PTL 1 discloses an imaging apparatus configured to image an imaging target such as a tool and to effect an image processing on an acquired image, thereby to detect the shape of the imaging target. With this imaging apparatus in operation, light is irradiated from a light projecting section onto the tool and the light passing through a lens is detected by an area sensor provided in the light receiving section. The area sensor has a configuration of sensor elements arranged in form of a rectangular face. With this, the tool as a whole can be imaged for allowing measurement of its shape.
PTL 2 discloses a tool measuring apparatus using both an area sensor and a line sensor in combination. The shape of a tool is measured by the area sensor. On the other hand, the line sensor is used for detecting whether the tool has advanced to a position appropriate for the field of vision of the area sensor, which vision constitutes the measurement area thereof. When a detection signal of the line sensor is outputted to a machining center, the machining center stops the advancing operation of the tool, thus keeping the tool in the measurement area.