Authored By Julia Zhang, HunjuYi, Mike Grove and Alexandra Culler

Introduction

To design a Head-Up Display (HUD) system in OpticStudio, it is convenient to begin by using Speos for the initial design setup. Speos allows for easy configuration of HUD projector elements, mirrors, eyebox, and virtual image. The CAD platform offers graphical interactivity and user-friendly operations, making it easier to apply constraints and volume constraints visually. This ensures a proper fit within the car from the beginning, allowing for the placement of optical elements embedded in car assemblies, such as the windshield and dashboard.

This article is one in a series of four that discusses the setup and optimization workflow for the HUD projection optical system, using Speos and OpticStudio.

This part discusses the Speos HUD optical design tool used in the workflow. It includes the routine steps for creating a starting point HUD design with specified design parameters. Additionally, it provides a procedure to align the global coordinate system so that it is consistent in both Speos and OpticStudio.

Head-up Display projection system: from Speos to OpticStudio - part2

Preparation of HUD optical design in Speos

Defining geometry constraints directly in a CAD platform can be extremely useful for creating the starting point of the head-up display (HUD) projection system. This approach allows for a visual outline of the volume of the HUD projector system in graphic window, which includes mirrors and the picture generation unit (PGU). It facilitates the spatial arrangement of optical elements by interacting with the car windshield and other STEP parts and assemblies. We will not discuss the elements included in a HUD system that uses the windshield as the combiner. 

Which tools to use when working on a Head-up-Display ?

Head-up Display: from OpticStudio to Speos

HUD Optical Design (HOD) is a Speos tool used to create the optical system for a HUD mirror projection system. It provides optimized results with freeform mirror and helps build the entire optical system based on input specifications, such as size dimensions and distance/locations.

OpticStudio users may initially find it difficult to perform operations with CAD parts or assemblies in the graphical window of Speos. This is because the method of rotating, moving, and zooming in and out of elements in the Speos graphic window is different from that in OpticStudio layout/ shaded model. Additionally, there is no option/setting available to make the operations consistent between the two software. The section "Speos navigation for OpticStudio users" in the article is a useful resource for OpticStudio users to quickly become familiar with the navigation in Speos.

Building starting point design in Speos

The procedure of the Speos HOD tool involves constructing the optical system based on the path length and directions of the critical rays (center rays), combined with the user’s input of certain element dimensions.

To create a HUD optical design, follow the routine steps and include an additional step for aligning the coordinate systems between Speos and OpticStudio. We'll first discuss the coordinates alignment steps, followed by the routine HUD creation steps.

Figure 1.1: Speos coordinate alignment step

Coordinate system alignment

The purpose of the coordinate system alignment is to use the same global coordinate reference in both software, so that the location values and size values retrieved from Speos can be used in OpticStudio.

There is a world origin in Speos (SpaceClaim CAD platform), which is fixed and equivalent to the global reference to be set in OpticStudio. In Speos, when selecting an object or component and clicking on Design > Editor > Move, another origin appears at the center of the object/component. This origin allows the object/component to be rotated or translated based on it, similar to the local axis or local coordinate reference in the OpticStudio sequential system.

During the initial setup of HUD design in OpticStudio, the system will be set reversely, with the center of the eyebox as the global origin/vertex, and the optical axis as the global Z-axis. Coordinate alignment will be performed in Speos using the following continuous steps:

1. Click on Design> Edit> Select, select all the components that need to be moved, either from the graphic window or from the left structure tree (press Ctrl to select multiple geometries).
   

   
   Figure 1.2: Coordinate system alignment - step1

2. With the geometries selected, navigate to Design> Edit > Move. There, options for the movement operation will appear. Click on the Anchor option first, followed by the eyebox center point.
   The highlighted move handle above will act as the new reference orientation for the selected components. Its vertex is coincident with the chosen eyebox center point.
   

   
   (a) Anchor operation 
   
   (b) Move handle coincident with eyebox center
   Figure 1.3: Coordinate system alignment- step2

3. Next, select the ”Up To” option to move the handle of the selected components, aligning

   the vertex with the Speos global origin. The center point of the eyebox is now located at the Speos global origin, with the relative positions of other selected components remaining the same.

   
   Figure 1.4: Coordinate system alignment- step3

4. Rotate 90 degrees around the global Y-axis, so that the global +Z-axis points towards the windshield element.
   

   
   (a) Rotation operation 
   
   (b) Tilt about Y 90 degrees 
   Figure 1.5: Coordinate system alignment - step4
   
   
   Figure 1.6: Final result

Speos HOD routine steps

The routine steps start with creating a design under Design > Optical Part Design > HOD Optical Design in Speos.

1. Define two directions: vehicle direction and top direction. These two directions enable the rays to be directed (backward) from the virtual image surface to the eyebox surface in the correct manner.
2. Choose the center of the eyebox in the graphics window.
3. Select the inner surface of the windshield where the rays will be reflected of.
4. The first three steps generate pre-calculated geometries, which are displayed in the graphics window. This allows the user to interactively visualize in a graphical window and adjust the dimensions and locations of each element from Speos objects definition.
5. The main options to be adjusted include:
   • Eyebox dimension
   • Target image size and location
   • PGU size and location
   • Projector mirrors size and location

Figure 1.7: Speos HOD creation steps

For more detailed instructions and learning materials on this topic, refer to the Ansys Learning Hub.