JP2008160290A - Imaging apparatus, and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an image from losing a feeling of resolution owing to excessive noise reduction processing during multiple exposure photography. <P>SOLUTION: An image decision unit 81 decides whether an image photographed through multiple exposure is the same during multiple exposure photography. When it is decided that the image is the same, priority is given to resolution and settings are made mitigating noise reduction processing parameter values. When it is decided that the image is not the same, priority is given to noise reduction and settings of normal noise reduction processing parameters are made. Based upon the set noise reduction processing parameters, image processing including the noise reduction processing for an added image is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and an imaging method, and more particularly, to an imaging apparatus and an imaging method capable of multiple exposure photography.

2. Description of the Related Art A technique for performing multiple exposure shooting by performing digital addition processing on an image for each shooting in an imaging apparatus including an imaging element such as a CCD is known. Patent Document 1 describes a digital camera that prohibits functions related to digital image processing during the second and subsequent shootings in such multiple exposure shooting. Further, Patent Document 2 describes a digital still camera that warns when a photographing condition changes between photographed images to a predetermined threshold value or more.
JP 2002-218313 A JP 2002-112075 A

  When the same image is taken in multiple exposure, random noise is superimposed, so that each cancels out and noise is reduced. Therefore, if normal noise reduction processing is performed at the time of multiple exposure shooting, the noise reduction processing becomes excessive, resulting in an image with a loss of resolution. In addition, when the sensitivity is changed during multiple exposure shooting, if noise reduction processing is performed with the sensitivity setting at a specific exposure without considering the sensitivity change, the noise reduction processing will be excessive or insufficient, It becomes not an image. Patent Document 1 and Patent Document 2 have no description regarding such noise reduction.

  The present invention has been made in view of such circumstances. When images are the same at the time of multiple exposure shooting, the resolution is reduced by setting the noise reduction process weaker than the normal noise reduction process. An object of the present invention is to provide an imaging apparatus capable of obtaining an image quality that is not lost. It is another object of the present invention to provide an imaging apparatus capable of performing appropriate noise reduction processing by changing the noise reduction processing parameters according to the sensitivity before and after the change when the sensitivity is changed during shooting. And

  In order to achieve the above object, in an imaging apparatus according to the present invention, storage means for storing a plurality of images taken in a multiple exposure mode and the plurality of images stored by the storage means are substantially the same. Image determining means for determining whether or not, image generating means for digitally adding the plurality of images stored in the storage means to generate an added image, and reducing noise of the added image with a predetermined parameter Noise reduction processing means, and parameter setting means for setting a noise reduction processing parameter of the noise reduction processing means, wherein the parameter setting means changes the noise reduction parameter according to the determination of the image determination means. And

  As described above, it is possible to perform appropriate noise reduction processing by determining whether or not a plurality of images taken in the multiple exposure mode are the same and changing the noise reduction parameter based on the result.

  Preferably, the parameter setting means sets a parameter that weakens noise reduction when the image determination means determines that the plurality of images are the same.

  Thereby, it is possible to obtain an image quality without losing a sense of resolution.

  In order to achieve the above object, an image pickup apparatus according to the present invention stores storage means for storing a plurality of images taken in a multiple exposure mode, shooting sensitivity setting means for setting shooting sensitivity, and storage means. Image generating means for digitally adding the plurality of images to generate an added image, noise reduction processing means for reducing noise of the added image with predetermined parameters, and noise reduction processing parameters of the noise reduction processing means are set Parameter setting means, and the parameter setting means changes the noise reduction parameter according to the shooting sensitivity when the shooting sensitivity setting means changes the shooting sensitivity during the shooting of the plurality of images. It is characterized by.

  Thereby, even if the sensitivity is changed during shooting in the multiple exposure mode, an appropriate image can be obtained by calculating an appropriate noise reduction parameter.

  In order to achieve the above object, an imaging method according to the present invention includes a storage step of storing a plurality of images taken in a multiple exposure mode, and whether or not the plurality of images stored in the storage step are the same. An image determination step for determining the image, an image generation step for digitally adding the plurality of images stored in the storage step to generate an added image, and a noise reduction process for reducing noise of the added image with a predetermined parameter And a parameter setting step for setting a noise reduction processing parameter of the noise reduction processing step, wherein the parameter setting step changes the noise reduction parameter according to the determination of the image determination step.

  As described above, it is possible to perform appropriate noise reduction processing by determining whether or not a plurality of images taken in the multiple exposure mode are the same and changing the noise reduction parameter based on the result.

  In order to achieve the above object, an imaging apparatus according to the present invention stores a plurality of images captured in a multiple exposure mode, a storage step for setting a shooting sensitivity, a shooting sensitivity setting step for setting shooting sensitivity, and the storage step. An image generation step for generating an addition image by digitally adding the plurality of images, a noise reduction processing step for reducing noise of the addition image with predetermined parameters, and a noise reduction processing parameter for the noise reduction processing step are set. A parameter setting step for changing the noise reduction parameter according to the shooting sensitivity when the shooting sensitivity setting step changes the shooting sensitivity during shooting of the plurality of images. It is characterized by.

  Thereby, even if the sensitivity is changed during shooting in the multiple exposure mode, an appropriate image can be obtained by calculating an appropriate noise reduction parameter.

  According to the present invention, when the images are the same at the time of multiple exposure shooting, noises cancel each other out. By setting the noise reduction processing to be weak, it is possible to obtain an image quality that does not lose the sense of resolution. it can. If the images are not identical, the noise can be made inconspicuous by performing a normal noise reduction process. In addition, when the sensitivity is changed in the middle of photographing, appropriate noise reduction processing can be performed by changing the noise reduction processing parameters according to the sensitivity.

  Hereinafter, preferred embodiments of an imaging device according to the present invention will be described with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a perspective view of a digital camera 10 according to a first embodiment of the present invention as viewed obliquely from the front. FIG. 1A shows a lens barrel 14 retracted into a camera casing, and a lens cover 14 is shown. The closed state is shown, and FIG. 5B shows the state in which the lens barrel 12 is extended.

  FIG. 2 is a perspective view of the digital camera 10 as viewed obliquely from the rear.

  The digital camera 10 has a function of recording and reproducing still images and moving images, and a power button 20, a shutter button 22, and a mode lever 24 are provided on the upper surface. By rotating the mode lever 24, it is possible to set any one of a scene position in which an auto shooting mode, a manual shooting mode, a portrait mode, a landscape mode, a night view mode, and the like can be selected, and a moving image shooting mode. ing.

  A shutter button 22 provided in the center of the mode lever 24 is turned on when the shutter button 22 is half-pressed to perform shooting preparation such as focus lock, photometry, and the like. S2.

  On the back of the digital camera 10, as shown in FIG. 2, a zoom key 26, a playback button 28, a photo mode button 30 for displaying a menu screen for setting the number of pixels, sensitivity, and the like, and a multi-function cross key composed of up / down / left / right keys 32, a menu / OK button 34, a display / return button 36, and a liquid crystal monitor 38 are provided.

  The liquid crystal monitor 38 displays a moving image (through image) and can be used as an electronic viewfinder, and also displays a photographed image before recording (preview image), a reproduced image read from a memory card loaded in the camera, and the like. Can do. The liquid crystal monitor 38 displays various menu screens for manually setting the camera operation mode, white balance, the number of pixels of the image, sensitivity, and the like according to the operation of the menu / OK button 34 or the photo mode button 30. Then, a screen for a graphical user interface (GUI) capable of setting manual setting items in accordance with the operation of the cross key 32 and the menu / OK button 34 is displayed.

  FIG. 3 is a block diagram illustrating an example of the internal configuration of the digital camera 10.

  In the figure, the CPU 50 includes the power button 20, shutter button 22, mode lever 24, zoom key 26, playback button 28, photo mode button 30, cross key 32, menu / OK button 34, and display / return button 36 described above. An input of the operation switch 64 is input via the operation switch interface 63, and controls each circuit in the digital camera 10 based on this input, and executes processing according to the camera control program.

  Control of each circuit of the CPU 50 is performed via the BUS 51. The CPU 50 exchanges necessary data with the RAM 68 and the ROM 69 via the memory interface 67.

  The ROM 69 stores a camera control program, an opening image at start-up, an ending image at stop, a GUI image such as a menu image used for operating the digital camera 10, an image for a screen saver, and a progress display during processing. Audio data indicating an image (such as an hourglass image whose scale changes), a key operation sound (such as a shutter sound), a warning sound, and an error sound are recorded.

  First, when the power button 20 is operated, the CPU 50 detects this, turns on the power in the camera, displays the opening image stored in the ROM 69 for a certain period, and then enters the shooting standby state in the shooting mode. In this photographing standby state, the CPU 50 extends the retractable lens barrel 12 via the motor drive unit 42 (see FIG. 1A), and normally displays a moving image (through image) on the liquid crystal monitor 38.

  A user (photographer) performs framing while viewing a through image displayed on the liquid crystal monitor 38, confirms a subject to be photographed, confirms an image after photographing, and sets photographing conditions.

  When the shutter button 22 is pressed in the shooting standby state, the CPU 50 detects this, performs focus control, photometry, and exposure control, drives the focus lens and diaphragm in the optical unit 41 via the motor drive unit 42, and A subject image is formed on the light receiving surface of the CCD 43 via the optical unit 41. At this time, if necessary, the flash 62 is caused to emit light with the electric charge boosted and charged by the charging unit 61 and used as auxiliary photographing light.

  The CCD 43 converts the subject image formed on the light receiving surface into a signal charge having an amount corresponding to the amount of light. The signal charges converted in this way are read to the shift register by the read gate pulse applied from the timing generator 44, and sequentially read as a voltage signal corresponding to the signal charge by the register transfer pulse.

  The voltage signal output from the CCD 43 is subjected to analog processing such as correlated double sampling and amplification by the analog signal processing unit 45, and then added to the A / D converter 46 as R, G, and B signals for each pixel. It is done. The A / D converter 46 converts the analog R, G, and B signals sequentially added from the analog signal processing unit 45 into digital R, G, and B signals, respectively. These R, G, and B signals are temporarily stored in the RAM 68.

The digital signal processing unit 47 reads the R, G, B raw data stored in the RAM 68 and applies a digital gain corresponding to the type of light source to adjust the white balance, and also performs gamma (gradation conversion). Processing, sharpness processing, etc. are performed to generate R, G, B signals. Further, YC signal processing is performed to generate a luminance signal Y and chroma signals Cr and Cb (YC signal), and then the Y signal is used to perform noise reduction processing by low-pass filter operation and median filter operation, and finally processed YC. The signal is stored in the RAM 68 again.

  The image determination unit 81 determines whether or not the image data obtained by each exposure in the multiple exposure mode described later is the same, and inputs the result to the image processing setting determination unit 82. The image processing setting determination unit 82 sets parameters for noise reduction processing based on the determination result of the image determination unit 81. The digital signal processing unit 47 performs noise reduction processing based on the noise reduction processing parameters set by the image processing setting determination unit 82.

  The YC signal stored in the RAM 68 as described above is compressed into a predetermined format by the compression / decompression processing circuit 70 and then recorded on the memory card 72 detachably attached to the digital camera 10 via the external memory interface 71. .

  When the menu / OK button 34 is pressed while the through image is displayed on the liquid crystal monitor 38, a menu screen is displayed on the liquid crystal monitor 38. While the menu screen is displayed, the cross key 32 is operated to select desired items such as shooting conditions and image sizes, or by pressing the menu / OK button 34 again to confirm the selection items. Execution of processing can be instructed. The display / return button 36 is used to switch the display on the liquid crystal monitor 38 or to return to the previous operation state.

  On the other hand, when the playback mode is selected by operating the playback button 28, the image file of the last frame recorded on the memory card 78 is read out via the external memory interface 71. The compressed data of the read image file is expanded into an uncompressed YC signal via the compression / expansion processing circuit 70.

  The expanded YC signal is converted into a signal format for display by the LCD interface 65 and output to the liquid crystal monitor 38. As a result, the last frame image recorded on the memory card 72 is displayed on the liquid crystal monitor 38.

  Thereafter, when the forward frame advance switch (the right key of the cross key 32) is pressed, the frame is advanced in the forward direction, and when the reverse frame advance switch (the left key of the cross key 32) is pressed, the frame is advanced in the reverse direction. . Then, the image file at the frame position where the frame is advanced is read from the memory card 72, and the image is reproduced on the liquid crystal monitor 38 in the same manner as described above.

  Next, the operation of the digital camera 10 in the multiple exposure mode will be described with reference to FIG. The digital camera 10 according to the first embodiment of the present invention sets the noise reduction processing to be weak when a plurality of images taken in the multiple exposure mode are the same.

  FIG. 4 is a flowchart showing the operation of the digital camera 10 in the multiple exposure mode.

  First, the multiple exposure mode is set using the photo mode button 30 (step S41). In the multiple exposure mode, the number of multiple exposures is also set. Here, the cross exposure 7 and the menu / OK button 8 are used to set three exposures.

  Thereafter, when shooting is performed (step S42), shooting data is stored in the RAM 68 for each exposure.

  When the three exposures are completed and the photographing is finished, the image determination unit 81 reads the exposure data for the three times from the RAM 68, and determines whether or not the three images in each exposure are the same (step S44). The image determination unit 81 calculates a difference between the corresponding coordinate signals of each image, and determines that the images are the same when the integrated value of the difference is less than a predetermined threshold.

  When the image determination unit 81 determines that the three images are the same, the image processing setting determination unit 82 sets the noise reduction processing of the added image as a resolution priority setting (step S45). Conversely, if the image determination unit 81 determines that the three images are not the same, the image processing setting determination unit 92 sets the noise reduction processing for the added image as noise reduction priority setting (step S46).

  Next, the three images are subjected to addition processing, and noise reduction processing is performed on the added image based on the noise reduction processing parameters set as described above (step S47).

  In this way, when all the images taken in the multiple exposure mode are the same, it is determined that the noise has been canceled out, and the noise reduction processing parameters are set to be weak, thereby giving priority to a sense of resolution. Can be obtained. If they are not the same, noise can be made inconspicuous by performing normal noise reduction processing.

  Although the number of exposures has been described here as three times, any number of exposures can be used, and the number of times that data can be stored in the RAM 68 can be set.

<Second Embodiment>
In the multiple exposure mode of the digital camera 10 according to the second embodiment of the present invention, the noise reduction process of the added image is performed using the noise reduction parameter corresponding to the shot sensitivity, but the sensitivity was changed during the shooting. In this case, an optimum noise reduction parameter is calculated from the photographing sensitivity of each image, and the noise reduction processing of the added image is performed using the parameter.

  FIG. 5 is a block diagram illustrating an example of the internal configuration of the digital camera 10. Portions common to those in the block diagram shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted. The block diagram shown in FIG. 3 is different from the block diagram shown in FIG. 3 in that the image determination unit 81 is not provided and the sensitivity determination unit 83 is provided.

  FIG. 6 is a flowchart showing the operation of the digital camera 10 in the multiple exposure mode.

  First, the multiple exposure mode is set using the photo mode button 30 (step S61). In the multiple exposure mode, the number of multiple exposures is also set. Here, the cross exposure 7 and the menu / OK button 8 are used to set three exposures.

  Thereafter, when shooting is performed (step S62), shooting data is stored in the RAM 68 for each exposure. When the exposure is completed three times and the photographing is finished, the sensitivity determination unit 83 determines the photographing sensitivity of the three exposures (step S63). If all the shooting sensitivities are the same, the noise reduction parameter is set to the shooting sensitivity parameter (step S64).

  If the shooting sensitivity of the three exposures is not the same, an appropriate noise reduction processing parameter is calculated from each shooting sensitivity (step S65). For example, if the three exposures are ISO 100, ISO 100, and ISO 400, respectively, the noise reduction processing parameter equivalent to ISO 200, which is the average of these, is used. You may obtain | require by weighting for each sensitivity instead of a simple average.

  Thereafter, the CPU 50 reads the exposure data for three times from the RAM 68 (step S66), adds the three images, and performs noise reduction processing for the added image based on the noise reduction processing parameters set as described above. This is performed (step S67).

  As described above, in the multiple exposure mode, when the shooting sensitivity is changed during shooting, an appropriate noise reduction processing parameter is set according to the shooting sensitivity for each exposure to perform an appropriate noise reduction process. be able to.

FIG. 1 is a perspective view of a digital camera according to the present invention as viewed obliquely from the front. FIG. 2 is a perspective view of the digital camera 10 as viewed obliquely from the rear. FIG. 3 is a block diagram illustrating an example of an internal configuration of the digital camera 10 according to the first embodiment. FIG. 4 is a flowchart showing the operation of the digital camera 10 according to the first embodiment in the multiple exposure mode. FIG. 5 is a block diagram showing an example of the internal configuration of the digital camera 10 according to the second embodiment of the present invention. FIG. 6 is a flowchart showing the operation in the multiple exposure mode of the digital camera 10 according to the second embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Digital camera, 22 ... Shutter button, 32 ... Cross key, 34 ... Menu / OK button, 38 ... Liquid crystal monitor, 41 ... Optical unit, 43 ... CCD, 45 ... Analog signal processing part, 46 ... A / D converter, 47 ... Digital signal processing unit, 50 ... CPU, 67 ... Memory interface, 68 ... RAM, 69 ... ROM, 81 ... Image determination unit, 82 ... Image processing setting determination unit, 83 ... Luminance determination unit

Claims (5)

Storage means for storing a plurality of images taken in the multiple exposure mode;
Image determining means for determining whether or not the plurality of images stored by the storage means are substantially the same;
Image generating means for digitally adding the plurality of images stored by the storage means to generate an added image;
Noise reduction processing means for reducing noise of the added image with predetermined parameters;
Parameter setting means for setting a noise reduction processing parameter of the noise reduction processing means,
The imaging apparatus according to claim 1, wherein the parameter setting means changes the noise reduction parameter according to the determination by the image determination means.   The imaging apparatus according to claim 1, wherein the parameter setting unit sets a parameter that weakens noise reduction processing when the image determination unit determines that the plurality of images are the same. Storage means for storing a plurality of images taken in the multiple exposure mode;
Shooting sensitivity setting means for setting shooting sensitivity;
Image generating means for digitally adding the plurality of images stored by the storage means to generate an added image;
Noise reduction processing means for reducing noise of the added image with predetermined parameters;
Parameter setting means for setting a noise reduction processing parameter of the noise reduction processing means,
The imaging apparatus according to claim 1, wherein the parameter setting unit changes the noise reduction parameter in accordance with the shooting sensitivity when the shooting sensitivity setting unit changes the shooting sensitivity during the shooting of the plurality of images. A storage step for storing a plurality of images taken in the multiple exposure mode;
An image determination step for determining whether or not the plurality of images stored in the storage step are the same;
An image generating step for digitally adding the plurality of images stored in the storing step to generate an added image;
A noise reduction processing step for reducing noise of the added image with predetermined parameters;
A parameter setting step for setting a noise reduction processing parameter of the noise reduction processing step,
The parameter setting step changes the noise reduction parameter according to the determination in the image determination step. A storage step for storing a plurality of images taken in the multiple exposure mode;
Shooting sensitivity setting step for setting shooting sensitivity;
An image generating step for digitally adding the plurality of images stored in the storing step to generate an added image;
A noise reduction processing step for reducing noise of the added image with predetermined parameters;
A parameter setting step for setting a noise reduction processing parameter of the noise reduction processing step,
In the imaging method, the parameter setting step changes the noise reduction parameter in accordance with imaging sensitivity when the imaging sensitivity setting step changes imaging sensitivity during imaging of the plurality of images.

Images