telescope
  • Imaging Techniques

Protect Telescope Designs Using OpticStudio Black Box

When collaborating with customers or system integrators, optical designers are often required to share telescope design data so downstream work—such as mechanical integration, stray-light analysis, or system-level ray tracing—can proceed.

However, sharing ray-traceable design files risks exposing the intellectual property (IP) of the original optical designer.

Zemax OpticStudio provides a robust solution to this problem through the Black Box Lens Surface. This tool enables full ray-tracing fidelity while completely hiding internal optical design data.

 

What Is a Black Box Lens Surface?

A Black Box Lens Surface encapsulates a group of optical surfaces into a single, non-editable entity that:

  • Traces real rays correctly for any:

    • Field point

    • Wavelength

    • Conjugate

  • Produces identical ray-trace results to the original design

  • Prevents access to:

    • Radii

    • Thicknesses

    • Materials

    • Curvatures

    • Internal apertures

From the end user’s perspective, rays enter the black box and exit exactly as if the full telescope design were present—without revealing any internal structure.

 

When to Convert a Telescope Design into a Black Box

Black Box export is typically performed:

  • After the telescope or sub-system design is finalized
  • Before sharing files externally

However, it can be done at any stage of the design cycle if IP protection is required early.

Typical use cases include:

  • Sharing eyepiece or relay lens designs
  • Supplying telescope data to system integrators
  • Protecting proprietary optical layouts in collaborations

 

Preparing the Telescope Design for Black Box Export

1. Define Export Boundaries with Dummy Surfaces

It is best practice to:

  • Add two dummy surfaces to define the start and end planes of the export region

  • Place these at:

    • Mechanical datums

    • Housing boundaries

    • Pupil locations

 

In this telescope example, dummy surfaces are used to define the mechanical housing that contains the eyepiece lens group.

 

2. Fix Apertures Before Export

Before exporting:

  • All surfaces within the export range must have fixed apertures
  • Use: LDE Toolbar → Apertures → Convert Semi-Diameters to Circular Apertures

Key notes:

  • Any aperture type may be used except User-Defined Apertures (UDA)
  • Apertures define the mechanical extent of the optics inside the black box

This step is critical to ensure correct ray behavior after playback.

 

Exporting the Telescope Design as a Black Box

When running the Black Box export, leave “Create and load test file” checked.

This causes OpticStudio to:

  1. Create the Black Box file
  2. Delete the original surfaces in the selected range
  3. Load the Black Box Lens Surface automatically
  4. Save the new design file

This workflow provides a built-in quality assurance step, allowing direct verification that ray-trace results are identical before and after black-boxing.

 

Behavior and Limitations of Black Box Optics

Because a Black Box Lens Surface hides all internal data, certain consequences apply.

 

What You Can Do

  • Ray trace normally through the black box

  • Perform:

    • FFT PSF / MTF

    • Huygens PSF

    • Image-space analysis

  • Optimize and analyze surfaces outside the black box

 

What You Cannot Do

  • Access or modify internal surfaces

  • Perform:

    • Tolerancing

    • Thermal analysis

    • Optimization operands inside the black box

    • ZPL commands on internal surfaces

The black box is immutable once created.

 

Ray-Tracing Considerations

  • OpticStudio cannot distinguish why a ray fails inside a black box
  • If a ray enters but does not exit, a generic Ray Miss error is reported
  • This differs from standard error reporting (clipping, TIR, etc.)

Note: If the chief ray cannot be traced (e.g., telescopes with central obscuration), wavefront analysis will not be possible, as no chief-ray reference exists.

 

Constraints on Surface Placement

  • Object, Stop, and Image surfaces cannot be inside a Black Box

    • OpticStudio requires full ray data on these surfaces

  • Coordinate breaks and tilts/decenters can be included internally

  • The first and last surfaces of the Black Box must:

    • Share the same coordinate system

    • Be separated only by a thickness

The reported thickness in the Lens Data Editor represents only the distance between input and output planes, revealing no internal optical details.

 

Alternative IP-Protection Methods

An alternative approach to IP protection is the use of Zernike surfaces, which approximate optical behavior without revealing design geometry.
This method will be discussed in a future article.

 

Why Use Black Box for Telescope Designs?

  • Full ray-trace fidelity
  • Complete IP protection
  • Safe external collaboration
  • Identical optical performance
  • Industry-proven workflow

Black Box Lens Surfaces are one of the most effective ways to share telescope designs securely while preserving proprietary optical know-how.

 

References:

  1. Laikin, Milton. Lens Design. CRC Press, 2007.
  2. https://www.zemax.com/
  3. The design file used in this particle is attached. How to make your telescope design as Black Box / How to make your telescope design as Black Box_BB