Rigid-body motions (RBMs) in STAR, Part 3: Evaluate performance with and without RBMs
Rigid-body motions (RBMs) in STAR, Part 3: Evaluate performance with and without RBMs
After loading FEA deformation data on an example singlet, the Structural Data Summary allows users to turn the deformations and RBMs independently, using check boxes. Values for the RBMs can be seen in the Properties of each surface, as well.
The images below show the RBMs for the front and back of the singlet lens example. The lens as a whole has a decenter of Y = 1 mm and Tilt about X = 3°. (The rear surface has an additional decenter due to the thickness of the lens.)
Inspecting RBMs on the front surface of the lens.Inspecting RBMs on the rear surface of the lens.
With both RBMs and higher-order deformations turned off, we can see the spherical aberration present in the starting singlet.
The spot diagram with the original lens can be observed by turning both Deformations and RBMs off.
After turning on the higher-order deformations, the front of the lens is converted to aspheric and the system performance improves.
Higher-order deformations turned on, showing that the higher-order deformation data corrects the spherical aberration.
And if the RBMs are turned on, the tilt and decenter of the lens introduces coma and astigmatism into the spot diagram.
The spot diagram with both deformations and RBMs turned on is dominated by astigmatism and coma, as one would expect.
We can plot the effect of both the RBMs and higher-order deformations on the system performance using the STAR/Performance Analysis tool. The RBMs can be considered surface-by-surface. For the singlet example, the spot size improves due the (artificial) higher-order deformations that correct the spherical aberration. But the spot size increases due to the large RBMs.
Performance plot that shows the effect on the spot diagram, of RBMs and higher-order deformations individually.
