JP2009105861A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain continuity of image quality by reducing the difference of noise amounts between temporally preceding and following images during consecutive photographing of a high-speed moving object. <P>SOLUTION: A camera 1 is provided which includes: an image sensor 9 for photographing the image of a subject; an entire controller 15 which compares two images continuously taken by the image sensor 9 to detect a difference; an exposure adjusting section 19 which adjusts the exposure time of the image sensor 9 for an image to be next taken and adjusts sensitivity of the image sensor 9 so as to obtain proper exposure; and an image processing section 21 which performs noise amount reduction processing on the image taken by the image sensor 9. The entire controller 15 adjusts the amount of noise to be reduced by the image processing section 21 on the basis of the sensitivity of the image sensor 9 adjusted by the exposure adjusting section 19. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a camera.

  Conventionally, digital cameras that capture images at a continuous shooting speed of 8 to 9 frames / second are known. However, image sensors capable of high-speed shooting are being developed, and depending on cameras equipped with such sensors. For example, it is possible to shoot at a continuous shooting speed of 30 to 60 frames / second or more. When shooting a high-speed moving object with such a camera capable of high-speed continuous shooting, there is a problem that the shot subject is blurred unless the shutter speed is appropriately controlled according to the movement of the subject.

To deal with this problem, Patent Document 1 discloses that during continuous shooting, the faster the subject moves, the higher sensitivity shooting is performed, that is, the ISO speed is increased and the shutter speed is shortened to control shooting blur. Techniques to do this have been proposed.
JP 2004-120576 A

  However, in the method disclosed in Patent Document 1, since the ISO sensitivity is changed during continuous shooting, the amount of noise changes abruptly and continuously between images moving back and forth in time during shooting of a high-speed moving object. When played back, there is a problem that the difference in image quality appears remarkably and the balance of image quality cannot be maintained.

  The present invention has been made in view of such circumstances, and maintains the continuity of image quality by reducing the difference in the amount of noise between temporally moving images during continuous shooting of a high-speed moving object. It is an object to provide a camera that can be used.

In order to solve the above problems, the present invention employs the following means.
The present invention provides an imaging device that captures an image of a subject, a difference detection unit that detects a difference by comparing two images continuously captured by the imaging device, and a difference detected by the difference detection unit And an exposure adjusting unit that adjusts the exposure time of the image sensor for the next image to be captured and adjusts the sensitivity of the image sensor so that proper exposure is obtained, and noise of the image captured by the image sensor Provided is a camera comprising: an image processing unit that performs an amount reduction process; and a noise amount adjustment unit that adjusts a noise reduction amount by the image processing unit based on the sensitivity of the imaging device adjusted by the exposure adjustment unit. .

  According to the present invention, when the difference between two consecutive images detected by the difference detection unit is large, for example, when the moving speed of the subject increases, the exposure adjustment unit shortens the exposure time of the image sensor. By adjusting, the occurrence of blurring in the next photographed image is suppressed. In this case, the exposure adjusting unit improves the sensitivity of the image sensor, so that proper exposure can be obtained even if the exposure time is kept short.

  In this case, if the sensitivity of the image sensor is increased, the amount of noise in the image increases. However, the noise amount adjustment unit controls the image processing unit in accordance with the sensitivity of the image sensor, and performs processing for reducing the amount of noise in the image. As a result, a bright image with a reduced amount of noise can be acquired. Therefore, even if the subject moves suddenly, it is possible to suppress a rapid change in the brightness and noise amount of the image.

In the above invention, the noise amount adjustment unit may adjust the amount of noise reduction so that the noise amount of the image is approximated to the noise amount of the image captured immediately before.
With this configuration, it is possible to maintain continuity of image quality between consecutive images.

In the above invention, when the noise amount adjustment unit performs shooting with the same sensitivity after increasing the noise reduction amount by the image processing unit, the noise reduction amount is gradually decreased as shooting is performed. It may be adjusted.
With such a configuration, it is possible to increase the definition of an image while maintaining continuity of image quality between a plurality of consecutive images.

  According to the present invention, during continuous shooting of a high-speed moving object, there is an effect that it is possible to reduce the difference in the amount of noise between images that move back and forth in time and maintain the continuity of image quality.

[First Embodiment]
Hereinafter, a camera according to a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the camera 1 according to the present embodiment includes a shutter operation unit 3 that performs a shutter operation for acquiring an image, and an overall control unit that controls the entire camera 1 by the shutter operation of the shutter operation unit 3. 5, a lens unit 7 that collects light from the outside and forms an image of the subject, an image pickup device 9 such as a CCD that takes an image of the subject formed by the lens unit 7, and the image pickup device 9. The acquired analog image data is amplified by an analog gain amplifier (not shown) and then converted to digital image data (hereinafter simply referred to as “AFE”) 11, and the digital image data converted by the AFE 11 is converted into digital image data. And a memory unit 13 for storage. The camera 1 includes a shooting mode switching unit (not shown) and can switch between a single shooting mode and a continuous shooting mode.

  The shutter operation unit 3 is, for example, a push button type shutter button that can be pushed in a vertical direction with respect to the upper end surface of the camera 1 formed in a substantially rectangular parallelepiped shape. The shutter operation unit 3 is configured to output a shutter signal for closing the shutter to the overall control unit 5 when the user presses a predetermined amount.

  The overall control unit 5 receives the shutter signal from the shutter operation unit 3 and controls the lens unit 7, the image sensor 9 and the AFE 11, and adjusts the noise amount of the digital image data (difference detection unit, noise amount). Adjustment unit) 15, a lens unit control unit 17 that controls the lens unit 7 in response to a control signal from the overall controller 15, and an exposure time and sensitivity of the image sensor 9 in response to a control signal from the overall controller 15. And an image processing unit 21 that performs image processing such as color correction of digital image data, JPEG compression, and noise reduction processing.

  The overall controller 15 calculates an aperture value for adjusting the amount of light from the outside obtained by the lens unit 7 to the lens unit control unit 17 and outputs it as a control signal. The shutter speed for controlling the exposure time of the element 9 and the ISO sensitivity value for controlling the sensitivity are calculated and output as control signals. As a result, the overall controller 15 acquires digital image data of proper exposure and outputs it to the memory unit 13.

  Here, in the continuous shooting mode, the overall controller 15 compares two acquired digital image data and calculates a difference in the amount of movement of the subject, that is, a difference between the digital image data. It has become. Then, the overall controller 15 calculates the shutter speed and ISO sensitivity value for the next shooting depending on whether or not the calculated difference exceeds a predetermined threshold value.

  That is, when the difference between two pieces of digital image data acquired successively is larger than a predetermined threshold, the subject has moved abruptly, and the shutter speed is increased to suppress blurring. . On the other hand, when the shutter speed is increased, the exposure amount decreases, so that the ISO sensitivity value is increased so that proper exposure can be obtained. As a result, even when the subject moves abruptly between continuously captured digital image data, the occurrence of blurring is suppressed and a bright image can be obtained.

  Further, the overall controller 15 outputs a noise adjustment signal for noise reduction processing corresponding to the calculated ISO sensitivity value to the image processing unit 21. Specifically, the overall controller 15 outputs a noise adjustment signal ON for turning on the noise processing operation when the ISO sensitivity value is larger than a predetermined threshold value, while noise is generated when the ISO sensitivity value is smaller than the predetermined threshold value. A noise adjustment signal OFF for turning off the processing operation is output. As a result, the amount of noise in the digital image data can be suppressed even when the image sensor 9 is photographed with increased sensitivity.

  The exposure adjustment unit 19 includes a timing control unit 23 to which the shutter speed and the ISO sensitivity value are input as control signals from the overall controller 15, and a gain control unit 25 to which only the ISO sensitivity value is input from the overall controller 15 as a control signal. I have.

  The timing controller 23 sets the drive timing of the image sensor 9 based on the input shutter speed. Further, the timing control unit 23 sets the drive frequency of an AD converter (not shown) in the AFE 11 with the drive timing of the image sensor 9 as a sampling timing.

  The gain controller 25 sets the input ISO sensitivity value as the gain value of the analog gain amplifier in the AFE 11. Thereby, in the AFE 11, the gain of the analog image data is amplified according to the exposure time of the image sensor 9, and is converted into digital image data with appropriate brightness.

  The image processing unit 21 performs image processing on all digital image data, and also performs noise removal processing on the digital image data to which the noise adjustment signal ON is input from the overall controller 15, while the noise adjustment signal OFF is input. The processed digital image data is not subjected to noise removal processing.

  The memory unit 13 temporarily stores the digital image data sent from the overall controller 15, displays the shooting range via the lens unit 7, and displays the digital image data stored in the buffer memory 27. A liquid crystal display (hereinafter simply referred to as “LCD”) 29 for displaying and a card interface 31 for storing digital image data stored in the buffer memory 27 are provided.

The operation of the camera 1 according to this embodiment configured as described above will be described.
When the camera 1 according to the present embodiment is activated, an image of a subject formed through the lens unit 7 is captured by the image sensor 9 and output to the AFE 11 as analog image data. Digital image data converted from analog image data in the AFE 11 is sent to the image processing unit 21 for image processing, and sent to the LCD 29 via the overall controller 15 for display.

  In this situation, when the shutter operation unit 3 is pushed in a predetermined amount, in the single shooting mode, the aperture value of the lens unit 7 calculated by the overall controller 15 is set via the lens unit control unit 17, and the whole The shutter speed of the image sensor 9 and the ISO sensitivity value of the AFE 11 calculated by the controller 15 are set via the exposure adjustment unit 19.

  As a result, the lens unit 7, the image sensor 9 and the AFE 11 are controlled so as to achieve proper exposure, and digital image data for proper exposure is acquired. Then, after the digital image data is sent to the image processing unit 21 and subjected to image processing, the digital image data is output to the buffer memory 27 via the overall controller 15 and temporarily stored. The photographed image data stored in the buffer memory 27 is sent to the LCD 29 via the overall controller 15 and displayed as a still image or sent to the card interface 31 and stored by the user's operation.

Next, the operation at the time of continuous shooting of the camera 1 according to the present embodiment will be described in detail with reference to the flowchart shown in FIG.
When the shooting mode switching means is set to the continuous shooting mode (step SA1), first, the shutter speed, ISO sensitivity, and noise reduction processing are automatically set by the overall controller 15 so as to obtain a properly exposed image. (Step SA2).

  The overall controller 15 controls the lens unit 7, the image sensor 9, and the AFE 11 through the lens unit control unit 17 and the exposure adjustment unit 19. In addition, a noise adjustment signal OFF that does not perform noise processing is input from the overall controller 15 to the image processing unit 21.

  When the shutter operation unit 3 is pushed in a predetermined amount, the image of the subject is sequentially acquired as digital image data of appropriate exposure by the lens unit 7, the image sensor 9, and the AFE 11. It is sent to the overall controller 15 (step SA3).

  In the overall controller 15, when the second digital image data is sent, the first digital image data and the second digital image data are compared, and the difference in the amount of movement of the subject, that is, A difference between the digital image data is detected (step SA4). When it is determined that the detected difference exceeds a predetermined threshold, that is, when the subject moves suddenly between the image 1 and the image 2 as shown in FIG. The overall controller 15 sets the shutter speed for the next image 3 to be taken fast, calculates the ISO sensitivity value so that proper exposure can be obtained even at the high shutter speed, and according to the calculated ISO sensitivity value. Noise processing is set (step SA5).

  In the timing control unit 23 of the exposure adjusting unit 19, the drive timing of the image sensor 9 is advanced, the exposure time is set short, and the image 3 is taken. Thereby, generation | occurrence | production of a blur can be suppressed. In the gain control unit 25 of the exposure adjustment unit 19, the gain of the AFE 11 is amplified, and the sensitivity of the image sensor 9 is improved. This makes it possible to acquire bright digital image data even with a short exposure time.

  On the other hand, when the sensitivity of the image sensor 9 is improved, the amount of noise in the digital image data increases. However, since the image processing unit 21 performs a process for reducing the amount of noise in the digital image data, a bright digital image with a reduced amount of noise is performed. Data can be acquired.

In addition, between the images 2 to 5 where the moving speed of the object is fast, the overall controller 15 maintains the parameters of the shutter speed, the ISO sensitivity value, and the noise reduction amount for the next photographed image.
On the other hand, when the moving speed of the subject between the image 5 and the image 6 is slow, the overall controller 15 sets a slow shutter speed for shooting the next image 7 and obtains proper exposure at the slow shutter speed. In this way, the ISO sensitivity is calculated, and noise processing corresponding to the calculated ISO sensitivity value is set.

  In the timing control unit 23 of the exposure adjusting unit 19, the drive timing of the image sensor 9 is returned to the original speed, the exposure time is set longer, and the image 7 is taken. Thereby, digital image data with an appropriate amount of light can be acquired. Further, in the gain control unit 25 of the exposure adjustment unit 19, the gain of the AFE 11 is returned to the original gain, and the sensitivity of the image sensor 9 is lowered. Thereby, digital image data with less noise can be acquired without performing noise amount reduction processing by the image processing unit 21.

  Returning to the flowchart of FIG. 2, while the continuous shooting mode is set, it is determined by the overall controller 15 whether or not the shutter operation unit 3 is kept pressed (step SA6). If the overall controller 15 determines that the shutter operation unit 3 is being pressed (step SA6 “YES”), the process returns to step SA2 and the operations in steps SA2 to SA6 are repeated. On the other hand, if it is determined that the depression of the shutter operation unit 3 has been released (step SA6 “NO”), the continuous shooting mode ends (step SA7).

  As described above, according to the camera 1 according to the present embodiment, even when the subject moves suddenly between two consecutive images, a rapid change in image brightness and noise amount can be obtained while obtaining proper exposure. Can be suppressed.

  In the present embodiment, the image processing unit 21 switches whether the noise reduction processing operation is performed or not. Instead, for example, the strength of the noise reduction level (noise reduction amount) is switched. It is good as well. That is, when the ISO sensitivity is high, a noise adjustment signal “strong” for performing noise reduction processing at a strong noise reduction level is set, and when the ISO sensitivity is low, a noise adjustment signal “weak” for performing noise reduction processing at a weak noise reduction level is set. May be set.

  In addition, the noise reduction level is switched to a plurality of stages such as “strong”, “medium”, and “weak”, and the overall controller 15 detects noise of digital image data taken immediately before the digital image data to be acquired next. It is good also as adjusting so that it may approximate to quantity. In this way, the continuity of image quality between successive digital image data can be maintained.

[Second Embodiment]
Hereinafter, a camera 101 according to a second embodiment of the present invention will be described with reference to the drawings.
The camera 101 according to the present embodiment is different from the first embodiment in that the manner in which the overall controller 15 adjusts the amount of noise reduction changes the noise reduction level instead of ON / OFF of the noise reduction processing.
In the following, parts having the same configuration as those of the camera 1 according to the first embodiment are given the same reference numerals and description thereof is omitted.

  When the photographing is continuously performed with the ISO sensitivity value set to a high value, that is, when photographing is performed with the same sensitivity after increasing the noise reduction amount, the overall controller 15 reduces the noise reduction level as the photographing is performed. Is adjusted to gradually lower. As a result, if the shooting is continued while the noise reduction level is high with respect to a high ISO sensitivity value, the noise amount is reduced, but the sharpness of the image is lowered, but the noise amount is reduced by lowering the noise reduction level. Even if the image quality increases slightly, the sharpness of the image can be increased, and the amount of noise and the sharpness of the image can be balanced.

  The overall controller 15 adjusts the amount of noise reduction by the image processing unit 21 by dividing the noise reduction level into three stages. Specifically, when the ISO sensitivity value is smaller than the first threshold A, the noise adjustment signal “weak” having a low noise reduction level is set, and the ISO sensitivity value is between the first threshold A and the second threshold B. The noise adjustment signal “medium” having a moderate noise reduction level is set when the magnitude is between, and the noise adjustment signal “strong” having a high noise reduction level is set when the ISO sensitivity value is larger than the second threshold B. It is supposed to be.

The operation of the camera 1 according to this embodiment configured as described above will be described.
As shown in FIG. 4, when the fast moving speed of the subject is maintained between the image 20 and the image 30, a high ISO sensitivity value is maintained in the overall controller 15 for the image 40 to be captured next. (See step SB5 in FIG. 5). On the other hand, since the high ISO sensitivity value is maintained, the noise adjustment signal “medium” is calculated, and the noise reduction level is lowered from a strong state to a medium level (step SB6). Accordingly, although the noise amount of the image 40 (residual noise “medium”) is increased as compared with the noise amount of the image 30 (residual noise “low”), the sharpness of the image can be increased from a low state to a medium level. .

  Further, when the fast moving speed of the subject is maintained between the image 30 and the image 40, the high ISO sensitivity value is maintained in the overall controller 15 for the next image 50 to be captured. “Medium” is calculated and the noise reduction level is maintained at a medium level.

  On the other hand, when the moving speed of the object is slow between the image 40 and the image 50 (moving speed “medium”), the ISO sensitivity value of the overall controller 15 is medium for the next image 60 to be taken. Be lowered. In this case, since the amount of noise generated in the image 60 is reduced (generated noise “medium”), the noise amount can be reduced (residual noise “low”) even if the noise reduction level is maintained at a medium level. The sharpness can be maintained at a medium level.

  Subsequently, since the moving speed of the object is further decreased between the image 50 and the image 60, a low ISO sensitivity value is set in the overall controller 15 for the image 70 to be photographed next. Further, the ISO sensitivity value is lowered, so that the noise adjustment signal “weak” is calculated, and the noise reduction level is lowered from a medium level to a weak state. Thereby, it is possible to increase the sharpness of the image from a medium level to a high level while maintaining a state in which the amount of noise is small.

  As described above, according to the camera 1 according to the present embodiment, sharpness of an image is suppressed while suppressing abrupt changes in image brightness and noise amount, and maintaining noise amount between a plurality of consecutive images, that is, continuity of image quality. Can be raised.

  Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention.

1 is a block diagram illustrating a schematic configuration of a camera according to a first embodiment of the present invention. It is a flowchart figure which shows the continuous shooting of the camera of FIG. It is a figure which shows the relationship between the image of FIG. 1, a noise reduction process, etc. It is a figure which shows the relationship of the image of a camera which concerns on the 2nd Embodiment of this invention, noise reduction processing, etc. FIG. It is a flowchart figure which shows the continuous shooting photography of the camera of FIG.

Explanation of symbols

1 Camera 9 Image sensor 15 Overall controller (difference detection unit, noise amount adjustment unit)
19 Exposure adjustment unit 21 Image processing unit

Claims (3)

An image sensor for capturing an image of a subject;
A difference detection unit that detects a difference by comparing two images continuously captured by the image sensor;
An exposure adjustment unit that adjusts the exposure time of the image sensor for an image to be photographed next and adjusts the sensitivity of the image sensor so that proper exposure is obtained according to the difference detected by the difference detection unit;
An image processing unit that performs a noise amount reduction process of an image captured by the image sensor;
A camera comprising: a noise amount adjusting unit that adjusts a noise reduction amount by the image processing unit based on the sensitivity of the image sensor adjusted by the exposure adjusting unit.   The camera according to claim 1, wherein the noise amount adjustment unit adjusts a noise reduction amount so as to approximate the noise amount of the image to the noise amount of an image captured immediately before.   2. The noise amount adjustment unit adjusts the noise reduction amount so that the noise reduction amount is gradually decreased as shooting is performed when shooting with the same sensitivity is performed after increasing the noise reduction amount by the image processing unit. Item 3. The camera according to item 2.

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