An imaging device comprising: an image sensor configured to capture an image of an object at a prescribed frame rate and to output image data indicating the image; and a display configured to display the image based on the image data in synchronization with dot clocks, the display having a counter being configured to count the number of the dot clocks being output for a lengthened horizontal synchronization period that is lengthened with respect to a standard horizontal synchronization period, the standard horizontal synchronization period being set as a vertical synchronization period of the display divided by a number of lines per frame of the display, each horizontal synchronization period being a display cycle for a display line, the dot clocks being a synchronization signal used when the image is displayed on the display; wherein the output number of dot clocks counted by the counter is used for controlling the display timing in the display, the counter has a maximum value (Cdd_MAX) that is determined in advance depending on the display, and an overflow occurs in the counter and the display malfunctions if a higher number of dot clocks than the maximum value (Cdd_MAX) is generated within one horizontal synchronization period, and the imaging device further comprises: a determination unit configured to determine whether or not the counted number of the dot clocks in the lengthened horizontal synchronization period has exceeded a threshold value, the threshold value being a value greater than a standard number of the dot clocks (TH1/Tdd1) for the standard horizontal synchronization period, and the threshold value being a value smaller than the maximum value (Cdd_MAX) of the counter, wherein: the display is configured to switch from a first frequency (1/Tdd1) of the dot clock to a second frequency (1/Tdd2) of the dot clock, the second frequency being lower than the first frequency, if the determination unit determines that the counted number of the dot clocks, in the lengthened horizontal synchronization period, has exceeded the threshold value. an image sensor configured to capture an image of an object at a prescribed frame rate and to output image data indicating the image; and a display configured to display the image based on the image data in synchronization with dot clocks, the display having a counter being configured to count the number of the dot clocks being output for a lengthened horizontal synchronization period that is lengthened with respect to a standard horizontal synchronization period, the standard horizontal synchronization period being set as a vertical synchronization period of the display divided by a number of lines per frame of the display, each horizontal synchronization period being a display cycle for a display line, the dot clocks being a synchronization signal used when the image is displayed on the display; wherein the output number of dot clocks counted by the counter is used for controlling the display timing in the display, the counter has a maximum value (Cdd_MAX) that is determined in advance depending on the display, and an overflow occurs in the counter and the display malfunctions if a higher number of dot clocks than the maximum value (Cdd_MAX) is generated within one horizontal synchronization period, and the imaging device further comprises: a determination unit configured to determine whether or not the counted number of the dot clocks in the lengthened horizontal synchronization period has exceeded a threshold value, the threshold value being a value greater than a standard number of the dot clocks (TH1/Tdd1) for the standard horizontal synchronization period, and the threshold value being a value smaller than the maximum value (Cdd_MAX) of the counter, wherein: the display is configured to switch from a first frequency (1/Tdd1) of the dot clock to a second frequency (1/Tdd2) of the dot clock, the second frequency being lower than the first frequency, if the determination unit determines that the counted number of the dot clocks, in the lengthened horizontal synchronization period, has exceeded the threshold value. a determination unit configured to determine whether or not the counted number of the dot clocks in the lengthened horizontal synchronization period has exceeded a threshold value, the threshold value being a value greater than a standard number of the dot clocks (TH1/Tdd1) for the standard horizontal synchronization period, and the threshold value being a value smaller than the maximum value (Cdd_MAX) of the counter, wherein: the display is configured to switch from a first frequency (1/Tdd1) of the dot clock to a second frequency (1/Tdd2) of the dot clock, the second frequency being lower than the first frequency, if the determination unit determines that the counted number of the dot clocks, in the lengthened horizontal synchronization period, has exceeded the threshold value. the display is configured to switch from a first frequency (1/Tdd1) of the dot clock to a second frequency (1/Tdd2) of the dot clock, the second frequency being lower than the first frequency, if the determination unit determines that the counted number of the dot clocks, in the lengthened horizontal synchronization period, has exceeded the threshold value.