1. An optical tomographic imaging apparatus comprising: a processor and a memory, cooperating to function as units comprising: (a) an image forming unit configured to form a tomographic image of an object based on an interference light generated by a measuring light which has passed through the object and a reference light which has passed through a reference optical path; (b) an image display unit configured to display the tomographic image on a display device; (c) an area setting unit configured to set, based on a user's operation, first and second partial areas within the tomographic image displayed on the display device; (d) an image quality obtaining unit configured to obtain an image quality of an image of the second partial area as an image quality of the tomographic image, based on first values in the first partial area and second values in the second partial area, the first values in the first partial area being used as a reference value for calculating the image quality of the image of the second partial area; (e) a determination unit configured to determine whether a value indicating the image quality obtained by the image quality obtaining unit satisfies a specific determination reference; (f) an output unit configured to display, on the display device, a result of a determination of the determination unit; and (g) a control unit configured to control at least one of an amount of the measuring light for the object, a spectral shape of the measuring light, a polarization state of the measuring light, an incident position of the measuring light, and an optical path of the reference light, in accordance with the result of the determination, wherein the image forming unit forms a new tomographic image based on the controlling by the control unit.