart S1. The magnitude relationship with the gradient of the color component amount of green (G) is reversed.

  Therefore, by comparing Ed (hereinafter referred to as “EdRG”) based on the red (R) color component amount and the green (G) color component amount with a threshold value, the image is compared with the edge E1 of the monochrome chart S1. Which of the front pin state and the rear pin state is determined is based on the following formulas (7) and (8).

ここで、Σ（Ｒ／Ｇ）は、赤（Ｒ）の色成分量を画像における同一の位置での緑（Ｇ）の色成分量で除算した値を、区間Δ１に亘って加算した総和を示している。そして、その総和を区間Δ１の長さで除算した値がＥｄＲＧとして算出される。なお、区間Δ１は、図７（ａ）において赤（Ｒ）の色成分量と緑（Ｇ）の色成分量とが交わる交点Ｐ１よりも右側に位置する区間のうち、緑（Ｇ）の色成分量に勾配がある区間の一部として規定される。

Here, Σ (R / G) is a sum obtained by adding the value obtained by dividing the red (R) color component amount by the green (G) color component amount at the same position in the image over the section Δ1. Show. Then, a value obtained by dividing the sum by the length of the section Δ1 is calculated as EdRG. The section Δ1 is the color of green (G) in the section located to the right of the intersection P1 where the red (R) color component amount and the green (G) color component amount intersect in FIG. It is defined as a part of a section where the component amount has a gradient.

  And when Formula (7) is materialized, EdRG has shown that an image is a back pin state with respect to the edge E1 of the black-and-white chart S1. On the other hand, when the formula (8) is established, EdRG indicates that the image is in the front pin state with respect to the edge E1 of the black and white chart S1. The difference between EdRG and the threshold value “1” indicates the defocus amount of the edge E1 of the black and white chart S1 in the image.

  Note that whether the image is in the front pin state or the rear pin state with respect to the edge E1 of the black and white chart S1 may be determined based on the following equations (9) and (10). .

ここで、Σ（Ｒ／Ｇ）は、赤（Ｒ）の色成分量を画像における同一の位置での緑（Ｇ）の色成分量で除算した値を、区間Δ２に亘って加算した総和を示している。そして、その総和を区間Δ２の長さで除算した値がＥｄＲＧとして算出される。なお、区間Δ２は、図７（ａ）において赤（Ｒ）の色成分量と緑（Ｇ）の色成分量とが交わる交点Ｐ１よりも左側に位置する区間のうち、緑（Ｇ）の色成分量に勾配がある区間の一部として規定される。

Here, Σ (R / G) is a sum obtained by adding the value obtained by dividing the red (R) color component amount by the green (G) color component amount at the same position in the image over the section Δ2. Show. Then, a value obtained by dividing the sum by the length of the section Δ2 is calculated as EdRG. The section Δ2 is the color of green (G) in the section located on the left side of the intersection P1 where the red (R) color component amount and the green (G) color component amount intersect in FIG. It is defined as a part of a section where the component amount has a gradient.

  And when Formula (9) is materialized, EdRG has shown that the image is a front pin state with respect to the edge E1 of the black-and-white chart S1. On the other hand, when the formula (10) is established, EdRG indicates that the image is in the rear pin state with respect to the edge E1 of the black and white chart S1. The difference between EdRG and the threshold value “1” indicates the defocus amount of the edge E1 of the black and white chart S1 in the image.

  As described above, in the above formulas (7) to (10), the image is applied to the edge E1 of the black and white chart S1 by using the ratio of the red (R) color component amount and the green (G) color component amount. On the other hand, it is determined which of the front pin state and the rear pin state. However, using the difference between the red (R) color component amount and the green (G) color component amount, the image is in either the front pin state or the rear pin state with respect to the edge E1 of the black and white chart S1. You may determine whether there is.

  Similarly, as shown in FIG. 7B, when the image is in the front pin state with respect to the edge E1 of the black and white chart S1, the gradient of the color component amount of blue (B) is green (G). It becomes larger than the gradient of the color component amount. On the other hand, when the image is in a back-pin state with respect to the edge E1 of the black and white chart S1, the gradient of the blue (B) color component amount is smaller than the gradient of the green (G) color component amount. Therefore, the gradient of the blue (B) color component amount and the green (G) color component amount at the edge E1 of the black-and-white chart S1 depending on whether the image is in the front pin state or the rear pin state. The magnitude relationship with the gradient is reversed.

  Therefore, by comparing Ed (hereinafter referred to as “EdBG”) based on the blue (B) color component amount and the green (G) color component amount with a threshold value, the image is compared with the edge E1 of the monochrome chart S1. Which of the front pin state and the rear pin state is determined is based on the following formulas (11) and (12).

ここで、Σ（Ｂ／Ｇ）は、青（Ｂ）の色成分量を画像における同一の位置での緑（Ｇ）の色成分量で除算した値を、区間Δ３に亘って加算した総和を示している。そして、その総和を区間Δ３の長さで除算した値がＥｄＢＧとして算出される。なお、区間Δ３は、図７（ｂ）において青（Ｂ）の色成分量と緑（Ｇ）の色成分量とが交わる交点Ｐ２よりも右側に位置する区間のうち、緑（Ｇ）の色成分量に勾配がある区間の一部として規定される。

Here, Σ (B / G) is a sum obtained by adding a value obtained by dividing the blue (B) color component amount by the green (G) color component amount at the same position in the image over the section Δ3. Show. Then, a value obtained by dividing the sum by the length of the section Δ3 is calculated as EdBG. The section Δ3 is the green (G) color in the section located on the right side of the intersection P2 where the blue (B) color component amount and the green (G) color component amount intersect in FIG. It is defined as a part of a section where the component amount has a gradient.

  When the expression (11) is satisfied, EdBG indicates that the image is in a front pin state with respect to the edge E1 of the black and white chart S1. On the other hand, when the formula (12) is established, EdBG indicates that the image is in the rear pin state with respect to the edge E1 of the black and white chart S1. The difference between EdBG and the threshold value “1” indicates the defocus amount of the edge E1 of the black and white chart S1 in the image.

  Note that whether the image is in the front pin state or the rear pin state with respect to the edge E1 of the black and white chart S1 may be determined based on the following equations (13) and (14). .

ここで、Σ（Ｂ／Ｇ）は、青（Ｂ）の色成分量を画像における同一の位置での緑（Ｇ）の色成分量で除算した値を、区間Δ４に亘って加算した総和を示している。そして、その総和を区間Δ４の長さで除算した値がＥｄＢＧとして算出される。なお、区間Δ４は、図７（ｂ）において青（Ｂ）の色成分量と緑（Ｇ）の色成分量とが交わる交点Ｐ２よりも左側に位置する区間のうち、緑（Ｇ）の色成分量に勾配がある区間の一部として規定される。

Here, Σ (B / G) is a sum obtained by adding the value obtained by dividing the blue (B) color component amount by the green (G) color component amount at the same position in the image over the section Δ4. Show. Then, a value obtained by dividing the sum by the length of the section Δ4 is calculated as EdBG. The section Δ4 is the color of green (G) in the section located on the left side of the intersection P2 where the blue (B) color component amount and the green (G) color component amount intersect in FIG. It is defined as a part of a section where the component amount has a gradient.

  When the formula (13) is established, EdBG indicates that the image is in a rear pin state with respect to the edge E1 of the black and white chart S1. On the other hand, when the formula (14) is established, EdBG indicates that the image is in the front pin state with respect to the edge E1 of the black and white chart S1. The difference between EdBG and the threshold value “1” indicates the defocus amount of the edge E1 of the black and white chart S1 in the image.

  As described above, in the above formulas (11) to (14), the image is applied to the edge E1 of the black-and-white chart S1 by using the ratio of the blue (B) color component amount and the green (G) color component amount. On the other hand, it is determined which of the front pin state and the rear pin state. However, using the difference between the color component amount of blue (B) and the color component amount of green (G), the image is in either the front pin state or the rear pin state with respect to the edge E1 of the black and white chart S1. You may determine whether there is.

  Note that, as an evaluation value for determining whether the image is in the front pin state or the rear pin state with respect to the edge E1 of the black and white chart S1, instead of Ed, a defocus amount reference value (Width of Subtraction) or Line Spread Function may be employed.

  Next, an outline of a lens drive control processing routine executed when the MPU 16 of the image processing engine 14 of the present embodiment controls the in-focus position of the image will be described with reference to the flowchart of FIG.

  Now, when the camera 10 is turned on, the MPU 16 starts a lens drive control processing routine shown in FIG. In step S <b> 11, the image processing unit 26 of the MPU 16 takes in the pixel signal output from the image sensor 13 to generate a through image, and displays the generated through image on the monitor 24.

  Subsequently, in step S12, as a region extraction step, the region extraction unit 31 of the MPU 16 extracts a mask region as an example of a specific region from the through image generated in the previous step S11. In this case, a mask region is extracted from the through image by performing a labeling process on the through image. Here, the labeling technique detects pixel data for each feature amount from a through image, and sequentially detects pixel areas whose positions in the image are adjacent among pixel areas in which the detected pixel data are close to each other. This is a technique for extracting a mask region from a through image by making it into a picture. In the present embodiment, the feature amount used for the labeling process includes a motion vector, hue, saturation, brightness, texture (pattern), contrast, and the like.

  Note that the MPU 16 may extract a mask area from the through image by performing pattern recognition processing on the through image. For example, in the present embodiment, the face recognition unit 29 of the MPU 16 performs face recognition processing, which is a type of pattern recognition processing, on the through image, thereby recognizing the person's face from the through image, and recognizing the recognized human face. You may extract as a mask area | region. In this case, the face recognition unit 29 of the MPU 16 also functions as a region extraction unit that extracts a mask region from the through image.

  Then, the area extraction unit 31 of the MPU 16 stores the image of the mask area extracted from the through image in the buffer memory 22 in, for example, the Exif (Exchangeable Image File Format) format.

  Next, in step S13, the region extracting unit 31 of the MPU 16 excludes the noise mask from the mask regions extracted in the previous step S12. Here, the noise mask means a mask region that cannot be focused in a through image, such as an elongated mask region, an extremely small mask region, or an extremely large mask region. This is because the mask area is not an area that is assumed to be noticed by a person in the through image. Then, the area extraction unit 31 of the MPU 16 stores data indicating that the target is out of focus in the buffer memory 22 as additional information of the noise mask image.

  Subsequently, in step S14, the region extracting unit 31 of the MPU 16 sets priorities for mask regions other than the noise mask among the mask regions extracted in the previous step S12. This priority means a degree that a person is expected to pay more attention in the mask area, and is defined by a total value of scores calculated for each feature amount of the mask area. Note that the feature quantity that defines the priority of the mask area includes a motion vector, a position, a hue, a degree of heterogeneity, and the like. Here, the degree of heterogeneity means the degree of unique distribution in the histogram of the feature amount. For example, when red flowers are blooming on a green background, the red hue is uniquely distributed in the hue histogram. For this reason, the red flower is recognized as a mask region having a high degree of heterogeneity, so that the score regarding the degree of heterogeneity is set high. Then, the area extracting unit 31 of the MPU 16 stores the score data calculated for each feature amount of the mask area in the buffer memory 22 as additional information of the image of the mask area.

  Then, in step S15, the area extraction unit 31 of the MPU 16 has the highest score calculated for each feature amount of the mask area set with the highest priority in the previous step S15, that is, the mask area. A high mask area is determined as a subject mask.

  Subsequently, in step S16, the area extracting unit 31 of the MPU 16 determines whether or not there are a plurality of mask areas determined as subject masks in the previous step S15. When the plurality of mask areas are determined as subject masks (step S16 = YES), the area extracting unit 31 of the MPU 16 proceeds to step S17.

  In step S <b> 17, the region extraction unit 31 of the MPU 16 sets a subject mask positioned on the closest side in the depth direction of the through image among the plurality of subject masks as a focus target. When multiple mask areas are determined as subject masks, subject masks whose hue is flesh-colored, subject masks that have been stationary for a certain period of time, or subject masks that have a unique distribution of feature amount histograms May be set as a focus target. Further, when a plurality of mask areas are determined as subject masks, a subject mask to be focused may be manually selected.

  On the other hand, if there is only one mask area determined as the subject mask (step S16 = NO), the area extraction unit 31 of the MPU 16 proceeds to step S18. In step S18, the area extracting unit 31 of the MPU 16 sets the subject mask determined in the previous step S15 as a focus target.

Next, in step S19, the edge detection unit 32 of the MPU 16 detects the edge of the subject mask set as a focus target.
Specifically, as illustrated in FIG. 9, the edge detection unit 32 of the MPU 16 scans the image portion of the subject mask S <b> 2 set as a focus target in the through image using a differential filter (for example, raster scan). To do. As a result, feature quantities such as brightness, saturation, and hue in the image portion of the subject mask S2 are calculated. Then, the edge detection unit 32 of the MPU 16 detects a portion having a large calculated feature amount as an edge E2 suitable for evaluating axial chromatic aberration in the contour portion of the subject mask S2. In the example shown in FIG. 9, the edge detection unit 32 of the MPU 16 detects three edges E2 from the contour portion of the subject mask S2.

  Here, it is assumed that the edge detection unit 32 of the MPU 16 detects the edge E2 of the subject mask S2 by scanning the lightness or saturation in the image portion of the subject mask S2 with a differential filter. In this case, the contrast of the color component amount of each color component at the detected edge E2 is not always sufficiently large. If the contrast of the color component amount of each color component at the edge E2 is small, a sharp waveform cannot be obtained as a normalized output of the color component amount of each color component at the edge E2. Therefore, the value of Ed cannot be accurately calculated as the evaluation value of the longitudinal chromatic aberration at the edge E2. As a result, it is difficult to determine using Ed whether the through image is in the front pin state or the rear pin state with respect to the subject mask S2, and the subject mask S2 in the through image is defocused. It is also difficult to calculate the magnitude of the quantity using Ed. That is, it is difficult to calculate the defocus feature amount of the subject mask S2 using Ed. The same problem occurs when a defocus amount reference value or a line spread function is adopted as the evaluation value of the longitudinal chromatic aberration at the edge E2.

  Therefore, in step S20, the feature amount calculation unit 33 of the MPU 16 can calculate the defocus feature amount of the subject mask S2 based on the evaluation value of the axial chromatic aberration at the edge E2 detected in the previous step S19. Determine whether or not. When the feature amount calculation unit 33 of the MPU 16 determines that the defocus feature amount of the subject mask S2 cannot be calculated (step S20 = NO), the process proceeds to step S21.

  Next, in step S21, the lens drive control unit 35 of the MPU 16 detects the focus position that is the lens position of the focus lens 11 that focuses the through image on the subject mask S2 by performing a normal contrast scan. . In this normal contrast scan, the lens drive control unit 35 of the MPU 16 first moves the focus position of the live view over the entire range from the closest side to the infinity side in the depth direction of the live view. The focus lens 11 is driven in the optical axis direction. Then, the lens drive control unit 35 of the MPU 16 obtains the contrast value of the subject mask S2 of the through image at each position, and detects the lens position of the focus lens 11 at which the contrast value of the subject mask S2 is the highest as the focus position.

  On the other hand, when the feature amount calculation unit 33 of the MPU 16 determines that the defocus feature amount of the subject mask S2 can be calculated (step S20 = YES), the evaluation value of the longitudinal chromatic aberration at the edge E2 is used as the focus detection step. Based on the above, the defocus feature amount of the subject mask S2 is calculated. In the example shown in FIG. 9, the feature amount calculator 33 of the MPU 16 defocuses the subject mask S2 based on the average value of the axial chromatic aberration evaluation values at the three edges E2 detected in the previous step S19. The feature amount is calculated.

  In step S22, the lens drive control unit 35 of the MPU 16 sets the drive direction of the focus lens 11 based on the direction index of the defocus feature amount of the subject mask S2 calculated in the previous step S20.

  Specifically, the lens drive control unit 35 of the MPU 16 moves the focus lens 11 away from the image sensor 13 in the optical axis direction when the direction index of the defocus feature value of the subject mask S2 indicates the front pin state. The driving direction of the AF motor 18 by the focus driving circuit 17 is set. That is, when the lens drive control unit 35 of the MPU 16 determines that the through image is in focus closer to the near point side than the subject mask S2, the focus position of the through image is set to infinity in the depth direction of the through image. The driving direction of the AF motor 18 by the focus driving circuit 17 is set so as to be moved to the side and matched with the position of the subject mask S2.

  On the other hand, the lens drive control unit 35 of the MPU 16 performs focus drive so that the focus lens 11 is brought closer to the image sensor 13 in the optical axis direction when the direction index of the defocus feature value of the subject mask S2 indicates the rear pin state. The driving direction of the AF motor 18 by the circuit 17 is set. That is, when the lens drive control unit 35 of the MPU 16 determines that the through image is in focus on the far point side of the subject mask S2, the focus position of the through image is set to the closest side in the depth direction of the through image. The driving direction of the AF motor 18 by the focus driving circuit 17 is set so as to match the position of the subject mask S2.

Subsequently, in step S23, the reliability calculation unit 34 of the MPU 16 calculates the reliability N of the defocus feature amount of the subject mask S2 calculated in the previous step S20.
Specifically, as shown in FIG. 9, the reliability calculation unit 34 of the MPU 16 first divides the image portion of the subject mask S2 in the through image into a plurality of divided regions R in a grid pattern. Then, the reliability calculation unit 34 of the MPU 16 calculates the number of divided regions R including the edge E2 detected in the previous step S19. In the example shown in FIG. 9, the number of divided regions R including the edge E2 is eight.

  Then, the reliability calculation unit 34 of the MPU 16 calculates the ratio of the number of the divided regions R including the edge E2 to the total number of the divided regions R as the reliability N. That is, in this embodiment, when calculating the defocus feature amount, the ratio of the edge E2 that is the target of the evaluation of the longitudinal chromatic aberration to the entire subject mask S2 is calculated. . The calculated ratio is defined as the reliability N of the defocus feature amount of the subject mask S2. In the example shown in FIG. 9, since the total number of the divided regions R is 64, the ratio of the number of the divided regions R including the edge E2 to the total number of the divided regions R is 1/8. .

  Next, in step S24, the lens drive control unit 35 of the MPU 16 determines whether or not the reliability N calculated in the previous step S23 is greater than or equal to the first threshold value T1. For the first threshold value T1, the lens drive control unit 35 of the MPU 16 sets the drive amount of the focus lens 11 based on the defocus amount of the defocus feature amount of the subject mask S2 calculated in the previous step S20. This is a reference value for determining whether or not this is appropriate. Therefore, if the lens drive control unit 35 of the MPU 16 determines that the reliability N calculated in the previous step S23 is less than the first threshold T1 (step S24 = NO), the calculation is performed in the previous step S20. It is determined that it is not appropriate to set the drive amount of the focus lens 11 based on the defocus amount of the defocus feature amount of the subject mask S2.

  In step S25, the lens drive control unit 35 of the MPU 16 drives and controls the focus drive circuit 17 so as to drive the focus lens 11 from the current lens position in the drive direction set in the previous step S22. The lens drive control unit 35 of the MPU 16 obtains the contrast value of the subject mask S2 in the through image at each position, and detects the lens position of the focus lens 11 at which the contrast value of the subject mask S2 is the highest as the focus position. .

  On the other hand, if the lens drive control unit 35 of the MPU 16 determines that the reliability N calculated in the previous step S23 is equal to or higher than the first threshold T1 (step S24 = YES), the calculation is performed in the previous step S20. It is determined that it is appropriate to set the driving amount of the focus lens 11 based on the defocus amount of the defocus feature amount of the subject mask S2.

  In step S26, the lens drive controller 35 of the MPU 16 first estimates the focus position of the focus lens 11 based on the defocus amount of the defocus feature amount of the subject mask S2 calculated in the previous step S20. To do. Subsequently, the lens drive control unit 35 of the MPU 16 calculates the drive amount of the focus lens 11 from the current lens position to the estimated focus position as the target drive amount X. The target drive amount X is represented by the number of pulses of the drive signal of the AF motor 18 required to drive the focus lens 11 from the current lens position to the estimated focus position.

  Next, in step S27, the lens drive control unit 35 of the MPU 16 determines whether or not the reliability N calculated in the previous step S23 is equal to or greater than the second threshold T2. For the second threshold T2, the lens drive control unit 35 of the MPU 16 sets the target drive amount X calculated in the previous step S25 as the drive amount of the focus lens 11 from the current lens position to the in-focus position. This is a reference value for determining whether or not is appropriate. In order to set the target drive amount X as the drive amount of the focus lens 11 from the current lens position to the in-focus position, the focus lens 11 is adjusted based on the defocus amount of the defocus feature amount of the subject mask S2. It is required to accurately estimate the focal position. In this case, since it is necessary to increase the reliability N of the defocus feature amount of the subject mask S2, the second threshold value T2 is set to be larger than the first threshold value T1.

  When the lens drive control unit 35 of the MPU 16 determines that the reliability N calculated in the previous step S23 is equal to or higher than the second threshold T2 (step S27 = YES), the calculation is performed in the previous step S26. It is determined that it is appropriate to set the set target drive amount X as the drive amount of the focus lens 11 from the current lens position to the in-focus position.

  In step S28, the lens drive control unit 35 of the MPU 16 sets the target drive amount X calculated in the previous step S26 as the drive amount of the focus lens 11 from the current lens position to the in-focus position.

  Subsequently, in step S29, the lens drive control unit 35 of the MPU 16 drives the focus lens 11 from the current lens position by the target drive amount X toward the drive direction set in the previous step S22. 17 is driven and controlled. As a result, the lens position of the focus lens 11 moves to the in-focus position, so that the through image is in focus at the position of the subject mask S2.

  On the other hand, if the lens drive control unit 35 of the MPU 16 determines that the reliability N calculated in the previous step S23 is less than the second threshold T2 (step S27 = NO), the calculation is performed in the previous step S26. It is determined that it is not appropriate to set the target drive amount X as the drive amount of the focus lens 11 from the current lens position to the in-focus position.

  In step S30, the lens drive control unit 35 of the MPU 16 sets a value smaller than the target drive amount X calculated in the previous step S26 as the drive amount of the focus lens 11 from the current lens position. In this case, the drive amount of the focus lens 11 may be set to a drive amount obtained by multiplying the target drive amount X by a predetermined ratio. For example, a drive amount that is 80% of the target drive amount X may be set as the drive amount of the focus lens 11. Further, the drive amount of the focus lens 11 may be set as the drive amount of the focus lens 11 up to a position shifted by a predetermined distance with respect to the focus position estimated in the previous step S26. For example, even if the driving amount of the focus lens 11 is set to a position that is shifted by a distance corresponding to 10 pulses as the number of pulses of the driving signal of the AF motor 18 from the estimated in-focus position. Good.

  Subsequently, in step S31, the lens drive control unit 35 of the MPU 16 drives the focus lens 11 from the current lens position by the drive amount set in the previous step S30 toward the drive direction set in the previous step S22. The focus drive circuit 17 is controlled to be driven. As a result, the position of the focus lens 11 moves to the vicinity of the in-focus position.

  Next, in step S32, the lens drive control unit 35 of the MPU 16 drives and controls the focus drive circuit 17 so as to drive the focus lens 11 from the current lens position toward the drive direction set in the previous step S22. To do. The lens drive control unit 35 of the MPU 16 obtains the contrast value of the subject mask S2 in the through image at each position, and detects the position of the focus lens 11 at which the contrast value of the subject mask S2 is the highest as the focus position.

  Subsequently, in step S33, the lens drive control unit 35 of the MPU 16 calculates the drive amount of the focus lens 11 from the current lens position to the focus position detected in the previous step S32. Then, the lens drive control unit 35 of the MPU 16 drives and controls the focus drive circuit 17 so as to drive the focus lens 11 by the calculated drive amount. As a result, the through image is brought into focus at the position of the subject mask S2 by moving the position of the focus lens 11 to the focus position.

  In step S33, the lens drive control unit 35 of the MPU 16 focuses from the current lens position to the in-focus position in the same manner as when the in-focus position is detected in previous step S21 or previous step S25. The driving amount of the lens 11 is calculated. Then, the lens drive control unit 35 of the MPU 16 drives and controls the focus drive circuit 17 so as to drive the focus lens 11 by the calculated drive amount. As a result, the through image is brought into focus at the position of the subject mask S2 by moving the position of the focus lens 11 to the focus position.

  Next, in step S34, the MPU 16 determines whether or not a photographing instruction signal has been input. This photographing instruction signal is input as an operation signal to the image processing engine 14 when the release button 39 is fully pressed. When the monitor 24 is a touch panel, a shooting instruction signal is input to the image processing engine 14 as an operation signal when the monitor 24 is touch-operated for shooting an image. If the MPU 16 determines that the shooting instruction signal has not been input (step S34 = NO), the MPU 16 returns the process to step S11 and repeats the processes of steps S11 to S33 until the shooting instruction signal is input. On the other hand, if the MPU 16 determines that the imaging instruction signal has been input (step S34 = YES), the process proceeds to step S35.

  In step S35, the image processing unit 26 of the MPU 16 stores the still image generated based on the pixel signal output from the image sensor 13 at that time in the nonvolatile memory 21 as a captured image.

Next, the operation of the camera 10 configured as described above will be described below, particularly focusing on the operation when the MPU 16 controls the in-focus position of the through image as an example of the image.
When the edge E2 is detected from an arbitrary image portion in the through image, the edge E2 is not necessarily the edge E2 located in the image portion that is assumed to be noticed by the person in the through image. Therefore, even if the focus position of the live view image is controlled using the detected evaluation value of the axial chromatic aberration at the detected edge E2, the live view image is appropriately focused on an image portion that is expected to be noticed by a person. There was a possibility that I could not.

  In this regard, in the present embodiment, the subject mask S2 is extracted as an image portion that is assumed to be noticed by a person in the through image, and the axial chromatic aberration is evaluated from the image portion of the extracted subject mask S2. The target edge E2 is detected. Therefore, by controlling the focus position of the live view image using the evaluation value of the longitudinal chromatic aberration at the edge E2, the live view image is appropriately focused on the image portion that is expected to be noticed by a person.

  Further, in the present embodiment, even if the subject mask S2 is located in any image portion of the through image, the edge E2 to be evaluated for the longitudinal chromatic aberration is detected from the image portion of the subject mask S2. Is possible. For this reason, even if an image portion assumed to be noticed by a person is located at any position in the through image, the through image is suitably focused on the image portion.

  In this embodiment, the defocus feature amount of the subject mask S2 is calculated using the evaluation value of the axial chromatic aberration at the edge E2 detected from the through image. Therefore, it is not necessary to move the focus lens 11 in the optical axis direction in order to calculate the defocus feature amount of the subject mask S2. That is, in the present embodiment, a configuration in which the defocus feature amount of the subject mask S2 is calculated using a plurality of images with different lens positions of the focus lens 11, or a single image taken while moving the focus lens 11 in the optical axis direction. This is different from the configuration in which the defocus feature amount of the subject mask S2 is calculated using an image. Therefore, wobbling does not occur due to the movement of the focus lens 11 in the optical axis direction, so that the display of the through image on the monitor 24 is suppressed from being disturbed.

  In the present embodiment, the driving mode of the focus lens 11 from the current lens position toward the in-focus position is changed according to the reliability N of the defocus feature amount of the subject mask S2.

  That is, as shown in FIG. 10, when the reliability N of the defocus feature amount of the subject mask S2 is less than the first threshold T1, the through image is in the front pin state or the rear pin state with respect to the subject mask S2. By determining which state is, the driving direction of the AF motor 18 is set. Specifically, when the through image is in the front pin state with respect to the subject mask S2, the driving range of the focus lens 11 is limited to the infinity side from the current lens position. On the other hand, when the through image is in the rear pin state with respect to the subject mask S2, the driving range of the focus lens 11 is limited to the closest side from the current lens position. Therefore, the scan range of the contrast scan is narrower than that in the case of the normal contrast scan, and the through image is quickly focused at the position of the subject mask S2.

  When the reliability of the defocus feature amount of the subject mask S2 is equal to or higher than the first threshold T1 and less than the second threshold T2, first, the defocus feature amount of the subject mask S2 is set to the defocus amount. Based on this, the in-focus position is estimated. Then, after the focus lens 11 is driven to the vicinity of the estimated focus position, a contrast scan is performed within a scan range set on both sides before and after the focus position so as to include the estimated focus position. For this reason, since the scanning range of the contrast scan is further narrowed, the through image is focused more quickly at the position of the subject mask S2.

  When the reliability N of the defocus feature amount of the subject mask S2 is equal to or higher than the second threshold T2, the focus position is estimated based on the defocus amount of the defocus feature amount of the subject mask S2. Thus, the focus lens 11 is directly driven from the current lens position. Therefore, since the contrast scan is not performed, the through image is focused more rapidly at the position of the subject mask S2.

According to the above embodiment, the following effects can be obtained.
(1) The defocus feature amount of the subject mask S2 is calculated based on the color component amount of the edge E2 of the subject mask S2 extracted from the image, and the image of the subject mask S2 is calculated based on the calculated defocus feature amount. A focus position for focusing at the position is detected. That is, when the focus position is detected, the drive amount for driving the focus lens 11 that performs focus adjustment is reduced, so that the focus position is detected more quickly than in the case of the contrast scan method. Therefore, by driving the focus lens 11 based on the detection result of the focus position, the image can be quickly focused at the position of the subject mask S2.

(2) Since the driving amount for driving the focus lens 11 when detecting the in-focus position is reduced, it is possible to suppress the image from being blurred due to wobbling.
(3) The defocus feature amount of the subject mask S2 extracted from the image is calculated by analyzing the color component amount of the image. Therefore, it is not necessary to provide a dedicated sensor for calculating the defocus feature amount of the subject mask S2. Therefore, the defocus feature amount of the subject mask S2 can be calculated with a simple configuration.

  (4) Regardless of the position of the edge E2 of the subject mask S2 on the imaging surface of the image sensor 13, it is extracted from the image by analyzing the color component amount of the edge E2. The defocus feature amount of the subject mask S2 can be calculated.

  (5) The subject mask S2 is extracted from the image as a region expected to be noticed by a person, and the defocus feature amount of the subject mask S2 is calculated based on the color component amount of the edge E2 of the subject mask S2. . For this reason, the edge E2 of the region expected to be watched by a person is selected from the edges E2 included in the image. Therefore, compared with the case where an edge is detected from the entire image, the image can be suitably focused in a region where a person is expected to pay attention.

  (6) The edge E2 of the subject mask S2 extracted from the image is detected, and the defocus feature amount of the subject mask S2 is calculated based on the detected color component amount of the edge E2. Then, based on the calculated defocus feature amount, a focus position for focusing the image at the position of the subject mask S2 is detected. Therefore, by driving the focus lens 11 based on the detection result of the focus position, the image can be quickly focused at the position of the subject mask S2.

  (7) The driving direction of the focus lens 11 from the current lens position is limited depending on whether the image is focused on the near point side or the far point side with respect to the edge E2 of the subject mask S2. . For this reason, the scan range of the contrast scan is reduced as compared with the case where the entire range from the closest side to the infinite side of the movable range of the focus lens 11 is the scan range of the contrast scan. Therefore, the image can be focused more quickly at the position of the subject mask S2.

  (8) When the reliability N of the defocus feature amount of the subject mask S2 is equal to or higher than the first threshold T1, not only the driving direction of the focus lens 11 from the current lens position but also the current lens position The driving amount of the focus lens 11 is set. Therefore, the scan range of the contrast scan is reduced as compared with the case where the contrast scan is started at the same time as the drive of the focus lens 11 from the current lens position in one drive direction is started. Therefore, the image can be focused more quickly at the position of the subject mask S2.

  (9) When the reliability N of the defocus feature amount of the subject mask S2 is equal to or greater than the second threshold T2, the target drive amount X corresponding to the defocus amount of the subject mask S2 included in the defocus feature amount Only the focus lens 11 is driven from the current lens position. As a result, the focus lens 11 is disposed at a focusing position where the image is focused at the position of the subject mask S2. That is, since the focus lens is arranged at the in-focus position without performing contrast scan, the image can be focused more quickly at the position of the subject mask S2.

  (10) When the reliability N of the defocus feature amount of the subject mask S2 is equal to or higher than the first threshold T1 and less than the second threshold T2, the subject mask S2 included in the defocus feature amount The focus lens 11 is driven from the current lens position by a drive amount smaller than the target drive amount X corresponding to the defocus amount. As a result, the focus lens 11 approaches from the current lens position toward the focusing position at which the image is focused at the position of the subject mask S2. Therefore, when the contrast scan is performed on the image while further driving the focus lens 11 in the driving direction from the approached position, the scan of the contrast scan is performed by the amount that the focus lens 11 approaches the in-focus position. The range is reduced. Therefore, the image can be focused more quickly at the position of the subject mask S2.

  (11) When the ratio of the number of divided regions R including the edge E2 of the subject mask S2 to the number of divided regions R including the subject mask S2 is high, the subject mask S2 calculated based on the color component amount of the edge E2 The reliability of the defocus feature amount is increased. On the other hand, when the ratio of the number of divided areas R including the edge E2 of the subject mask S2 to the number of divided areas R including the subject mask S2 is low, the subject mask S2 calculated based on the color component amount of the edge E2 The reliability of the defocus feature amount is low. Therefore, the reliability N of the defocus feature amount of the subject mask S2 can be calculated based on the ratio of the number of the divided regions R including the edge E2 of the subject mask S2 to the number of the divided regions R including the subject mask S2. .

  (12) By performing a labeling process on the image, it is possible to extract a mask area that is a candidate for the subject mask S2, which is an area that a person is expected to pay attention to from the image.

  (13) By performing pattern recognition processing on the image, it is possible to extract from the image a mask area that is a candidate for the subject mask S2, which is an area that a person is expected to pay attention to.

  (14) Even when a plurality of subject masks S2 are extracted from the image, the subject mask S2 that is assumed to attract more attention to the subject mask S2 located on the closest side among these subject masks S2 It can be determined that the image is present, and the image can be suitably focused on the subject mask S2.

In addition, you may change the said embodiment into another embodiment as follows.
In the above embodiment, when the reliability N of the defocus feature amount of the subject mask S2 is less than the first threshold T1, the current lens position is determined according to the defocus amount of the defocus feature amount of the subject mask S2. The driving mode of the focus lens 11 toward the in-focus position may be changed.

  For example, as shown in FIG. 11, when the defocus feature amount of the subject mask S2 is a defocus amount D1 smaller than the threshold value D, the entire region from the current lens position to the closest side is scanned by contrast scanning. It may be set as a range. On the other hand, when the defocus feature amount of the subject mask S2 is the defocus amount D2 larger than the threshold value D, half of the region located on the closest side out of the region from the current lens position to the close side is subjected to contrast scanning. May be set as the scan range. In this case, after the focus lens 11 is driven to the middle between the current lens position and the closest position, a contrast scan is performed in the half area on the near side set as the scan range. For this reason, since the scanning range of the contrast scan is further narrowed, the through image is focused more quickly at the position of the subject mask S2. In the example shown in FIG. 11, the threshold value D is set as the defocus amount of the subject mask S2 located at a position that is biased closer to the near side than the middle of the region from the current lens position to the close side.

  In the above embodiment, the feature amount calculation unit 33 of the MPU 16 determines that the edge E2 is detected when the edge detection unit 32 detects a plurality of edges E2 suitable for the evaluation of the longitudinal chromatic aberration in the contour portion of the subject mask S2. A priority order may be set for. Then, the defocus feature amount of the subject mask S2 may be calculated using the evaluation value of the longitudinal chromatic aberration at the edge E2 having the highest priority. In this case, the priority is set based on edge strength, edge color component, edge contrast, edge SN ratio, width of a flat range in the edge waveform, edge length, and the like.

  In the above embodiment, the reliability calculation unit 34 of the MPU 16 calculates an evaluation value serving as a reference for determining whether or not the edge E2 of the subject mask S2 is suitable for evaluation of axial aberration, and calculates the calculated edge E2 The reliability of the defocus feature amount of the subject mask S2 may be calculated based on the evaluation value. In this case, for example, the edge score is evaluated using the edge strength, edge color component, edge contrast, edge SN ratio, width of the flat area of the edge waveform, edge length, etc. as evaluation items. The total value of the calculated scores is calculated as the evaluation value of the edge E2.

  In the above embodiment, the lens drive control unit 35 of the MPU 16 determines the target drive amount X from the current lens position to the in-focus position when the reliability N of the defocus feature value of the subject mask S2 is equal to or greater than a predetermined threshold. The driving amount of the focus lens 11 may be set uniformly. Further, the lens drive control unit 35 of the MPU 16 sets a value smaller than the target drive amount X from the current lens position to the focus position when the reliability N of the defocus feature value of the subject mask S2 is equal to or greater than a predetermined threshold. The driving amount of the focus lens 11 may be set uniformly.

  In the above embodiment, the defocus feature amount of the subject mask S2 may not include the defocus amount of the subject mask S2. In this case, the lens drive control unit 35 of the MPU 16 sets the drive direction of the focus lens 11 without setting the drive amount of the focus lens 11 based on the defocus feature value of the subject mask S2.

  In the above embodiment, the edge detection unit 32 of the MPU 16 may not be configured to scan the image portion of the subject mask S2 with the differential filter. In this case, the feature amount calculation unit 33 of the MPU 16 calculates the defocus feature amount of the subject mask S2 based on the evaluation value of the longitudinal chromatic aberration in the contour portion of the subject mask S2 extracted by the labeling process or the pattern recognition process. .

  In the above embodiment, the MPU 16 may control the in-focus position of the moving image by executing processing similar to the lens drive control processing routine shown in FIG. In this case, in particular, since the driving amount for driving the focus lens 11 when detecting the in-focus position of the moving image is reduced, it is possible to suppress the image content of the moving image from being blurred due to wobbling.

  In the above-described embodiment, the image processing engine 14 may be mounted as a lens drive control device that controls driving of a lens that performs focus adjustment on an electronic device other than the camera 10 that has an image shooting function. Note that examples of the electronic device having an image shooting function include a video camera, a personal computer, a mobile phone, and a portable game machine.

  DESCRIPTION OF SYMBOLS 10 ... Digital camera as an example of an electronic camera, 11 ... Focus lens as an example of a lens, 13 ... Image pick-up element as an example of an imaging part, 14 ... Image processing engine as an example of a lens drive control apparatus, 31 ... Area extraction , 32... Edge detection unit, 33... Feature amount calculation unit as an example of focus detection unit, 34... Reliability calculation unit, 35... Lens drive control unit, E 2. , S2 ... Subject mask as an example of specific area, T1 ... first threshold, T2 ... second threshold, X ... target drive amount.

Claims (11)

An area extraction unit for extracting a specific area from an image;
A focus detection unit that detects a focus state of the specific region based on a color component amount of an edge of the specific region extracted by the region extraction unit;
A lens drive control unit that controls driving of a lens that performs focus adjustment based on a focus state of the specific region detected by the focus detection unit, and the specific region is divided into a plurality of divided regions, and the specific region based on the ratio of the number of the divided region including the edge of the specific area to the number of the divided regions including the calculation section for calculating a reliability of the detection result of the focus state of the specific region by the focus detection unit And a lens drive control device. An edge detection unit that detects, for each color component, the edge of the specific region extracted by the region extraction unit;
The lens drive control according to claim 1, wherein the focus detection unit detects a focus state of the specific region based on a color component amount of the edge of the specific region detected for each color component by the edge detection unit. apparatus. The in-focus state includes a direction indicator indicating that the image is in focus on the near point side or the far point side of the specific region,
The lens drive control device according to claim 1, wherein the lens drive control unit sets a drive direction of the lens based on the direction indicator detected by the focus detection unit. The in-focus state further includes a defocus amount of the specific area,
The lens drive control unit sets the drive amount of the lens based on the defocus amount detected by the focus detection unit when the value calculated by the calculation unit is equal to or greater than a predetermined threshold. 4. The lens drive control device according to 3. As for the value calculated by the calculation unit, when the predetermined threshold is the first threshold, a second threshold is further set as a threshold larger than the first threshold,
When the value calculated by the calculation unit is equal to or greater than the second threshold value, the lens drive control unit focuses the image in the specific region based on the defocus amount detected by the focus detection unit. The lens drive control device according to claim 4, wherein a target drive amount of the lens to be calculated is calculated, and the calculated target drive amount is set as the drive amount of the lens. When the value calculated by the calculation unit is greater than or equal to the first threshold value and less than the second threshold value, the lens drive control unit sets a value smaller than the target drive amount as the lens drive amount. The lens drive control device according to claim 5, wherein the lens drive control device is set. Said region extraction unit, the lens drive control device according to any one of claims 1 to 6 for extracting the specific region by performing labeling processing on the image. Said region extraction unit, the lens drive control device according to any one of claims 1 to 6 for extracting the specific region by performing pattern recognition processing on the image. When the region extraction unit extracts a plurality of the specific regions from the image, the focus detection unit is based on the color component amount of the specific region located on the closest side in the depth direction of the image among the plurality of specific regions. The lens drive control device according to any one of claims 1 to 8 , wherein an in-focus state of the specific region is detected. An imaging unit for imaging a subject;
An electronic camera comprising: the lens drive control device according to any one of claims 1 to 9 that controls driving of a lens that performs focus adjustment of an image according to a subject imaged by the imaging unit. On the computer,
An area extraction step for extracting a specific area from the image;
A focus detection step of detecting a focus state of the specific region based on the color component amount of the edge of the specific region extracted in the region extraction step;
A lens driving control step for controlling driving of a lens for performing focus adjustment based on a detection result of a focusing state of the specific area in the focusing detection step;
The specific area is divided into a plurality of divided areas, and detected in the focus detection step based on a ratio of the number of the divided areas including the edge of the specific area to the number of divided areas including the specific area. A lens driving control program for executing a calculation step of calculating a reliability of a detection result of an in- focus state of the specific region.

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