A spectral image is corrected for optical aberrations. Tissue is exposed to a high-intensity, narrow band of light. The narrow band of light is scattered by at least one analyte in the tissue. Raman signals are optically collected from the scattered light. The Raman signals are directed to a wavelength-separating device. The Raman signals are detected as a function of intensity and wavelength to create the spectral image. The spectral image is corrected for optical aberrations using a software algorithm to spatially reassign intensity. The software may be adapted to use a reference image to make dynamic corrections. Fluorescence signals may also be collected.