Optical system phase acquisition method and optical system evaluation method

An optical system generalized phase distribution calculation method of calculating, by a processing apparatus (Up), a generalized phase distribution Ψ(u, v), which is information corresponding to a phase distribution on a phase defining plane (T) in a virtual optical system having an optical system (Ot) comprising one or more image forming optical elements, a virtual light emitting point that virtually illuminates the optical system (Ot), and the virtual phase defining plane (T) located at a prescribed relative position with respect to an output side of the optical system (Ot), the method comprising:

• (a1) arranging the optical system (Ot) and an imaging element (Uf);
• (a2) arranging one or more light sources (Psj) (j =1, 2, . . . ;
• the same applies hereinafter) at spatial coordinates (xsj, ysj, zsj) on an opposite side of the imaging element (Uf) as viewed from the optical system (Ot);
• (a3) illuminating the optical system (Ot) with an illumination light flux (Fsj) emitted from each of the light sources (Psj) and guiding a real output light flux output from the optical system (Ot) to the imaging element (Uf);
• (a4) superimposing reference light flux (Fr), which is a light flux coherent with the real output light flux, on the real output light flux to generate an interference image, and, at the same time, imaging the interference image with the imaging element (Uf) to acquire interference image data (Df), and transmitting the interference image data (DO to the processing apparatus (Up);
• (b) after performing processing of steps (a2) to (a4) one or more times, calculating measured generalized phase distributions Ψsj(u, v), which belong to each of the light sources (Psj) on the phase defining plane (T) and are information corresponding to the generalized phase distribution based on measured data, based on the interference image data (Df) by calculation processing by the processing apparatus (Up);
• (c) calculating a group of expanding coefficients Ajn belonging to each of the light sources (Psj) and configured to expand each of the measured generalized phase distributions Ψsj(u, v) by expanding functions μn(u, v) having coordinates (u, v) on the phase defining plane (T) as a variable and represent a resultant sum as a sum with coefficients Σn{Ajn·μn(u, v)}, by the calculation processing by the processing apparatus (Up);
• (d) when the virtual light emitting point is virtually disposed at spatial coordinates (x, y, z), applying interpolation calculation to the group of expanding coefficients Ajn based on a position occupied by spatial coordinates (x, y, z) at the virtual light emitting point among a set of spatial coordinates (xsj, ysj, zsj) of the light sources (Psj) to calculate a group of interpolation expanding coefficients An, which are values of the expanding coefficients after interpolation processing, by the calculation processing by the processing apparatus (Up);
• and
• (e) determining the sum with coefficients Σn{Ajn·μn(u, v)}of the expanding functions μn(u, v) based on a value of an interpolation expanding coefficient An calculated in step (d) to a value of specific coordinates (u, v) on the phase defining plane (T), and, at the same time, calculating the generalized phase distribution Ψ(u, v) based on a determination result, by the calculation processing by the processing apparatus (Up).