1. A spectrophotometric system comprising: (a) a spectral energy source for sequentially producing spectral energy in different wavelength bands; (b) an imaging device including an array of sensors for detecting spectral energy; (c) a first spectral energy director for directing spectral energy produced by said spectral energy source onto a target surface; (d) a second spectral energy director for directing spectral energy reflected from the target surface to the array of sensors; (e) a reference detector for detecting changes in the spectral energy of each wavelength band produced by the spectral energy source; (f) a memory storing a set of calibration data representing irregularities in the spectral energy as detected by the array of sensors; and (g) an adjusting device coupled to the array of sensors, the reference detector, and the memory for adjusting the spectral energy detected by the array of sensors based on the changes in illumination detected by the reference detector and irregularities in the spectral energy as detected by the array of sensors represented by the set of calibration data stored in the memory.