spectroscopy apparatus for spectrochemical analysis of a sample having an excitation source for providing spectral light of the sample for analysis . the spectral light is analysed via an optical system that includes a polychromator and solid state multielement array detector . the elements of the detector are serially reel by means to provide light intensity measurements as a function of wavelength . a problem is that the elements of the detector continue to accumulate change during the serial read - out . this is avoided by providing an optical shutter for blocking the spectral light whilst elements of the detector are being serially read . shutter has a piezoelectric actuator which is preferably a bimorph mounted as a cantilever . it is preferably located adjacent to the entrance aperture of the polychromator . bimorph structures for the actuator and drive and protective circuit arrangements are also disclosed .