the enlarged screen image a depth range corresponding to the height of the enlargement specifying area that is the same depth range may be displayed in the enlarged screen image if displaying the depth range slightly wider than the height of the enlargement specifying area in the enlarged screen image as shown in fig6 b it may be desirable to display a portion indicative of the outside or the inside of the depth range actually specified may be displayed in a lighter color or displayed by lines in this case the correspondence between the depth range of the enlargement specifying area actually specified in the normal entire screen image and the depth range in the enlarged screen image can be intelligible intuitively in the foregoing specification specific embodiments of the present invention have been described however one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below accordingly the specification and figures are to be regarded in an illustrative rather than a restrictive sense and all such modifications are intended to be included within the scope of present invention the benefits advantages solutions to problems and any element s that may cause any benefit advantage or solution to occur or become more pronounced are not to be construed as a critical required or essential features or elements of any or all the claims the invention is defined solely.