Alex's MM Design

Here is my attempt at a MM unobscured design. As you can see, it is not exactly "unobscured," but this was the best solution I was able to come up with so far. Both mirrors are tilted conics (the primary is only slightly tilted by 0.175 degrees while the secondary is tilted by only 0.190 degrees). Everything fits in a 1U cubesat with this design.

EFFL: 393 mm EPD: 80 mm FOV: +/- 0.33 degrees Wavelengths: F, d, C

Layout

3DLayout

Spot Diagram

OPD Fan

Jashcraf commented 3 years ago

Confocal Cassegrain Design

I realized that I had never really wrote-up how you design a system to be confocal before - and figured now would be a neat time to do so. First - look to the cassegrain equations to figure out our power balance. Our spec (#10') gives us a 393mm focal length, and the 2U volume constrains the track length to be < 200mm. Let's call the M1-2 separation 150mm with 0.5U reserved for camera stuff.

I have them in a spreadsheet to make it easier on me. Let's put these in OpticStudio.

WoW a Cassegrain Objective - go us. Vary the M2 conic to get perfect on-axis performance!

Now we say goodbye to the layout view and hello to the 3D viewer because it's time to bust some coordinates. A feature of confocal systems perturbed with respect to it's internal foci is that the on-axis performance is functionally perfect, let's see if we can set this up. This isn't a terribly complicated system so we only need to set up the virtual focus behind M2 to be coincident with the image from M1. We need to ask OpticStudio to travel to the image created by M1, and then move forward a distance corresponding to (M1 Image distance - M1-2 distance). This is how I set it up The marginal ray solve takes us to the image and gives us the distance we need to account for. Adding a coordinate break immediately after the image allows for perturbations (e.g. tilts) with respect to the image plane location. Adding 3 degrees of X tilt makes the design look weird

But we recover the on-axis performance

Getting the mirrors out of eachother's business

Now this is interesting from a theoretical perspective, but the reality is we are loosing most of our light. In Optics, we call this "not good". So let's turn the primary into an OAP for some additional clearance.

Regrettably we are now TOTALLY violating our 2U volume constraint by decentering the system in one direction. Let's try and use our tilt DOF to fix that!

A 20 degree X Tilt of M2 about the virtual focus gives us a much more compact package with no change to the on-axis performance!

Dropping in some fields will tell us more about how this system actually performance heheh not so good huh? This is what we have XY-Polynomials for though!

@trentjbrendel thoughts on making this a POW white paper topic?

Practical-Optical-Design-Seminar / Designs