Hello,

I have made a system with two off-axis parabolas (in fact acting as a single parabola) and find that the input field semi diameter is different from the output field semi-diameter, although the spot diagram (with a paraxial lens) states that the image is perfect. Looking at the 3-D model and making an overlay of two images that are flipped alonng the z-axis, I notice that the rays on either side of the focus of the OAP do not seem to have the same angle, which indeed then would lead to a different semi-diameter. Anything to fix this? I have added a screenshot of the focal region of the off-axis parabola, with two identical images shown, but one transparant and flipped. I would have expected to have these images be symmetric to the mirroring.