JP2021015200A - Imaging apparatus - Google Patents

Abstract

To solve the problem that a face cannot be detected, accuracy is deteriorated, and reliability is lowered, when luminance of the face is extremely low and dark due to strong backlight or the like.SOLUTION: A imaging apparatus has image acquisition means (116) for acquiring an image, face area detection means for detecting face areas (404, 434) of a subject using the acquired image, face detection area determination means for determining a dark area in the acquired image as face detection areas (403, 433), and illumination means (300) for illuminating the subject. The face detection area determination means determines the face detection area from the image before the illumination means emits light, and the face area detection means detects the face detection area determined by the face detection area determination means from the image being emitted by the illumination means.SELECTED DRAWING: Figure 3

Description

The present invention relates to an imaging device such as a digital camera, a photometric sensor, and a flash control method, and relates to a technique of pre-flashing before flash photography and face detection of a subject.

Conventionally, face detection is performed under constant light such as sunlight or indoor lighting.

FIG. 8 is a diagram showing an image of a conventional method of detecting a face detection region under constant light.

As shown in FIG. 8A, if the subject 501 is sufficiently illuminated, it is easy to detect the face region 504 by performing face detection within the face detection region 503 of the entire screen.

However, as shown in FIG. 8B, when the subject 501 is in a strong backlight state due to the sun 502, a dark shadow is generated on the face, and the face cannot be detected, or even if it can be detected, the accuracy is poor and the reliability is low. Or become.

In Patent Document 1, the face of the subject is detected and the face area is measured to obtain the brightness, and the entire screen is divided and the light is measured to obtain the brightness of each area.

Then, from the brightness of the face region and the brightness of the divided background region, the amount of light emitted by the flash is controlled so that both the face and the background can be photographed with appropriate brightness.

JP-A-2009-63674

In the prior art disclosed in Patent Document 1 above, the face region and the background region are set to appropriate brightness from the brightness of the face region detected by detecting the face of the subject before shooting and the brightness measured by dividing the screen. The light emission of the flash is controlled so as to be.

Therefore, if the background is bright and the brightness of the face area is extremely low and dark due to strong backlight of the subject before the flash is fired, face detection may not be possible or the accuracy may be poor and the reliability may be low. The flash cannot be controlled so that the brightness of the image and the background area are appropriate.

In order to achieve the above object, the imaging apparatus according to the present invention is
Image acquisition means to acquire images and
Face area detection means that detects the face area of the subject using the acquired image,
A face detection area determining means for determining a dark area in the image of the acquired image as a face detection area, and
Lighting means to illuminate the subject and
Have,
The face detection area is determined by the face detection area determination means from the image before the lighting means emits light.
It is characterized in that the face detection area determined by the face detection area determining means is detected by the face area detecting means from the image in which the lighting means is emitting light.

According to the image pickup apparatus according to the present invention, when the subject is dark or the face cannot be detected due to backlight, the face is detected with the subject's face illuminated by the pre-flash. This makes it possible to detect the face. Further, regarding the shooting sequence of the camera, since the still image shooting is continuously performed after the flash pre-flash, it is necessary to shorten the time from the flash pre-flash to the still image shooting as much as possible. If this time is long, the shooting rhythm will get worse. According to the image pickup apparatus according to the present invention, after illumination by flash pre-emission, the face detection area is limited to the area where the face cannot be detected due to backlight or the like, and the detection range is narrowed to shorten the time. Can be done.

The figure which showed the schematic structure of the digital single-lens reflex camera which concerns on embodiment of this invention. Diagram showing the actual placement of blocks in the camera The figure which showed the photographed image which concerns on embodiment of this invention A flowchart showing a sequence of flash still image shooting according to an embodiment of the present invention. The figure which showed the image of the detection method of the face detection area which concerns on embodiment of this invention. The figure which showed the image of the detection method of the face detection area which concerns on embodiment of this invention. The figure which showed the photographed image which concerns on embodiment of this invention The figure which showed the image of the detection method of the face detection area which concerns on a conventional embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

Here, in the embodiment of the present invention, an example in which a digital single-lens reflex camera is applied as the image pickup apparatus according to the present invention will be described.

FIG. 1 is a diagram showing a schematic configuration of a digital single-lens reflex camera according to an embodiment of the present invention. This is a block diagram of the first embodiment, in which the digital single-lens reflex camera 100 is the main body of the camera and the interchangeable lens 200 is an interchangeable lens. Further, FIG. 2 is a diagram showing an actual arrangement of the blocks in the camera.

In FIGS. 1 and 2, the overall control / calculation unit 101 is an overall control / calculation unit that comprehensively controls various arithmetic processes and the entire digital single-lens reflex camera 100, the interchangeable lens 200, and the flash 300, which are the imaging devices. is there.

The interchangeable lens 200 is an interchangeable lens for a digital single-lens reflex camera, and the photographing lens 202 is an imaging lens that forms an optical image of a subject on the imaging element A106.

The lens drive device 203 is a drive device that drives the photographing lens so that it is in focus, the aperture mechanism 204 is an aperture mechanism that controls the amount of light reflected from the subject image passing through the lens, and the aperture drive device 205 is an aperture mechanism. It is a drive device that drives the lens.

The interchangeable lens 200 for photography and the digital single-lens reflex camera 100 can be removed for lens exchange, and the interchangeable lens 200 and the digital single-lens reflex camera 100 communicate with each other for information exchange. .. Regarding the communication at this time, regarding the digital single-lens reflex camera 100, the overall control / calculation unit 101 and the lens control unit 201 are communicating with each other to manage transmission / reception.

The digital single-lens reflex camera 100 is the main body of the imaging device.

The QR mirror 102 is generally called a quick return (QR) mirror, and guides an optical image that has passed through the photographing lens 202 to the finder and the AE image sensor B116 when the finder is used, and jumps up the optical image during the image pickup element A106. Lead to.

The QR mirror drive device 103 is a drive device that drives the QR mirror 102.

The shutter mechanism 104 is a shutter mechanism having a shutter curtain corresponding to a focal plane type front curtain / rear curtain used in a so-called single-lens reflex camera, and controls the exposure time of an optical image passing through the photographing lens 202 and blocks light. Do.

The shutter drive device 105 is a shutter drive device that drives the shutter mechanism 104.

The image sensor A106 is a (solid) image sensor A for capturing an optical image of a subject imaged by the photographing lens 202 as an image signal. The image sensor A106 is formed with an XY address such as a CMOS sensor.

The image pickup signal processing unit A107 performs various corrections such as amplification processing of the image signal output from the image pickup element A106, A / D conversion processing for converting from analog to digital, and scratch correction for the image data after A / D conversion. Processing, compression processing for compressing image data, or the like is performed.

The timing generation unit A108 is a timing generation unit that outputs various timing signals to the image sensor A106 and the image pickup signal processing unit A107.

The memory unit 109 temporarily stores the image data and the like processed by the image pickup signal processing unit A107, and permanently stores various adjustment values and a program for executing various controls by the overall control / calculation unit 101. It is a memory part for storing.

The recording medium control interface unit 110 is a recording medium control interface (I / F) unit for recording image data or the like on the recording medium 111 or reading image data or the like from the recording medium 111.

The recording medium 111 is a removable recording medium made of a semiconductor memory or the like for recording various data such as image data.

The display drive device 112 is a drive unit that drives the display device 113 that displays captured still images, moving images, and the like.

The external interface unit 114 is an external interface, and exchanges information such as image signals and control signals with an external device such as a computer 115.

The image sensor B116 is an image sensor for acquiring an AE signal / light source detection signal / flicker frequency signal, and is a sensor with an RGB Bayer arrangement.

The image pickup signal processing unit B117 performs various corrections such as amplification processing of the image signal output from the image pickup element B116, A / D conversion processing for converting from analog to digital, and scratch correction for the image data after A / D conversion. Processing, compression processing for compressing image data, or the like is performed. This sensor is also used to detect the flicker frequency of the subject light.

The timing generation unit B118 is a timing generation unit that outputs various timing signals to the image sensor B116 and the image pickup signal processing unit B117.

The light rays bent by the pentaprism 119 and the QR mirror 102 are guided to the finder 123 and the image sensor B116.

The flash 300 is a lighting device that illuminates a subject and is a flash, but the flash 300 is generally not limited to the flash if it is a lighting device.

The light emitting unit 302 is a light emitting unit that is inside the flash 300 and actually emits light.

The lighting device control unit 301 is a lighting device control unit that controls light emission of the light emitting unit 302 in response to a signal from the overall control / calculation unit 101 of the digital single-lens reflex camera 100.

FIG. 3 is a diagram showing a photographing image according to the embodiment of the present invention.

FIG. 4 is a flowchart showing a sequence of flash still image shooting according to the embodiment of the present invention.

An embodiment of the present invention will be described with reference to this flowchart and the figure.

At # 100, the still image shooting of the digital single-lens reflex camera 100 using the flash 300 is started.

In # 101, a dark area in the photographing area is detected. This corresponds to FIG. 3A, and the subject 401 is backlit by the sun 402. At this time, the face detection area 403, which cannot detect the face because it is dark due to backlight in the shooting area, is detected in advance.

In # 102, as shown in FIG. 3B, the flash 300 is pre-flashed, the reflected light amount of the subject 401 is measured, and the light emission amount of the flash 300 at the time of still image shooting is determined. By illuminating the subject 401 at the same time, the face can be detected.

By performing face detection only within the face detection area 403 as shown in FIG. 3C in # 103, the face area 404 can be determined in a clearly shorter time than when the entire shooting area is detected. ..

The brightness of the face area 404 detected by # 103 in # 104 is calculated, and flash photography is performed with the amount of light emitted by the flash 300 in consideration of the brightness in # 105. Since the pre-flash of the flash 300 at # 102 and the still image shooting of # 105 are executed continuously, the time from # 102 to # 105 should not be long. If it gets longer, the rhythm of shooting gets worse.

At # 106, the flash shooting sequence ends.

In the present embodiment, the face detection region 403 may be one location, or may be a plurality of regions depending on conditions such as a plurality of subjects.

FIG. 5 is a diagram showing an image of a method for detecting a face detection region according to an embodiment of the present invention.

FIG. 5A shows a state before distance measurement, and the distance measurement point display 414 is shown by a plurality of dotted quadrangles. Further, the subject 411 is semi-backlit by the sun 412.

FIG. 5B shows a state after distance measurement, in which the focusing focus measurement point display 415 is shown by a plurality of solid quadrangles. As shown in the figure, the face detection area 413 that becomes dark due to such semi-backlight and cannot detect the face becomes about half of the subject 411, and the face detection area 413 as it is cannot detect the face of the subject 411. Therefore, from the state of the focus detection point display 414 shown by the plurality of dotted quadrangles before the distance measurement in FIG. 5A, the focusing state of the focusing focus measurement point display 415 after the distance measurement in FIG. 5B can be seen as shown in FIG. 5C. The face detection area 413 is expanded to the in-focus position.

By expanding the face detection area 413, the face detection area 413 includes the subject 411 as shown in FIG. 5C, and the face of the subject 411 can be reliably detected.

FIG. 6 is a diagram showing an image of a method for detecting a face detection region according to an embodiment of the present invention.

FIG. 6A shows a state before distance measurement, and the distance measurement point display 424 is indicated by a plurality of dotted quadrangles. Further, due to the sun 422, the subject 421 on the near side and the subject 426 on the far side are backlit.

FIG. 6B shows a state after distance measurement, in which the focusing focus measurement point display 425 is shown by a plurality of solid quadrangles.

In such a state, the face detection area 423 becomes an area including both the near subject 421 and the distant subject 426 as shown in the figure, and when the face detection area 423 becomes wide, the face is detected. It takes time to do so.

Therefore, using the defocus information of the phase difference distance measuring unit 121, the face is focused as shown in FIG. 6C by focusing only the near subject 421 except for the distant subject 426 as after the distance measurement in FIG. 6B. The detection area 413 is narrowed to the position of the focusing focus point display 425.

FIG. 7 is a diagram showing a photographing image according to the embodiment of the present invention.

In FIG. 7A, the image of the flash 300 before the pre-flash is acquired, in which the subject 431 is backlit by the sun 432.

In FIG. 7B, the pre-flash of the flash 300 acquires an image in which the subject 431 is illuminated.

In FIG. 7C, the image of FIG. 7A before the pre-flash of the flash 300 is subtracted from the image of FIG. 7B of the pre-flash of the flash 300. By performing such subtraction, the constant light portion that is the background of the subject 431 becomes "0", and the image appears only in the portion illuminated by the pre-emission. This image portion is designated as a face detection area 433, and the face area 434 is detected only from this area. By limiting the face detection area 433 in this way, it is possible to shorten the time required for face detection.

100 Digital SLR camera, 101 Overall control / calculation unit,
102 QR mirror, 103 QR mirror drive,
104 shutter mechanism, 105 shutter drive,
106 image sensor A, 107 image sensor processing unit A,
108 Timing generator A, 109 Memory unit,
110 Recording medium control interface unit,
111 recording medium, 112 display drive,
113 Display, 114 External interface,
115 computer, 116 image sensor B, 117 image sensor processing unit B,
118 Timing generator B, 119 Pentaprism,
120 AF section drive, 121 Phase difference AF, 200 interchangeable lens,
201 lens control unit, 202 shooting lens, 204 aperture mechanism,
300 flash, 203 lens drive, 205 aperture drive,
301 Lighting device control unit, 302 light emitting unit, 401 subject, 402 sun,
403 face detection area, 404 face area, 411 subject, 412 sun,
413 Face detection area, 414 Focusing point display, 415 Focusing focusing point display,
421 Near subject, 422 sun, 423 face detection area,
424 AF point display, 425 Focused AF point display,
426 Out-of-focus AF point display, 427 distant subject, 431 subject,
432 sun, 433 face detection area, 434 face area, 501 subject,
502 Sun, 503 face detection area, 504 face area

Claims (6)

Image acquisition means to acquire images and
Face area detection means that detects the face area of the subject using the acquired image,
A face detection area determining means for determining a dark area in the image of the acquired image as a face detection area, and
Lighting means to illuminate the subject and
Have,
The face detection area is determined by the face detection area determination means from the image before the lighting means emits light.
An imaging device characterized in that a face detection area determined by a face detection area determining means is detected by the face area detecting means from an image in which the lighting means is emitting light. When a plurality of face detection areas are determined by the face detection area determining means from the image before the lighting means emits light, a plurality of faces determined by the face detection area determining means from the image during which the lighting means emits light. The imaging device according to claim 1, wherein the detection region is detected by a face region detecting means. If the face detection area is not determined by the face detection area determining means from the image before the lighting means emits light, the entire image is determined as the face detection area, and the face of the entire image is determined from the image during which the lighting means emits light. The imaging device according to claim 1, wherein the detection region is detected by a face region detecting means. A distance measuring means for measuring the distance to the subject at a plurality of points within the shooting range, a focusing area determining means for separating the focused area and the out-of-focus area based on the distance measuring result of the distance measuring means, The face detection area is determined by the face detection area determining means from the image before the lighting means emits light, and the face detection area is changed based on the focusing area determining means so that the lighting means is emitting light. The imaging device according to claim 1, wherein a changed face detection region is detected from an image by a face region detection means. From the image before the lighting means emits light, the face detection area is determined by the face detection area determining means, and when a plurality of focusing areas are determined by the focusing area determining means, a plurality of focusing areas are set. The imaging device according to claim 4, wherein the face detection area is changed based on the method, and a plurality of changed face detection areas are detected by the face area detection means from an image in which the lighting means is emitting light. Image acquisition means to acquire images and
Lighting means to illuminate the subject and
Face area detection means that detects the face area of the subject using the acquired image,
Area designation means designated as a face detection area illuminated by the illumination means in the image of the acquired image, and
Have,
The image before the lighting means emits light and the image when the lighting means emits light are acquired.
Obtain a difference image obtained by subtracting the image before the lighting means emits light from the image during which the lighting means emits light.
An imaging device characterized in that a face detection area designated by the area designation means is detected by the face area detection means.