Optical power measurement method and an optical intensity measurement device

Acquiring an image of predefined detected object detection target region having an area is arrayed analyzes the acquired image, a method for measuring the light intensity of each detection target region was obtained among the region extracted based on the light intensity from the image, extracts a region consisting of an area smaller than the specified area of ​​the detection subject region as a noise region, removed from the image. Light intensity measuring device includes a light irradiating means for irradiating light to the detection object, an image capturing means for obtaining an image of the detection object which the light is irradiated, a storage means for storing the acquired image, a extracting means for extracting a region from the stored image composed of smaller area than the specified area of ​​the detection subject region as a noise region, and image processing means for removing the noise area from the image the storage.