A LiDAR cover window affects both the transmitted pulse and the returning signal. Its material, coating, position, and tilt can change the optical power reaching the receiver even when the enclosure meets every mechanical requirement. A window reflection may also create a path from the transmitter into the receiver housing.
LiDAR window optical design in SOLIDWORKS starts with the actual enclosure geometry. RayViz supports assigning optical properties and visualizing traced rays within that assembly. Use this early review to identify clipping and possible ghost paths, then transfer the model to TracePro for quantitative optical analysis. [1]
For an architecture in which outgoing and returning light cross a cover window, the window contribution to the useful signal is the product of the outbound and inbound transmissions. If those values are T_out and T_in, the combined factor is T_out × T_in. It becomes T² only when both transmissions are equal.
As an illustrative calculation, 95 percent transmission on each crossing gives 90.25 percent combined transmission. This is a window-only power factor, not a prediction of detection range. Target reflectance, atmospheric loss, receiver sensitivity, and the detection algorithm also affect range.
Separate transmit and receive apertures may see different window regions and incidence angles. Trace those paths separately before combining their losses. Each crossing already includes the relevant front and rear interfaces and bulk absorption; do not count those losses twice.
Include the window, receiver aperture, emitter aperture, mounts, seal lips, nearby housing surfaces, and any partition between transmit and receive compartments. Use the intended source wavelength and angular distribution. Check center and edge scan positions, where clipping and incidence angles may differ most.
The CAD assembly represents the modeled configuration. It does not become an as-built model simply because it contains production parts. Create additional configurations for credible bracket tolerances, seal compression, window displacement, and tilt. Record the dimensions varied so that the optical comparison can be reproduced.
In RayViz, assign material and surface properties and define the surface source before tracing. Preserve those assignments with the model for the subsequent TracePro analysis. Use consistent property databases during the handoff. [2]
Obtain wavelength-dependent refractive index and absorption data for the substrate, along with coating reflectance and transmission across the required incidence angles and polarization states. A visible-light transmission value is insufficient for a near-infrared LiDAR design.
Determine what the supplier measurement includes. Data for a finished, coated window may already include both interfaces, substrate absorption, and surface treatments. Applying that total transmission independently to each face would overstate the loss. Conversely, coating-only data need to be combined with a suitable substrate model.
Use measurements of the complete stack when anti-fog, hydrophobic, protective, or other layers matter. Their optical effects are not necessarily the sum of independent transmission penalties. Ask suppliers for compatible test conditions and uncertainty when screening alternatives.
Trace the outgoing bundle and examine reflections from both window faces and nearby surfaces. Look for paths entering the receiver aperture directly or after another reflection from the enclosure. In this article, these are transmitter-to-receiver coupling paths; they are distinct from light leaking between detector channels after a target return enters the receiver.
A ray crossing the receiver aperture establishes a possible geometric path. It does not establish the amplitude or timing of a false return. Follow the path through the receive optics and compare the coupled energy with detector and electronics behavior in the full system assessment.
Candidate changes include window tilt, wedge, a transmit–receive partition, aperture placement, and surface treatment. Tilting a window can move a reflection, but it can also change beam displacement, incidence angle, and mechanical clearance. Recheck the full scan field and tolerance configurations after each change.
Export the optical model from RayViz to TracePro for analysis and reporting. TracePro provides flux reports and ray-history tools that support comparison of candidate designs and investigation of unwanted paths. [1, 3]
Keep source power, wavelength, aperture definitions, detector collection region, and numerical settings consistent between candidates. Define transmission at explicit reference planes so the result does not accidentally include target reflectance or geometric collection efficiency.
A complete source-to-target-to-receiver trace may be useful, but a distant target and a small receive aperture can require careful sampling. For a window budget, normalized outbound and inbound calculations can be more practical, provided each represents the appropriate angular distribution and position. Document how the two factors are combined.
For weak ghost paths, verify that ray counts and flux thresholds resolve the level of interest. A trace with no detected ghost rays is not proof of zero coupling. Repeat or refine the calculation until the estimate or detection limit is adequate for the requirement.
Compare candidate windows using the same geometry, source conditions, and reporting definitions. Review useful transmission and unwanted coupling together: a coating that improves one metric may leave the dominant mechanical reflection path unchanged.
Temperature, contamination, wear, and condensation require explicit model inputs. Use measured optical properties for the relevant condition and geometry changes from a thermal or mechanical assessment. An optical ray trace does not independently predict coating aging, condensation growth, seal motion, or thermal deformation.
A practical comparison records the nominal and tolerance configurations, data source for each material and coating, window power factors, receiver-coupled ghost power, and numerical convergence. Validate the selected configuration with representative hardware, including the operating conditions that drive the design decision.
Bring the optical window into the enclosure review while tilt, baffles, and aperture positions are still adjustable. RayViz gives the mechanical team a way to inspect optical paths in SOLIDWORKS; TracePro supports the quantitative analysis needed to evaluate transmission and stray light. [1]
Request a RayViz demo to review your LiDAR window geometry in SOLIDWORKS and plan the transmission and stray light analysis in TracePro.