An input device comprising: an irradiation component configured to emit a scanning infrared laser beam relative to an input region of a projected image; a light receiver configured to receive reflected light of the infrared laser beam to output a detection signal; a coordinate detector configured to calculate coordinates indicated by an indicator relative to the input region based on the detection signal from the light receiver; and a controller configured to set an irradiation parameter of the infrared laser beam from the irradiation component based on the input region; wherein the controller is further configured to determine a unicursal scanning path based on key arrangement of the input region such that the scanning path passes through each of a plurality of horizontal rows of key input images, and to set the irradiation parameter related to a frame rate in the input region so that the infrared laser beam passes through each of the rows of the key input images at a single scan line along a first direction in a horizontal direction in the input region, and the key input images are provided for an input operation relative to the input region, with the key input images being arranged in rows in the horizontal direction of the input region; the input device being characterised in that the key input images are at least partially offset with respect to each other in a direction that intersects with the horizontal direction; the irradiation component is further configured to turn off the infrared laser beam at a scan line along a second direction in the input region, the first and second directions being substantially opposite; adjacent pairs of scan lines that scan the rows of input keys are offset by an amount in the vertical direction; and the controller is further configured to set the irradiation parameter so that the infrared laser beam will pass through at a single scan line for all of the key input images arranged horizontally in each row. an irradiation component configured to emit a scanning infrared laser beam relative to an input region of a projected image; a light receiver configured to receive reflected light of the infrared laser beam to output a detection signal; a coordinate detector configured to calculate coordinates indicated by an indicator relative to the input region based on the detection signal from the light receiver; and a controller configured to set an irradiation parameter of the infrared laser beam from the irradiation component based on the input region; wherein the controller is further configured to determine a unicursal scanning path based on key arrangement of the input region such that the scanning path passes through each of a plurality of horizontal rows of key input images, and to set the irradiation parameter related to a frame rate in the input region so that the infrared laser beam passes through each of the rows of the key input images at a single scan line along a first direction in a horizontal direction in the input region, and to determine a unicursal scanning path based on key arrangement of the input region such that the scanning path passes through each of a plurality of horizontal rows of key input images, and to set the irradiation parameter related to a frame rate in the input region so that the infrared laser beam passes through each of the rows of the key input images at a single scan line along a first direction in a horizontal direction in the input region, and the key input images are provided for an input operation relative to the input region, with the key input images being arranged in rows in the horizontal direction of the input region; the input device being characterised in that the key input images are at least partially offset with respect to each other in a direction that intersects with the horizontal direction; the irradiation component is further configured to turn off the infrared laser beam at a scan line along a second direction in the input region, the first and second directions being substantially opposite; adjacent pairs of scan lines that scan the rows of input keys are offset by an amount in the vertical direction; and the controller is further configured to set the irradiation parameter so that the infrared laser beam will pass through at a single scan line for all of the key input images arranged horizontally in each row.