 The usual purpose is to enhance the sensitivity (e.g., surface-enhanced Raman), to improve the spatial resolution (Raman microscopy), or to acquire very specific information (resonance Raman).Terms such as "spontaneous Raman spectroscopy" or "normal Raman spectroscopy" summarize Raman spectroscopy techniques based on Raman scattering by using normal far-field optics as described above.Variants of normal Raman spectroscopy exist with respect to excitation-detection geometries, combination with other techniques, use of special (polarizing) optics and specific choice of excitation wavelengths for resonance enhancement.