JP2009055415A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camera capable of attaining reduction of an image processing time. <P>SOLUTION: A camera comprises: an imaging device 2 for capturing an image formed by a photographing optical system 1; a face detecting means 10 for detecting an image region corresponding to the face of a person from the picked-up image captured by the imaging device 2, and an image processing means 10 for performing correction processing on the captured image based on optical characteristics of the photographing optical system 1. Furthermore, in a case where at least a part of the image region detected by the face detecting means 10 is included in a predetermined imaging region influenced by aberration of the photographing optical system 10, the image processing means 10 may also perform the correction processing on the captured image so as to reduce the influence of aberration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a camera that captures a subject image using an image sensor.

  2. Description of the Related Art Conventionally, there is known a digital camera that reduces the influence of aberration by correcting aberration (for example, distortion) caused by optical characteristics of a photographing lens by image processing (see, for example, Patent Document 1).

JP 2006-139350 A

  However, it takes time to perform image processing for reducing the influence of the optical characteristics of the photographing lens. In conventional cameras, aberration reduction processing is always performed even in cases where the aberration is inconspicuous and there is no need for aberration reduction processing, so after the image processing time for aberration reduction has been released It took a long time to record the image data, and the usability was bad.

According to a first aspect of the present invention, there is provided a camera according to a first aspect of the present invention. And image processing means for correcting the captured image based on the optical characteristics of the photographing optical system when the image area is detected by the face detection means.
According to a second aspect of the present invention, in the camera according to the first aspect, it is determined whether or not to perform a correction process based on at least one of a position and a size of the image area detected by the face detection means in the imaging area. Determining means for performing correction processing when the determination means determines that correction processing is to be performed.
According to a third aspect of the present invention, in the camera according to the second aspect, the correction process is performed when at least a part of the image area detected by the face detecting means is included in a predetermined imaging area where the influence of the optical characteristic is generated. It is a thing.
According to a fourth aspect of the present invention, in the camera according to any one of the first to third aspects, the optical characteristic is an aberration characteristic of the photographing optical system, and correction processing is performed so as to reduce the influence of the aberration of the photographing optical system. It is what you do.
According to a fifth aspect of the present invention, in the camera according to the fourth aspect, when at least a part of the image area detected by the face detection means is in a peripheral area within the imaging area, the influence of the aberration of the photographing optical system is reduced. In addition to the correction process for reducing, the correction process for reducing the decrease in the amount of light in the peripheral area is also performed.
A camera according to a sixth aspect of the present invention detects an image area corresponding to a human face from an image pickup element that picks up an image formed by a photographing optical system, and a picked-up image picked up by the image pickup element. An image for correcting the captured image based on the optical characteristics of the imaging optical system when the focus adjustment unit that adjusts the focus adjustment state of the imaging optical system with respect to the subject and at least a part of the image area is included in the predetermined imaging area And a processing means.

  According to the present invention, the image processing time can be shortened in the case of a subject that has no human face and in which aberrations are not noticeable.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a camera of the present invention. The camera includes a photographing lens 1, an image sensor 2, an A / D converter 3, a buffer memory 4, an image processing circuit 5, a monitor 6, a memory card interface 7, a recording medium 8, a flash RAM 9, a CPU 10, and an operation unit 11. ing. The A / D converter 3, the buffer memory 4, the image processing circuit 5, the monitor 6, the memory card interface 7, the flash RAM 9, and the CPU 10 are connected to each other via a bus 12.

  The taking lens 1 forms a subject image on the image pickup surface of the image pickup device 2. A CCD-type or MOS-type solid-state image pickup device is used as the image pickup device 2 and outputs an electric signal corresponding to the light intensity of the subject image formed on the image pickup surface. An image signal from the image sensor 2 is converted from an analog signal to a digital signal by the A / D converter 3.

  The image processing circuit 5 performs image processing such as interpolation, gamma correction, and white balance adjustment on the image data supplied from the A / D conversion unit 3. The white balance adjusted R, G, and B signals are subjected to gamma correction processing and then converted into luminance signals (Y signals) and color difference signals (Cr, Cb signals). The image processing circuit 5 also performs compression processing of the image data for which image processing has been completed and decompression processing for the compressed image data.

  The compressed image data is recorded on a recording medium 8 such as a memory card (semiconductor memory) via the memory card interface 7. The recording medium 8 is detachably attached to the camera.

  The buffer memory 4 is a frame memory capable of storing data for a plurality of frames imaged by the image sensor 2, and the A / D converted signal is temporarily stored in the buffer memory 4. The image processing circuit 5 reads the data stored in the buffer memory 4 and performs the above-described processes, and the processed data is stored in the buffer memory 4 again.

  The monitor 6 displays various menus, and displays a reproduced image based on a subject image captured by the image sensor 2 and image data stored in the recording medium 8. For example, a liquid crystal display panel is used for the monitor 6. There are two forms of display of the captured image on the monitor 6. One is a display form when the release operation is not performed, and is a display form called a through image that sequentially updates and displays images repeatedly picked up by the image sensor 2. The other is a display form called a freeze image in which an image captured by the image sensor 2 is displayed for a predetermined time after the release operation.

  The CPU 10 performs camera operation sequence control, automatic exposure control, autofocus control, and the like. Further, face recognition processing and aberration correction processing described later are also performed by the CPU 10. The flash RAM 9 stores camera control software, software for face recognition processing and aberration correction processing described above, and aberration (distortion aberration, chromatic aberration, etc.) information of the photographing lens 1. The operation unit 11 connected to the CPU 10 is provided with a release button operated by a user, a power switch, operation buttons for various settings, a selection button for mode switching, and the like.

  In the present embodiment, the face recognition process and the aberration correction process are performed by software processing in the CPU 10, but the image processing circuit 5 may perform hardware processing. Hereinafter, a case where software processing is performed will be described as an example.

  Incidentally, distortion and lateral chromatic aberration due to the optical characteristics of the photographing lens 1 occur in the captured image. FIG. 2 shows an example of an image when distortion occurs. This is a chart taken with a plurality of straight lines L1, L2 and six large and small circles C1 to C6 drawn at equal intervals vertically and horizontally, and there is a “barrel-shaped” distortion aberration. The image of is shown. In the case of “barrel-shaped” distortion, the image is formed so that the corners of the screen are shrunk, and the circles C3 to C6 arranged at the four corners are imaged so that the shape is distorted. In the case of chromatic aberration of magnification, a difference in image magnification occurs as it goes to the periphery of the screen due to a difference in light wavelength, and the color appears to be blurred.

  In particular, when a person's face is reflected in a peripheral region having a large aberration, unnaturalness due to distortion or color blur is conspicuous. Therefore, in the camera according to the present embodiment, when a human face is reflected in a region where the aberration is remarkable, an image processing that reduces the aberration is performed to obtain a captured image with less aberration. .

[Description of operation]
FIG. 3 is a flowchart for explaining the aberration correction processing by image processing, and shows a series of processing from the release operation (release button full-press operation) until the image data is stored in the recording medium 8. . When the release button provided on the operation unit 11 is fully pressed, the CPU 10 starts a series of processes shown in the flowchart of FIG.

  In step S100, shooting operation processing is executed. Specifically, after the mirror-up operation, the image pickup device 2 is caused to store charge for photographing and sweep out the stored charge, and perform the mirror-down operation. In step S110, the image data obtained by imaging is sent to the image processing circuit 5 to perform the above-described series of image processing to generate a YCbCr image.

  In step S120, it is determined whether or not the camera is in a face recognition mode. The face recognition mode is a mode in which a face area is detected based on captured image data. In this embodiment, aberration reduction processing is performed when the face recognition mode is set. If it is determined in step S110 that the face recognition mode is set (YES), the process proceeds to step S120, and if it is determined NO, the process proceeds to step S180 without performing the aberration reduction process.

  In step S130, a known face recognition process is performed based on the image generated in step S110 (see, for example, JP-A-2004-206688). For example, based on color information (hue) for each pixel of the YCbCr image, pixels whose hue is close to the face color (skin color) are extracted and grouped, and grouped with the image magnification (focal length of the taking lens 1). Face detection can be performed by extracting a pixel area estimated as a face area based on the size of the skin color pixel area.

  In step S140, it is determined whether a pixel area estimated as a face area in step S130 is detected. If it is determined in step S140 that no face is detected (NO), the process proceeds to step S180 without performing the aberration reduction processing. On the other hand, if face detection is determined in step S140, the process proceeds to step 150, and the position and size of a pixel area recognized as a face (hereinafter referred to as a face area) is obtained.

  FIG. 4 shows an example of a face recognition image, and hatched areas M1 to M4 are pixel areas (face areas) recognized as faces. A circle 102 indicated by a broken line is a circle whose center is the center of the imaging range 100 and whose diameter is the short side of the imaging range 100. The outer region 120A of the circle 102 is a region where relatively large distortion occurs. The size of the circle 102 may be set according to the magnitude of distortion of the photographing lens 1.

  In step S150, it is determined whether the face region is in the outer region 120A or the inner region 120B of the circle 102. For example, when more than half of the face area is included in the outer area 120A like the face area M1, the position of the face area M1 is determined to be outside the circle 102, and more than half of the face area like the face area M2 is determined. If it is included in the inner region 120B, the position is determined to be inside the circle 102. If there is a face area in the outer area 120A, the distortion of the person's face becomes conspicuous, so an aberration reduction process is performed as will be described later.

  Further, in a scene where the face size is relatively large, such as a face up, distortion is conspicuous at the vertical position of the face even if the position of the face area is the inner area 120B. Therefore, in step S150, in addition to the face position described above, the ratio Kx of the horizontal dimension X and the ratio Ky of the vertical dimension Y to the short side of the imaging range 100 are obtained. When the ratio Kx or Ky is greater than or equal to a predetermined value, distortion of the person's face becomes conspicuous, and aberration reduction processing is performed as will be described later. The magnitude of the predetermined ratio is set according to the aberration of the taking lens 1. For example, the predetermined ratio is set to 2/3.

  Next, in step S160, it is determined whether or not the position and size (ratio Kx, Ky) of the face area obtained in step S150 satisfies a predetermined condition (a) or (b). The predetermined condition (a) is a condition that the position of the face area is included in the outer area 120A, and the predetermined condition (b) is that the ratio Kx or Ky related to the face area is greater than or equal to the predetermined ratio. It is a condition. If it is determined in step S160 that the condition is satisfied, the process proceeds to step S170. If it is determined that the condition is not satisfied, the process proceeds to step S180.

  In step S <b> 170, the CPU 10 performs an aberration reduction process for the image data based on the aberration (distortion aberration, chromatic aberration, etc.) information of the photographing lens 1 stored in the flash RAM 9. Since aberration reduction processing is a known technique (see, for example, JP-A-2006-139350), description thereof is omitted here. The aberration is determined by each position in the imaging range 100 and is stored as a map. In step S180, the CPU 10 compresses the image data after the aberration reduction processing in the image processing circuit 5, and records the image data after the compression processing on the recording medium 8.

  As described above, in this embodiment, when the face is included in the peripheral region 120A where the aberration is conspicuous, or when the size of the face is equal to or larger than the predetermined size, the aberration reduction processing is performed. The aberration reduction processing is not performed because the aberration is inconspicuous. Therefore, unlike cameras that perform aberration reduction processing regardless of whether there is a face or whether aberrations are noticeable as in the past, image processing is performed by not performing aberration reduction processing when aberrations are not noticeable. Time can be shortened. When a person's face is reflected in a region where the aberration is significant, a captured image with little aberration is obtained by performing aberration reduction processing.

  As described above, in this embodiment, the aberration reduction processing is performed when the peripheral area 120A of the imaging range 100 includes a face. However, if a face is detected regardless of the area, the aberration reduction is performed. Processing may be performed. Also in this case, when the face is not detected, the aberration reduction processing is not performed, so that the image processing time can be shortened. Even if the face recognition mode is not set, control may be performed to automatically reduce aberrations when a face is detected.

  In the above-described determination process of step S160, regarding any one of the plurality of detected face regions M1 to M4, the position is included in the outer region 120B or the ratios Kx and Ky are greater than or equal to the predetermined ratio. However, the determination conditions are not limited to this, and various conditions can be considered. For example, by operating the operation unit 11 and manually specifying a desired face area from the plurality of face areas M1 to M4, the CPU 10 performs the aberration reduction processing only when the specified face area satisfies the condition of step S160. May be performed.

  Further, face recognition AF for focusing on a subject recognized as a face is known. In this face recognition AF mode, the face area that is the target of face recognition AF is the above conditions (a) and (b). Aberration reduction processing may be performed when the above is satisfied. Further, only one of the conditions (a) and (b) may be set as the determination condition. Furthermore, when the size of the face region is small, the influence of distortion is small even if the position is the outer region 120A. In such a case, the aberration reduction processing may not be performed.

  In the above-described embodiment, the face recognition is performed on the image data to be recorded on the recording medium 8 and the aberration reduction process is performed. However, the aberration reduction process as described above is performed on the through image for monitor display. Alternatively, the image data already recorded on the recording medium 8 may be read out as a reproduced image, and an additional aberration reduction process may be performed on the image data. When aberration reduction processing is performed on a reproduced image, a list of reproduced images is displayed on the monitor 6, a desired image is selected from them, and the aberration reduction processing is instructed. In that case, if the image data after the aberration reduction processing is saved with a file name different from that of the original image data, the user can select a preferred image.

  By the way, depending on the optical characteristics of the photographic lens 1, the amount of light may decrease as it approaches the periphery of the imaging range 100. Regarding such a light amount reduction, for example, when the face region is in a predetermined region in the peripheral portion, the influence of the light amount reduction may be reduced by image processing. Further, the aberration reduction process and the light amount reduction correction process may be performed simultaneously.

  The present invention can be applied not only to a lens-integrated camera in which the photographing lens 1 and the camera body are integrated, but also to an interchangeable lens camera in which an interchangeable lens is detachably attached to the camera body. it can. In the case of an interchangeable lens type camera, aberration information stored in the memory on the interchangeable lens side is read into the memory on the camera body side.

  In addition, the above description is an example to the last, and this invention is not limited to the said embodiment at all unless the characteristic of this invention is impaired.

It is a block diagram which shows one Embodiment of the camera of this invention. It is a figure which shows the example of an image when a distortion aberration arises. It is a flowchart explaining an aberration correction process. It is a figure which shows an example of a face recognition image.

Explanation of symbols

  1: photographing lens, 2: imaging device, 5: image processing circuit, 6: monitor, 8: recording medium, 9: flash RAM, 10: CPU, 11: operation unit, 100: imaging range, 120A: outer region, 120B : Inner area, M1 to M4: face area

Claims (6)

An image sensor for imaging an image formed by the imaging optical system;
Face detection means for detecting an image region corresponding to a human face from a captured image captured by the image sensor;
A camera comprising: an image processing unit that corrects the captured image based on an optical characteristic of the photographing optical system when the image area is detected by the face detection unit. The camera of claim 1,
Determination means for determining whether to perform the correction processing based on at least one of a position and a size of the image area detected by the face detection means in the imaging region;
The camera according to claim 1, wherein the image processing unit performs the correction process when the determination unit determines to perform the correction process. The camera according to claim 2,
The camera according to claim 1, wherein the image processing means performs the correction process when at least a part of the image area detected by the face detection means is included in a predetermined imaging area where the influence of the optical characteristic is generated. The camera according to any one of claims 1 to 3,
The optical characteristic is an aberration characteristic of the photographing optical system,
The camera according to claim 1, wherein the image processing unit performs correction processing so as to reduce an influence of aberration of the photographing optical system. The camera according to claim 4, wherein
In a case where at least a part of the image region detected by the face detection unit is in a peripheral region within the imaging region, the image processing unit performs correction processing for reducing the influence of the aberration of the photographing optical system. A camera that also performs correction processing to reduce a decrease in light amount in the peripheral area. An image sensor for imaging an image formed by the imaging optical system;
A focus adjustment unit that detects an image region corresponding to a human face from a captured image captured by the image sensor, and adjusts a focus adjustment state of the photographing optical system with respect to a subject in the image region;
A camera comprising: an image processing unit that corrects the captured image based on an optical characteristic of the imaging optical system when at least a part of the image region is included in a predetermined imaging region.

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