Abstract:
An electronic binoculars includes: first and second imaging units with a predetermined horizontal distance therebetween disposed in a housing; optical members that guide image light beams to the first and second imaging units; a sensor that detects angular acceleration or acceleration acting on the housing; an image processor that processes image signals produced by the first and second imaging units and corrects the image signals in terms of the change in motion of the housing in accordance with the angular acceleration or acceleration detected by the sensor; and first and second displays with a horizontal distance therebetween disposed in the housing, the first and second displays displaying the image signals processed by the image processor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to binoculars used by a user to view an enlarged remote scene or other objects with both eyes, and particularly to electronic binoculars that digitizes and displays images captured through imaging systems. 
     2. Description of the Related Art 
     There has been an apparatus developed or proposed as what is called digital binoculars including imaging units that convert image light beams into electric image signals and display units that display the images captured by the imaging units. The binoculars of this type are suitable to view a stationary subject or a nearly stationary subject. 
     That is, each of the imaging units includes an optical system, such as a lens having a relatively high magnification, enlarges and displays a remote, stationary subject, and shows the enlarged subject to a user who wears the digital binoculars. Since digital processing can be performed on the image signals, a variety of image processing operations can be carried out. For example, images captured in a dark environment are brightened before displayed, or hand-shake correction (the “hand-shake” used herein refers to a shake caused by hands) is made, as performed in a digital video camcorder. 
     JP-A-2004-133185 discloses an example of the electronic binoculars of this type. 
     SUMMARY OF THE INVENTION 
     The reason why such proposed electronic binoculars are used to view stationary objects is that when a moving object is viewed, it is difficult to continuously keep the object in focus even when the user tries to follow the moving object and keep it within the field of view. 
     That is, when an autofocus capability is equipped, for example, it is possible to some extent to follow a moving object and keep it in focus. However, consider a case where a relatively large area in a stadium where soccer or any other similar sport competition is in progress. When the user continuously follows a player, as a subject, moving across the large playing field, simply bringing the subject into focus by using an autofocus technology used in a video camcorder of related art may not be good enough to obtain images with the subject being in sharp focus. Specifically, another player in the field of view may be in focus, and which player in the field of view will be in focus disadvantageously depends on the conditions at the time of imaging. 
     Further, a hand-shake correction mechanism equipped in a video camcorder of related art is designed to provide a stable image by simply preventing the image being captured from being blurred due to a hand-shake. When such hand-shake correction is combined with the action of following a moving object, images viewed through the binoculars may not necessarily be appropriate. 
     While the above description has been made with reference to autofocusing and hand-shake correction, there have been a variety of problems with other features as well as focusing when these features are applied to electronic binoculars or image processing used in a video camcorder of related art is applied to these features. 
     Thus, it is desirable to provide electronic binoculars capable of comfortably viewing a moving subject. 
     An electronic binoculars according to an embodiment of the invention includes first and second imaging units with a predetermined horizontal distance therebetween disposed in a housing, optical members that guide image light beams to the first and second imaging units, a sensor that detects angular acceleration or acceleration acting on the housing, and an image processor. The image processor processes image signals produced by the first and second imaging units and corrects the image signals in terms of the change in motion of the housing in accordance with the angular acceleration or acceleration detected by the sensor. The embodiment further includes first and second displays with a horizontal distance therebetween disposed in the housing, and the first and second displays display the image signals processed by the image processor. 
     According to the embodiment of the invention, using image signals produced by the two imaging units to make motion correction in the image processor allows motion correction equivalent to what is called hand-shake correction on the housing to be made. In this case, using image signals produced by the two imaging units disposed with a horizontal distance therebetween to perform image processing allows sophisticated image processing suitable for the electronic binoculars to be performed. 
     According to the embodiment of the invention, using image signals produced by the two imaging units disposed with a horizontal distance therebetween to perform image processing in the image processor allows sophisticated image processing suitable for the electronic binoculars to be performed. For example, even when the electronic binoculars are inclined, motion correction can be made on the displayed images in such a way that the horizontal lines are kept oriented in a fixed direction. Alternatively, the image processor can extract only a subject of interest and display an image with the background removed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are cross-sectional views showing an exemplary configuration of electronic binoculars according to an embodiment of the invention, wherein  FIG. 1A  is a transverse cross-sectional view and  FIG. 1B  is a longitudinal cross-sectional view; 
         FIG. 2  explains an example showing how to wear the electronic binoculars according to the embodiment of the invention; 
         FIG. 3  is a block diagram showing an exemplary internal configuration of the electronic binoculars according to the embodiment of the invention; 
         FIG. 4  is a block diagram showing an exemplary focus control configuration of the electronic binoculars according to the embodiment of the invention; 
         FIG. 5  is a block diagram showing an exemplary hand-shake correction configuration of the electronic binoculars according to the embodiment of the invention; 
         FIGS. 6A and 6B  explain an example of a linear sliding mechanism of the electronic binoculars according to the embodiment of the invention; 
         FIG. 7  explains the principle of autofocus control used in the electronic binoculars according to the embodiment of the invention is performed; 
         FIGS. 8A and 8B  explain exemplary displayed images produced by the electronic binoculars according to the embodiment of the invention; 
         FIG. 9  explains the principle on which the background and an object are automatically identified in the electronic binoculars according to the embodiment of the invention; 
         FIGS. 10A to 10C  explain exemplary displayed images acquired in the example shown in  FIG. 9 ; 
         FIG. 11  explains the principle of automatic identification of an object neighborhood and an object in the electronic binoculars according to the embodiment of the invention; 
         FIGS. 12A to 12C  explain exemplary displayed images acquired in the example shown in  FIG. 11 ; 
         FIGS. 13A and 13B  explain exemplary right and left images to which the processes of the embodiment of the invention are applied, and  FIG. 13C  explains an exemplary combined image; 
         FIGS. 14A and 14B  explain exemplary right and left images to which the processes of the embodiment of the invention are applied, and  FIG. 14C  explains an exemplary combined image; 
         FIGS. 15A and 15B  explain exemplary right and left images to which the processes of the embodiment of the invention are applied, and  FIGS. 15C and 15D  explain an exemplary combined image; 
         FIG. 16  is explains the principle of the image processing related to the hand-shake correction according to the embodiment of the invention; 
         FIGS. 17A and 17B  explain sensor arrangement and coordinate definition of the electronic binoculars according to the embodiment of the invention; 
         FIG. 18  explains an example showing how an object image changes due to a hand-shake-related shift (small shift around the yaw axis) of the electronic binoculars according to the embodiment of the invention; 
         FIGS. 19A and 19B  explain exemplary displayed images acquired in the example shown in  FIG. 18 ; 
         FIG. 20  explains an example showing how an object image changes due to a hand-shake-related shift (shift in the X axis) of the electronic binoculars according to the embodiment of the invention; 
         FIGS. 21A and 21B  explain exemplary displayed images acquired in the example shown in  FIG. 20 ; 
         FIG. 22  explains an example showing how an object image changes due to a hand-shake-related shift (shift in the X axis) of the electronic binoculars according to the embodiment of the invention; 
         FIGS. 23A to 23C  explain exemplary displayed images acquired in the example shown in  FIG. 22 ; 
         FIGS. 24A to 24E  are time sequence diagrams used in an example of image processing (autofocusing and hand-shake correction) performed in the electronic binoculars according to the embodiment of the invention; and 
         FIGS. 25A to 25E  are time sequence diagrams used in another example of image processing (using a previous image) performed in the electronic binoculars according to the embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An exemplary embodiment of the invention will be described below with reference to the accompanying drawings. 
     Electronic binoculars  100  according the present exemplary embodiment are integrally incorporated in a housing  120 , and a user wears the electronic binoculars  100 , when using it, on the face in front of the right and left eyes, for example, as shown in  FIG. 2 . Although  FIG. 2  does not particularly show any mechanism for allowing the user to wear the electronic binoculars  100  on the face, the user may wear the electronic binoculars  100  like glasses, or may hold the electronic binoculars  100  in the user&#39;s hands like typical binoculars. 
       FIGS. 1A and 1B  are cross-sectional views showing the internal configuration of the electronic binoculars  100  according to the present exemplary embodiment.  FIG. 1A  is a transverse cross-sectional view taken along the horizontal direction (transverse direction), and  FIG. 1B  is a longitudinal cross-sectional view taken along the vertical direction (longitudinal direction). 
     The housing  120  of the electronic binoculars  100  houses a lens fixing mount  101   a  on the front side of the housing  120 . The lens fixing mount  101   a  contains right and left lens systems  101 L,  101 R with a predetermined distance therebetween in the horizontal direction (transverse direction). Image light beams produced by the lens systems  101 L and  101 R are picked up by right and left imaging units  102 L,  102 R and converted into electric image signals. Each of the lens systems  101 L and  101 R is formed of a plurality of lenses including a focus lens, and moving the focus lens along the optical axis allows focus adjustment. Each of the lens systems  101 L and  101 R forms what is called a zoom lens the focal length of which can be changed. The zoom magnification that is typically used ranges from 2 to 10. 
     The imaging units  102 L and  102 R can be a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or any other suitable types of image sensors. A readout circuit suitable for the image sensor to be used is also provided. The distance between the two imaging units  102 L and  102 R is preferably at least several centimeters, which corresponds to the distance between the right and left eyes of the user who wears the electronic binoculars  100 . The image sensor that forms each of the imaging units  102 L and  102 R has what is called a high-speed shuttering capability that allows the single-frame exposure period to be reduced. 
     The image signals produced by the right and left imaging units  102 L,  102 R are supplied to an image processor  104  and undergo a variety of image processing operations in the image processor  104  and its peripheral circuits. The imaging units  102 L,  102 R and the image processor  104  are disposed on the front or rear side of a substrate  103 , on which a gyroscopic sensor  106  and an acceleration sensor  107  are also mounted. The outputs from the sensors  106  and  107  are used for hand-shake correction. The configuration for making the hand-shake correction will be described later in detail. 
     A linear motor  108  is attached to the substrate  103 , and driving the linear motor  108  allows the focus lens in each of the lens systems  101 L and  101 R to be moved for focus adjustment. The right and left lens systems  101 L,  110 R are incorporated in the single lens fixing mount  101   a  and moved as a whole by the linear motor  108 . 
     Right and left liquid crystal displays  110 L,  110 R are disposed with a predetermined distance therebetween on the rear side of the housing  120 , and a sliding mechanism  109  is attached to the right and left liquid crystal displays  110 L,  110 R. The sliding mechanism  109  can adjust the horizontal distance between the two liquid crystal displays  110 L and  110 R. The detail of the adjustment mechanism will be described later. While the liquid crystal displays are used as a display means, the liquid crystal displays  110 L and  110 R may be replaced with any other suitable types of image displays. 
       FIG. 3  shows an exemplary overall configuration for performing the image processing in the electronic binoculars of the present embodiment. 
     As shown in  FIG. 3 , the image signals produced by the right and left imaging units  102 L,  102 R are supplied to the image processor  104 , and the data are stored in a memory  105  connected to the image processor  104 . In this process, image display signals are produced at the same time. The image processor  104  also serves as a controller when the image processing is performed. The produced image signals are supplied to and displayed on the right and left liquid crystal displays  110 L,  110 R. The image signals supplied to the right and left liquid crystal displays  110 L,  110 R may be used in either of the following two ways: Separate images representing the image signals captured by the right and left imaging units  102 L,  102 R are displayed, or a combined single image signal produced by image processing in the image processor  104  is supplied and displayed. 
     The outputs from the gyroscopic sensor  106  and the acceleration sensor  107  are supplied to the image processor  104 , where image processing for hand-shake correction, which will be described later, is performed in accordance with the outputs from the sensors. 
     In accordance with a focus adjustment state detected in the image processor  104 , a drive signal is supplied from the image processor  104  to the linear motor  108  to bring the image light beams captured by the imaging units  102 L and  102 R into focus. 
     A switch  111  is disposed at a predetermined location on the housing  120  of the electronic binoculars  100 , and imaging and displaying-related processes are carried out by supplying operational instructions through the switch  111  to the image processor  104  and other components. Mode setting made by operating the switch  111  may be used to set whether or not hand-shake correction, which will be described later, and a variety of other image processing operations are carried out. The current mode setting may be displayed on the liquid crystal displays  110 L and  110 R. 
     An exemplary configuration for performing each of the image processing operations will be described below in detail. 
     First, the configuration for performing autofocus adjustment will be described with reference to  FIG. 4 . 
     As shown in  FIG. 4 , the image signals produced by the right and left imaging units  102 L,  102 R are converted into digital image data by analog/digital converters (ADCs)  112 L and  112 R, respectively. The converted image data are supplied to the image processor  104  and temporarily stored in the memory  105  as necessary. 
     The image processor  104  extracts a target subject from the image data produced by the two imaging units  102 L and  102 R and calculates the distance to the target subject. The calculated position is used as a target focus position, and the target position data is supplied as positional instruction data to a subtracter  114 , where the current position of the optical systems  101 L and  101 R detected by a linear encoder  113  is subtracted from the positional instruction, and the position to be provided to the linear motor  108  is calculated. The calculated positional data is supplied to a PID controller  115  to produce a drive signal for driving the linear motor  108 , and the drive signal (drive current Im) is supplied to the linear motor  108  through an amplifier  116 . The PID controller  115  is a control means that performs feedback control using three elements, the deviation from the target value, the integral value of the deviation, and the derivative value of the deviation. 
     The configuration for making hand-shake correction will next be described with reference to  FIG. 5 . 
     Data detected by the gyroscopic sensor  106  and the acceleration sensor  107  are digitized by analog/digital converters  117  and  118 , respectively, and the converted digital data are supplied to the image processor  104 , where the supplied sensor data along with the swinging state of the housing  120 , which is the body of the electronic binoculars  100 , are used to determine the hand-shake state. The captured image data undergo image processing according to the determined hand-shake state in the image processor  104 . In the image processing, image data representing a previous frame stored in the memory  105  may be used in some cases. An example of the image processing for hand-shake correction will be described later in detail. 
     An exemplary configuration of the sliding mechanism  109 , which adjusts the distance between the right and left liquid crystal displays  110 L,  110 R, will be described with reference to  FIGS. 6A and 6B . 
       FIG. 6A  is a transverse cross-sectional view of the electronic binoculars  100  taken along the horizontal direction (transverse direction), and  FIG. 6B  is a longitudinal cross-sectional view of the electronic binoculars  100  taken along the vertical direction (longitudinal direction).  FIGS. 6A and 6B  show only the mechanism related to the sliding mechanism  109 . 
     The sliding mechanism  109  has screws  201 L and  201 R integrally disposed in series in the transverse direction, as shown in  FIG. 6A . The integrated screws  201 L and  201 R can be rotated by a drive mechanism (not shown). It is noted that the directions in which the screws  201 L and  201 R are threaded are opposite to each other. The drive mechanism may be driven by a motor or manually rotated by the user. 
     The screw  201 L disposed on the left side fits into a slidable member  202 L to which the liquid crystal display  110 L is attached, and rotating the screw  201 L changes the position of the slidable member  202 L (that is, the position of the liquid crystal display  110 L) along the screw  201 L. Similarly, the screw  201 R disposed on the right side fits into a slidable member  202 R to which the liquid crystal display  110 R is attached, and rotating the screw  201 R changes the position of the slidable member  202 R (that is, the position of the liquid crystal display  110 R) along the screw  201 R. 
     Since the directions in which the screws  201 L and  201 R are threaded are opposite to each other, the two liquid crystal displays  110 L and  110 R slide and separate from each other (or approach) in accordance with the direction in which the screws  201 L and  201 R are rotated. The user can therefore arbitrarily adjust the distance between the two liquid crystal displays  110 L and  110 R. 
     The principle on which the autofocus adjustment is carried out will now be described with reference to  FIG. 7  and  FIGS. 8A and 8B . 
       FIG. 7  shows exemplary processes for focusing the electronic binoculars  100  on an object A present in a position spaced apart from the electronic binoculars  100  by a predetermined distance Lx.  FIG. 8A  shows a displayed image # 1  obtained by supplying the image signal captured by the left imaging unit  102 L to the liquid crystal display  110 L and displaying the image signal thereon.  FIG. 8B  shows a displayed image # 2  obtained by supplying the image signal captured by the right imaging unit  102 R to the liquid crystal display  110 R and displaying the image signal thereon. 
     Now, let L 0  be the distance between the two lens systems  101 L and  101 R, as shown in  FIG. 7 . The inter-lens distance L 0  and the distance Lx from the electronic binoculars  100  to the object A determine the angle θx between each of the optical axes of the lens systems  101 L,  101 R and the direction toward the object. The distance Lx from the electronic binoculars  100  to the object A can therefore be calculated by determining the angle θx, because the inter-lens distance L 0  is fixed. 
     Specifically, the discrepancy Lg between the positions of the object A in the two displayed images corresponds to the angle θx, as shown in  FIGS. 8A and 8B , and the discrepancy Lg can be converted into the angle θx. The distance Lx to the object A shown in  FIG. 7  is then calculated. 
     The thus calculated distance Lx is used as the target value to carry out the focusing processes in the processing system that has been described with reference to  FIG. 4 . 
     The autofocus adjustment will be described using a formula. The distance Lx can be calculated by using the following approximate equation:
 
Distance  Lx=L 0/tan(θ x ),  Equation (1)
 
When the distance Lx is substantially greater than the inter-lens distance L 0 , the above equation is approximated as follows:
 
tan(θ x )≈ K 0× Lg,   Equation (2)
 
     where K 0  is a positive integer determined in accordance with the magnification of the lens. 
     Therefore, the distance Lx is given by the following equation:
 
Distance  Lx=L 0/( K 0× Lg ),  Equation (3)
 
     In the present embodiment, the distance to the object is calculated based on the equation (3), and the object is automatically identified, for example, by carrying out the processes described later with reference to the example shown in  FIG. 9 . Therefore, even when the extracted object moves at high speed in the field of view, it is possible to follow the object and keep it in focus. 
     Identification of an object and a background image and image processing based on the identification performed in the electronic binoculars  100  of the present embodiment will be described with reference to  FIG. 9  to  FIGS. 15A to 15D . 
     First, the principle on which an object is distinguished from a background image will be described with reference to  FIG. 9  and  FIGS. 10A to 10C . 
       FIG. 9  shows a state in which an object A and a rearward background B are imaged by the imaging units  102 L and  102 R and viewed through the electronic binoculars  100 . It is assumed that the object A is located in a substantially central portion in the field of view of the electronic binoculars  100 . 
     In this case, the image (displayed image # 1 ) captured by the left imaging unit  102 L and displayed on the liquid crystal display  110 L has the object A displayed in front of the rearward background B, as shown in  FIG. 10A . In the displayed image # 1 , the object A is displayed in a position slightly to the left of the center. 
     The image (displayed image # 2 ) captured by the right imaging unit  102 R and displayed on the liquid crystal display  110 R has the object A displayed in front of the rearward background B, as shown in  FIG. 10B . In the displayed image # 2 , the object A is displayed in a position slightly to the right of the center. 
     After the two displayed images # 1  and # 2  are obtained, one of the two images is subtracted from the other in the image processor  104  to remove the rearward background B common to the two images and produce an image containing only the object A, as shown in  FIG. 10C . However, since the resultant image shows two objects A spaced apart from each other by the distance Lg, as shown in  FIG. 10C , the two objects A are separated, and images each of which has the corresponding object A are displayed on the liquid crystal displays  110 L and  110 R. 
     As described above, providing the mode in which the background image is removed and performing the relevant image processing in the image processor  104  allow the background image to be removed and only the object to be displayed. The user is therefore provided with a very easy-to-see display mode because only the object is displayed. Further, removing the background image and extracting the object allow the object image to be readily identified, whereby the object can be identified and the distance to the object can be quickly calculated. 
     The principle of automatic identification of an object neighborhood and an object will be next described with reference to  FIG. 11  and  FIGS. 12A to 12C . 
       FIG. 11  shows a state in which the imaging units  102 L and  102 R image an object A. In this example, it is again assumed that the object A is located in a substantially central portion in the field of view of the electronic binoculars  100 . 
       FIG. 12A  shows an image (displayed image # 1 ) captured by the left imaging unit  102 L and displayed on the liquid crystal display  101 L in the case described above. 
     An image (displayed image # 2 ) captured by the right imaging unit  102 R and displayed on the liquid crystal display  110 R has the object A in front of the rearward background B, as shown in  FIG. 12B . The conditions described above are the same as those shown in  FIG. 9 . 
     After the two displayed images # 1  and # 2  are obtained, one of the two images is subtracted from the other in the image processor  104  to remove the rearward background B common to the two images and produce an image containing only the object A, as shown in  FIG. 12C . In the present example, not only the image of the object A but also the image of a neighborhood of the object A (part of the background image) are extracted and displayed, as indicated by the broken lines in the  FIGS. 12A and 12B . 
     As an example of identifying an object in an image described above, for example, consider a case where a stadium is under observation. In general, a stadium has a flat ground having a uniform color, such as grass, in many cases. To extract an object under the condition, color analysis is performed on representative points (color information at 10 to 100 regularly arranged points) in the image data shown in  FIGS. 12A and 12B .  FIG. 12B  shows an example of the representative points. The neighborhood color that is the color in a larger area is subtracted from the images shown in  FIGS. 12A and 12B , whereby only the color of the object is left. Calculating the difference between the image data thus obtained from  FIGS. 12A and 12B  by subtracting one of the image data from the other allows only A to be extracted, as shown in  FIG. 12C . 
     The positional discrepancy between the thus extracted object in the two images (Lg in  FIG. 12C ) can be used to calculate the distance to the object by using the equation (3) described above. 
     In practice, the image data only in the object neighborhood are processed to make the processing faster, whereby the computation time is reduced and realtime focusing is achieved. 
     Viewing region setting will next be described with reference to the images shown in  FIGS. 13A to 13C . 
       FIG. 13A  shows an image captured by the left imaging unit  102 L, and  FIG. 13B  shows an image captured by the right imaging unit  102 R. It is noted that the images shown in  FIGS. 13A and 13B  are not actual images but the difference between the right and left object positions is enhanced. 
     The object positioned slightly to the right of the center of the image imaged by the left imaging unit  102 L as shown in  FIG. 13A  is the same as the object positioned slightly to the left of the center of the image imaged by the right imaging unit  102 R as shown in  FIG. 13B . In this description, the region where the object is present is called a viewing region. 
     The image signals produced by the two imaging units  102 L and  102 R are combined as appropriate in the image processor  104  in such a way that the viewing region is located at the center.  FIG. 13C  shows an example of the combined image. 
     The focusing adjustment is then carried out in such a way that the object in the viewing region is brought into focus. The processes that have been described with reference to  FIG. 7  are used to determine the distance to the object and focus the binoculars on that position. Since the viewing position is likely in the vicinity of the center in the observation using binoculars, setting the viewing region and bringing that region into focus as described above allow the distance to a fast-moving object to be quickly calculated and the object to be brought into focus in real time. 
     The processes of extracting only the image within the viewing region set on a screen and displaying an image with the background removed will be described with reference to  FIGS. 14A to 14C  and  FIGS. 15A to 15D . 
       FIG. 14A  shows an image captured by the right imaging unit  102 R, and  FIG. 14B  shows the right-side image from which a viewing region is extracted.  FIG. 14C  shows an example of the image of the viewing region from which the grass portion having a substantially uniform color is removed. 
     Similarly,  FIG. 15A  shows an image captured by the left imaging unit  102 L, and  FIG. 15B  shows the left-side image from which the viewing region is extracted.  FIG. 15C  shows an example of the image of the viewing region from which the grass portion having a substantially uniform color is removed. 
     Subtracting one of the right-side object image shown in  FIG. 14C  and the left-side object image shown in  FIG. 15C  from the other provides an image with the background removed shown in  FIG. 15D . The distance Lg, which corresponds to the difference between the two images, is thus detected. The distance Lg in the image is used to calculate the distance to the object, and a variety of image processing operations, including bringing the object into focus, can be performed. 
     An example of the hand-shake correction made in the electronic binoculars  100  of the present embodiment will be described with reference to  FIG. 16  to  FIGS. 23A to 23C . 
     First,  FIG. 16  shows the principle of the hand-shake correction in the present embodiment. The X and Z axes shown in  FIG. 16  are the horizontal and vertical axes of the scene imaged through the electronic binoculars  100 . The X and Z axes may be determined from the output from the gyroscopic sensor  106 , or may be determined by image processing performed on a captured image. 
     It is assumed that the X and Z axes obtained in the imaging process using the image sensors in the imaging units  102 L and  102 R in the electronic binoculars  100  are shifted by the amount of shake θr, as shown in  FIG. 16 . 
     In the hand-shake correction, a captured original images Vorg(xo,yo) is used to form a hand-shake corrected image Vcom(x, y), and the corrected image is displayed. The correction is made, for example, in the image processor  104  on an area set by cutting out part of the image in each frame formed by a captured image signal. 
     The process of converting the original image into an image with the amount of shake (θr) corrected to eliminate the effect of hand-shake will be described below by using a formula. The hand-shake angle θr is calculated by the following equation:
 
θ r=θr 0+∫(ω r ) dt  
 
(In the equation, ωr represents the sensor signal, and θr 0  represents the initial horizontal angle obtained from the acceleration sensor.)
 
     The thus measured hand-shake angle θr is used to convert the coordinates of the original image data Vorg(xo,yo) into the coordinates of the hand-shake angle corrected image Vcom(x, y) by using the following equation:
 
 L 0=√( x 0^2 +y 0^2)
 
Θ0=arctan( x 0/ y 0)
 
 V cmp( x,y )= V org( L 0*cos(θ0+θ r ),  L 0*sin(θ0+θ r ))
 
     In this way, image data with the hand-shake-related change corrected are obtained. 
     The shakes related to the shifts in the Z and Y axis directions can also be corrected on the same principle. 
     It is assumed in the present example that the hand-shake corrected image obtained as described above is an image in which the X and Z axes in the horizontal and vertical directions always coincide with the original X and Z axes. While the correction in the present example is described with reference to hand-shake correction, a state in which the electronic binoculars  100  that the user is holding is simply temporarily inclined may be similarly corrected by keeping the X and Z axes fixed. 
     An arrangement of the sensors necessary to make the hand-shake correction described above and the definition of the coordinates detected by the sensors will be described with reference to  FIGS. 17A and 17B . 
       FIG. 17A  is a longitudinal cross-sectional view of the electronic binoculars  100  showing the sensor arrangement, and  FIG. 17B  is a transverse cross-sectional view of the electronic binoculars  100  showing the sensor arrangement. In  FIGS. 17A and 17B , the X axis represents the horizontal axis; the Y axis represents the optical axis; and the Z axis represents the vertical axis. 
     As shown in  FIGS. 17A and 17B , the gyroscopic sensor  106  is disposed to detect the angular velocities (ωp, ωr, ωy) around the three axes. The acceleration sensor  107  is disposed to detect the angular acceleration values (Ax, Ay, Az) in the three axes. 
     That is, the gyroscopic sensor signal (ωp, ωr, ωy) from the three-dimensional gyroscopic sensor  106  incorporated in the electronic binoculars  100  and the three-dimensional acceleration sensor signal (Ax, Ay, Az) from the acceleration sensor  107  also incorporated therein can be used to detect the rotation angles (θp, θr, θy) and the angular velocities (ωp, ωr, ωy) of the binoculars. 
     The acceleration sensor  107  is configured in such a way that when the Z axis is stationary and coincides with the direction in which the gravity acts, the output from the acceleration sensor (Ax, Ay, Az) is 0 [V] (zero volts) and the polarities of the sensor outputs are reversed in accordance with the direction. 
     When the X and Y axes are stationary in the horizontal plane in  FIGS. 17A and 17B , the three-dimensional gyroscopic sensor signal and the three-dimensional acceleration sensor signal for each dimension are set to 0 [V], and the polarities of the sensor signals are reversed in accordance with the direction. The pitch angle θp, the roll angle θr, and the yaw angle θy that form the rotation angle of the binoculars are calculated by using the following equation:
 
θ p=θp 0+∫(ω p ) dt , where θ p 0 represents the initial pitch angle
 
 θr=θr 0+∫(ω r ) dt , where θ r 0 represents the initial roll angle
 
 θy=θy 0+∫(ω y ) dt , where θ y 0 represents the initial yaw angle
 
     The initial values θp 0 , θr 0 , and θy 0  are determined by using the following equations along with the acceleration sensor signal in the stationary state.
 
 θp 0=arcsin( Ay )
 
 θr 0=arcsin( Ax )
 
θ y 0=0
 
     The screen can be always displayed in the horizontal position by using the above equations to perform coordinate conversion in such a way that the image is always displayed in the horizontal position, as shown in  FIG. 16 , in response to the change in the rotation angle of the binoculars. 
     The correction described above is applicable to a case where each of the sensor signals has a frequency characteristic high enough to respond at a sufficiently high speed to the motion due to an actual hand-shake of the binoculars. 
     When the hand-shake motion is fast or the binoculars vibrate in the horizontal (vertical) direction, and the gyroscopic sensor  106  and the acceleration sensor  107  may not detect a shift, that is, the sensor output signals are very small, the image signals are used to detect a horizontal (vertical) shift, and images having undergone image conversion for shift correction are outputted in the form of video images. Video images of an object in question that are not affected by the vibration and shift of the binoculars are thus outputted. When a certain type of shift of the binoculars may not be detected by the sensors (the examples shown in  FIGS. 19A ,  19 B and  FIG. 20  described later), image/video information is used to reduce the effect of the shift of the binoculars. 
       FIG. 18  to  FIGS. 23A to 23C  show examples of the hand-shake correction. 
       FIG. 18  shows a state in which a small shift occurs around the yaw axis (θy axis in  FIG. 17A ), and  FIGS. 19A and 19B  show how the produced image changes when no hand-shake correction is made.  FIG. 19A  shows an image produced when the electronic binoculars  100  are in a position A in  FIG. 18 , and  FIG. 19B  shows an image produced when the electronic binoculars  100  are in a position B in  FIG. 18 . 
     As seen from  FIGS. 19A and 19B , an object A disadvantageously moves in the horizontal direction in response to the small shift. 
       FIG. 20  shows a state in which the binoculars  100  translate in the transverse direction (horizontal direction) due to a hand-shake, and  FIGS. 21A and 21B  show how the produced image changes when no hand-shake correction is made.  FIG. 21A  shows an image produced when the electronic binoculars  100  are in the position A in  FIG. 20 , and  FIG. 21B  shows an image produced when the electronic binoculars  100  are in a position C in  FIG. 20 . 
     In the case shown in  FIG. 20  as well, an object A in the image disadvantageously moves in the horizontal direction in response to the shift. 
       FIG. 22  shows a case where the binoculars translate as in the case shown in  FIG. 20  when the user is in a stadium, for example, that shown in  FIGS. 14A to 14C , and uses the electronic binoculars  100  to view an object A in a competition area (or inside a competition line) in the stadium. 
       FIG. 23A  shows a case where the binoculars  100  are in the position A in  FIG. 22 . In this case, the competition area is seen at the center, and the object A is displayed at the center of the competition area.  FIG. 23B  shows a case where the binoculars  100  are in the position C in  FIG. 22  and no correction is made. In this case, the competition area is seen on the left, and the object A is also displayed on the left accordingly. 
     Making the hand-shake correction described in the present example allows the displayed image shown in  FIG. 23C  to be achieved. Specifically, the correction based on the principle shown in  FIG. 16  allows the competition area to be seen at the center and the object A to be displayed at the center of the competition area, as in the case shown in  FIG. 23A . 
     While the above figures show only the correction of the horizontal motion, the motions in the other directions are similarly corrected. 
     A description will be made of an example showing how the processes described above are carried out when the electronic binoculars  100  are actually used for observation with reference to the timing charts in  FIGS. 24A to 24E  and  FIGS. 25A to 25E . 
       FIGS. 24A to 24E  show a case where not only the autofocusing in which an object is automatically brought into focus but also the hand-shake correction are performed. 
     In the example shown in  FIGS. 24A to 24E , the right and left imaging units  102 L,  102 R perform high-speed shuttering so that a single frame period of 1/30 seconds is achieved. In this example, the timing at which the right imaging unit  102 R performs imaging as shown in  FIG. 24A  is the same as the timing at which the left imaging unit  102 L performs imaging as shown in  FIG. 24B . 
       FIG. 24C  shows the change in the level of the sensor signal detected by each of the gyroscopic sensor  106  and the acceleration sensor  107 , and a threshold of the sensor signal for judging whether an image blur occurs is set in advance, as indicated by the broken line. 
       FIG. 24D  shows how the autofocus control and the hand-shake prevention control are carried out in the image processor  104  and its peripheral circuits.  FIG. 24E  shows the timing at which images are displayed on the right and left liquid crystal displays  110 L,  110 R. 
     As shown in  FIG. 24D , the image signals captured in each frame cycle are stored in the memory and undergo the autofocus control and the hand-shake prevention control, and the processed image signals are read from the memory and displayed as shown in  FIG. 24E . The displayed images are thus updated on a frame basis. 
     It is assumed in the example shown in  FIGS. 24A to 24E  that the acceleration or the angular acceleration becomes greater than the threshold at the timing of a frame period K and a hand-shake that is too large to be corrected occurs accordingly. 
     In this case, the images captured in a frame period K−1, which is one frame before the frame period K, and stored in the memory are read again in the frame period K and displayed on the liquid crystal displays  110 L and  110 R. 
     Thereafter, when the acceleration or the angular acceleration becomes smaller than the threshold in the following frame period K+1, the control returns to the display process using the signals captured in the frame period K+1. When the state in which the acceleration or the angular acceleration is greater than the threshold continues, the images captured and stored when the acceleration or the angular acceleration was smaller than or equal to the threshold value in the past are kept being displayed. It is noted, however, that the control may return to the display process using the current captured images after the state in which the acceleration or the angular acceleration is greater than the threshold has continued for a certain period. 
       FIGS. 25A to 25E  are timing charts used in another example of imaging processes. 
     In the example shown in  FIGS. 25A to 25E , a single frame period is set to 1/60 seconds, and what is called double-speed shuttering is performed to shift the imaging timing by 1/120 seconds between the right and left imaging units  102 L,  102 R. 
     That is, in this example, the timing at which the right imaging unit  102 R performs imaging as shown in  FIG. 25A  is shifted by 1/120 seconds from the timing at which the left imaging unit  102 L performs imaging as shown in  FIG. 25B . 
       FIG. 25C  shows the change in the level of the sensor signal detected by each of the gyroscopic sensor  106  and the acceleration sensor  107 , and a threshold of the sensor signal for judging whether an image blur occurs is set in advance, as indicated by the broken line. 
       FIG. 25D  shows the timing at which the image signals are held in the memory in preparation for image processing in the image processor  104 .  FIG. 25E  shows the timing at which images are displayed on the right and left liquid crystal displays  110 L,  110 R. 
     As shown in  FIG. 25D , the image signals captured in each frame cycle are held in the memory, undergo image processing, and are then displayed on the right and left liquid crystal displays  110 L,  110 R. The image signals captured at each timing are, for example, simultaneously supplied to the right and left liquid crystal displays  110 L,  110 R, and updates the images on the displays in the one-half cycle (a cycle of 1/120 seconds in this example). In  FIG. 25D , the periods during which the autofocus control and the hand-shake prevention control are performed are omitted, but they can be performed in the same manner as in the example shown in  FIG. 24D . The displayed images are thus updated on a frame basis. 
     It is assumed in the example shown in  FIGS. 25A to 25E  that the acceleration or the angular acceleration becomes greater than the threshold at the timing of a frame period K and a hand-shake that is too large to be corrected occurs accordingly. 
     In this case, the images captured by the other-side imaging unit in a frame period K−1, which is one frame before the frame period K, and stored in the memory are read again in the frame period K and displayed on the two liquid crystal displays  110 L and  110 R. 
     Thereafter, when the acceleration or the angular acceleration becomes smaller than the threshold in the following frame period K+1, the control returns to the display process using the signals captured in the frame period K+1. 
     As described above, performing what is called double-speed shuttering can effectively prevent blurred images due to a hand-shake from being displayed by temporarily displaying previous images in accordance with the state at the time of display. Further, performing the double-speed shuttering as shown in the present example is equivalent to imaging twice a frame even in the timing setting in which each of the imaging units performs imaging once a frame, whereby double-speed processing is achieved without increasing the amount of signal processing and power consumption necessary for the double-speed processing. 
     As described above, the electronic binoculars according to the present embodiment enables a sophisticated display operation different from that in electronic binoculars that has been proposed in related art. That is, performing not only the hand-shake correction but also the autofocusing enables a stable, well-defined display operation. Since the hand-shake correction is made by keeping the horizontal lines fixed, as shown in  FIG. 16 , the user who is looking at displayed images can view stable images displayed in a least blurred manner and comfortably follow an object in the field of view. 
     Further, performing the autofocusing using the distance between the two imaging units achieves appropriate focusing using an intrinsic configuration of the binoculars. In particular, since an object present in a substantially central portion in the field of view is identified and used in the focusing process, even a subject moving at high speed can be brought into focus in a satisfactory manner. 
     Moreover, since the present embodiment allows the background image to be removed and prevents it from being displayed, only an object can be displayed. Binoculars capable of comfortably viewing only a necessary object are thus provided. 
     The present application contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2008-159726 filed in Japan Patent Office on Jun. 18, 2008, the entire contents of which is hereby incorporated by reference. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.