Abstract:
An imaging apparatus comprises an optical magnification changing mechanism which optically changes a magnification of an image, and an electronic magnification change mechanism which reduces or expands a magnification with respect to image data by signal processing. The optical magnification changing mechanism is configured so that a magnification is discrete and a focal position changes together with a focal distance. The electronic magnification change mechanism carries out an interpolation process such that the number of pixels is increased with respect to a predetermined region of read image data during an expanding process, and carried out a process for discretely sampling a wide region as compared with a readout region obtained by the sampling provided when no magnification conversion is made, during a reducing process, thereby offsetting a change of the focal position in the optical magnification changing mechanism.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2004-316365, filed Oct. 29, 2004, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an imaging apparatus comprising an optical magnification changing mechanism and an electronic magnification change mechanism. 
   2. Description of the Related Art 
   In a video camera or a digital camera having a zoom lens system, a zoom ratio is changed by moving a zoom lens, whereby a focal distance is changed to a telephoto side or a wide-angle side while a focal position is kept constant, thereby changing an object distance. However, when configuring a small imaging element, optical zooming from the wide-angle side to the telephoto side changes not continuously but in a stepwise manner when a design is made such that a group number of lenses is decreased. 
   As shown in  FIG. 10 , an optical system includes: a first lens group  1001  having a negative refractive power, the first lens group being fixed during magnification change or focusing; and a second lens group  1002  which moves during magnification change or focusing, sequentially from an object side. In the optical system, an image surface changes in a curved shape as illustrated in the case where a position of the second lens group  1002  has been moved as illustrated. Because there is only one group of drive sections, a focus and an image magnification unavoidably change at the same time, and a configuration desired by a user cannot be always produced. 
   In the case where the object has moved to a position which corresponds to a curve indicated by a′ while focusing is carried out for an object which corresponds to a curve indicated by “a” shown in  FIG. 10 , an angle of view moves to the wide-angle side by carrying out focusing. 
   As is obvious from  FIG. 10 , a′ is close to an infinite point compared with “a”. That is, when an object of interest is distant near a wide angle, an angle of view moves to the wide-angle side due to focusing, resulting in unnatural feeling. In addition, in the case of the telephoto side, the object is made distant, whereby the angle of view becomes small. In this case, the object is made distant, whereby an expansion direction is obtained, and thus, a problem is not so serious as that at the wide-angle side. 
   On the other hand, as shown in  FIG. 12 , when lens types  1031 ,  1032 , and  1033  having positive, negative, and positive configurations, respectively, are used, the object is made distant at the wide-angle side, whereby the object is zoomed in. In some cases, a preferable result is obtained. However, at the telephoto side, the angle of view changes in a wider direction due to focusing with respect to a distant object. In this case, a framing change occurs due to lens focusing rather than framing intended by the user, and this change is unavoidably used. Further, there occurs a problem with focusing and framing of a still object as well. 
     FIG. 13  is a view adopted to explain this problem. In  FIG. 13 , as a result of that the user focuses with an attempt to image objects “a” and “b” while intending to obtain an angle of view  1022 , the angle of view  1022  appears like an element  1023 , and part of the object “b” becomes missing. 
   Furthermore, in the case of macro imaging, a focal change is large, and thus, a change of an angle of view is also large. However, a zoom optical system in which only one group shown in  FIGS. 10 to 12  is movable can reduce the number of lenses and can simplify a drive section. This makes possible a configuration of stepwise zooming while achieving downsizing and low cost. 
   Jpn. Pat. Appln. KOKAI Publication No. 6-339083 discloses that magnifications of a two-focus optical system and an optical finder with a zoom are coincided with each other by using a magnification changing process with electronic zooming. A technique of compensating for a change of an angle of view at the time of focusing by means of electronic zooming is disclosed in Jpn. Pat. Appln. KOKAI Publication Nos. 2002-182302 and 11-23949, in which unnatural feeling of the user is reduced by smoothly changing a magnification of electronic zooming to a target magnification. In addition, Jpn. Pat. Appln. KOKAI Publication No. 2003-283910 discloses that, in order to substantially match angles of view of an optical finder and imaging system while a drive control system of the optical finder and a stepwise zooming imaging lens is used in common, the stepwise zooming at a magnification, which does not exceed a magnification of the optical finder but is proximal thereto, is selected when the magnification is specified, and adjustment of an angle of view is carried out by electronic zooming. 
   On the other hand, in recent years, a video camera has incorporated an electronic zooming function for electronically changing an image magnification by using an imaging element other than such optical zooming. The electronic zooming function is a function of changing a focal distance to the telephoto side without moving a zoom lens so as to convert an imaging signal in the region which is smaller than a light receiving screen area of the imaging element to a video signal which corresponds to the light receiving screen size. 
   In a video camera having such an electronic zooming function, an imaging region which is greater than the area of the image sensor cannot be obtained. For this reason, zooming to the wide-angle side has not be successfully achieved although zooming to the telephoto side can be achieved. In contrast, there is proposed an apparatus and a method for substantially generating an image at the wide-angle side while fixing a lens by utilizing a difference between the number of pixels of the imaging element and the number of pixels of an output image. An imaging apparatus enabling such electronic zooming includes an imaging apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-295530, for example. This publication discloses a solid state imaging apparatus having photoelectric conversion pixels arranged two-dimensionally, for randomly providing an access to the photoelectric conversion pixels, the apparatus comprising first skipping means for reading out an arbitrarily specified pixel in an arbitrarily specified region and second skipping means for reading out an image region which is smaller than an image frame read out by the first skipping means, wherein the number of pixels read out by the first and second skipping means are made equal to each other. 
   Further, Jpn. Pat. Appln. KOKAI Publication No. 10-42183 discloses an imaging apparatus comprising: first adjusting means for optically changing an angle of view of an image; a second adjusting means for electrically changing an angle of view of an image; and control means for controlling the first adjusting means and the second adjusting means to determine an angle of view, wherein the control means has been configured to adjust an angle of view to a desired angle of view by the second adjusting means and substantially move the control of the angle of view from the second adjusting means to the first adjusting means while maintaining the angle of view. The imaging apparatus uses a CCD type imaging element. When electronic zooming is carried out, all pixels are read out from the CCD type imaging element, and the read-out pixels are temporarily stored in a frame memory or the like. Then, an electrical interpolating process is carried out on the basis of a pixel signal relating to a small number of pixels included in a partial area of a full angle of view. 
   Moreover, Jpn. Pat. Appln. KOKAI Publication No. 2002-314868 discloses an imaging apparatus using an imaging element which is capable of specifying a readout position and range on the imaging element by reading out a photoelectric conversion signal on the imaging element in accordance with an X-Y address system, and further, carrying out thinning-out readout based on the same number of clocks. There is disclosed that the imaging apparatus makes control by using electronic zooming means for carrying out electronic zooming for changing an isolation angle of view which is obtained as an isolation range of an imaging position and an imaging angle of view; and the electronic zooming and optical zooming in combination, whereby a zooming range of an output angle of view associated with a finally output image signal is controlled so as to be substantially wider than any of an optical zoom range which can be produced by only a change of the imaging angle of view and an electronic zoom range which can be produced by only a change of the isolation angle of view. 
   In addition, Jpn. Pat. Appln. KOKAI Publication No. 2002-249968 proposes a method of reducing distortion of an image obtained during readout with respect to distortion of an image caused by thinning-out readout by using spatial and temporal interpolation, and obtaining a high quality image, wherein a step width of the thinning-out readout can be finely produced to a certain degree. 
   BRIEF SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention, there is provided an imaging apparatus having an imaging element which converts an optically formed image to an electrical signal by means of photoelectric conversion, thereby acquiring image data, the imaging apparatus comprising: an optical magnification changing mechanism which optically changes a magnification of an image; and an electronic magnification change mechanism which reduces or expands a magnification with respect to image data by signal processing, the imaging apparatus providing a magnification-changed image according to a predetermined magnification based on the optical magnification changing mechanism and the electronic magnification change mechanism, wherein the optical magnification changing mechanism is a configuration in which a magnification is discrete and a focal position changes together with a focal distance, and the electronic magnification change mechanism carries out an interpolating process such that the number of pixels is increased with respect to a predetermined region of read image data during an expanding process; and carries out a process for discretely sampling a wide region as compared with a readout region obtained by the sampling provided when no magnification change is made, during a reducing process, and converting the sampled region data to predetermined image data by a correcting process, thereby offsetting a change of the focal position in the optical magnification changing mechanism. 
   According to a second aspect of the present invention, there is provided an imaging apparatus according to the first aspect, comprising a focus adjusting section which detects a focus state of an object and moves a movable section of the optical magnification changing mechanism according to a result of the detection. 
   According to a third aspect of the present invention, there is provided an imaging apparatus according to the first aspect, wherein the optical magnification changing mechanism includes an optical system in which a magnification is produced as x−1 at an arbitrary position in an interval at which a partial group having the largest change of a delay magnification relating to a telephoto point during movement can move from among partial groups of lens systems which moves on an optical axis. 
   According to a fourth aspect of the present invention, there is provided an imaging apparatus according to the first aspect, wherein the optical magnification changing mechanism includes an optical system which includes: a first lens group fixed during magnification change/focusing; and a second lens group that moves during magnification change or focusing sequentially from the object side, and in which a magnification is produced as x−1 at an arbitrary position in an interval at which the second lens group can move. 
   According to a fifth aspect of the present invention, there is provided an imaging apparatus according to the first aspect, wherein a total number of pixels read from the imaging element for the purpose of the expanding process by the electronic magnification change mechanism and a total number of pixels read from the imaging element for the purpose of the reducing process by the electronic magnification change mechanism are constant. 
   According to a sixth aspect of the present invention, there is provided an imaging apparatus according to the first aspect, wherein the optical magnification changing mechanism includes an optical system which includes: a first lens group having a negative refractive power, the first lens group being fixed during magnification change/focusing; and a second lens group having a positive refractive power, the second lens group moving during magnification change or focusing, sequentially from the object side, and in which a magnification is produced as x−1 at an arbitrary position in an interval at which the second lens group can move. 
   According to a seventh aspect of the present invention, there is provided an imaging apparatus according to the first aspect, wherein the optical magnification changing mechanism includes an optical system which includes: a first lens group having a negative refractive power, the first lens group being fixed during magnification change/focusing, a second lens group having a positive refractive power; the second lens group moving during magnification change or focusing; and a third lens group having a positive refractive power, the third lens group being fixed during magnification change/focusing, sequentially from the object side, and in which a magnification is produced as x−1 at an arbitrary position in an interval at which the second lens group can move. 
   According to an eighth aspect of the present invention, there is provided an imaging apparatus according to the sixth aspect, wherein, when, in one lens disposition at a wide-angle side, a focal surface corresponding to an object of interest is present to be closer than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the expanding process is carried out by the electronic magnification change mechanism in order to compensate for widening of an angle of view together with movement of the moving group caused by focusing. 
   According to a ninth aspect of the present invention, there is provided an imaging apparatus according to the seventh aspect, wherein, when, in one lens disposition at a wide-angle side, a focal surface corresponding to an object of interest is present to be closer than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the expanding process is carried out by the electronic magnification change mechanism in order to compensate for widening of an angle of view together with movement of the moving group caused by focusing. 
   According to a tenth aspect of the present invention, there is provided an imaging apparatus according to the sixth aspect, wherein, when, in one lens disposition at a wide-angle side, a focal surface corresponding to an object of interest is present to be more distant than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the reducing process is carried out by the electronic magnification change mechanism in order to compensate for high magnification of an angle of view together with movement of the moving group caused by focusing. 
   According to an eleventh aspect of the present invention, there is provided an imaging apparatus according to the sixth aspect, wherein, when, in one lens disposition at a wide-angle side, a focal surface corresponding to an object of interest is present to be more distant than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the reducing process is carried out by the electronic magnification change mechanism in order to compensate for high magnification of an angle of view together with movement of the moving group caused by focusing. 
   According to a twelfth aspect of the present invention, there is provided an imaging apparatus according to the sixth aspect, wherein, when, in one lens disposition at a high magnification side, a focal surface corresponding to an object of interest is present to be closer than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the reducing process is carried out by the electronic magnification change mechanism in order to compensate for high magnification of an angle of view together with movement of the moving group caused by focusing. 
   According to a thirteenth aspect of the present invention, there is provided an imaging apparatus according to the seventh aspect, wherein, when, in one lens disposition at a high magnification side, a focal surface corresponding to an object of interest is present to be closer than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the reducing process is carried out by the electronic magnification change mechanism in order to compensate for high magnification of an angle of view together with movement of the moving group caused by focusing. 
   According to a fourteenth aspect of the present invention, there is provided an imaging apparatus according to the sixth aspect, wherein, when, in one lens disposition at a high magnification side, a focal surface corresponding to an object of interest is present to be more distant than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the expanding process is carried out by the electronic magnification change mechanism in order to compensate for widening of an angle of view together with movement of the moving group caused by focusing. 
   According to a fifteenth aspect of the present invention, there is provided an imaging apparatus according to the seventh aspect, wherein, when, in one lens disposition at a high magnification side, a focal surface corresponding to an object of interest is present to be more distant than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the expanding process is carried out by the electronic magnification change mechanism in order to compensate for widening of an angle of view together with movement of the moving group caused by focusing. 
   According to a sixteenth aspect of the present invention, there is provided an imaging apparatus according to the first aspect, wherein the optical magnification changing mechanism includes an optical system which includes: a first lens group having a positive refractive power, the first lens group being fixed during magnification change/focusing; a second lens group having a negative refractive power, the second lens group moving during magnification change or focusing; and a third lens group having a positive refractive power, the third lens group being fixed during magnification change or focusing, and in which a magnification is produced as x−1 at an arbitrary position in an interval at which the second lens group can move. 
   According to a seventeenth aspect of the present invention, there is provided an imaging apparatus according to the twelfth aspect, wherein, when, in one lens disposition at a wide-angle side, a focal surface corresponding to an object of interest is present to be closer than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the reducing process is carried out by the electronic magnification change mechanism in order to compensate for high magnification of an angle of view together with movement of the moving group caused by focusing. 
   According to an eighteenth aspect of the present invention, there is provided an imaging apparatus according to the sixth aspect, wherein, when, in one lens disposition at a wide-angle side, a focal surface corresponding to an object of interest is present to be more distant than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, expansion is carried out by the electronic magnification change mechanism in order to compensate for widening of an angle of view together with movement of the moving group caused by focusing. 
   According to a nineteenth aspect of the present invention, there is provided an imaging apparatus according to the seventh aspect, wherein, when, in one lens disposition at a wide-angle side, a focal surface corresponding to an object of interest is present to be more distant than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, expansion is carried out by the electronic magnification change mechanism in order to compensate for widening of an angle of view together with movement of the moving group caused by focusing. 
   According to twentieth aspect of the present invention, there is provided an imaging apparatus according to the sixth aspect, wherein, when, in one lens disposition at a high magnification side, a focal surface corresponding to an object of interest is present to be closer than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, expansion is carried out by the electronic magnification change mechanism in order to compensate for widening of an angle of view together with movement of the moving group caused by focusing. 
   According to a twenty-first aspect of the present invention, there is provided an imaging apparatus according to the seventh aspect, wherein, when, in one lens disposition at a high magnification side, a focal surface corresponding to an object of interest is present to be closer than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, expansion is carried out by the electronic magnification change mechanism in order to compensate for widening of an angle of view together with movement of the moving group caused by focusing. 
   According to a twenty-second aspect of the present invention, there is provided an imaging apparatus according to the sixth aspect, wherein, when, in one lens disposition at a high magnification side, a focal surface corresponding to an object of interest is present to be more distant than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the reduction process is carried out by the electronic magnification change mechanism in order to compensate for high magnification of an angle of view together with movement of the moving group caused by focusing. 
   According to a twenty-third aspect of the present invention, there is provided an imaging apparatus according to the seventh aspect, wherein, when, in one lens disposition at a high magnification side, a focal surface corresponding to an object of interest is present to be more distant than the imaging element surface if viewed from a main plane of a final lens in the lens disposition, the reduction process is carried out by the electronic magnification change mechanism in order to compensate for high magnification of an angle of view together with movement of the moving group caused by focusing. 
   Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
       FIG. 1  is a diagram showing a configuration of an imaging apparatus to which the present invention is applied; 
       FIGS. 2A to 2C  are views for explaining a magnification change using electronic zooming; 
       FIGS. 3A to 3C  are views for explaining correction of an angle of view; 
       FIG. 4  is a diagram showing a configuration of an imaging apparatus  200  comprising a distortion correcting unit which carries out a distortion correcting process; 
       FIG. 5  is a view of thinning-out readout in which two of eight pixels is read out in each of a horizontal direction and a vertical direction; 
       FIG. 6A  is a conceptual view (example 1) of the distortion correcting process; 
       FIG. 6B  is a conceptual view (example 2) of the distortion correcting process; 
       FIG. 7  is a diagram showing a pipeline configuration of the thinning-out readout process; 
       FIG. 8  shows an operation (state transition) of a pipeline process of a filter processing section  142  shown in  FIG. 4 ; 
       FIG. 9A  is a view (example 1) schematically showing how a reference position is shifted in a readout range in repetitive readout of 6/8 thinning-out readout; 
       FIG. 9B  is a view (example 2) schematically showing how a reference position is shifted in a readout range in repetitive readout of 6/8 thinning-out readout; 
       FIG. 10  is a view showing a conventional optical system composed of negative and positive configurations; 
       FIG. 11  is a view showing a conventional optical system composed of negative, positive, and positive configurations; 
       FIG. 12  is a view showing a conventional optical system composed of positive, negative, and positive configurations; and 
       FIG. 13  is a view for explaining a problem with a conventional optical system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.  FIG. 1  is a diagram showing a configuration of an imaging apparatus to which the present invention is applied, wherein the imaging apparatus includes an imaging system having optical zooming and a signal processing system for electronically changing a magnification. Movement of a magnification changing optical system  101  is controlled by a lens movement control system  108 , thereby changing an image forming magnification on an imager  102  and carrying out optical zooming. In addition, a filter process in the case where a demosaicing process (full coloring) at a demosaicing processing/filter processing section and thinning out readout as described later have been carried out is carried out for an image signal photoelectrically converted by the imager  102 . The filter-processed image data is stored in an image memory  104 . A magnification changing processing section  105  carries out a magnification changing process in accordance with a technique such as linear interpolation by using the image data recorded in the image memory  104 . 
   Thereafter, the image data is transmitted to a display/recording section  106  to be displayed/recorded. A readout region setting section  107 , as described later, is a section which reads out a predetermined range from among the pixels on the imager  102  in accordance with a predetermined readout rule. The readout region setting section  107  further provides a signal relating to information on magnification change to the lens movement control system  108 , the demosaicing processing/filter processing section  103 , and the imager  102 . 
     FIGS. 2A to 2C  are views for explaining a magnification change using electronic zooming.  FIG. 2A  shows an example of a reduction process,  FIG. 2B  shows an example of full pixel readout, and  FIG. 2C  shows an example of an expansion process. 
   In the full pixel readout shown in  FIG. 2B , all pixels of a region on the imager  102  are sampled, and an image is formed without carrying out electronic magnification change. In contrast, in the thinning-out readout shown in  FIG. 2A , pixel data contained in a readout region  201  which is wider than a readout region  203  shown in  FIG. 2B  is read out by thinning-out, and an image of size which is equal to that shown in  FIG. 2B  is finally formed. Therefore, this implies that the reduction process is carried out in the sampling shown in  FIG. 2A . 
   The filter processing section  103  shown in  FIG. 1  carries out correction of as image distortion or the like in the case where thinning-out readout has been carried out. 
   In the process shown in  FIG. 2C , full pixel readout similar to that shown in  FIG. 2B  is carried out, and then, magnification change is made by the magnification change section  105  shown in  FIG. 1 . An image of size which is equal to that of an image generated by carrying out full pixel readout is formed from a partial region of the image data obtained by the full pixel readout shown in  FIG. 2B . Therefore, this implies that the expansion process is carried out in the process shown in  FIG. 2C . 
   As explained with respect to  FIG. 13 , in the optical system shown in  FIG. 11 , there has been a problem that a focus and an angle of view change at the same time. In addition to the optical system shown in  FIG. 11 , an optical magnification changing mechanism having a three-group configuration as shown in  FIG. 12  is provided. The mechanism is an optical system which includes a first lens group  1031  having a positive refractive power, the first lens group being fixed during magnification change and focusing; a second lens group  1032  having a negative refractive power, the second lens group moving during magnification change or focusing; and a third lens group  1033  having a positive refractive power, the third group force being fixed during magnification change or focusing, from an object side. In the optical system, a telephoto focal surface moves as illustrated as the second lens group moves. Therefore, in this case as well, when a design has been made so that a telephoto image is formed on an image surface at a certain zoom magnification (focal distance) A, there are only a maximum of two zoom magnifications including A, such that the telephoto image is formed on the image surface, in the same manner as that described above. Similarly, there are only a maximum of two zoom magnifications such that an image can be focused at a predetermined focal distance, and an angle of view also changes during focusing, as described above. 
   Then, correction of an angle of view is carried out so as to cancel a magnification changed by focusing in accordance with an electronic magnification changing method described below with reference to  FIG. 3 . 
     FIG. 3A  shows a method of storing and outputting pixels of 0.3 M (VGA) in a memory by means of thinning-out readout from pixels of 0.37 M in an imager of 1.3 M, wherein the current state corresponds to a wide angle (WIDE) state.  FIG. 3B  shows a method of reading out one pixel from pixels of 0.3 M in an imager of 1.3 M, and storing and outputting it in a memory as is.  FIG. 3C  shows a method of reading out one pixel from pixels of 0.3 M in an imager of 1.3 M, storing it in a memory, reading out data of 0.25 M therefrom, and expanding and outputting the data to 0.3 M, wherein the current state corresponds to a telephoto (TELE) state. 
   That is, when an angle of view has been changed from ×0.9 ( FIG. 3C ) to ×1 ( FIG. 3B ), and then, to ×1.1 ( FIG. 3A ) by means of focusing, an electronic magnification changing process is carried out so as to expand an image reduced at the time of ×0.9 and so as to reduce an image expanded at ×1.1. 
   When, in the configuration shown in  FIG. 1 , a directional focus of an angle of view which changes due to focusing from a state of a lens control system has been moved to a wide angle direction, an expanding process is carried out in a direction in which such movement is eliminated. Conversely, when the above focus has been moved to an expanding direction, a reducing process is carried out so as to eliminate such movement. 
   Therefore, in the case where an object is distant at the wide-angle side in a negative and positive configuration as shown in  FIG. 11  or in a positive, negative, and positive configuration as shown in  FIG. 12 , an image expanding process is carried out so as to restrict a change of an angle of view. At the telephoto side, conversely, a change of an angle of view is compensated for by the reducing process. In this case, conversely, at the wide side, an angle of view changes in a narrower direction with respect to a distant object, and, at the telephoto side, this angle is compensated for because it changes at a wider angle. 
   In addition, an algorithm of angle-of-view compensation can be selectively stopped for a user who does not intend to carry out such a process. 
   In the meantime, when an electronic magnification change is made, the expanding process and reducing process are carried out. In the case of carrying out the reducing process, a region of the pixels whose number is larger than that of images to be output is acquired on the imager  102 , and an output image is generated by a magnification changing process such as an interpolating process. In this case, a total clock number of the acquired pixels is different depending on the size of an area to be imaged. That is, as a magnification changes to the wide-angle side, a larger number of clocks is required. In other words, as long as there occurs a use situation such that no problem occurs even if the clock number or processing time of imaging for acquiring one screen changes due to an angle of view (zooming), there is no need for carrying out readout using pixel mixing or thinning-out readout as shown in  FIG. 2 . In contrast, as shown in  FIG. 2 , only width of a readout region can be changed without changing the number of clocks by using thinning-out readout. 
   However, merely by carrying out thinning-out readout, image distortion occurs and image quality degradation is unavoidable, for example, when an inter-frame interpolation process has been carried out. A filter process is carried out such that an image produced by thinning-out readout is reduced to the minimum. 
     FIG. 4  shows a configuration of an imaging apparatus  200  comprising a distortion correcting section which carries out a distortion correcting process after carrying out thinning-out readout of a pixel on the imager  102 . The imaging apparatus  200  has: the optical magnification changing system  101  which forms an optical image of an object; and the imager  102  which outputs an image signal in a predetermined region of the optical image formed by the optical magnification changing system  101 . 
   The imager  102  has an area-shaped photoelectric converting element  222  which photoelectrically converts the optical image formed by the optical magnification changing system  101  to acquire digital image data (a set of pixel data); and a readout control section  224  which reads out by thinning-out the image data acquired by the photoelectric converting element  222  as required. 
   Further, a region setting section  132  sets which region of the imager  102  is output as an image. A readout rule selecting section  234  is a section which selects a readout rule on the basis of the set readout region. A readout phase control section  230  is a section which shifts a reference position of a range of pixel data read out by the readout control section  224 . 
   Here, in the case where a difference is present between a size of an image to be output and a size of a region on the imager  102 , the image on the imager  102  is read out by thinning-out, and further, is subjected to distortion correction by a distortion correcting process section  140 . The distortion correcting section  140  has a filter coefficient setting section  144  and a filter processing section  142 , the filter coefficient setting section  144  having a LUT storage section  146  and a filter coefficient selecting section  148 . 
   Now, a distortion correcting process for thinning-out readout will be described in detail.  FIG. 5  shows an example of thinning-out readout in which two of eight pixels is read out in each of a horizontal direction and a vertical direction. A step is produced on an image in the readout method according to the example of  FIG. 5 . Therefore, as shown in  FIG. 6A , let us consider an operation of padding a skipped pixel in accordance with linear interpolation using the peripheral pixels, thereby producing eight-pixel data, and changing the produced data to six-pixel data in accordance with linear interpolation. That is, as shown in  FIG. 6B , a process for changing samplings at non-uniform pixel intervals to uniform samplings is carried out. 
   Here, let us consider readout of one line with thinning-out.  FIG. 7  shows a pipeline configuration of the thinning-out readout process, wherein the pipeline configuration is composed of a shift register  162 , a pair of selectors  164  and  166 , a pair of multipliers  174  and  176 , and an adder  178 . The pixel positions read out with the top left shown in  FIG. 5  being a reference are Ri 0 , Gi 1 , Ri 2 , Gi 3 , Ri 4 , Gi 5 , Ri 6 , and Gi 7 , and subsequently, repetition in the same rule is achieved. Matrix expression of distortion correction (change) in this example is obtained by: 
   
     
       
         
           
             
               
                 
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   In  FIG. 7 , the shift register  162  shifts maintained image data a one by one basis in a right direction every one operation that follows a clock. The selector  164  selects either of a first item and a third item from among five items of pixel data i 0  to i 5  adjacent thereto, the pixel data being maintained in the shift register  162 . In addition, the selector  166  selects either of a third item and a fifth item from among five items of pixel data i 0  to i 5  adjacent to each other, the pixel data being maintained in the shift register  162  in accordance with a selection signal  2 . 
   The multiplexer  174  multiplies a coefficient k 1  of a weighted addition for an output d 1  of the selector  164 ; the multiplier  176  multiplies a coefficient k 2  of a weighted addition for an output d 2  of the selector  166 ; and the adder  178  adds an output of a multiplier  194  and an output of a multiplexer  196 . 
     FIG. 8  represents an operation (state transition) of a pipeline process at the filter processing section  142  shown in  FIG. 4 . 
   A pixel data train (i 0 , i 1 , i 2 , . . . ) supplied to the shift register  162  is shifted in the right direction every one operation that follows a clock while C 1 =i 0 , C 2 =i 1 , C 3 =i 2 , . . . are defined as an initial state. Concurrently, the selector  164  selects C 1  when s 1  is 0 (therefore, d 1 =C 1  is obtained), and selects C 3  when s 1  is 1 (therefore, d 1 =C 3  is obtained). On the other hand, the selector  166  selects C 3  when s 2  is 1, and selects C 5  when s 2  is 1 (therefore, d 2 =C 5  is obtained.) 
   In addition, in synchronism with a clock, the coefficient k 1  and the coefficient k 2  are supplied to the multiplexer  174  and the multiplexer  176 , respectively, from the memory contained in the filter coefficient setting section  144  shown in  FIG. 4 . Therefore, out=k 1  ×d 1  +k 2  ×d 2  is output from the adder  178 . 
   As is evident from  FIG. 8 , a pipeline process including a pixel phase operation (selector changing) is carried out by carrying out shifting of serial data; selector switching in accordance with a state of s 1  and s 2  ; outputting the weight coefficients k 1  and k 2  in accordance with the thinning-out rule shown in formula (2); and a weighting additive computation in synchronism with each other. 
   An imaging apparatus according to the present embodiment assumes a case of a mobile image as an input image, so that an interlace operation interpolates pixel data which are missing each other between the two continuous frames so as to interpolate pixel data which is missing each other between two fields. For example, the readout phase control section  230  shifts a reference position of a range of the pixel data read out by the readout control section  224  such that image data in a plurality of continuous frames does not have these items of the entirely missing pixel data. It is preferable that a shift quantity be in order of two to eight pixels. 
     FIGS. 9A and 9B  schematically shows how a reference position is shifted within the readout range in repetitive readout of 6/8 thinning-out readout. In  FIGS. 9A and 9B , [x, y] represents a pixel position of a pixel array of a photoelectric converting element  222  and (x, y) represents pixel data in the readout range. 
   As shown in  FIGS. 9A and 9B , the number of pixels of the photoelectric converting element  222  can be represented as [0, 0], and the position of the bottom right pixel can be represented as [k, 1]. In addition, the number of pixels in the readout range of one frame are “m” pixels in a horizontal direction and “n” pixels in a vertical direction, respectively. Therefore, the readout start position at the top left of the frame can be represented as (0, 0), and the readout end position at the bottom right thereof can be represented as (m, n). The readout range of the frame shown in  FIG. 9B  is shifted by +2 pixels in the horizontal direction and +2 pixels in the vertical direction with respect to the readout range of the frame shown in  FIG. 9A . 
   In the frame shown in  FIG. 9A , the top left readout start position (0, 0) coincides with the top left pixel position [0, 0] of the photoelectric converting element  222 . Namely,
 
(0, 0)=[0, 0]  (3)
 
is obtained. In addition, the readout end position (m, n) is:
 
( m, n )=[ k− 1,  i− 2]  (4)
 
   On the other hand, in the frame shown in  FIG. 9B , the top left readout start position is:
 
(0, 0)=[2, 2]  (5)
 
In addition, the readout end position is:
 
(m, n)=[k, 1]  (6)
 
   An image range selection processing section  240  selects a range common to the frame shown in  FIG. 9A  and the frame shown in  FIG. 9B . That is, a range of a rectangle with (2, 2) and (m, n) being diagonal apexes is selected with respect to the frame shown in  FIG. 9B , and a range of a rectangle with (0, 0) to (m−2, n−2) being diagonal apexes is selected with respect to the frame shown in  FIG. 9A . The range selected by the image range selection processing section  240  always has (m−2)×(n−2) items of pixel data. 
   In addition, in consideration of a range to be cropped in advance, it is necessary to configure an image size and a phase shift component of an output for a total number of images read out from the imager  102 . The image range selection processing section  240  changes a cropping range on the basis of information on the readout start position. 
   Frame memories  252 ,  254 , and  256  are First-In First-Out(FIFO) memories, and an inter-frame computation processing section  260  generates an output image by using the data contained in a first frame which are present in their frame memories  252 ,  254 , and  256  and the pixels at the same positions in a second frame which is different from the first frame. 
   For example, in the case of two frames, a composite image out(i, j) is:
 
out( i, j )=0.5 l ( k, i, j )+0.5 l ( k− 1 , i, j )  (7)
 
   Here, i, j represents a pixel position, and l (k, i, j) denotes intensity of an image signal at the pixel positions i, j of a k-th frame. 
   In addition, in the case of three frames, by using a weighted component, a composite image out(i, j) is obtained as follows: 
   
     
       
         
           
             
               
                 
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   Image data read out in the readout rules different from between a plurality of frames, with respect to the image data being subjected to a distortion correction filter process, a position shift of an image between frames is corrected by the image range selection processing section  240 . Data for a predetermined frame is accumulated by the frame memories  252 ,  254 , and  256 ; inter-frame computation is carried out by an inter-frame computation processing section  250 ; and predetermined processing operation is carried out by an image signal processing section  152 . Then, data is output to an image display section  154  and an image recording section  156 . By carrying out inter-frame interpolation, in addition to advantage effect of distortion correction, an image smoothing effect using a low path can be obtained. 
   In this manner, a change of an angle of view produced when carrying out focusing in an imaging apparatus comprising an optical magnification changing mechanism in which a focal position changes is compensated for together with a focal distance by means of an expansion/reduction electronic magnification changing process, thereby enabling imaging at an angle of view intended by a user and making it possible to suppress a change of the angle of view caused by movement of an object.