Floating Apertures and Lens Edge Settings in QUADOA® Optical CAD
A floating aperture in QUADOA® Optical CAD is a lens surface aperture whose radius is calculated automatically from the ray trace: it is always the smallest radius that lets every traced ray pass. This tutorial shows how to switch a surface from a fixed to a floating aperture, add an aperture margin for mounting or polishing, give both surfaces of a lens the same aperture, and keep a single physical aperture across all configurations of a zoom system.
Key points
- Click the lock icon next to Aperture Radius in the Optical Design Editor. Open lock = floating, closed lock = fixed.
- Aperture margins only work with floating apertures.
- A radial margin grows the aperture perpendicular to the optical axis. An along-surface margin grows it along the surface tangent.
- Edge thickness is always calculated from the full aperture, including the margin, so set the margin before optimizing.
- Link Aperture gives both surfaces of a lens the larger of their two apertures.
- Link Configs applies the largest aperture of all configurations to every configuration.
Terms used in this article
- Clear aperture
- The region of a surface that all traced rays pass through.
- Fixed aperture
- An aperture whose radius is set explicitly by the value the user enters.
- Floating aperture
- An aperture whose radius QUADOA® calculates from the ray trace: the smallest circle around all rays of all sequences that pass the surface.
- Aperture margin
- Extra width added outside the clear aperture, so the physical aperture is larger than the clear aperture.
- Physical aperture
- The full aperture of the lens: the clear aperture plus any aperture margin.
How to activate a floating aperture
By default, each surface in QUADOA® has one circular aperture whose radius can be fixed or floating. You switch between the two in the lens parameters of the Optical Design Editor.
| Setting | Lock icon | How the radius is set | Aperture margin |
|---|---|---|---|
| Fixed aperture | Closed | Value entered by the user | Not applied |
| Floating aperture | Open | Calculated from the ray trace (minimum radius that passes all rays) | Applied |
Steps
- In the Optical Design Editor, go to the lens data that shows the Aperture Radius field.
- Click the lock icon next to the Aperture Radius field.
- Check that the lock icon is shown as unlocked. The floating aperture is now active.
Good to know
- The floating radius is calculated from the rays of all sequences that pass the surface, and a floating aperture never blocks rays.
- To lock or unlock the apertures of the whole model at once, use Lock all Apertures and Unlock all Apertures in the menu bar of the Optical Design Editor.
- If a surface with a floating aperture is not part of any sequence, its radius becomes zero and the surface is no longer visible.
- The floating radius belongs to the default circular aperture of the surface. As soon as you add an aperture item, for example a rectangular aperture, it replaces the default aperture and defines the physical size of the surface; further aperture items define the clear aperture.
- The aperture also defines the mechanical size used in the 3D view and for CAD export.
How to open the Lens Settings Editor
Aperture margins, linked apertures, linked configurations, and lens edge features such as flanges and chamfers are set in the Lens Settings Editor. You open it from the Optical Design Editor.
Steps
- Select the lens element in the Optical Design Editor.
- Click the plus (+) icon next to the lens type description.
- The Lens Settings Editor opens.
For lens edge geometry, see the article on chamfers and flanges in QUADOA® and the chamfers and flanges video tutorial.
What is an aperture margin?
An aperture margin enlarges the aperture by a set amount beyond the clear aperture. For example, a radial aperture margin of 2 mm makes the physical aperture radius 2 mm larger than the clear aperture radius. Use it to leave room for mechanical mounts or for polishing outside the clear aperture.
Important: Aperture margins are only applied when the floating aperture is enabled (lock icon open). With a fixed aperture radius, the margin has no effect.
Steps
- Check that the floating aperture is active (lock icon next to Aperture Radius unlocked).
- Open the Lens Settings Editor with the plus (+) icon of the lens.
- Enter the Aperture Margin, for example 2 mm.
- Select the Margin Type: Radial or Along Surface.
- Click Update. The aperture in the 3D view grows by the margin.
Radial vs. along-surface margin
QUADOA® offers two ways to add the margin to the floating aperture radius:
| Margin type | Direction | Increase in aperture radius |
|---|---|---|
| Radial | Perpendicular to the optical axis | Exactly the entered margin m |
| Along Surface | Along the surface tangent | m × cos(θ), where θ is the surface angle at the edge of the clear aperture |
On a flat or gently curved surface the two types give almost the same result. On a strongly curved surface, an along-surface margin adds less radius than a radial margin of the same value, because the margin follows the slope of the surface.
How aperture margins affect optimization
During optimization it usually makes sense to keep apertures floating, so that they follow changes in the ray footprint. Because the physical aperture is larger than the clear aperture, edge thicknesses and air gaps must be checked at the physical aperture.
- Edge thickness is always calculated from the full aperture, including any aperture margin.
- If your merit function constrains edge thickness or air gaps, define the aperture margin before you start optimizing. Otherwise the optimizer works with apertures that are too small.
How to give both lens surfaces the same aperture (Link Aperture)
For manufacturing, both surfaces of a singlet lens usually need the same aperture size. The Link Aperture option in the lens edge settings does this automatically.
Steps
- Open the Lens Settings Editor.
- Enable the Link Aperture checkbox.
- Click Update.
- Repeat for every lens that needs matched apertures.
What QUADOA® does
- Calculates the floating aperture radius of both surfaces.
- Determines which of the two radii is larger.
- Resizes the smaller aperture to match the larger one.
For example, if the second surface has the larger floating aperture, the aperture of the first surface is enlarged to the same radius.
How to use one aperture across all configurations (Link Configs)
In multi-configuration models such as zoom lenses, the floating aperture radius of a lens can differ between configurations. When you click through the configuration states, or show all configurations together in the 3D view, you can see the aperture change size. The real lens, however, has only one physical aperture, which must be large enough for every configuration. The Link Configs option models this.
Steps
- Open the Lens Settings Editor.
- Enable the Link Configs option.
- Click Update.
- Repeat for every lens that appears in more than one configuration.
What QUADOA® does
- Calculates the floating aperture radius in every configuration.
- Identifies the largest radius.
- Applies that radius to all configurations.
The aperture then stays the same size when you switch between configuration states.
Combining the settings
All settings can be used together on the same lens:
| Setting | Where | Purpose |
|---|---|---|
| Floating aperture | Optical Design Editor, lock icon | Aperture radius follows the ray trace |
| Aperture margin (Radial or Along Surface) | Lens Settings Editor | Room for mounting or polishing outside the clear aperture |
| Link Aperture | Lens Settings Editor | Same aperture on both surfaces of a lens |
| Link Configs | Lens Settings Editor | One physical aperture across all configurations |
Together, they give full control over aperture geometry, edge behavior, manufacturability and consistency between configurations.
Video tutorial: floating apertures and lens edge settings
This 5-minute video shows the different floating aperture settings and how lens edges are defined in QUADOA® Optical CAD.
Video length: 5:04 min · Also on YouTube: Floating Apertures in QUADOA® Optical CAD
Frequently asked questions
A floating aperture is a surface aperture whose radius QUADOA® calculates automatically from the ray trace. It is the smallest radius that lets all traced rays pass. A fixed aperture, by contrast, uses the radius the user enters.
Aperture margins are only applied when the floating aperture is enabled, which means the lock icon next to the Aperture Radius field must be open. With a fixed aperture radius the margin is ignored.
A radial margin adds the entered value straight outward, perpendicular to the optical axis. An along-surface margin adds the value along the surface tangent, so the aperture radius grows by the margin multiplied by the cosine of the surface angle at the clear aperture.
With it. During optimization, edge thickness is always calculated from the full aperture, including any aperture margin. Define the margin before optimizing if the merit function constrains edge thickness or air gaps.
Enable Link Aperture in the Lens Settings Editor. QUADOA® computes the floating aperture of both surfaces and resizes the smaller one to match the larger one.
Enable Link Configs in the Lens Settings Editor. QUADOA® computes the floating aperture in every configuration and applies the largest radius to all configurations.
A floating aperture is calculated from the rays that pass the surface. If the surface is not part of any sequence, no rays reach it, its radius becomes zero and the surface is no longer visible.
Use Unlock all Apertures in the menu bar of the Optical Design Editor. Lock all Apertures fixes all floating apertures at their current size.