Abstract:
The invention relates to an imaging device. An imaging device includes an image sensor for producing an image data related an object image; an optical system for forming on the image sensor the object image in which a predetermined region having as center a position that is different from a center position of the image sensor is expanded and a peripheral region thereof is compressed with distortion; and a distortion correction circuit for correcting the compressed distortion with respect to image data related to the object image from the image sensor.

Description:
PRIORITY CLAIM  
       [0001]     Priority is claimed on Japanese Patent Application No. 2005-229215, filed with the Japanese Patent Office on Aug. 8, 2005, the content of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to an imaging device, and particularly to an imaging device that simultaneously obtains a plurality of angles of view such as a wide angle image and a telescopic image.  
         [0004]     2. Description of the Related Art  
         [0005]     Zoom functions in an image input device such as a video camera, a digital camera or a monitoring camera have been widely used these days, by which a change of the focal distance of a lens or scale-up or scale-down of an image is easily performed, according to a distance to or a size of an angle of view toward an object to be shot. The zoom functions can be classified into an optical zoom function and an electronic zoom function. The optical zoom function can be realized by mechanically moving a lens inside. On the other hand, the electronic zoom function may make use of part of an image output from an imager to generate an image by complementing a new pixel among pixels and magnify it. The electronic zoom function has an advantage that it may be realized as compact without a driving portion and at a low cost, compared with the optical zoom function. However, it has a problem that it is inferior in image quality.  
         [0006]     In order to solve the problem, there is proposed an electronic zoom image input system as shown in  FIG. 14 , which includes an image input optical unit with a fixed focal distance for compressing a circumferential part of an input image, a photo detector with a uniform density of pixels for receiving the image through the system, and a unit for complementing and correcting the image received by the photo detector having distortion caused by the compression. The image input system is characteristic of obtaining a zoomed image of an equivalent resolution in the operating region. See, for example, Japanese Patent Publication Hei 10-233950. The system is expected to produce an image having less deterioration in the middle of both a wide angle image and a telescopic image, regardless of unavoidable deterioration in a peripheral part thereof.  
         [0007]     The image input system of the prior art described above has a structure as shown in  FIG. 16 , in which a zoom center position of a lens agrees with a center position of an imager. The zoom center position is defined by a position in which the lens can form the most magnified optical image. Under the situation, the optical image incident on the photo detector, as shown in  FIG. 17 , the central portion is expanded and the circumferential portion is compressed. As a result of this, since the image contains more pixel information in the central portion, image processing can produce a fine, zoomed image for the central portion. By contrast, because the image has less pixel information in the circumferential portion, a fine, zoomed image therefore cannot be obtained. This is a problem.  
         [0008]     Under the situation, when there is no object in the middle, the prior art described above, as shown in  FIG. 15 , discloses that two cuneate prism lenses are inserted, each being rotated independently.  
       SUMMARY OF THE INVENTION  
       [0009]     The invention provides an imaging device having the following structure.  
         [0010]     The imaging device of the invention comprises an image sensor for producing an image data related an object image; an optical system, for forming on the image sensor the object image in which a predetermined region having as center a position that is different from a center position of the image sensor is expanded and a peripheral region thereof is compressed with distortion; and a distortion correction circuit for correcting the compressed distortion with respect to image data related to the object image from the image sensor.  
         [0011]     Preferably, the imaging device finer comprises a position changing unit for changing a position of the predetermined region with respect to the image sensor.  
         [0012]     Preferably, the position changing unit includes a changing information input section for inputting changing information related to the change of the position; a movement value calculator for calculating a movement value of the optical system based on the input changing information; and a driver for moving the position of the predetermined region based on the calculated movement quantity.  
         [0013]     Advantageously, the position changing unit includes a frame memory for storing a reference image; an object position detector for detecting a position of an object of interest based on the reference image and an image subsequent to the reference image; a movement value calculator for calculating a movement value of the optical system based on the position of the object; and a driver for moving the optical system based on the calculated movement value.  
         [0014]     Advantageously, the object position detector detects the position of the object of interest based on at least one differential of color or luminance between the reference image and the subsequent image.  
         [0015]     Advantageously, the object position detector detects the position of the object of interest based on the motion vector between the reference image and the subsequent image.  
         [0016]     Advantageously, the position changing unit includes a rotation speed input section for inputting a rotation speed; and a rotator for rotating the position of the predetermined region according to the rotation speed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a diagram for showing a positional relationship between a lens and a photo detector in accordance with the invention.  
         [0018]      FIG. 2  is a diagram for showing a construction of a monitoring camera system in accordance with a first embodiment of the invention.  
         [0019]      FIG. 3  is a block diagram for showing a construction of an imaging unit in the monitoring camera system in accordance with the first embodiment.  
         [0020]      FIG. 4  is a block diagram for showing a construction of a controller in the monitoring camera system in accordance with the first embodiment.  
         [0021]      FIG. 5  shows a case in which a main object is in a right upper portion.  
         [0022]      FIG. 6A  is a diagram for showing a positional relationship between a lens and a photo detector before the lens is rotated.  
         [0023]      FIG. 6B  is a diagram for showing a positional relationship between the lens and the photo detector after the lens has been rotated.  
         [0024]      FIG. 7A  shown an image obtained when the positional relationship between the lens and the photo detector is shown in  FIG. 6A .  
         [0025]      FIG. 7B  shown captured image data when the positional relationship between the lens and the photo detector is shown in  FIG. 6B .  
         [0026]      FIG. 8  is a diagram for showing a variation of the positional relationship between the lens and the photo detector.  
         [0027]      FIG. 9  is a block diagram for showing a construction of a controller in a monitoring camera system in accordance with a second embodiment.  
         [0028]      FIG. 10  is a diagram for explaining how a main object is detected according to a change of brilliance.  
         [0029]      FIG. 11  is a diagram for explaining how a main object is detected according to a motion vector.  
         [0030]      FIG. 12  is a block diagram for showing a construction of an imaging unit in a monitoring camera system in accordance with a third embodiment.  
         [0031]      FIG. 13  is a block diagram for showing a construction of a controller in the monitoring camera system in accordance with the third embodiment.  
         [0032]      FIG. 14  shows a construction of an electronic zoom image input system of prior art.  
         [0033]      FIG. 15  shows a construction of the electronic zoom image input system of the prior art.  
         [0034]      FIG. 16  is a diagram for showing a positional relationship between a lens and a photo detector in the prior art.  
         [0035]      FIG. 17  shows captured image data when the positional relationship between the lens and the photo detector is shown in  FIG. 16 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]     The imaging device in accordance with the embodiments of the invention will be described below in detail with reference to FIGS.  1  to  13 .  
         [0037]     The imaging device in accordance with a first embodiment of the invention is directed to a monitoring camera system.  
         [0038]      FIG. 1  is a diagram for showing a positional relationship between a lens  101  and a photo detector  102  in accordance with the invention. In  FIG. 1 , the lens  101  is one that has the optical aberration characteristics, through which an image around the center of a zoom is magnified and an image around the periphery thereof is compressed. The photo detector  102  is eccentrically placed so that a zoom center position for the lens  101  disagrees with or deviates from a center position for the photo detector  102 . The lens  101  is rotated about the center position for the photo detector  102 .  
         [0039]      FIG. 2  is a diagram for showing a construction of a monitoring camera system in accordance with a first embodiment of the invention. The monitoring camera system, as shown in  FIG. 2 , includes an imaging unit  201 , a transmission line  202 , and a controller  203 . An image obtained by the imaging unit  201  in the system is transferred through the transmission line  202  to the controller  203 , where the image is displayed and stored. When some operation is applied to the controller  203 , information corresponding to the operation is conveyed to the imaging unit  201  by way of the transmission line  202 . The transmission line  202  can be realized by either being wired or wireless.  
         [0040]      FIG. 3  is a block diagram for showing a construction of the imaging unit  201  in the monitoring camera system in accordance with the first embodiment. The imaging unit  201 , as shown in  FIG. 3 , contains a lens (corresponding to an optical system)  301 , a photo detector (also called an image sensor)  302 , a lens position detector  303 , a lens rotation controller  304 , a rotation driver (also called a driver)  305 , and a network  306 . The photo detector  302  may be constructed by, for example, a CMOS sensor or a CCD sensor.  
         [0041]     The lens  301  and the photo detector  302  are placed, as in  FIG. 1 , so that a zoom center position for the lens  301  disagrees with a center position for the photo detector  302 . The lens  301  is rotated about the center position for the photo detector  302 .  
         [0042]      FIG. 4  is a block diagram for showing a construction of the controller  203  in the monitoring camera system in accordance with the first embodiment. The controller  203 , as shown in  FIG. 4 , includes an image processor (also called a distortion correction circuit)  401 , an image display  402 , an image recorder  403 , an operating section (also called a modification information input section)  404 , a lens angle calculator (also called a movement quantity calculator)  405 , and a network I/F  406 .  
         [0043]     An operation of each structural element of the imaging unit  201  in the first embodiment will be explained next.  
         [0044]     An optical image derived through the lens  301  is incident upon the photo detector  302 , where the optical image is converted to an electrical signal. The electrical signal is supplied to the network I/F  306 , from which the electrical signal is output externally The lens position detector detects a relative position of a rotational direction of the lens  301  relative to the photo detector  302 , which is finished to the network I/F  306  to be output externally as lens position information.  
         [0045]     The lens rotation controller  304  controls rotations of the rotation driver  305 , based on lens angle setting information from the network I/F  306  and lens position information from the lens position detector  303  so that the lens  301  is positioned at an angle designated by the lens angle calculator  405 . The rotation driver  305  rotates the lens  301  in the direction shown in  FIG. 1  in response to the lens rotation controller  304  to vary a relative position in the rotational direction of the lens  301  and the photo detector  302 .  
         [0046]     An effect caused by changing a relative position in the rotational direction of the photo detector  302  through the rotation of the lens  301  will be explained referring to  FIGS. 5-8 .  
         [0047]      FIG. 5  shows a case in which a main object is in a right upper portion.  FIG. 6A  is a diagram for showing a positional relationship between a lens and a photo detector before the lens is rotated;  FIG. 6B  is a diagram for showing a positional relationship between the lens and the photo detector after the lens has been rotated.  FIG. 7A  shown captured image data when the positional relationship between the lens and the photo detector is shown in  FIG. 6A ;  FIG. 7B  shown captured image data when the positional relationship between the lens and the photo detector is shown in  FIG. 6B .  FIG. 8  is a diagram for showing a variation of the positional relationship between the lens and the photo detector.  
         [0048]     The zoom center position of the lens  301  disagrees with the central position of the photo detector  302  with respect to the invention. For example, when the lens  301  and the photo detector  302  are placed as shown in  FIG. 6A , an optical image incident on the photo detector  302  is shown in  FIG. 7A , in which the upper portion of the image plane can be derived with higher resolution.  
         [0049]     Where a main object is present in the right upper portion as shown in  FIG. 5 , for example, the lens  301  may be rotated about the center position of the photo detector  302  as shown in  FIG. 6B , which moves the zoom center to the right upper portion of the image plane. This produces an optical image incident upon the photo detector  302  that is shown in  FIG. 7B . Because the produced optical image has higher resolution in the right upper portion of the image plane, image processing can generate a zoom image having higher resolution in the right upper portion of the image plane.  
         [0050]     As described above, a zoom image for a peripheral portion can be obtained, because the zoom center position of the lens  301  is placed to disagree with the central position of the photo detector  302  and the lens  301  is rotated about the central position of the photo detector  302 . It is assumed in the embodiment that the lens  301 , whose zoom central position is in the middle thereof, is placed to disagree with the central position of the photo detector  302 . However, as shown in  FIG. 8 , it is of course possible to use a lens whose zoom central position is originally away from the center of the lens.  
         [0051]     An operation of each structural element in the controller  203  in accordance with the first embodiment will be described.  
         [0052]     The image processor  401  seeks a zoom central position in an image plane based on the lens position information from the network I/F  406 . Based on this, an image signal from the network I/F  406  undergoes distortion correction processing in the image processor  401  to be displayed on the image display  402  at a desired zoom magnification.  
         [0053]     The lens position information and the image signal before the distortion correction processing are stored in a storing medium in the image recorder  403 . The operating section  404  outputs zoom position setting information designated by an operator to the lens angle calculator  405 , which calculates how much the lens should be rotated in order to match the zoom central position of the lens to a designated zoom position and outputs the calculated result to the network I/F  406  as lens angle setting information.  
         [0054]     The network I/F  406  can be connected to the network I/F  306 . The image signal and lens position information from the network I/F  406  are the same as those that are applied to the network I/F  306 , respectively.  
         [0055]     As described above, the controller  203  sets the lens rotation angle to move the central position of the lens  301  at the designated zoom position. The imaging unit  201  rotates the lens  301  based on the set angle and shoots the designated position with higher resolution. Accordingly, the operator can obtain a zoomed image at an arbitrary position within a movable range by the rotation of the lens  301 .  
         [0056]     The overall system and the structure of the imaging unit of a second embodiment are identical to those of the first embodiment. Therefore, the identical portion will not be described.  
         [0057]      FIG. 9  is a block diagram for showing a construction of a controller in a monitoring camera system in accordance with a second embodiment. The controller  2203  in accordance with a second embodiment, as shown in  FIG. 9 , contains an image processor  901 , an image display  902 , a frame memory  904 , a comparator  905 , a zoom position determiner (also called an object detector)  906 , a lens angle calculator (also called a movement calculator)  907 , and a network I/F  908 .  
         [0058]     An operation of each structural element in the controller  2203  in accordance with the second embodiment will be described.  
         [0059]     An image signal from the network I/F  908  is applied to the image processor  901 , where a zoom central position in an image plane is sought based on lens position information from the network I/F  908 . The image signal receives distortion correction processing based on the zoom central position to be displayed at a desired zoom magnification on the image display  902 .  
         [0060]     The image signal and the lens position information are stored in a storing medium in the image recorder  903 . The frame memory  904  stores a past image as a reference image. The comparator  905  compares a present image with the reference image to extract a feature value variation from the two images. The zoom position determiner  906  determines the position of a main object, that is, the zoom position, based on the feature value derived from the comparator  905 . The lens angle calculator  907  calculates a lens rotation angle necessary for moving the zoom center of the lens  301  to the zoom position and outputs the calculated angle as lens angle setting information to the network I/F  908 .  
         [0061]      FIG. 10  is a diagram for explaining how a main object is detected according to a change of brilliance. The method of using a change of brilliance in the comparator  905  will be discussed as an example of extracting, referring to  FIG. 10 .  
         [0062]     An image of the monitoring camera does not change when nothing extraordinary happens. However, when the image has changed, there is a strong possibility that a main object is present there. Consequently, the position of the main object can be detected as follows as one example. A change of brilliance at the same position in an image plane, as shown in  FIG. 10 , is calculated between the reference image and the present image. A position having the largest absolute value of a change of brilliance is detected. Then, the portion having the largest change in the image plane, i.e., the position of the main object can be detected. The detection of a change of colors can detect the position of the main object instead of a change of brilliance.  
         [0063]      FIG. 11  is a diagram for explaining how a main object is detected according to a motion vector. The method of using a motion vector will be explained as another example of extracting the feature value, referring to  FIG. 11 .  
         [0064]     According to this method, a motion vector is obtained by the so-called block matching process between the reference image and the present image, a position having the largest motion vector is detected, and then a portion having had the greatest movement in the image plane, that is, the position of the main object can be detected.  
         [0065]     As explained above, in the controller  2203 , the reference image and the present image are compared to obtain the feature quality, which detects the position of the main object automatically. Since the imaging unit  2201  shoots the position with higher resolution, the zoom center is automatically moved to the position of the main object in a movable range by a rotation of the lens  301 . Accordingly, a zoom image of the main object can be obtained even if an operator is not available.  
         [0066]     An overall system of a third embodiment is identical to that of the first embodiment. Therefore, the identical portion will not be described.  
         [0067]      FIG. 12  is a block diagram for showing a construction of an imaging unit in a monitoring camera system in accordance with a third embodiment. An imaging unit  3201  in accordance with the third embodiment, as shown in  FIG. 12 , includes a lens  1201 , a photo detector  1202 , a lens position detector  1203 , a lens rotation controller (also called a rotation unit)  1204 , a rotation driver  1205 , and a network I/F  1206 .  
         [0068]     The positional relationship between the lens  1201  and the photo detector  1202  is the same as that of the first embodiment. As shown in  FIG. 1 , the lens  1201  and the photo detector  1202  are eccentrically placed so that a zoom center position for the lens  1201  disagrees with a center position for the photo detector  1202 . The lens  1201  is rotated about the center position for the photo detector  1202 .  
         [0069]      FIG. 13  is a block diagram for showing a construction of a controller in the monitoring camera system in accordance with the third embodiment. The controller  3203  of the third embodiment, as shown in  FIG. 13 , includes an image processor  1301 , an image display  1302 , an image recorder  1303 , an operating section (also called a rotation speed input section)  1304 , and a network I/F  1305 .  
         [0070]     An operation of each structural element of the imaging unit  3201  in the third embodiment will be explained next.  
         [0071]     An optical image derived through the lens  1201  is incident upon the photo detector  1202 , where the optical image is converted to an electrical signal. The electrical signal is supplied to the network I/F  1206 , from which the electrical signal is output externally. The lens position detector detects a relative position of a rotational direction of the lens  1201  relative to the photo detector  1202 , which is finished to the network I/F  1206  to be output externally as lens position information.  
         [0072]     The lens rotation controller  1204  controls rotations of the rotation driver  1205 , based on automatic rotation speed setting information from the network I/F  1206  and lens position information from the lens position detector  1203  so that the lens  1201  is rotated at a speed designated. The rotation driver  1205  rotates the lens  1201  at a constant speed, as shown in  FIG. 1 , in response to the lens rotation controller  1204 .  
         [0073]     An operation of each structural element of the controller  3203  in accordance with the third embodiment will be described.  
         [0074]     The image processor  1301  seeks the zoom central position in an image plane based on the lens position information from the network I/F  1305 . Based on this, an image signal from the network I/F  1305  undergoes distortion correction processing to be displayed on the image display  1302  at a desired zoom magnification.  
         [0075]     The lens position information and the image signal before the distortion correction processing are stored in a storing medium in the image recorder  1303 . The operating section  1304  outputs a rotation speed designated by an operator to the network I/F  1305  as automatic rotation speed setting information.  
         [0076]     As described above, the controller  3203  sets the automatic rotation speed, while the imaging unit  3201  rotates the lens  1201  at the constant speed set and circulates the zoom center for shooting. Accordingly, when the operator sets a rotation speed once, zoom images at a plurality of positions within a movable range by the rotation of the lens can be continuously obtained.  
         [0077]     The embodiments in accordance with the invention will be described in detail referring to the figures. However, the invention is not limited to the specific structure of these embodiments and includes design change within the scope of its gist. For example, the embodiments in accordance with the invention employ the structure in which the zoom center position of the lens and the center position of the photo detector are arranged eccentrically, so that rotating the lens about the center position of the photo detector produces zoom images in the peripheral portion. The lens may be moved in the X direction and/or Y direction on the plane coordinates so that zoom images in the peripheral portion are derived.  
         [0078]     The invention has the advantage that the zoom position can be changed for shooting without changing a shooting angle.  
         [0079]     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.