Patent Publication Number: US-2012033050-A1

Title: Imaging apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus to which a 3D conversion lens for enabling a stereoscopic image to be shot with a single lens imaging apparatus can be attached. 
     2. Related Art 
     JP2001-222083A discloses an imaging apparatus to which a stereo adapter for enabling a stereoscopic image to be shot with a single lens camera can be connected. This imaging apparatus can capture a left-eye image and a right-eye image as a side-by-side image with the stereo adapter attached to the imaging apparatus. The imaging apparatus carries out exposure metering based on brightness of either one of a left-eye image and a right-eye image in exposure control. With this method, the imaging apparatus realizes the exposure metering of a side-by-side image. 
     The inventors of this application found the phenomenon in that when a device such as a stereo adapter for enabling shooting of a stereoscopic image is attached to a single lens imaging apparatus, light falloff occurs locally on an image captured by an imaging device or the imaging apparatus. 
     The light falloff which is caused by the attachment of such a stereo adapter and is different from a normal light falloff influences accuracy of the exposure metering in the exposure control so that suitable exposure metering is prohibited. 
     SUMMARY OF THE INVENTION 
     The present invention has been devised in order to solve the above problem, and has an object to provide an imaging apparatus that can carry out accurate exposure metering in the exposure control even when the stereo adaptor (a 3D conversion lens) is attached. 
     An imaging apparatus according to the present invention includes an imaging device configure to generate image data from a subject image, a connecting unit configured to connect a 3D conversion lens for enabling a left-eye image and a right-eye image to be simultaneously formed on the imaging device, a measuring unit configured to obtain brightness of an image formed on the imaging device and generate measuring information representing the brightness of the image formed on the imaging device based on the obtained brightness of the image, an exposure adjusting unit configured to control exposure on the imaging device based on the measuring information, and a light amount correcting unit configured to reduce an influence of light falloff occurring in the image formed on the imaging device to the measuring information, when the 3D conversion lens is connected to the connecting unit. 
     According to the present invention, when a 3D conversion lens is attached to the imaging apparatus, an influence of light falloff in the exposure metering information, which occurs on an image and is caused by the 3D conversion lens, is reduced. As a result, the influence of the light falloff caused by the 3D conversion lens can be eliminated, so that the exposure metering can be carried out accurately. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a digital video camera to which a 3D conversion lens is attached. 
         FIG. 2  is a diagram describing an example of an image formed on a CCD image sensor of the digital video camera to which the 3D conversion lens is attached. 
         FIG. 3  is a block diagram illustrating a configuration of the digital video camera. 
         FIG. 4  is a diagram describing optical systems of the 3D conversion lens and the digital video camera. 
         FIG. 5  is a diagram describing an image of a side-by-side format generated by the digital video camera to which the 3D conversion lens is attached. 
         FIGS. 6A and 6B  are diagrams for describing light falloff at a center caused by the 3D conversion lens. 
         FIG. 7  is a flowchart for describing exposure metering and exposure control operations of the digital video camera. 
         FIGS. 8A and 8B  are diagrams for describing center-weighted exposure metering for shooting a 2D image. 
         FIGS. 9A and 9B  are diagrams for describing the center-weighted exposure metering for shooting a 3D image. 
         FIG. 10  is a diagram describing a correction coefficient to be used for correcting a light amount. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiments according to the present invention will be described below with reference to the accompanying drawings. 
     1. First Embodiment 
     1-1. Overview 
     An outline of a digital video camera according to a first embodiment of the present invention will be described with reference to  FIGS. 1 and 2 .  FIG. 1  is a perspective view illustrating a state that a 3D conversion lens  500  is attached to a digital video camera  100 . 
     The 3D conversion lens  500  can be attached to the digital video camera  100  via a connecting section  640 . The digital video camera  100  can magnetically detect attachment/detachment of the 3D conversion lens  500  with a detection switch. 
     The 3D conversion lens  500  has a right-eye lens for guiding light for forming a right-eye image in a 3D (three dimensions) image to an optical system of the digital video camera  100 , and a left-eye lens for guiding light for forming a left-eye image to the optical system. 
     The light incident via the 3D conversion lens  500  is imaged as a 3D image of a side-by-side format as shown in  FIG. 2  on a CCD image sensor of the digital video camera  100 . Particularly, the 3D conversion lens  500  has an optical property such that light falls off near a boundary between a left-eye image  182  and a right-eye image  134  (hereinafter referred to as “light falloff at a center”). A configuration of the digital video camera enabling suitable exposure metering without being influenced by such an optical property of the 3D conversion lens  500  (the light falloff at a center) will be described below. 
     1-2. Configuration 
     1-2-1. Configuration of Digital Video Camera 
     An electrical configuration of the digital video camera  100  according to the first embodiment will be described with reference to  FIG. 3 .  FIG. 3  is a block diagram, illustrating a configuration of the digital video camera  100 . The digital video camera  100  has an optical system  101 , a CCD image sensor  180 , an image processor  190 , a liquid crystal display (LCD) monitor  270 , a detector  120 , a zoom motor  130 , an OIS actuator  150 , a detector  160 , a memory  200 , a controller  210 , a zoom lever  260 , an operation member  250 , an internal memory  280 , a gyro sensor  220 , a card slot  230 , and a detection switch  290 . The digital video camera  100  captures a subject image formed by the optical system  101  with the CCD image sensor  180 . Video data generated by the CCD image sensor  180  is subject to various processes in the image processor  190 , and is stored in a memory card  240 . Further, the video data stored in the memory card  240  can be displayed on the LCD monitor  270 . The configuration of the digital video camera  100  will be described in detail below. 
     The optical system  101  of the digital video camera  100  includes a zoom lens  110 , an OIS  140 , and a focus lens  170 . The zoom lens  110  moves along an optical axis of the optical system  101  to enlarge or reduce a subject image. The focus lens  170  moves along the optical axis of the optical system  101  to adjust a focus of the subject image. 
     The OIS  140  has inside a correction lens that can move on a plane vertical to the optical axis. The OIS  140  drives the correction lens to a direction in which a shake of the digital video camera  100  is cancelled so as to reduce blur of a subject image. 
     The zoom motor  130  drives the zoom lens  110 . The zoom motor  130  may be realized by a pulse motor, a DC motor, a linear motor, or a servo motor. The zoom motor  130  may drive the zoom lens  110  via a cam mechanism or a mechanism such as a ball screw. The detector  120  detects a position on the optical axis where the zoom lens  110  is present. The detector  120  outputs a signal relating to a position of the zoom lens using a switch such as a brush according to the motion of the zoom lens  110  to a direction of the optical axis. 
     The OIS actuator  150  drives the correction lens in the OIS  140  on a plane vertical to the optical axis. The OIS actuator  150  can be realized by a planar coil, an ultrasonic motor, or the like. Further, the detector  160  detects a amount of move of the correction lens in the OIS  140 . 
     A diaphragm  295  adjusts an amount of light incident on the CCD image sensor  180 . Narrowing the diaphragm  295  allows the amount of the light incident on the CCD image sensor  180  to be reduced. Opening the diaphragm  295  allows the amount of the light incident on the CCD image sensor  180  to be increased. A diaphragm actuator  300  is an actuator for driving the diaphragm  295 . 
     The CCD image sensor  180  captures a subject image formed on the optical system  101  to generate video data. The CCD image sensor  180  performs various operations such as exposure, transfer and electronic shutter. 
     The image processor  190  executes various processes on the video data generated by the CCD image sensor  180 . The image processor  190  generates video data to be displayed on the LCD monitor  270 , and generates video data to be restored in the memory card  240 . For example, the image processor  190  executes various processes, such as gamma correction, white balance correction, and scrape correction on the video data generated by the CCD image sensor  180 . The image processor  190  compresses the video data generated by the CCD image sensor  180  according to a compressing format con forming to H.264 standards and MEG2 standards. The image processor  190  can be realized by DSP or a microcomputer. 
     The controller  210  is a control unit for controlling the entire operation of the digital video camera. The controller  210  can be realized by a semiconductor element or the like. The controller  210  may be realized by only hardware or by combination of hardware and software. The controller  210  can be realized by a microcomputer or the like. 
     The memory  200  functions as a work memory for the image processor  190  and the controller  210 . The memory  200  can be realized by, for example, a DRAM or a ferroelectric memory. 
     The LCD monitor  270  can display an image represented by the video data generated by the CCD image sensor  180  and an image represented by the video data read from the memory card  240 . 
     The gyro sensor  220  includes a vibration material such as a piezoelectric element. The gyro sensor  220  converts a force caused by a Coriolis force occurring on vibrating the vibration material such as the piezoelectric element at a constant frequency into a voltage to acquire angular velocity information. The digital video camera  100  acquires the angular velocity information from the gyro sensor  220 , and drives the correction lens in the CTS  140  in a direction for canceling the vibration, so as to correct a camera shake caused by a user. 
     The memory card  240  can be attached to/detached from the card slot  230 . The card slot  230  can be mechanically and electrically connected to the memory card  240 . The memory card  240  includes a flash memory and a ferroelectric memory and can store data. 
     The internal memory  280  includes a flash memory or a ferroelectric memory. The internal memory  280  stores a control program or the like for entirely controlling the digital video camera  100 . 
     The operation member  250  is a member that receives an operation from the user. The zoom lever  260  is a member that receives an instruction for changing zoom magnification from the user. 
     The detection switch  290  can magnetically detect attachment (connection) of the 3D conversion lens  500  to the digital video camera  100 . When detecting the attachment of the 3D conversion lens  500 , the detection switch  290  sends a signal representing the attachment to the controller  210 . In this manner, the controller  210  can detect that the 3D conversion lens  500  is attached to or detached from the digital video camera  100 . 
     1-2-2. Configuration of 3D Conversion Lens 
       FIG. 4  is a diagram describing configurations of an optical system  501  of the 3D conversion lens  500  and the optical system  101  of the digital video camera  100 . The optical system  501  of the 3D conversion lens  500  has a right-eye lens  600  for guiding light for forming a right-eye image on a 3D image, a left-eye lens  620  for guiding light for forming a left-eye image, and a common lens  610 , which is made integrally by a right eye lens and a left eye lens, for guiding the light incident through the right-eye lens  600  and the light incident through the left-eye lens  620  to an optical system  101  of the digital video camera  100 . The light incident to the right-eye lens  600  and the left-eye lens  620  of the 3D conversion lens  500  is guided to the optical system  101  of the digital video camera  100  via the common lens  610  to image an image of a side-by-side format as shown in  FIG. 2 , for example, on the CCD image sensor  180  of the digital video camera  100 , so that image data is generated by the CCD image sensor  180 . 
     The image data generated by the CCD image sensor  180  is expanded in a vertical direction by the image processor  190 , and finally image data of a side-by-side format as shown in  FIG. 5  is generated. 
     1-3. Light Falloff at Center 
     The light falloff caused by the 3D conversion lens  500  will be described. As shown in  FIG. 6A , when the 3D conversion lens  500  is attached to the digital video camera  100 , an image for a left eye is formed on a region  182  of the CCD image sensor  180 , and an image for a right-eye is formed on a region  184 .  FIG. 6B  is a diagram describing a change in an amount of light incident or the CCD image sensor  180  with respect to a horizontal position of the CCD image sensor  180  with the 3D conversion lens  500  attached to the digital video camera  100 . As shown in  FIG. 63 , the light fallout (light falloff at a center) occurs near a center of the CCD image sensor  180  in the horizontal direction. The light falloff at the center is considered to be caused by, as shown in  FIG. 4 , the two optical systems included in the 3D conversion lens  500 , including the right-eye lens  600  and the left-eye lens  620 . The digital video camera  100  according to the first embodiment has a function for reducing an influence or the light falloff at the center as shown in  FIG. 6B  at the time of exposure metering (The details will be described later.). 
     1-4. Exposure Metering and Exposure Control Operations 
     The exposure metering and exposure control operations in the digital video camera  100  according to the first embodiment will be described with reference to  FIGS. 7 to 9 .  FIG. 7  is a flowchart for describing the exposure metering and exposure control operations in the digital video camera  100 .  FIG. 8  is a diagram for describing center-weighted exposure metering for capturing a 2D image.  FIG. 9  is a diagram for describing the center-weighted exposure metering for capturing a 3D image. 
     Referring to  FIG. 7 , when the digital video camera  100  is set to a shooting mode by a user (S 100 ), the controller  210  determines whether or not the 3D conversion lens  500  is attached to the digital video camera  100  based on a signal from the detection switch  290  (S 110 ). When the determination is made that the 3D conversion lens  500  is not attached, the controller  210  sets a metering region for capturing a 2D image in the captured image (S 115 ), and carries out the center-weighted exposure metering on the metering region ( 5120 ). The metering region and the center-weighted exposure metering will be described below. 
     When a 2D image is captured, the metering region is set as shown in  FIG. 8A . The center-weighed exposure metering is carried out on a metering region  191 . The center-weighted exposure metering is a method including dividing an image captured by the CCD image sensor  180  into a plurality of regions and metering brightness of the image with a focus on the center portion. Concretely, the digital video camera  100  divides the metering region  191  of the image captured by the CCD image sensor  180  into thirty regions of 6×5 as shown in  FIG. 8A . A weight coefficient 1.0 is set for six regions at the center portion of the divided regions. A weight coefficient 0.5 is set for six regions adjacent to the center portion. Further a weight coefficient 0.3 is set for eighteen regions around these regions. At the time of capturing a 2D image, the controller  210  obtains a weighted average (E) of the brightness of the image captured by the CCD image sensor  180  according to the following equation (1). The weighted average (E) of the brightness of the image is a metering value obtained by the center-weighted exposure metering. 
     
       
         
           
             
               
                 
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                           Wij 
                         
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     In the equation (1), “W” is a weight coefficient of each divided region, and “Y” is brightness of an image of each divided region (for example, an average value of brightness of pixels included in the divided regions). Where, “i” and “j” are subscripts for specifying x and y positions of the divided regions. 
     When the 3D conversion lens  500  is attached to the digital video camera  100 , the light falloff at the center occurs. For this reason, when the 3D conversion lens  500  is attached to the digital video camera  100 , the exposure metering operation in consideration of the light falloff at the center should be performed. On the contrary, when a 2D image is captured with the 3D conversion lens  500  not attached to the digital video camera  100 , the light amount becomes uniform in the metering region  191  as shown in  FIG. 5B . In this case, during the exposure metering operation, the light falloff at the center does not have to be taken into consideration.  FIG. 8A  illustrates the metering region for capturing a 2D image, which is different from the metering region for capturing a 3D image. The metering region for capturing a 3D image will be described later. 
     Returning to  FIG. 7 , after the completion of the center-weighted exposure metering (S 120 ), the controller  210  performs the exposure control using a metering value (E) obtained by the center-weighted exposure metering (S 130 ). Concretely, the controller  210  adjusts an aperture value of the diaphragm  295 , a shutter speed of the CCD image sensor  130 , and a gain provided to a captured image so that the metering value (E) becomes a predetermined target value. That is, the controller  210  controls the diaphragm actuator  300 , the CCD image sensor  180 , and the image processor  190 . 
     On the other hand, the determination is made in step S 110  that the 3D conversion lens  530  is attached to the digital video camera  100 , the controller  210  sets the metering region for capturing a 3D image (S 140 ). Concretely, as shown in  FIG. 9A , a metering region  193  is set in a left-eye image  182  of images  182  and  184  captured by the CCD image sensor  180 . The metering region  193  is also divided into thirty regions of 6×5, and the weighted average (E) of the brightness of the image is obtained by using the brightness of each divided region. 
     When the metering region is changed, the controller  210  corrects a light amount of a captured image (S 150 ). Concretely, as shown in  FIG. 98 , the light amount is corrected in a range in which the light amount on the metering region  193  falls off. That is, the light amount is corrected so that the light amount becomes constant regardless of the positions of the image in the horizontal direction. This is because, if such a correction of the light amount is not made, the center-weighted exposure metering cannot be accurately carried out due to an influence of the light falloff at the center that occurs in the metering region  193 . According to the present embodiment, when the 3D conversion lens  500  is attached to the digital video camera  100 , the digital video camera  100  corrects the light falloff at the center of the captured image, and carries out the center-weighted exposure metering with the corrected data. 
     The correction of the light falloff at the center on the captured image is realized by correcting the brightness of the image according to the following equation (2). 
         Y′ij−Yij·Ci   (2)
 
     In the equation (2), “Y” is the brightness (luminance) of an image on each divided region. “C” is a correction coefficient for the brightness of the image on each divided region, and “Y′” is the corrected brightness of the image on each divided region. Where, “i” and “j” are subscripts for specifying x and y positions on the divided regions. The correction coefficient C is set based on a property of the light falloff at the center so that the property after the correction becomes fiat as shown in  FIG. 93 .  FIG. 10  illustrates an example of the correction coefficient C. Information about the correction coefficient is stored in the internal memory  280 . 
     After the light amount is corrected (S 150 ), the controller  210  carries out the center-weighted exposure metering using the corrected image data according to the equation (3) (S 160 ). After the center-weighted exposure metering is carried cut, the controller  210  performs the exposure control using the metering value (E) calculated by the center-weighted exposure metering (S 170 ). 
     
       
         
           
             
               
                 
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     As described above, when the 3D conversion lens  500  is attached, the digital video camera  100  according to the present embodiment corrects the light falloff at the center of the captured image, and carries out the center-weighted exposure metering on the corrected data. That is, the metering value is corrected based on the property of the light falloff at the center, and the center-weighted exposure metering is carried out based on the corrected metering value. Such correction of the metering value in view of the light falloff at the center allows the influence of the light falloff caused by the 3D conversion lens  500  to be eliminated, so that the accurate exposure metering can be realized. Therefore, even when the 3D conversion lens  500  providing non-uniform light amount in the metering region is attached, the suitable center-weighted exposure metering can be carried out. 
     1-5. Correspondence to the Invention 
     The CCD image sensor  190  is one example of an imaging device according to the present invention. The connecting section  640  is one example of a connecting unit according to the present invention. The controller  210  is one example of a metering unit according to the present invention. The configuration including the diaphragm  295 , the diaphragm actuator  300 , the CCD image sensor  180  and the image processor  190  is one example of an exposure adjusting unit according to the present invention. The controller  210  is one example of a correcting unit according to the present invention. The metering value obtained by the center-weighted exposure metering is one example of the measuring information according to the present invention. 
     2. Other Embodiments 
     In the foregoing, the first embodiment has been described as an embodiment of the present invention. However, the present invention is not limited to the above embodiment. Therefore, other embodiments of the present invention will be described here. 
     The optical system and the drive system in the digital camera  100  according to the present embodiment are not limited to those shown in  FIG. 1 . For example,  FIG. 3  illustrates the optical system composed of three groups, but it may be composed of other number of groups. Further, the respective lenses may be composed of one lens or a lens group including a plurality of lenses. 
     The first embodiment illustrates the CCD image sensor  180  as the imaging unit, but the imaging unit is not limited to this. For example, the imaging unit may be implemented by a CMOS image sensor or an NMOS image sensor. 
     In the first embodiment, the center-weighted exposure metering is used as an exposure metering system, but the metering system is not limited to this. The metering system may be another metering method, such as division exposure metering or spot exposure metering. 
     In the first embodiment, as shown in  FIG. 9A , the motoring region is provided in a region of a left-eye image, but it may be provided in a region of a right-eye image. 
     In the first embodiment, in order to eliminate influence of the light falloff at the center to the metering value E, when the 3D conversion lens  500  is attached, the metering value E is obtained using the corrected brightness of the image. It is not limited to this method. In order to eliminate influence of the light falloff at the center to the metering value E, the weight (W) may be corrected and the metering value E may be obtained by using the corrected weight (W′). For example, in a region where the light falloff occurs in the captured image, the weight (W) may be multiplied by a correction coefficient. Specifically, the metering value (E) may be calculated according to the following equations (4a) and (4b). In the equations (4a) and (4b), “C” is a predetermined correction coefficient, which has, as shown in  FIG. 10 , a value of 1 on a region of the captured image where the light falloff at the center does not occur and has a value larger than 1 on a region where the light falloff at the center occurs. “W′” is a weight multiplied by the correction coefficient (C) 
     
       
         
           
             
               
                 
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     In other words, in the respective embodiments of the present invention, when the 3D conversion lens  500  is attached to the digital video camera  100 , the metering value obtained from a captured image is corrected based on the correction coefficient set based on the light falloff at the center, and the exposure control is carried out by using the corrected metering value. Such correction of the metering value in consideration of the light falloff at the center allows the influence of the light falloff caused by the 3D conversion lens  500  to be eliminated, thereby realizing the accurate exposure metering. 
     INDUSTRIAL APPLICABILITY 
     The present invention is useful for imaging apparatuses such as a digital video camera and a digital still camera to which a 3D conversion lens for enabling a stereoscopic image to be shot, by a single lens imaging apparatus can be attached.