JP4528349B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus having an image processing function.

  Needless to say a so-called video camera, a subject image using an image sensor, such as an electronic still camera mainly configured as a still image recording device, represented by a digital camera using a memory card or the like that has become popular in recent years as a recording medium. 2. Description of the Related Art An electronic imaging device that captures images and records them in the form of electrical signals is widely known.

  In the electronic imaging apparatus, since the signal can be processed by an electric circuit, various image processing for improving the image quality is performed when the recorded image is generated. Usually, the conventional silver salt film camera system is used. The image quality is still inferior to the image quality of the image.

  On the other hand, when image processing for improving image quality is performed, various possibilities are widened by performing different processing depending on regions. There are some techniques that have been attempted from this point of view. For example, Japanese Patent Laid-Open No. 8-51632 discloses an area-corresponding white balance process in which white balance control of a stroboscopic image is processed in units of blocks on the basis of a luminance comparison between the stroboscopic image and an image captured with only external light. Technology is disclosed.

JP-A-8-51632

  In general, when strobe photography is performed under artificial lighting and also incorporates external light, images of different colors can be obtained because the illumination color temperature of the main subject such as a person and the background are different. An image with a different color tone between the main subject and the background is unnatural and defective. In principle, it is impossible to take measures against this problem at the time of photographing with a silver salt film camera. In an electronic imaging device, it is considered and attempted to use an image processing technique.

  Specifically, the conventional example disclosed in the publication discloses white balance control of a strobe photographed image based on a comparison between a strobe photographed image that is a main photograph and a photographed image only with outside light under the same exposure conditions. By processing in units of blocks, different white balance control is performed for the block mainly contributed by the strobe light and the block mainly contributed by the external light, thereby trying to solve the above problem. However, although this method is excellent in basic philosophy, it has some problems.

  That is, since there is no area setting means for discriminating the main subject area from the background area and setting the area, a malfunction occurs when camera shake occurs at the time of shooting, and this cannot be dealt with at all. . That is, when a shift occurs between the two images due to camera shake (camera shake), the levels of the two images in the same pixel (pixel block) are different to reflect the contrast of the subject (reflectance level). When block processing is performed by simple level comparison that does not involve subject area recognition (discrimination between main subject area and background area) as in the conventional example disclosed in the above publication, the level difference due to this image shift is detected by the strobe light. Since it cannot be distinguished from the level difference depending on the presence or absence, there is a problem that an erroneous white balance setting occurs.

  In the conventional example, since the processing is simply performed in units of blocks, block distortion accompanying the processing occurs. That is, when the boundary between the main subject and the background exists in the processing block, the white balance processing of the block is performed based on the comparison result of the block representative pixels according to the example described in the above publication. The overall setting is an alternative setting between processing based on strobe and processing based on outside light. Therefore, at least in the block including the subject boundary, there is a pixel that is subjected to white balance adjustment different from the one that should be originally received, and all adjacent pixels are subjected to appropriate white balance adjustment because the subject boundary is not included. There is a problem that a color step occurs at the block boundary with the block. In addition, since the two images to be compared also require the same exposure conditions (same aperture value, same exposure time) that differ only in the presence or absence of a strobe, the applicable subject condition range becomes narrower. Met.

  The present invention has been made in order to solve the above-described problems in the conventional imaging apparatus, and is capable of adjusting white balance appropriately for both the main subject and the background in strobe shooting under external light. An object is to provide an imaging device. To describe the purpose of each claim, the invention according to claim 1 is based on each region of the subject image set for discrimination, and generates a recorded image by combining images obtained by extracting each region. As a result, it is possible to perform good white balance adjustment for all subject areas without performing balance adjustment processing, and to prevent the occurrence of malfunctions during block processing without conventional subject area recognition. It aims at realizing an imaging device. According to the second aspect of the present invention, different white balance adjustment processing can be performed for each region of the subject image that has been set to be discriminated, and the occurrence of malfunction during block processing that does not involve region recognition of a conventional subject can be prevented. It is another object of the present invention to realize an imaging apparatus that can simplify the circuit configuration and control without requiring processing such as image synthesis when generating an image. An object of the present invention is to realize an imaging apparatus that can easily solve the block distortion problem of the prior art when performing white balance adjustment processing.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a first image obtained by performing exposure with an exposure unit including an object illumination device, an exposure control unit for controlling the exposure unit, and at least irradiation with the illumination device. Based on image information, region setting means for discriminating the main subject region and the background region from the entire image region and setting the region, the first image, and the first image are caused by at least external light Recorded image generating means for generating a third image which is a target image for recording or the like based on a second image captured without performing irradiation by the illumination device under an exposure condition substantially including an exposure component to be recorded Image quality adjusting means for performing different white balance adjustment processing on the first and second images, and in the process of generating the third image by the recorded image generating means, the area setting means Selection means for selecting an image corresponding to each of the first and second images with respect to the set main subject area and background area, and the exposure control means captures the first image. In this case, in order to eliminate the influence of external light, the image pickup apparatus is configured to be characterized in that the substantial exposure time is made shorter than that at the time of taking the second image.

  According to a second aspect of the present invention, there is provided an image area based on information of an exposure unit including an object illumination device, an exposure control unit for controlling the exposure unit, and a first image captured by performing irradiation with the illumination device. Area setting means for discriminating and setting the main subject area and background area from the whole, and irradiation by the illuminating device under an exposure condition substantially including an exposure component due to at least external light different from the first image In the process of generating the third image by the recorded image generating means, a recorded image generating means for generating a third image that is a use target image such as recording based on the second image captured by performing Image quality adjustment means for performing different white balance adjustment processing on the main subject area and background area set by the area setting means, and the exposure control means includes the first image. It is when imaging in order to eliminate the influence of external light, as characterized by being composed substantially exposure time to less than that during the imaging of the second image, and constitutes the imaging device.

  According to a third aspect of the present invention, in the imaging apparatus according to the first or second aspect, the region setting by the region setting means is performed in a unit equal to or less than a minimum unit of an image related to color processing. is there.

  According to the present invention, it is possible to realize an imaging apparatus capable of performing appropriate white balance adjustment for both the main subject and the background in flash photography under external light. In particular, according to the first aspect of the present invention, since the main subject area and the background area can be discriminated and set, the recorded image is generated by combining the images extracted from the areas based on the discriminated subject image areas. As a result, it is possible to perform good white balance adjustment for all subject areas without performing different white balance adjustment processing for each area, and in the conventional technology, a simple level without subject area recognition. Since block processing is performed by comparison, it is possible to solve the problem that a malfunction occurs due to an image shift caused by camera shake or the like. According to the second aspect of the present invention, it is possible to perform different white balance adjustment processing for each region of the subject image that has been set to be discriminated, and to generate a malfunction during block processing that does not involve region recognition of a conventional subject. In addition, it is possible to prevent a circuit configuration, control, and the like since processing such as image synthesis is not required when generating an image. According to the invention of claim 3, in the white balance adjustment process, it is possible to effectively prevent the occurrence of block distortion caused by the subject boundary in the case of the block process.

1 is a block configuration diagram illustrating an embodiment of an imaging apparatus according to the present invention. It is the schematic which shows the 2nd image by exposure without strobe irradiation (light emission), and the 1st image by exposure with strobe irradiation.

  Next, the best mode for carrying out the present invention will be described.

  Next, examples will be described. FIG. 1 is a block diagram showing an embodiment of an imaging apparatus (digital camera) according to the present invention. In FIG. 1, 1 is a lens system, 2 is a lens driving mechanism, 3 is an exposure control mechanism, 4 is a filter system, 5 is a CCD imaging device, 6 is a CCD driver, and 7 is a preprocess circuit including an A / D converter, A digital process circuit 8 includes a memory as hardware and performs all digital process processing. 9 is a memory card interface, 10 is a memory card, 11 is an LCD image display system, 12 is a system controller including a microcomputer as a main configuration, 13 is an operation switch system, 14 is an operation display system including a display LCD and a sounding buzzer, 15 Is a strobe, 16 is a lens driver, and 17 is an exposure control driver. The imaging device is provided with a release button (not shown).

  In the digital camera configured as described above, the main operations, such as region discrimination setting, white balance processing, generation of a recorded image that is a use target image by image selection or synthesis, are all used in the system. Control is performed by the controller 12, and the system controller 12 controls an exposure control driver 17 as necessary to perform an exposure operation including strobe light emission. The digital camera according to the present embodiment has a switchable AWB mode corresponding to conventional auto white balance shooting and a HWB (Hyper White Balance) mode unique to the present embodiment as a shooting mode. 13 can be switched and selected prior to shooting. The camera control in the following description is all executed by the system controller 12 appropriately controlling each unit.

  First, when the photographer operates the release button in the HWB mode, first exposure is performed with strobe irradiation. At this time, there are several modes for controlling the aperture and shutter depending on the method of area discrimination processing. However, in this embodiment, the aperture is opened and the exposure time is less than the strobe light emission time regardless of the exposure value of the actual photographing. Set to the shortest possible time. The amount of light emitted from the strobe is appropriately adjusted by a known technique such as flashmatic or photometry. By opening the aperture, it is possible to increase the reach limit of the strobe light, and it is possible to reduce the influence of external light by shortening the exposure time. The image obtained at this time is defined as a first image. In the following, it is assumed that the background is sufficiently far away from the main subject. Therefore, the strobe light reaching the background is sufficiently smaller than the main subject.

  Following the first exposure, the second exposure is immediately performed under the originally intended exposure conditions. However, strobe light is not emitted at this time. The image obtained at this time is defined as a second image. In many shootings, if the time difference between the two exposures is set to be sufficiently small, subject changes and camera shake can be ignored. Therefore, in the following description, the first and second images have practically exactly the same composition. It is assumed that the image is obtained.

  If the second image is an image as shown in FIG. 2A, the first image looks like an image whose background portion is almost dark as shown in FIG. That is, as described above, since the exposure time is set to the shortest in the first image, the exposure by the external light can be almost ignored. Also, since the background is far away, the exposure level by the strobe is small. The first image is subjected to level comparison with a predetermined level in units of pixels, pixel positions that are equal to or higher than the predetermined level are registered as main subject areas, and pixel positions that are lower than the predetermined level are registered as background areas. I mentioned earlier that exposure by external light is almost negligible, but in reality there can be some exposure, and there is also background exposure by strobe, so this level comparison process can reliably remove this effect. is there. If the strobe light control level at the time of the first exposure is set higher than that in normal shooting, the possibility of misjudgment with respect to the low reflectance portion of the main subject can be reduced. The area setting in the processing can be made more reliable.

  Subsequently, white balance adjustment for each image is performed by a conventionally known method. The first image is made appropriate for strobe light, and the second image is made appropriate for outside light. Next, image synthesis is performed as a recorded image generation. That is, the image of the main subject area of the first image and the image of the background area of the second image are combined to form a final recorded image. As a result, it is possible to obtain a single flash photographed image in which white balance is adjusted appropriately for both the main subject and the background.

  In the above description, it is assumed that the two images are practically the same composition, but if the main subject and the background are discriminated in the manner as shown in the above embodiment and the region is set and processed, Even if there is a slight shift between the two images due to camera shake, there is no problem as in the conventional example except for the vicinity of the subject boundary. Even in the vicinity of the subject boundary, since the region setting is performed based only on the first image, at least the main subject is appropriately adjusted for white balance without causing a problem. This is one manifestation of the direct effect of the processing based on the region setting.

  In the above embodiment, the region setting process is performed for each pixel. This is because, as described above, block distortion caused by the subject boundary occurs in general block processing. However, as long as the purpose is white balance processing, the processing unit is not necessarily the pixel of the image sensor or the memory pixel itself. For example, in the case of a system in which the minimum unit of color signal processing is a plurality of pixel units due to the limitation of the color band, for example, it may be equal to or less than the color signal processing unit.

  Although the present invention has been described based on the above embodiment, various modifications as shown below are conceivable for the above embodiment. As a first modified example, the one relating to exposure processing can be cited. In the above embodiment, the setting is made so as to exclude the external light when the first image is exposed. However, if the background is closer than assumed in the above embodiment, a malfunction may occur. In order to cope with this, it is conceivable that the exposure levels for external light are made equal in the first exposure and the second exposure, and the levels of the two images are compared as a condition for setting the region. In this way, it is possible to distinguish the main subject from the background by specifically considering the contribution of strobe light and external light. As a specific example, a case where an area where the contribution of strobe light is greater than that of external light is used as a main subject will be described. In this case, since the exposure level is important, the individual values of the aperture value and the exposure time can be arbitrarily set as long as the exposure value EV (Exposure Value) is constant. From the viewpoint of suppressing the waste of strobe light emission and extending the reach distance, control for opening the aperture is a preferable example.

  As a second modification, the first exposure and the area setting process are performed in the same manner as in the above-described embodiment, and the strobe is also emitted during the second exposure and is performed under the exposure conditions of the original target exposure. It is done. In this case, when the recorded image is generated, it is possible to perform different white balance processing for each region of the main subject and the background on the second image without using the first image. No processing is required.

DESCRIPTION OF SYMBOLS 1 Lens system 2 Lens drive mechanism 3 Exposure control mechanism 4 Filter system 5 CCD image pick-up device 6 CCD driver 7 Pre-process circuit 8 Digital process circuit 9 Memory card interface
10 Memory card
11 LCD image display system
12 System controller
13 Operation switch system
14 Operation display system
15 Strobe
16 Lens driver
17 Exposure control driver

Claims (3)

Exposure means including a subject illumination device;
Exposure control means for controlling the exposure means;
An area setting means for discriminating a main subject area and a background area from the entire image area based on information of a first image captured by performing irradiation with the illumination device;
Based on the first image and a second image captured without performing irradiation by the illumination device under an exposure condition substantially including an exposure component caused by external light at least different from the first image Recording image generating means for generating a third image that is a use target image such as recording;
Image quality adjustment means for performing different white balance adjustment processes on the first and second images,
In the process of generating the third image by the recorded image generating means, images of areas corresponding to the first and second images with respect to the main subject area and the background area set by the area setting means are displayed. Selecting means for selecting,
The exposure control means is configured to make the substantial exposure time shorter than that at the time of capturing the second image in order to eliminate the influence of external light when capturing the first image. An imaging device. Exposure means including a subject illumination device;
Exposure control means for controlling the exposure means;
An area setting means for discriminating a main subject area and a background area from the entire image area based on information of a first image captured by performing irradiation with the illumination device; and
An image to be used for recording or the like based on a second image captured by irradiating with the illumination device under an exposure condition that substantially includes an exposure component caused by at least external light different from the first image. Recorded image generating means for generating a third image;
Image quality adjusting means for performing different white balance adjustment processing on the main subject area and background area set by the area setting means in the third image generation process by the recorded image generating means,
The exposure control means is configured to make the substantial exposure time shorter than that at the time of capturing the second image in order to eliminate the influence of external light when capturing the first image. An imaging device.   The imaging apparatus according to claim 1 or 2, wherein the setting of the area by the area setting unit is performed in a unit equal to or less than a minimum unit of an image related to color processing.

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