A system and method for shaping a light spectrum

An apparatus for shaping a light spectrum, the apparatus comprising:

• a dispersive element adapted to produce a primary beam;
• a spatial light modulator comprising an array of cells, each cell being operable in a first state and a second state, for shaping the spectrum of the primary beam, wherein the second state is associated with a first logic value and the first state is associated with a second logic value;
• an optical device arranged to image the primary beam onto the spatial light modulator to produce a secondary beam having a shaped spectrum;
• a detector adapted to measure the shaped spectrum;
• and
• a controller configured to change the state of a subset of cells iteratively, based on a stochastic process, to shape the spectrum;
• wherein the controller is configured to perform a sequence of steps comprising:
• calculating a difference between the shaped spectrum and a target spectrum to obtain a difference spectrum having a plurality of spectral elements, each spectral element being associated with a corresponding set of cells in the array,
• calculating an error value and generating a list of random values for each set of cells,
• changing a state of one or more cells selected based on the list of random values;
• and
• repeating iteratively the sequence of steps to reduce the error values;
• wherein the controller is configured to generate for each set of cells a corresponding set of intermediate logic values, and to calculate an adjusted set of logic values for adjusting the state of the cells;
• wherein the adjusted set of logic values is obtained by performing a logic operation between the set of intermediate logic values and a previous set of logic values.