Illumination device and method of manufacturing the same

A method of manufacturing an illumination device,

• wherein the illumination device comprises
• a light source configured to emit coherent light,
• a collimating optical system configured to enlarge a beam diameter of the coherent light emitted from the light source and collimate the coherent light, and
• a diffractive optical element configured to diffract the coherent light collimated by the collimating optical system into a predetermined diffusion angle space, and illuminate a region to be illuminated defined at a predetermined position and having predetermined size and shape,
• wherein the diffractive optical element includes a plurality of element diffractive optical portions, each of the element diffractive optical portions illuminating at least a part of the region to be illuminated in producing the individual element diffractive optical portions included in the diffractive optical element, and
• wherein the method performs a process comprising:
• a first step of generating angular space distribution of intensity of first-order diffracted light emitted from the element diffractive optical portions based on a predetermined design illumination intensity distribution defined in the region to be illuminated;
• a second step of combining random phase distribution with the angular space distribution of intensity to generate complex amplitude distribution on the diffractive optical element;
• a third step of performing inverse Fourier transform for the complex amplitude distribution on the diffractive optical element to generate complex amplitude distribution on the region to be illuminated;
• a fourth step of modifying intensity of the complex amplitude distribution on the region to be illuminated in accordance with the design illumination intensity distribution to generate modified complex amplitude distribution on the region to be illuminated;
• a fifth step of performing Fourier transform for the modified complex amplitude distribution on the region to be illuminated to generate a modified complex amplitude distribution on the diffractive optical element;
• a sixth step of replacing intensity of the modified complex amplitude distribution on the diffractive optical element with intensity exhibited in the angular space distribution of intensity generated in the first step to generate replaced complex amplitude distribution on the diffractive optical element;
• a seventh step of executing the third step again using the replaced complex amplitude distribution on the diffractive optical element generated in the sixth step instead of the complex amplitude distribution on the diffractive optical element to repeatedly perform the process from the third step to the sixth step by a necessary number of times and setting a finally obtained replaced complex amplitude distribution on the diffractive optical element as finally complex amplitude distribution;
• and
• an eighth step of forming interference fringes constituting a hologram having a unique diffractive characteristic on a predetermined medium so that first-order diffracted light corresponding to the final complex amplitude distribution is emitted based on the coherent light entering from the collimating optical system.