Optical identifier and printed matter

An optical identifier comprising:

• a recording surface comprising:
• a red unit cell comprising a plurality of red pixels, each red pixel of the plurality of red pixels consists of a red diffraction grating occupying at most 50% of the pixel and a spatial phase modulator surrounding the diffraction grating;
• a green unit cell comprising a plurality of green pixels, each green pixel of the plurality of green pixels consists of a green diffraction grating occupying at most 50% of the pixel and a spatial phase modulator surrounding the diffraction grating;
• and
• a blue unit cell comprising a plurality of blue pixels, each blue pixel of the plurality of blue pixels consists of a blue diffraction grating occupying at most 50% of the pixel and a spatial phase modulator surrounding the diffraction grating;
• a deposition layer covering part or all of the recording surface, wherein
• each of the diffraction gratings of the red, green and blue unit cells has a spatial frequency expressed in a form of a relief structure;
• the diffraction gratings of the red, green and blue unit cells have regular intervals away from each other,
• a variable color image is recorded by the red, green and blue unit cells,
• the spatial phase modulator having thereon a distribution of phase differences recorded in a form of heights of the relief structure of the corresponding diffraction grating, the spatial phase modulator modulating a phase of light outputted from a point light source and displaying a reproduced image;
• the diffraction gratings of the red, green and blue unit cells diffract diffused light and deflect the diffused light by directional scattering, the diffraction gratings of the red, green and blue unit cells display the variable color image recorded in a form of heights of the respective relief structure.