JP5564961B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus.

  The following imaging devices are known. This imaging apparatus performs focus adjustment so as to focus on a subject that is present closest (for example, Patent Document 1).

JP 2007-293146 A

  However, the conventional imaging apparatus has a problem that even when there is a focus-unnecessary subject that is not desired to be focused closest to, the focus-unnecessary subject is focused. In addition, if there is a high-contrast non-focusing subject on the infinity side of the main subject, the non-focusing subject may be focused.

An imaging apparatus according to the present invention includes an edge detection unit that detects an edge of a hue component of an image in an evaluation area set in a shooting screen, and a horizontal edge between edges of the hue component detected by the edge detection unit. On the basis of the difference in hue and the amount of deviation of the edge in the vertical direction. An imaging condition setting means for setting an imaging condition, and an entire area scanning means for calculating a contrast evaluation value at each lens position by performing a whole area scan while moving a focus adjustment lens provided in the optical system. If multiple contrast evaluation value peaks are detected, the edge detection means, the exclusion means, and the imaging condition setting means are processed and controlled. When the peak of the strike evaluation values is not detected only one is characterized by not processed by the edge detection means and excluding means.
The evaluation area is an autofocus area used for focus adjustment, and the photographing condition setting unit may perform focus adjustment based on an image after removing an image including an unnecessary subject from the autofocus area. .
The whole area scanning means performs a whole area scan while moving the focus adjustment lens provided in the optical system from the closest side to the infinity side, calculates a contrast evaluation value at each lens position, an edge detection means, an exclusion means, and The imaging condition setting unit may perform processing when a plurality of contrast evaluation value peaks are detected between the closest side and the infinity side.

  According to the present invention, it is possible to prevent focusing on an unnecessary subject.

1 is a block diagram illustrating a configuration of an embodiment of a camera 100. FIG. It is a figure which shows the specific example of a picked-up image. It is a figure which shows the example of calculation of a contrast evaluation value. It is a flowchart figure which shows the flow of a calculation process of contrast evaluation value. It is a figure which shows the specific example of a hue edge image.

  FIG. 1 is a block diagram illustrating a configuration of an embodiment of a camera according to the present embodiment. The camera 100 includes an operation member 101, a lens 102, an image sensor 103, a control device 104, a memory card slot 105, and a monitor 106. The operation member 101 includes various input members operated by the user, such as a power button, a release button, a zoom button, a cross key, an enter button, a play button, and a delete button.

  The lens 102 is composed of a plurality of optical lenses, but is representatively represented by one lens in FIG. The lenses constituting the lens 102 include an AF lens (focus adjustment lens) for AF (Auto Focus / automatic focus adjustment) described later. The image sensor 103 is an image sensor such as a CCD or a CMOS, for example, and captures a subject image formed by the lens 102. Then, an image signal obtained by imaging is output to the control device 104.

  The control device 104 generates image data in a predetermined image format, for example, JPEG format (hereinafter referred to as “main image data”) based on the image signal input from the image sensor 103. Further, the control device 104 generates display image data, for example, thumbnail image data, based on the generated image data. The control device 104 generates an image file that includes the generated main image data and thumbnail image data, and further includes header information, and outputs the image file to the memory card slot 105.

  The memory card slot 105 is a slot for inserting a memory card as a storage medium, and the image file output from the control device 104 is written and recorded on the memory card. The memory card slot 105 reads an image file stored in the memory card based on an instruction from the control device 104.

  The monitor 106 is a liquid crystal monitor (rear monitor) mounted on the back surface of the camera 100, and the monitor 106 displays an image stored in a memory card, a setting menu for setting the camera 100, and the like. . Further, when the user sets the mode of the camera 100 to the shooting mode, the control device 104 outputs image data for display of images acquired from the image sensor 103 in time series to the monitor 106. As a result, a through image is displayed on the monitor 106.

  The control device 104 includes a CPU, a memory, and other peripheral circuits, and controls the camera 100. Note that the memory constituting the control device 104 includes SDRAM and flash memory. The SDRAM is a volatile memory, and is used as a work memory for the CPU to develop a program when the program is executed or as a buffer memory for temporarily recording data. The flash memory is a non-volatile memory in which data of a program executed by the control device 104, various parameters read during program execution, and the like are recorded.

  In the present embodiment, the control device 104 performs focus adjustment by executing AF (autofocus / automatic focus adjustment) processing during shooting. For example, the control device 104 executes AF processing when the release button is half-pressed by the user. For example, the AF method includes a contrast method and a phase difference method. In this embodiment, a case where AF processing is performed by the contrast method will be described. Note that the focus adjustment by the contrast method calculates the contrast evaluation value while moving the AF lens for focus adjustment for a plurality of autofocus areas (AF areas) set in the shooting screen, and the contrast evaluation value. Is a method of performing focus adjustment by detecting the position of the AF lens where the peak is as the in-focus position. Since the focus adjustment process using the contrast method is a known process, a detailed description thereof will be omitted.

  In this focus adjustment by the contrast method, the first contrast evaluation value peak in the AF area is detected as the in-focus position while moving the AF lens from the closest side to the infinity side. Can be made. However, when there is an unnecessary subject that you do not want to focus on the close side in the AF area, if you perform focus adjustment using the conventional contrast method, you will focus on the unnecessary subject that is closest to you. There was a problem.

  For example, as shown in FIG. 2, when an animal in a cage or fence is to be photographed, it is necessary to focus on the animal. There was a possibility that it was impossible to focus on the animal because it focused on the fence and fence. In the example shown in FIG. 2, when the entire area scan is performed while moving the AF lens from the closest side to the infinity side, for example, a contrast evaluation value is calculated as shown in FIG. In this case, according to the focus adjustment based on the contrast method described above, the AF lens position at the peak 3a of the contrast evaluation value existing on the near side is not the focus position, instead of the peak 3b of the contrast evaluation value on the far side which is originally desired to be focused. As a result, it will be in focus on the fence or fence. In the present embodiment, in order to solve such a problem, the control device 104 performs the following processing to calculate a contrast evaluation value.

  Note that the unnecessary subject existing on the near side is likely to be straight and have a uniform hue, such as a fence or a fence as shown in FIG. An object that is straight and has a substantially uniform hue is regarded as an unnecessary object.

  FIG. 4 is a flowchart showing a flow of processing for calculating a contrast evaluation value as an AF evaluation value in the present embodiment. In the process shown in FIG. 4, for example, the control device 104 scans the entire area of the AF lens from the closest side to the infinity side at the start of the AF process. As a result, as shown in FIG. It is executed by the control device 104 as a program that is activated when two peaks are detected. If only one peak of the contrast evaluation value is detected as a result of the whole area scan, the AF lens position at that peak may be detected as the in-focus position, and the process shown in FIG. 4 is not executed.

In step S <b> 10, the control device 104 acquires images in a plurality of AF areas set in the shooting screen input from the image sensor 103. The control device 104 converts the color space of the acquired image in the AF area from RGB to XYZ, and further converts it to Lab. Thereafter, the control device 104 calculates a hue angle by performing a hue calculation according to the following equation (1) based on the image in each AF area after the color space is converted to Lab.
h = tan ⁻¹ (b ^* / a ^* ) (1)

  Thereafter, the process proceeds to step S20, and the control device 104 detects the edge of the hue component in the horizontal direction in the AF area based on the hue angle calculated in step S10. As a result, as shown in FIG. 5A, it is possible to generate an image (hereinafter referred to as “hue edge image”) in which the edge of the hue component is extracted from the image shown in FIG. Note that the control device 104 may perform noise removal processing, gamma correction processing, or the like on the image in the AF area in advance so that the edge shape can be easily determined. And the control apparatus 104 detects the coordinate value in the image of the edge whose edge strength is more than a predetermined threshold among the detected edges, and records it in memory. Then, it progresses to step S30.

  In step S30, the control device 104 determines that the hue between the edge coordinates is within a predetermined range for each horizontal line of the hue edge image, for example, for each pixel line, based on the edge coordinate value detected in step S20. Extract edge ranges that are uniform. That is, the control device 104 compares the hues of two edges whose edge coordinates are adjacent to each other, and if the difference in hue is within a predetermined range, for example, the hue angle is within 15 degrees, the hue between the edges is determined. Are determined to be substantially uniform and are grouped, and an identification number is added to each group. Accordingly, for example, for the range 5a in the hue edge image shown in FIG. 5A, as shown in FIG. 5B, the range 5b to 5f in which the difference in hue is within a predetermined threshold is shown. Five edge ranges are extracted, and an identification number is added to each edge range.

  Thereafter, the process proceeds to step S40, and the control device 104 determines whether or not the extraction of the edge range has been completed for all the horizontal lines of the hue edge image. If a negative determination is made in step S40, the process returns to step S20. On the other hand, if a positive determination is made in step S40, the process proceeds to step S50.

  In step S50, the control device 104 calculates the vertical shift amount between the upper and lower sides for each edge range of the horizontal line extracted in step S30. Thereafter, the process proceeds to step S60, and the control device 104 determines whether or not the vertical shift amount calculated in step S50 is within a predetermined threshold, for example, within 5 pixels. If an affirmative determination is made in step S60, the process proceeds to step S70, and the control device 104 performs grouping so that the identification numbers added to the edge ranges whose deviation amounts are within a predetermined threshold are in the same group. Then, the process proceeds to step S80.

  As a result, it is possible to detect an object having a small horizontal hue difference and a small vertical deviation existing in the AF area, that is, an unnecessary subject having a linear and substantially uniform hue such as a fence or a fence. Edges with high characteristics can be grouped. In addition, when the amount of deviation in the vertical direction of the edge range is 0, the edge indicates a vertical line with a substantially uniform hue, and when the amount of deviation in the vertical direction is a non-zero value, The edges indicate diagonal lines with substantially uniform hue. Since such vertical lines and diagonal lines having a substantially uniform hue are likely to constitute an unnecessary subject such as a fence or a fence as described above, in this embodiment, there is a possibility that such an unnecessary subject is constituted. It is possible to detect a high edge with high accuracy.

  On the other hand, if a negative determination is made in step S60, the process proceeds directly to step S80. In step S80, the control device 104 determines whether or not the vertical shift amount determination and the identification number grouping for all the horizontal lines of the hue edge image have been completed. If a negative determination is made in step S80, the process returns to step S50. On the other hand, if a positive determination is made in step S80, the process proceeds to step S90.

  In step S90, the control device 104 calculates a ratio of the edge range in which the identification numbers are grouped in step S70 in the AF area. Thereafter, the process proceeds to step S100, and the control device 104 determines whether or not the ratio of the edge range calculated in step S90 is within a predetermined threshold. The threshold used at this time is, for example, a value within a range of 1/50 to 1/4 with respect to the size of the AF area. You may change according to the value of the hue which an edge image has. If a positive determination is made in step S100, the process proceeds to step S110. In step S110, the control device 104 excludes the image in the edge range from the images in the AF area from the calculation target of the contrast evaluation value, and proceeds to step S120.

  As a result, when the detected edge range is small relative to the size of the AF area, the edge range is likely to be an edge range based on the edge detected from the unnecessary subject. Images within the range can be excluded from the AF evaluation target with high accuracy. On the other hand, when the edge range detected with respect to the size of the AF area is large, it is highly possible that the edge range is not an edge range based on the edge detected from the unnecessary subject. The image inside can be left as an AF evaluation target, and the accuracy of AF can be improved.

  On the other hand, if a negative determination is made in step S100, the process proceeds to step S120. In step S120, the control device 104 calculates a contrast evaluation value for images outside the range excluded in step S110 among the images in the AF area. Thereafter, the process proceeds to step S130, and the control device 104 moves the AF lens to the next focal length and returns to step S10. The control device 104 calculates the AF evaluation value at each focal length, that is, the contrast evaluation value by repeating the above-described processing from step S10 to step S130 until the AF lens reaches the infinity end. The position of the AF lens that becomes the maximum is specified as the in-focus position.

  As described above, since the contrast evaluation value is calculated by excluding the image in the range where there is a high possibility that the unnecessary subject is present from the image in the AF area in advance, the AF lens is moved from the closest side to the infinity side. When the focus adjustment is performed while moving to the position, it is possible to prevent focusing on an unnecessary subject existing on the near side.

According to the present embodiment described above, the following operational effects can be obtained.
(1) The control device 104 detects an edge of a hue component of an image in a plurality of AF areas set in the shooting screen, and an unnecessary subject is included from the AF area based on the detected edge of the hue component. The range image was excluded. The control device 104 adjusts the focus based on the image in the AF area after the exclusion. Thus, when performing focus adjustment by the contrast method, it is possible to prevent focusing on an unnecessary subject that is present closest.

(2) The control device 104 excludes an image in a range including an unnecessary subject from the AF area based on a hue difference between horizontal edges and a vertical edge shift amount. In this way, taking into account that unnecessary subjects such as fences and fences are often almost uniform and linear subjects, exclude images in a range that includes unnecessary subjects with high accuracy from the AF area. Can do.

(3) The controller 104 scans the entire area while moving the AF lens from the close side to the infinity side, calculates a contrast evaluation value at each lens position, and as a result, between the close side and the infinity side. The above-described process is performed when two contrast evaluation value peaks are detected. Accordingly, when only one contrast evaluation value peak is detected, it is not necessary to execute the process, and the processing load can be reduced.

-Modification-
The camera according to the above-described embodiment can be modified as follows.
(1) In the above-described embodiment, the AF area set in the shooting screen is used as an evaluation area for focus adjustment, and an edge range where there is a high possibility that an unnecessary subject existing on the near side from the image in the AF area is included. The example in which the image is excluded and the focus adjustment is performed has been described. However, the present invention can also be applied to a case where an evaluation area other than the AF area is excluded from the evaluation target. For example, the present invention is also applicable to a case where an image in a range in which there is a high possibility that an unnecessary subject existing on the near side is included is excluded from an image in an evaluation area for performing AE (automatic exposure) and AWB (auto white balance). Is applicable.

(2) In the above-described embodiment, the control device 104 has described an example in which vertical lines and diagonal lines having substantially uniform hues in the AF area are detected as edges constituting an unnecessary subject. However, other geometric patterns such as horizontal lines and curves may be detected as edges constituting the unnecessary subject.

(3) In the above-described embodiment, the example in which the control device 104 automatically excludes an area that is likely to include an unnecessary subject from the AF area has been described. However, the control device 104 highlights on the screen an area or edge that is likely to contain an unnecessary subject in the AF area and notifies the user whether or not to exclude the area or edge as an unnecessary subject. May be selected by the user.

(4) In the above-described embodiment, the control device 104 performs the whole area scan while moving the AF lens from the closest side to the infinity side, and as a result, two peaks of contrast evaluation values are detected. The example of executing the process shown in FIG. 4 has been described. However, the processing shown in FIG. 4 may be executed even when two or more peaks of contrast evaluation values are detected. Alternatively, the processing shown in FIG. 4 may be executed when the mode of the camera 100 is set so as to perform the focus adjustment by performing the processing shown in FIG. Good.

(5) In the above-described embodiment, the example in which the unnecessary subject existing on the closest side is excluded has been described. However, the process shown in FIG. 4 may be executed even when an unnecessary subject having a substantially uniform edge exists on the infinity side of the main subject. In this case, it is possible to prevent focusing on the background rather than the main subject that is the subject of photographing.

(6) In the above-described embodiment, the case where the present invention is applied to the camera 100 has been described. However, the present invention can also be applied to other imaging devices having a photographing function, such as a mobile phone with a camera and a video camera.

  Note that the present invention is not limited to the configurations in the above-described embodiments as long as the characteristic functions of the present invention are not impaired. Moreover, it is good also as a structure which combined the above-mentioned embodiment and a some modification.

100 Camera, 101 Operation member, 102 Lens, 103 Image sensor, 104 Control device, 105 Memory card slot, 106 Monitor

Claims (3)

Edge detection means for detecting the edge of the hue component of the image in the evaluation area set in the shooting screen;
Based on the difference in hue between horizontal edges and the amount of deviation of the edges in the vertical direction at the edge of the hue component detected by the edge detection means, a range of unnecessary subjects from the evaluation area is included. Exclusion means to exclude images,
Shooting condition setting means for setting shooting conditions based on an image in the evaluation area after being excluded by the exclusion means;
A whole area scan unit that performs a whole area scan while moving a focus adjustment lens provided in the optical system, and calculates a contrast evaluation value at each lens position;
When a plurality of peaks of the contrast evaluation value are detected, the edge detection unit, the exclusion unit, and the imaging condition setting unit are processed, and when only one peak of the contrast evaluation value is detected, An imaging apparatus characterized by not performing processing by the edge detection means and the exclusion means. The imaging device according to claim 1,
The evaluation area is an autofocus area used for focus adjustment,
The imaging apparatus according to claim 1, wherein the photographing condition setting unit performs focus adjustment based on an image after removing an image including the unnecessary subject from the autofocus area. The imaging device according to claim 2,
The whole area scanning means performs a whole area scan while moving a focus adjustment lens provided in the optical system from the closest side to the infinity side, and calculates a contrast evaluation value at each lens position,
The edge detection unit, the exclusion unit, and the imaging condition setting unit perform processing when a plurality of peaks of the contrast evaluation value are detected between the close side and the infinity side. Imaging device.

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