1. A detecting device combining images with spectra in an ultra-wide waveband, comprising a scanning rotating mirror, a Cassegrain mirror assembly, a first spectroscope, a reflector, a first broadband lens assembly, a second broadband lens assembly, a third broadband lens assembly, a fourth broadband lens assembly, a second spectroscope, a third spectroscope, a visible and near-infrared lens assembly, a long wave lens assembly, a CCD imaging unit, an FPA imaging unit, a Fourier spectrum measuring unit and a grating spectrum measuring unit, wherein said scanning rotating mirror is controlled by a servo motor to aim at a target area and operable for reflecting light from the target area to said Cassegrain mirror assembly, said Cassegrain mirror assembly is operable for collecting the reflected light and reflecting it to said first spectroscope, said first spectroscope is operable for transmitting infrared light of 2˜14 um to said first broadband lens assembly and reflecting infrared light of 0.4˜2 um to said reflector, said second spectroscope is operable for transmitting a portion of light of a first predetermined waveband to said long wave lens assembly and reflecting the residual portion of light of said first predetermined waveband and light of the residual waveband to said second broadband lens assembly simultaneously, and said long wave lens assembly is operable for focusing light transmitted by said second spectroscope to said FPA imaging unit for imaging; said second broadband lens assembly is operable for focusing light reflected by said second spectroscope to said Fourier spectrum measuring unit for spectrum acquisition; said reflector is operable for reflecting light of 0.4˜2 um reflected by said first spectroscope to said third broadband lens assembly, said third spectroscope is operable for transmitting a portion of light of a second predetermined waveband to said visible and near-infrared lens assembly and reflecting the residual portion of light of said second predetermined waveband and light of the residual waveband to said fourth broadband lens assembly simultaneously, and said visible and near-infrared lens assembly is operable for focusing light transmitted by said third spectroscope to said CCD imaging unit for imaging; and said fourth broadband lens assembly is operable for focusing light reflected by said third spectroscope to said grating spectrum measuring unit for spectrum acquisition.