1. A detecting apparatus comprising: a wavelength filter configured to transmit at least near-infrared rays and not to transmit visible light; a phosphor configured to transmit near-infrared rays transmitted through the wavelength filter, and to generate fluorescence with respect to incident X-rays; a semiconductor sensor configured to sense near-infrared rays transmitted through the phosphor and the fluorescence; and a controller configured to control to read clusters of a predetermined number of pixels of the semiconductor sensor when the near-infrared rays are generated from a near-infrared ray source, so as to readout images at high speed in relation to an X-ray imaging.