When setting up an optical system in Sequential Mode in Zemax OpticStudio, one common challenge is modeling how a real-world mount allows an optic to rotate about a specific point in space. In reality, a mirror or lens doesn’t just “tilt in place” — it usually pivots around a mechanical mount point offset from the optic’s surface. If you want your simulation to accurately reflect this, you need to build a pivot point in your model that the optic can tip and tilt around. In this post, we’ll walk through how to create such a pivot point in Sequential Mode, so your virtual setup behaves more like the hardware on your optical bench.
Pivot Point Anywhere in Space
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First we need to understand Coordinate Breaks.
A Coordinate Break is a dummy surface in OpticStudio that lets you step out of the global coordinate system and define a new local one. You can apply shifts (decenters) and rotations (tilts) to position or pivot optics as if they were mounted in real hardware, then later “undo” the break to return to the global frame. The order flag controls whether tilts or decenters happen first, and the thickness sets the position of the next surface along the new axis.
Step 1: Open and Setup
Open Ansys OpticStudio Zemax and create a new project. Setup with Entrance Pupil Diameter of 10 mm and open a 3D Layout. Let the STOP be the first surface and use 100 mm for the Thickness. This is the plane our Mirror will sit on.
Step 2: Create a Parent Vertex
Add another surface at some distance away that you want your pivot plane to be at. This can be changed at any time.
Step 3: First Coordinate Break
Add a Coordinate Break surface manually right after the Parent Vertex. This is where we are going to break from the global coordinate system and define where our pivot location should be. We will call this Frame A, meaning we are moving from the Global Frame to Frame A. Make sure order is 0 and leave all parameters untouched for now. Also change the color of the row for bookkeeping purposes.
Step 4: Create Pivot Point Surface
Add another surface after the Coordinate Break. We already created the Pivot Plane, so now we need to go back to the Parent Vertex Surface because that is where our Mirror will be sitting. Use a pickup for later design changes and scale to -1.
Step 5: Second Coordinate Break
Now we need to add another Coordinate Break so that the Mirror can be correctly positioned in our mount that we are simulating. In other words, we need to be able to align our mirror to the pivot point. So, we went from Global Frame to Frame A and now to Frame B. Make sure the order is 0 and leave the parameters at 0 for now as well.
Step 6: Mirror Surface
We are ready to add our Mirror Surface (or whatever you need to model). This will be a model of a concave mirror that is 1 inch in diameter.
Step 7: Undo Frame B
Now we need to add another coordinate break surface manually. Make sure the order is 1, the order is telling Zemax to undo in the proper order because a shift and a tilt is not the same as a tilt and a shift. Since this surface is Returning to Frame A, that means we need to undo whatever tip/tilt/decenter that Frame B has done. So apply Pickups to Parameter 1, 2, 3, 4, and 5 (Decenter X, Decenter Y, Tilt About X, Tilt About Y, Tilt About Z respectively) for Frame B surface #5 and scale to -1. For the Thickness (which is parameter 6 technically because Zemax will consider this last anyway) we want properly go back through the Frames in order, so that means we need a position solve that takes us back for Frame A. Remember we went from Global Frame -> Frame A -> Frame B and now we want to correctly go back from Frame B to Frame A. So set the solve on the Thickness to be length 0 at Pivot Point surface #4.
Step 8: Undo Frame A
In order to return to Global Frame we need to undo Frame A. Add another Coordinate Break Surface and make sure the order is 1 and the Pickups undo Frame A surface #3 and scale to -1. For the Thickness we will also use a Pickup solve to take us back to the Global Frame before the Coordinate Break, which is the Parent Vertex surface #2, and scale it to -1.
Step 9: Image Plane Tracking
Next we need to make sure our IMAGE is always tracking the beam. We will use 1 more Coordinate Break that will define a local coordinate system for our IMAGE. We are going to use Chief Ray Solves for Par 1-5 and a Quick Focus for our Thickness. Order is 0 because we are not undoing anything.
Step 10: Clean Up
We can add our Local Coordinates Systems to the 3D Layout for better visuals by going to Surface 5 and Surface 3 properties -> Draw -> Check the boxes "Draw Local Axis" and "Draw Local Origin Point".
Also, we want to make sure the rays to not trace pass the Mirror because that is not physically what is happening. Go to Surface 2 properties -> Draw -> Check the boxes "Skip Rays to This Surface" and "Do Not Draw This Surface".
Next, Go to Surface 4 properties -> Draw -> Check the box "Skip Rays to This Surface"
This is a template for a pivot point that can be located anywhere in space. In the last step we will discuss how to use it.
How to Use Template
Downloadable Files
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