An image measurement system comprising: a controller; a projector for emitting illumination light in accordance with a radiation pattern (601, 602) specified from the controller; an imaging unit having a field of view in which an area irradiated with the illumination light exists; and a display unit adapted to display an image, the controller comprising: display control means for displaying on the display unit an image of the field of view captured by the imaging unit in a state in which the illumination light is emitted, characterized in that the controller further comprises: receiving means (112, 122) for receiving a setting of a mask area in association with the image displayed on the display unit, the mask area being an area in the field of view captured in the image in which the quantity of illumination light is to be reduced compared with another area in the field of view, and updating means for updating the radiation pattern (601, 602) to include an area corresponding to the set mask area in which the quantity of illumination light is reduced compared with another area of the radiation pattern (601, 602), based on a correspondence in position between the radiation pattern (601, 602) of the projector and a projection pattern (801, 802) produced in the field of view by the radiation pattern (601, 602); wherein the controller is configured to: control the projector to emit illumination light in accordance with the updated radiation pattern (601, 602); control the imaging unit to capture an image in a state in which the updated radiation pattern is emitted; and carry out image measurement processing on the captured image. a controller; a projector for emitting illumination light in accordance with a radiation pattern (601, 602) specified from the controller; an imaging unit having a field of view in which an area irradiated with the illumination light exists; and a display unit adapted to display an image, the controller comprising: display control means for displaying on the display unit an image of the field of view captured by the imaging unit in a state in which the illumination light is emitted, characterized in that the controller further comprises: receiving means (112, 122) for receiving a setting of a mask area in association with the image displayed on the display unit, the mask area being an area in the field of view captured in the image in which the quantity of illumination light is to be reduced compared with another area in the field of view, and updating means for updating the radiation pattern (601, 602) to include an area corresponding to the set mask area in which the quantity of illumination light is reduced compared with another area of the radiation pattern (601, 602), based on a correspondence in position between the radiation pattern (601, 602) of the projector and a projection pattern (801, 802) produced in the field of view by the radiation pattern (601, 602); receiving means (112, 122) for receiving a setting of a mask area in association with the image displayed on the display unit, the mask area being an area in the field of view captured in the image in which the quantity of illumination light is to be reduced compared with another area in the field of view, and updating means for updating the radiation pattern (601, 602) to include an area corresponding to the set mask area in which the quantity of illumination light is reduced compared with another area of the radiation pattern (601, 602), based on a correspondence in position between the radiation pattern (601, 602) of the projector and a projection pattern (801, 802) produced in the field of view by the radiation pattern (601, 602); wherein the controller is configured to: control the projector to emit illumination light in accordance with the updated radiation pattern (601, 602); control the imaging unit to capture an image in a state in which the updated radiation pattern is emitted; and carry out image measurement processing on the captured image. control the projector to emit illumination light in accordance with the updated radiation pattern (601, 602); control the imaging unit to capture an image in a state in which the updated radiation pattern is emitted; and carry out image measurement processing on the captured image.