JP4306584B2 - Digital camera - Google Patents

Description

  The present invention relates to a digital camera with a multiple exposure function that combines images captured by multiple exposure.

  The following digital camera is known from Patent Document 1. When a plurality of images picked up by multiple exposure are overlapped to form a single image, the image data of each frame is added and then divided by the number of frames to perform an averaging process.

JP 2003-69888 A

  However, in a conventional digital camera, when a plurality of images captured by multiple exposure are superimposed to form one image, the image data of each frame is added and then divided by the number of frames. If the number of images increases, data may overflow before division. In addition, since a plurality of image data picked up by multiple exposure are added as they are, there is a problem that overexposure may occur.

According to the first aspect of the present invention, there are provided storage means for storing a plurality of multiple exposure images picked up by the image sensor when the multiple exposure shooting mode is set, and a plurality of multiple exposure images . after imaging of the image to the gain calculating means sum based on the number of multiple exposure image stored in the storage means for calculating a gain to be 1, the multiple exposure of a plurality captured the calculated gain The image processing apparatus includes: a gain applying unit that applies to the image for use; and a combining unit that generates a multiple exposure photographed image by adding and combining a plurality of images for multiple exposure after the gain is applied by the gain applying unit.
According to a second aspect of the present invention, in the digital camera according to the first aspect, the multiple exposure photographing number setting means for setting the multiple exposure photographing number, and the interruption for interrupting the photographing before completion of the photographing of the multiple exposure photographing number And the gain calculating means has a total sum of 1 based on the number of images for multiple exposure stored in the storage means after imaging of the number of multiple exposure shots or after interruption of multiple exposure shooting by the interruption means. The gain is calculated so that
According to a third aspect of the present invention, in the digital camera according to the first or second aspect, the digital camera according to the first or second aspect further includes a switching unit that switches between enabling and disabling of gain applying by the gain applying unit. When enabled, the gain is added to the multiple exposure images.
According to a fourth aspect of the present invention, in the digital camera according to any one of the first to third aspects, the image processing means for executing various image processes on the multiple exposure photographed image generated by the synthesizing means. It is further provided with the feature .
The invention according to claim 5, in the digital camera according to claim 1, gain calculation means, after the imaging of a plurality of multiple-exposure image, based on the number of multiple exposure image stored in the storage means Thus, the gain to be added to each multiple exposure image is calculated such that the sum of the gains to be given to each multiple exposure image is 1, and the gain to be given to the multiple exposure image captured later becomes smaller or larger. It is characterized by doing.

  According to the present invention, a gain determined so that the sum is 1 based on the number of multiple exposure shots is applied to a plurality of captured images, and then the plurality of images are combined to perform multiple exposure shooting. An image was generated. As a result, it is possible to avoid data overflow during synthesis. In addition, it is possible to prevent overexposure at the time of synthesis, and it is possible to obtain a multiple exposure photographed image with appropriate exposure.

  FIG. 1 is a block diagram illustrating a configuration of an embodiment of a digital camera according to the present embodiment. The digital camera 100 includes a photographing lens 1, an image sensor 2 such as a CCD, an A / D conversion circuit 3 that converts an analog signal output from the image sensor 2 into a digital signal, and a timing signal for the image sensor 2. A timing generator (TG) 4 for giving, an image memory (semiconductor memory) 5 for temporarily storing a plurality of captured images, an image processing circuit 6 for executing various image processing described later, and image processing by the image processing circuit 6 The compressed image data is compressed and converted into an image format such as JPEG, the display circuit 8 performs display processing for displaying the captured image on a display device 9 such as a TFT, and the compression circuit 7 compresses the image data. A memory 10 for temporarily storing the image data and a removable memory card or the like for copying and saving the image data stored in the memory 10 And 憶媒 body 11, and a CPU12 which controls the digital camera 102, an input device 13, including a release button and various setting buttons operated by the user.

  In addition to the image display function described above, a menu for changing various setting values of the digital camera 100 is displayed on the display device 9, and the user operates the input device 13 in accordance with the displayed menu. The setting of the digital camera 100 can be changed.

  In the digital camera 100, when the user presses the release button, shooting is performed with an aperture and a shutter speed set according to the luminance of the subject, and the image sensor 2 stores charges corresponding to the subject image. The The electric charge accumulated in the image pickup device 2 is converted into a digital signal by the A / D conversion circuit 3, and raw image data before various image processing is performed, that is, RAW data is stored in the image memory 5. The image memory 5 is a buffer memory and can store a plurality of pieces of RAW data.

  The image processing circuit 6 reads RAW data stored in the image memory 5 and performs known image processing such as interpolation, color temperature correction, and gradation correction, automatic gain correction described later, and image synthesis. Thereafter, the compression circuit 7 compresses and converts the image data into a predetermined compression format, for example, JPEG format, and stores it in the memory 10. The image data stored in the memory 10 is copied or stored in the storage medium 11 automatically or in accordance with an instruction from the user. The image data that has been subjected to image processing by the image processing circuit 6 is subjected to display processing by the display circuit 8 and displayed on the display device 9.

  The digital camera 100 according to the present embodiment is capable of imaging by multiple exposure. When the multiple exposure shooting mode is set, an image having the number of frames (number of frames) preset by the user is displayed in the multiple exposure shooting mode. Take an image with. When the user designates the multiple exposure shooting mode, the multiple exposure setting screen shown in FIG. On the multiple exposure setting screen, first, the number of frames to be captured by multiple exposure is input and set in the frame number input field 2a. The number of frames can be arbitrarily set within a predetermined range, for example, between 2 frames and 10 frames. The user also sets whether or not to perform automatic gain correction, which will be described later. Whether or not to perform automatic gain correction is set by selecting either “do not” (invalid) or “enable” (valid) automatic gain correction in the automatic gain correction setting field 2b. Note that, when the number of frames is not set in the frame number input field 2a, imaging by multiple exposure is not performed.

  In the multiple exposure shooting mode setting state in which the number of frames for multiple exposure shooting is set by the user, each frame image is displayed with the exposure value set each time the release switch is pressed until the set number of frames is shot. Is imaged. Then, image data of each frame, that is, RAW data is stored in the image memory 5. For example, when the number of frames is set to 5, RAW data of 5 frames of image 1 to image 5 is stored in the image memory 5 as shown in FIG.

  The image processing circuit 6 adds and combines all the RAW data stored in the image memory 5. At this time, if the automatic gain correction is set to “OFF” on the multiple exposure setting screen shown in FIG. 2, all the RAW data stored in the image memory 5 are sequentially added and combined. That is, since each RAW data stored in the image memory 5 is digital data obtained by digitizing the charges output from each pixel of the image sensor 2, synthesis is performed by adding pixel data at the same position on the image. Is possible. Therefore, for example, after adding the image 2 to the image 1 (image 1 + image 2), and further adding the image 3 to the addition result, the images can be combined in order.

However, if the RAW data stored in the image memory 5 is synthesized as it is, there is a possibility that the image is overexposed. Therefore, in order to avoid this, it is necessary to set the exposure value underexposed according to the number of frames to be subjected to multiple exposure. For example, when performing multiple exposure of 5 frames, the following formula (1) Therefore, it is necessary to calculate and set an appropriate exposure value.
Proper exposure value = Log (1/5) /Log2=2.3 (1)
Accordingly, it is understood that when multiple exposure of 5 frames is performed, it is only necessary to set the exposure under 2.3 steps in advance before imaging.

However, it is not preferable to calculate the appropriate exposure according to the number of frames to be subjected to multiple exposure each time during photographing with multiple exposure as described above, because the work becomes complicated. Therefore, in the present embodiment, when the automatic gain correction is set to “Yes” on the multiple exposure setting screen shown in FIG. 2, each RAW data stored in the image memory 5 is digitally reduced in advance. Then, the pixel data at the same position on the image are added to be combined. For example, when multiple exposures of 5 frames are performed, the 5 pieces of RAW data stored in the image memory 5 are automatically gain set according to the following equation (2), that is, the gain is reduced and then added.
K1, image 1 + K2, image 2 + K3, image 3 + K4, image 4 + K5, image 5 (2)

  In Expression (2), variables K1 to K5 indicate the digital gain of each image, and are set so that the sum thereof is 1. For example, 1 is divided by the number of frames and multiplied (applied) to each image, such as K1 = K2 = K3 = K4 = K5 = 0.2, so that all images are gained down with the same digital gain. Can do. Further, by setting K1> K2> K3> K4> K5, the later captured RAW data becomes darker, and the image can be displayed so as to fade out, and K1 <K2 <K3 <K4 <K5. By doing this, the later captured RAW data becomes brighter and the image can be displayed so as to fade in.

  In this way, by multiplying each RAW data imaged by multiple exposure by a gain whose sum is 1 and reducing the gain, and adding the combined data, it is possible to prevent overexposure during synthesis. It is possible to obtain a multiple-exposure photographed image with proper exposure. In addition, in the method of combining the RAW data stored in the image memory 5 as it is, when there are a large number of frames to be captured with a preset multiple exposure, the data is added while the RAW data is being added. Although there is a possibility of overflow, according to the present invention, since the gain is reduced before adding, it is possible to avoid this.

  Furthermore, in the present embodiment, the following processing is performed so that a multiple-exposure photographed image with a proper exposure can be obtained even when multiple exposure is interrupted in the middle. In addition, as a case where multiple exposure is interrupted, for example, (A) when interruption of multiple exposure is instructed by a user's operation of the input device 13, (B) a digital camera for a preset predetermined time, (C) When the power is automatically turned off without being operated for a predetermined time in the case where it has a function of automatically turning off the power when 100 is not operated, (C) the input device 13 by the user. Is operated, and the power of the digital camera 100 is turned off.

  When the image processing circuit 6 determines that the multiple exposure is interrupted in the middle according to any of the above (A) to (C), the image processing circuit 6 uses the formula (2) based on the RAW data of the number of frames captured at the time of the interruption. ). For example, when the number of frames to be captured by multiple exposure is set to 8, if there is no interruption, the digital gain is set so that the sum of K1 to K8 is 1 for the captured 8 frames of RAW data. Based on (2), composition is performed with automatic gain setting, but if multiple exposure is interrupted at the time of five-frame imaging, the sum of K1 to K5 is 1 for the captured five-frame RAW data. In this way, the digital gain is set and the automatic gain is set based on the equation (2) to perform synthesis. As a result, even when multiple exposure is interrupted, a multiple exposure photographed image with appropriate exposure can be obtained.

  FIG. 4 is a flowchart showing the flow of processing in the digital camera 100 of the present embodiment. The processing shown in FIG. 4 is executed by the CPU 12 as a program that starts when the power of the digital camera is turned on. In step S10, it is determined whether or not the release button has been pressed by the user. If it is determined that the user has pressed the release button, the process proceeds to step S20. In step S <b> 20, the subject is imaged by the image sensor 2 through the photographing lens 1. At this time, if the exposure condition is the automatic exposure shooting mode, an appropriate exposure value is set according to the luminance of the subject. Thereafter, the process proceeds to step S30. In step S <b> 30, RAW data obtained by converting the charge accumulated in the image sensor 2 into a digital signal by the A / D conversion circuit 3 is stored in the image memory 5.

  Thereafter, the process proceeds to step S40, and it is determined whether the multiple exposure shooting mode is instructed on the multiple exposure setting screen shown in FIG. 2 by the user, that is, whether the number of frames to be captured by multiple exposure is set. If imaging by multiple exposure is not instructed, the process proceeds to step S100 described later. On the other hand, if the multiple exposure shooting mode is instructed, the process proceeds to step S50. In step S50, it is determined whether or not imaging of the number of frames to be captured with multiple exposure preset by the user is completed. If it is determined that the imaging of the number of frames to be imaged by the multiple exposure is completed, the process proceeds to step S70.

  On the other hand, if it is determined that the imaging of the number of frames to be imaged by multiple exposure is not completed, the process proceeds to step S60. In step S60, it is determined whether or not multiple exposure is interrupted in the middle for any of the reasons (A) to (C) described above. If it is determined that the multiple exposure is not interrupted, the process returns to step S10 and waits for the release switch to be pressed. When the release switch is pressed, the above-described processing is performed. On the other hand, if it is determined that multiple exposure has been interrupted, the process proceeds to step S70.

  In step S70, it is determined whether or not the automatic gain correction is set to “Yes” by the user on the multiple exposure setting screen shown in FIG. If it is determined that the automatic gain correction is set to “OFF”, the process proceeds to step S90. On the other hand, if it is determined that the automatic gain correction is set to “YES”, the process proceeds to step S80, and the image processing circuit 6 is stored in the image memory 5 based on the equation (2) as described above. The process proceeds to step S90 after the gain of each RAW data is reduced. As described above, since the gain K is set based on the number of frames, in the case of interruption, the gain determined according to the predetermined number of frames is not used, but based on the actual number of frames taken. Use the determined gain.

  In step S90, the image processing circuit 6 adds and synthesizes each RAW data stored in the image memory 5 or the RAW data after gain reduction in step S80, and proceeds to step S100. In step S100, known image processing such as interpolation, color temperature correction, and gradation correction is executed, and the process proceeds to step S110. In step S 110, the image synthesized by the image processing circuit 6 is compressed and converted into a predetermined compression format by the compression circuit 7 and stored in the memory 10. Then, the image data stored in the memory 10 is copied and stored in the storage medium 11 automatically or in accordance with an instruction from the user. The image synthesized by the image processing circuit 6 is displayed on the display device 9 by the display circuit 8.

  Thereafter, the process proceeds to step S120, and it is determined whether or not the power of the digital camera 100 is turned off. If it is determined that the power is not turned off, the process returns to step S10 and the process is repeated. On the other hand, if it is determined that the power is turned off, the process is terminated.

According to the present embodiment described above, the following operational effects can be obtained.
(1) If the automatic gain correction is set to “Yes” by the user, each RAW data stored in the image memory 5 is digitally gained in advance and then pixel data at the same position on the image Was added to synthesize. Thereby, it is possible to prevent overexposure at the time of composition, and it is possible to obtain a multiple exposure photographed image with appropriate exposure. In addition, it is possible to avoid overflow of data while adding RAW data.
(2) Each RAW data imaged by multiple exposure is multiplied by a digital gain whose sum is 1, and the gain is reduced. Thus, for example, the gain can be reduced by a digital gain calculated by dividing the sum 1 by the number of frames to be imaged by multiple exposure. If each frame is imaged by an appropriate exposure value, the image is captured by multiple exposure. A multiple-exposure photographed image with an appropriate exposure according to the number of frames can be obtained.

(3) When it is determined that the multiple exposure has been interrupted, the digital gain is calculated based on the number of imaging frames until the interruption, and image data obtained by multiplying the captured RAW data by the digital gain is synthesized. It was decided. This makes it possible to obtain a multiple exposure photographed image with appropriate exposure even when multiple exposure is interrupted.
(4) The user can set in advance whether the automatic gain setting is “Yes” or “No”. As a result, it is possible to capture an appropriate multiple-exposure photographed image in consideration of the subject imaging conditions.

In addition, it can also deform | transform as follows.
(1) In the above-described embodiment, when the automatic gain setting is set to “Yes”, the RAW data is temporarily stored in the image memory 5 and then the image processing circuit 6 is stored in the image memory 5. The example in which the RAW data is read, and the automatic gain is set and combined has been described. However, the present invention is not limited to this, and the RAW data may be stored in the image memory 5 after the automatic gain setting. If multiple exposure is interrupted halfway, it is necessary to perform automatic gain setting again based on the actual number of shot frames after the interruption.

(2) In the embodiment described above, an example in which image processing such as interpolation, color temperature correction, and gradation correction is performed on the combined image data after combining the RAW data has been described. However, the present invention is not limited to this. When image processing is performed on the RAW data, and if data that can be synthesized is obtained by adding pixel data at the same position on the image, various image processing is performed. Synthesis may be performed later.

(3) In the above-described embodiment, the example in which the image processing circuit 6, the compression circuit 7, and the display circuit 8 are mounted on the digital camera 100 has been described. However, the present invention is not limited thereto, and the image processing circuit 6 and the compression circuit 7 are not limited thereto. The functions realized by the display circuit 8 may be mounted on an external device such as a personal computer. In this case, various processes are performed after the RAW data imaged by the imaging device 2 is copied to a personal computer via a memory card or an interface cable.

  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.

  The correspondence between the constituent elements of the claims and the embodiment will be described. The imaging element 2 corresponds to an imaging unit, the image memory 5 corresponds to a storage unit, and the image processing circuit 6 corresponds to a gain applying unit, a combining unit, and an image processing unit. The input device 13 corresponds to switching means and interruption means, and the CPU 12 corresponds to interruption means. This correspondence is an example, and the correspondence is different depending on the configuration of the embodiment.

It is a block diagram which shows the structure of one Embodiment of a digital camera. It is a figure which shows the specific example of a multiple exposure setting screen. It is a figure which shows the specific example of the RAW data memorize | stored in the image memory. FIG. 4 is a flowchart showing a process flow in the digital camera 100.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shooting lens 2 Image pick-up element 3 A / D conversion circuit 4 Timing generator 5 Image memory 6 Image processing circuit 7 Compression circuit 8 Display circuit 9 Display apparatus 10 Memory 11 Storage medium 12 CPU
13 Input device

Claims (5)

Storage means for storing each of a plurality of multiple exposure image for each imaging by the imaging device when the multiple exposure shooting mode is set,
Gain calculating means for calculating a gain so that the sum is 1 based on the number of the multiple exposure images stored in the storage means after the multiple exposure images are captured ;
A gain applying means for applying the calculated gain to the plurality of multiple exposure image picked up,
A digital camera comprising: combining means for adding and combining the plurality of images for multiple exposure and generating a multiple exposure photographed image after applying gain by the gain applying means. The digital camera according to claim 1, wherein
Multiple exposure shooting number setting means for setting the number of multiple exposure shooting;
Interrupting means for interrupting imaging before completion of imaging of the multiple-exposure shooting number,
The gain calculating means has a sum of 1 and 1 based on the number of images for multiple exposure stored in the storage means after imaging of the number of images for multiple exposure shooting or after interruption of multiple exposure shooting by the interruption means. A digital camera characterized in that the gain is calculated as follows. The digital camera according to claim 1 or 2,
A switching means for switching between enabling and disabling gain application by the gain applying means;
The digital camera according to claim 1, wherein the gain applying unit applies the gain to the plurality of images for multiple exposure when the gain applying is enabled by the switching unit. The digital camera according to any one of claims 1 to 3,
The digital camera further comprising image processing means for performing various image processing on the multiple exposure photographed image generated by the synthesizing means. The digital camera according to claim 1 , wherein
The gain calculating means has a sum of gains to be applied to each of the multiple exposure images based on the number of the multiple exposure images stored in the storage means after taking the multiple exposure images. A digital camera characterized in that a gain to be applied to each multiple exposure image is calculated so as to become smaller or larger as a gain to be applied to a multiple exposure image captured later.

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