CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority under 35 U.S.C. §119 of Japanese Application No. 2014-145814, filed on Jul. 16, 2014, the disclosure of which is expressly incorporated by reference herein in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an image measuring apparatus. Specifically, the present invention relates to a graphical user interface (GUI) supporting an operation by a user to switch between lenses in an image measuring apparatus making use of a microscope that can switch between lenses of various types and magnifications. 
         [0004]    2. Description of Related Art 
         [0005]    Image measuring apparatuses are known which perform shape observation and dimension measurements of a work piece (measured object)  1  (for example, Japanese Patent No. 3917652, Japanese Patent Laid-open Publication No. 2001-281554).  FIG. 14  illustrates a system configuration of an image measuring apparatus. The image measuring apparatus includes an image measuring device (image measurer)  2  and a control computer  50 . The image measuring device  2  is equivalent to a microscope. The image measuring device  2  includes a base portion  10 , a stage  12 , a lens assembly  17 , and a CCD camera  3 . The base portion  10  includes a foundation  11 , and a support rail  16  rising to extend upward from the foundation  11 . The work piece (measured object)  1  is placed on the stage  12 , which is capable of displacement in X, Y, and rotational directions using an X direction adjustment handle  13 , a Y direction adjustment handle  14 , and a stage rotation knob  15 , respectively. 
         [0006]    The lens assembly  17  is supported by the support rail  16  so as to be capable of vertical movement. The lens assembly  17  includes a revolver  18  on a side facing the work piece (measured object)  1 , and is configured such that a field lens can be attached and detached with respect to each of a plurality of attachment slots on the revolver  18 . In this example, the revolver  18  has four slots. The revolver  18  is rotated electrically or manually, thereby switching between the field lenses. In this example, four field lenses  19   a,    19   b,    19   c,  and  19   d  each having a different magnification power are mounted to the revolver  18 . 
         [0007]    The lens assembly  17  includes an eyepiece  20  on an upper portion thereof, which the lens assembly  17  connects optically to the field lenses  19   a  to  19   d  via an upright trinocular barrel  21 . The lens assembly  17  is capable of adjusting vertical movement through manual operation of the handles  22  and  23 , or can be electrically driven. 
         [0008]    The CCD camera  3  is mounted on the upper portion of the upright trinocular barrel  21 . 
         [0009]    The control computer  50  includes a host computer  60  and an inputter/outputter  70 . The inputter/outputter  70  includes a touch panel display  71 , a keyboard  72 , and a mouse  73 . 
         [0010]    The host computer  60  is a computer configured by a CPU and memory. The host computer  60  processes image data obtained by the CCD camera  3  and displays results of the processing on the touch panel display  71 . In addition, the host computer  60  switches between the field lenses ( 19   a  to  19   d ) by rotating the revolver  18  in response to an operation input by a user, performs focusing, and the like. 
         [0011]    When observing a shape and measuring dimensions of a work piece (measured object) using image measurement, the user must specify which lens is currently being used and instruct the host computer  60  of this information (make a setting on the host computer  60 ). This is because when a magnification power or the like of the lens currently in use is not specified, the host computer  60  cannot calculate the dimensions of the work piece from the image data. 
         [0012]    Given this, a GUI screen such as that shown in  FIG. 15 , for example, is provided to the user as a screen to input and define lens information. This GUI screen performs display on the touch panel display  71  according to display control performed by the host computer  60 . The user performs an information input or selection operation on the GUI screen by performing a touch operation on the touch panel display  71 , or by performing keyboard input or mouse operation. 
         [0013]    A configuration of the GUI screen shown in  FIG. 15  is briefly described. The GUI screen shown in  FIG. 15  is referred to as a “lens selection screen  200 .” The lens selection screen  200  includes a revolver information display region  210  and a lens information display region  250 . The revolver information display region  210  displays which lens is mounted to which slot in the revolver  18 . The letters “A,” “B,” “C,” and “D” arranged in a vertical line on a left side of the revolver information display region  210  are identifiers ( 220 ) for each slot in the revolver  18 . Naturally, the identifiers “A,” “B,” “C,” and “D” for each slot are engraved into the revolver  18 , or the like, so as to enable the user to know the identifier for each slot. 
         [0014]    Beside each identifier is a lens name display frame  230  corresponding to each identifier. The lens name display frame  230  displays a name (type) of the lens mounted to the corresponding slot in the revolver  18 . The user may directly enter the name into the lens name display frame  230  by typing, or may select the lens name from a list provided in a drop-down format. Although not illustrated in detail, when the user clicks on a downward triangle  231  on a right end of each lens name display frame  230 , a list of lens names available for use is displayed as a drop-down list. Typically, the user has a stock of various kinds of lenses readily available. When performing image measurement of the work piece, the user selects several (for example, four) lenses to be used in the image measurement from among the stock of readily available lenses and mounts each lens to a slot in the revolver  18 . When each lens is mounted to a slot in the revolver  18 , the lens name display frame  230  displays which lens is mounted to which slot. 
         [0015]    A radio button  240  corresponding to the identifier  220  of each slot is provided between the slot identifier  220  and the lens name display frame  230 . The radio button  240  in an ON state (black dot in the center of the circle) represents the slot that is linked to the CCD camera  3 , out of all the slots in the revolver  18 . In other words, the radio button  240  in the ON state indicates the lens currently being used. The user can switch the lens being used by switching the selection of the radio button  240 . 
         [0016]    Information for the lens currently being used is displayed in the lens information display region  250 . In addition to lens information such as a lens name ( 251 ) and a serial number ( 252 ), the lens information display region  250  also displays optical performance information ( 260 ) and calibration value information ( 270 ). The optical performance information  260  includes magnification power  261  and numerical aperture  262 . The calibration value information  270  includes actual length per pixel ( 271 ) and optical axis offset (inclination of the optical axis) ( 272 ). These calibration values are obtained ahead of time, and are input into the host computer  60  and stored. (Although not described in detail, a separate GUI screen may be provided in which the calibration values for each lens are found efficiently, then entered and stored.) When the user selects the lens (changes any of the radio buttons  240  to ON), the host computer  60  retrieves the corresponding lens calibration values from the memory and displays the values in the lens information display region  250 . 
         [0017]    In a case where the revolver  18  is electric, the revolver  18  rotates automatically in accordance with the lens selection. For example, when the user presses a “CONFIRM” button  201 , the revolver  18  automatically rotates such that the lens selected by the radio button  240  becomes usable. 
         [0018]    When performing image measurement, correctly setting the calibration values for the lens is essential. When the calibration values are incorrect, an incorrect measured value may be output. Accordingly, although of course the correct calibration values for each lens are found, maintenance and oversight are required to ensure the calibration values remain correct. 
         [0019]    In this regard, a scenario is presented in which an image measuring apparatus is used. A user of the image measuring apparatus may be a parts processing company or a research laboratory, for example, where a plurality of people often share use of a single image measuring apparatus. There may be cases where a task of calibrating each lens is always performed by a designated person in charge of calibration, or where the task of calibrating each lens is performed by each user whenever required. In either such case, however, it may be difficult for the various users to know whether calibration has been performed, or whether the registered calibration values are valid. When a lens maintenance log or the like is prepared, the user may be able to tell who performed calibration and when by referring to the log each time. However, this is rather burdensome. In the case of a user who has not mastered using the image measuring apparatus, the user may inadvertently use a lens with incorrect calibration values. Such a mistake may be treated as an erroneous operation for which the user is responsible. However, when the user continues on to subsequent stages of a process based on the incorrect measured values, results are produced which are not favorable for the user, and therefore a mechanism to prevent such erroneous operation from occurring in the first place is still beneficial. 
       SUMMARY OF THE INVENTION 
       [0020]    An advantage of the present invention is to provide an image measuring apparatus that is easier to use and more user-friendly. More specifically, the present invention provides an image measuring apparatus GUI program which achieves an image measuring apparatus that is easier to use and more user-friendly. 
         [0021]    An image measuring apparatus according to the present invention includes an image measuring device capable of switching between one of a type of lens and a magnification power, the image measuring device obtaining an image of a measured object; a display displaying the image obtained by the image measuring device and providing an operation screen to a user; and a controller controlling operations of the image measuring device and the display. A calibration value and an expiration date for the calibration value are recorded by the controller for one of each type of lens and each magnification power. The controller communicates to the user, using the display, that one of the lens and the magnification power has an expired calibration value. 
         [0022]    In the present invention, when one of the lens and the magnification power having the expired calibration value is selected by the user, the controller preferably communicates to the user that the calibration value is expired. 
         [0023]    In the present invention, the operation screen preferably includes a directory display region providing a directory display of one of a lens and a magnification power that can be used in the image measuring device; and a mounted lens display region displaying one of the lens and the magnification power mounted to the image measuring device. When the controller detects that an image, symbol, or sequence of letters corresponding to one of the lens and the magnification power displayed in the directory display region has been moved to the mounted lens display region by a drag-and-drop operation, the controller preferably registers the one of the lens and the magnification power as the mounted lens. Moreover, in a case where the one of the lens and the magnification power has an expired calibration value, the controller preferably performs a display to communicate to the user that the calibration value is expired. 
         [0024]    In the present invention, the operation screen preferably includes a directory display region providing a directory display of one of a lens and a magnification power that can be used in the image measuring device; and a mounted lens display region displaying one of the lens and the magnification power mounted to the image measuring device. In a case where one of the lens and the magnification power has an expired calibration value, the controller preferably communicates to the user in the directory display region, using the display, that the one of the lens and the magnification power has an expired calibration value. 
         [0025]    In the present invention, the image measuring apparatus preferably communicates to the user, using highlighting or a message displayed on the display, that one of the lens and the magnification power has an expired calibration value. 
         [0026]    In the present invention, a thumbnail is preferably displayed on the display for one of each type of lens and each magnification power. Each thumbnail preferably displays one of an image in which a size of a prearranged reference pattern is adjusted to match each magnification power, and an image in which a size of an image currently being captured is adjusted to match each magnification power. 
         [0027]    An image measuring apparatus GUI program according to the present invention for an image measuring apparatus that includes: an image measuring device capable of switching between one of a type of lens and a magnification power, the image measuring device obtaining an image of a measured object; a display displaying the image obtained by the image measuring device and providing an operation screen to a user; and a controller controlling operations of the image measuring device and the display. The image measuring apparatus GUI program performs display control on the display by being programmed into the controller of the image measuring apparatus. The program retrieves from the controller information in which a calibration value and an expiration date of the calibration value are recorded for one of each type of lens and each magnification power, and communicates to the user, using the display, that one of the lens and the magnification power has an expired calibration value. 
         [0028]    According to the present invention, an image measuring apparatus that is easier to use and more user-friendly can be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
           [0030]      FIG. 1  illustrates an exemplary lens information table; 
           [0031]      FIG. 2  illustrates an exemplary configuration of a lens selection GUI screen; 
           [0032]      FIG. 3  illustrates an exemplary operation on the lens selection GUI screen; 
           [0033]      FIG. 4  illustrates the exemplary configuration of the lens selection GUI screen; 
           [0034]      FIG. 5  illustrates the exemplary configuration of the lens selection GUI screen; 
           [0035]      FIG. 6  illustrates an exemplary operation on the lens selection GUI screen; 
           [0036]      FIG. 7  illustrates a variation of a display on the lens selection GUI screen; 
           [0037]      FIG. 8  illustrates a variation of the display on the lens selection GUI screen; 
           [0038]      FIG. 9  illustrates a first modification; 
           [0039]      FIG. 10  illustrates a second modification; 
           [0040]      FIG. 11  illustrates an exemplary lens information table according to a third modification; 
           [0041]      FIG. 12  illustrates the exemplary lens selection GUI screen according to the third modification; 
           [0042]      FIG. 13  illustrates a fourth modification; 
           [0043]      FIG. 14  illustrates a system configuration of an image measuring apparatus according to a conventional example; and 
           [0044]      FIG. 15  illustrates an exemplary screen in a GUI according to a conventional example. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the forms of the present invention may be embodied in practice. 
       First Embodiment 
       [0046]    A description of the embodiment of the present invention is given with reference to the drawings and to the reference numerals assigned to each component in the drawings. A first embodiment of the present invention is described with reference to the drawings. A screen in a GUI utilized in a lens selection operation is described as the first embodiment with reference to  FIGS. 2 to 8 . The GUI screen is referred to as a lens selection GUI screen. The lens selection GUI screen performs display operations, described below, which are achieved by an image measuring apparatus GUI program stored in a host computer  60 . The host computer  60  includes a CPU and a memory, and performs display control of the lens selection GUI screen by running the image measuring apparatus GUI program stored in the memory. 
         [0047]    Prior to describing the display operations of the lens selection GUI screen, a lens information table required during display is described.  FIG. 1  illustrates an exemplary lens information table. Numbers printed outside a left column of the table are presented to facilitate description and need not be included. In order from left to right, “lens type,” “lens information,” “calibration values,” “calibrator,” “calibration date,” and “expiration date” can be recorded in the table. The table further includes a column recording “revolver slot” and a “flag” column to indicate which lens is in use. 
         [0048]    “Lens type” is substantially synonymous with a lens name. “Lens information” refers to optical information of the lens, such as magnification power, numerical aperture, signal-to-noise (SN) ratio, and the like. This information is provided by a lens manufacturer. The “lens type” and “lens information” may be registered for a stock of lenses readily available to a user, as well as for all lenses capable of being used in an image measuring device  2 . 
         [0049]    “Calibration values” is data for calibration values found for each lens. In this example, the calibration values are an actual length per pixel. When finding the calibration values, the image measuring device  2  is actually set up and a calibration task is performed with the lens being calibrated mounted to a revolver  18 . When the calibration values are found, the information is registered in the lens information table. At that point, a name of a person performing the calibration and the date when the calibration was performed are registered together with the calibration values. An expiration date for the calibration is also registered. 
         [0050]    Calibration must be performed on a regular schedule, e.g., once a month, every six months, or every year. In the example shown in  FIG. 1 , the expiration period of the calibration is set to one year. The fifth lens from the top is treated as expired. (The relevant portion is circled in the table shown in  FIG. 1  for ease of reference.) Moreover, no calibration values have been entered for the eighth or ninth lenses. These conditions may suggest the following scenario, for example. Although the eighth and ninth lenses are lenses that can be used with the image measuring device  2  and are sold by lens manufacturers, the user has not yet obtained the lenses and so there are no calibration values for either lens. 
         [0051]    The column recording “revolver slot” indicates to which revolver slot a particular lens has been mounted. The example illustrated in  FIG. 1  shows that a first lens is mounted in slot A, a second lens is mounted in slot B, and a third lens is mounted in slot C. The user registers this information in the lens information table after attaching (mounting) the lens to the revolver slot. A registration operation is executed on the lens selection GUI screen. This operation is described later. 
         [0052]    The “flag” column indicating which lens is in use contains a flag identifying which lens is currently in use. When the user switches the lens in use, that information is registered in the lens information table. The registration operation is executed on the lens selection GUI screen, and is described later. 
         [0053]    Next, display operations of the lens selection GUI screen according to the first embodiment are described with reference to  FIGS. 2 to 8 . In order to facilitate the description that follows, two points are to be raised at this juncture regarding characteristic advantages of the first embodiment. However, the advantages of the first embodiment are naturally not limited to these.
   (1) When attempting to register a lens with expired calibration values as a mounted lens, the user receives a warning with an easily understood color (highlighting) or the like. As a result, a misoperation in which a lens having incorrect calibration values is used in a measurement can be prevented from occurring.   (2) Displaying a thumbnail (reduced image) corresponding to each lens facilitates intuitive understanding of an observation field of each lens. As a result, measurement efficiency can be expected to improve drastically.   
 
         [0056]    A detailed description now follows.  FIG. 2  illustrates an exemplary configuration of a lens selection GUI screen  300 . In  FIG. 2 , the lens selection GUI screen  300  is broadly divided into three regions. A bottom, left-edge region is a “display format selection region  310 ;” a region occupying a majority of a bottom portion (except the portion occupied by the “display format selection region  310 ”) is a “directory display region  320 ;” and a top portion is a “mounted lens display region  330 .” 
         [0057]    Three icons  311 ,  312 , and  313  are presented in the display format selection region  310  enabling selection of a display format for the directory display region  320 . The three icons  311 ,  312 , and  313  are aligned vertically and each icon is, in order from top to bottom, a thumbnail compendium format icon  311 , a detailed display format icon  312 , and a simplified display format icon  313 .  FIG. 2  illustrates a state where the thumbnail compendium format ( 311 ) is selected. Accordingly, a thumbnail compendium is displayed in the directory display region  320 . When the detailed display format ( 312 ) is selected, the screen resembles that shown in  FIG. 7 , and when the simplified display format ( 313 ) is selected, the screen resembles that shown in  FIG. 8 . This will be discussed below. Each of the icons  311 ,  312 , and  313  is designed to match the respective display format and to be readily understood. 
         [0058]    A plurality of lenses are displayed in a compendium format in the directory display region  320 . In addition to the stock of lenses readily available to the user, candidate lenses provided by a manufacturer and capable of being used in the image measuring device  2  are displayed in a compendium. Specifically, the lens types registered in the lens information table ( FIG. 1 ) are all displayed in the directory display region. In a case where a single screen is insufficient to display all lenses, the directory display region is configured such that the remaining lens information is displayed by scrolling. 
         [0059]    In  FIG. 2 , the thumbnail compendium format ( 311 ) is selected. Therefore, a thumbnail compendium is displayed. In the thumbnail compendium format, a thumbnail (reduced image) is displayed, and a lens name is displayed below each thumbnail. The thumbnail is a graphic image corresponding to a magnification power of the lens. The graphic displayed as the thumbnail is an image where a prearranged pattern is expanded or reduced in accordance with the magnification power of each lens. In the example of  FIG. 1 , a pattern of dots arranged in a grid is used as the reference pattern, and a size of the pattern is adjusted to conform with the magnification power of each lens. Looking at the thumbnail (reduced image), the magnification power of the lens can be intuitively understood. 
         [0060]    The lenses attached (mounted) to the revolver  18  are displayed in the mounted lens display region  330 . The revolver  18  includes four slots A, B, C, and D. Therefore, the mounted lens display region  330  also includes four display frames corresponding to A, B, C, and D. In the beginning of image measurement, the user selects several readily available lenses from the stock of lenses to be used in measurement (observation) and attaches the lenses to the revolver  18 . The user registers this information in the lens information table after attaching (mounting) the lens to the revolver slot. The registration is performed as follows on the lens selection GUI screen  300 . In this example, a lens named “M Plan Apo 2×” is mounted to slot A. The user locates “M Plan Apo 2×” in the directory display region. As shown in  FIG. 3 , the user drags and drops the thumbnail for “M Plan Apo 2×” into the display frame “A” in the mounted lens display region  330 . 
         [0061]    As a result, as shown in  FIG. 3 , the thumbnail for “M Plan Apo 2×” is displayed in the display frame “A” in the mounted lens display region  330 . An emphasis display is simultaneously placed on “M Plan Apo 2×” in the directory display region  320  to convey that “M Plan Apo 2×” has been registered (see  FIG. 4 ). Examples of the emphasis display may include thickening the frame around the thumbnail for “M Plan Apo 2×,” changing its color, or changing a background color. The fact that “M Plan Apo 2×” has been mounted in slot “A” is then registered in the lens information table (see  FIG. 1 ). 
         [0062]      FIG. 4  illustrates a state where “M Plan Apo 5×” has been registered to the lens slot “B” and “M Plan Apo 10×” has been registered to the lens slot “C” in a similar manner. 
         [0063]    A case is now considered where the user also wishes to use “M Plan Apo 50×” and has mounted “M Plan Apo 50×” to slot “D” of the revolver  18 . The user finds “M Plan Apo 50×” in the directory display region  320 , then drags and drops it into the display frame “D” in the mounted lens display region  330 . At this point, when the host computer  60  detects the drag-and-drop operation by the user, “M Plan Apo 50×” is displayed in the display frame “D” in the mounted lens display region  330  and slot “D” is registered to “M Plan Apo 50×” in the lens information table ( FIG. 1 ). However, the calibration of “M Plan Apo 50×” is expired. In such a case where a lens having an expired calibration is registered in the mounted lens display region  330 , an emphasis display is provided indicating that it is expired. Examples of the emphasis display may include highlighting or a message display. In the example shown in  FIG. 5 , in addition to emphasis using a background color, a message is also displayed reading “Please calibrate prior to use.” Examples of highlighting may include emphasis display of a portion having symbols or a sequence of letters being displayed with inverted colors, a background color being changed, or the like. 
         [0064]    Measurement is performed while the user switches between the four lenses mounted to the revolver  18 . The user selects the lens to be used from among the registered lenses in the mounted lens display region  330 . For example, the user taps twice in succession on one of the thumbnails displayed in the mounted lens display region  330  ( FIG. 6 ). The revolver  18  then automatically rotates using electric drive, and the selected lens is placed in a state ready for use. In addition, an emphasis display indicating the lens that is currently in use is provided to the mounted lens display region  330 . Examples of the emphasis display may include changing the background color.  FIG. 6  illustrates a state where the “M Plan Apo 5×” mounted to slot “B” is selected for use. 
       (Variation of Display Formats) 
       [0065]      FIGS. 2 to 6  illustrate an exemplary thumbnail compendium format as the display format.  FIG. 7  illustrates an exemplary screen layout for the detailed display format. When the detailed display format ( 312 ) is selected, detailed information for each lens is displayed in the directory display region  320  in addition to the thumbnails. In the example shown in  FIG. 7 , in addition to lens optical information such as magnification power, numerical aperture, and SN ratio, the detailed display format also displays calibration values, calibration date, and next scheduled calibration date. The next scheduled calibration date is equivalent to the “expiration date” registered in the lens information table. 
         [0066]      FIG. 8  illustrates an exemplary screen layout for the simplified display format. The simplified display format ( 313 ) has a simple screen configuration which simply lists lens names. 
         [0067]    Naturally, a lens can be registered in the mounted lens display region  330  by a drag-and-drop operation from the directory display region  320  in the detailed display format ( FIG. 7 ) and the simplified display format ( FIG. 8 ), as well. 
       First Modification 
       [0068]    In the above-described embodiment, when a lens is registered by performing a drag-and-drop operation from the directory display region  320  to the mounted lens display region  330 , a display is provided reflecting the expiration date of the calibration (e.g.,  FIG. 5 ). In this regard, as a first modification, an emphasis display may be performed for a lens having an incorrect calibration value at the stage where the lens is displayed in the directory display region  320 . In  FIG. 9 , an emphasis display is provided to “M Plan Apo 50×” in the directory display region  320 . As a result, the user can recognize at a glance which lens or lenses have an expired calibration. 
         [0069]    Moreover, this modification may be configured to differentiate between a lens having expired calibration values and a lens for which no calibration values are entered. Such differentiation may be achieved by a simple difference in color. 
       Second Modification 
       [0070]    In the first embodiment described above, a prearranged reference pattern is displayed as a thumbnail image in which the size of the pattern is adjusted to match the magnification power of each lens. As a second modification, an image currently being captured may be displayed as the thumbnail image corresponding to each lens, in which the size of the image is adjusted to match the magnification power of each lens. (Refer to  FIG. 10 .) Take “M Plan Apo 5×” as the lens currently in use capturing an image of a gear, for example. In such a case, image data of the gear currently being captured is displayed as a thumbnail corresponding to “M Plan Apo 5×” in the lens selection GUI screen  300  in the mounted lens display region  330  as well as in the directory display region  320 . Moreover, image data of the gear is also displayed as a thumbnail corresponding to each of the other lenses. Specifically, an image corresponding to the magnification power of each lens is simulated based on the image data being captured by “M Plan Apo 5×.” Simulation results are then displayed as a thumbnail for each lens. Accordingly, the user can immediately and intuitively understand what image can be obtained when switching lenses. 
       Third Modification 
       [0071]    In the above-described embodiment, an image measuring device  2  was assumed in which a plurality of different types of lenses could be simultaneously mounted to the revolver  18 . Naturally, there are also image measuring devices having a configuration in which only one lens can be mounted at a time. The present invention can be effectively applied to such a case, as well. One example is an image measuring device in which only one lens is used and the magnification power is changed by optical zoom or digital zoom. In such a case, calibration values must be found for each magnification power. Although the type of lens is the same, calibration values are found for each magnification power and are stored in a lens information table such as that shown in  FIG. 11 , for example. 
         [0072]    Based on such a table, the lens selection GUI screen  300  such as that shown in  FIG. 12  may be provided to the user. An overview of selectable magnification powers is displayed in the directory display region  320 . When the thumbnail corresponding to the desired magnification power is moved to the mounted lens display region  330  by dragging and dropping, the magnification power in use can be changed. Magnification powers having expired calibration values may be highlighted in the directory display region  320 , or highlighting or a message may be displayed when such a magnification power is dragged into the mounted lens display region  330 . 
       Fourth Modification 
       [0073]    Naturally, there are also measurements of a type using an image measuring device capable of mounting only one lens and where the observation field is changed by switching out the lens, without using optical zoom or digital zoom. A screen configuration for such a case is readily analogized from the first embodiment. Whereas four lenses can be mounted to the revolver in the first embodiment, the fourth modification may be viewed as being capable of mounting only one.  FIG. 13  offers a merely exemplary screen configuration. 
         [0074]    Moreover, the present invention is not limited to the embodiments described above, and may be modified as needed without departing from the scope of the present invention. An image measuring apparatus GUI program may be stored in a non-volatile storage medium, or may be installed as needed. 
         [0075]    It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular structures, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. 
         [0076]    The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.
An image measuring apparatus including an image measurer capable of switching between one of a type of lens and a magnification power, the image measurer obtaining an image of a measured object; a display displaying the image obtained by the image measurer and providing an operation screen to a user; and a controller controlling operations of the image measurer and the display. A calibration value and an expiration date for the calibration value are recorded by the controller for one of each type of lens and each magnification power. The controller communicates to the user, using the display, that one of the lens and the magnification power has an expired calibration value.