Off-axis conics as base surfaces for freeform optics enable null testability.

When conducting interferometric tests of freeform optical surfaces, additional optical components, such as computer-generated holograms or deformable mirrors, are often necessary to achieve a null or quasi-null. These additional optical components increase both the cost and the difficulty of interferometric tests of freeform optical surfaces. In this paper, designs using off-axis segments of conics as base surfaces for freeforms are explored.

Efficient representation of freeform gradient-index profiles for non-rotationally symmetric optical design.

Conventional optical designs with gradient index (GRIN) use rotationally-invariant GRIN profiles described by polynomials with no orthogonality. These GRIN profiles have limited effectiveness at correcting aberrations from tilted/decentered or freeform systems. In this paper, a three-dimensional orthogonal polynomial basis set (the FGRIN basis) is proposed, which enables the design of GRIN profiles with both rotational and axial variations.

On-the-fly surface manufacturability constraints for freeform optical design enabled by orthogonal polynomials.

When leveraging orthogonal polynomials for describing freeform optics, designers typically focus on the computational efficiency of convergence and the optical performance of the resulting designs. However, to physically realize these designs, the freeform surfaces need to be fabricated and tested. An optimization constraint is described that allows on-the-fly calculation and constraint of manufacturability estimates for freeform surfaces, namely peak-to-valley sag departure and maximum gradient normal departure.

Degeneracy in freeform surfaces described with orthogonal polynomials.

Orthogonal polynomials offer useful mathematical properties for describing freeform optical surfaces. Their advantages are best leveraged by understanding the interactions between variables such as tip and tilt, base sphere and conic variables, and packaging variables that define the problem of design for manufacture. These interactions can cause degeneracy, which can complicate the interpretation of design specifications in manufacturing and, consequently, negatively impact the cost of fabrication and assembly.