Method for aligning an optical system utilizing focal plane image intensity data

A method of minimizing aberrations associated with the performance of a complex optical system by making compensating adjustment to the spatial and rotational relationships between different optical elements in said system, said method comprising the steps of:

• measuring the performance of said optical system as a function of the intensity of the image of a point source at different locations at the focal plane of said system compared to the corresponding intensity measurements of a predetermined perfectly aligned optical system free of any significant aberrations;
• making two sets of said performance measurements, one set prior to and one set subsequent to a physical adjustment to at least one of said spatial and rotational relationships;
• calculating an initial estimate of aberrations form a linear function "second difference" equation expressing the difference in focal plane image intensity prior to and subsequent to said physical adjustment, and producing representative signals of said initial estimates;
• calculating from the representative signals by a second order approximation algorithm the appropriate compensating adjustments to minimize the aberrations in said optical system, and
• making said spatial and rotational adjustments to said optical elements.

An improved optical system having a realignment capability comprising:

• an optical system having a number of individual optical units with complementary optical characteristics and spatial relationships to each other positioned on an optical axis extending from an object to an image side, a plurality of optical units being movably mounted relative to the optical axis and having an interactive effect on the image transmitting ability of image side optical units;
• means for moving the movably mounted optical units to change their respective spatial positions;
• means for providing signals indicative of an analytical optical model of an optimized optical system capable of providing the predetermined optical performance desired by the optical system;
• means for measuring a reference image at the focal plane to provide measurement signals representative of the intensity distribution of a point source image;
• means for comparing the measurement signals with the signals indicative of the analytical model by a second order approximation to generate alignment signals necessary to conform the optical performance of the analytical model to that of the measured optical system, and
• means for applying the adjustment signals to the means for moving the optical units to realign the spatial position of the optical units for conformance with the predetermined optical performance of the analytical optical model.