A protective window becomes part of a laser rangefinder’s optical path. A material that looks clear to an operator may transmit differently at the ranging wavelength, reflect light back into the receiver or obscure part of an aperture after assembly. A window drawing therefore needs more than a material name and a transmission percentage.
For an OEM enclosure, the useful deliverables are a controlled optical drawing and a comparison record for the installed assembly. The checklist below describes how to prepare those deliverables. Dimensions, coatings and acceptance limits must come from the selected module’s documentation and the application’s requirements.
Define the assembly before comparing suppliers
Record the module identity, document revision, window orientation, mounting datum and the relationship between the window and each optical opening. Include the bezel, seals and retention features. Reviewing a loose piece of glass misses obstructions or reflections introduced by the enclosure.
Do not transfer a window recipe from a similar-looking module. Transmit and receive geometry, coatings, mechanical clearances and permitted installation conditions can differ. When a drawing or manual identifies guidance as family-derived, obtain confirmation for the intended model and delivered revision.
| Field | What the record should establish |
|---|---|
| Material and traceability | The specified material grade, approved substitutions and the identity of the supplied part. |
| Clear aperture | The usable optical area after mounting, including seals and bezel overlap. |
| Thickness, wedge and orientation | The required geometry and tolerances, with the direction of any intentional wedge or tilt defined. |
| Coating | The coated surfaces, intended wavelength interval and permitted operating conditions. |
| Transmission | Whether the requirement applies to a surface or the complete window, at which wavelengths and incidence angles. |
| Mounting and spacing | The controlled relationship to the module, together with mechanical clearance and alignment requirements. |
| Inspection and cleanliness | The agreed inspection method, handling condition and evidence supplied with the part. |
These are fields to agree, not universal specifications. An unresolved field should remain visible on the review record rather than being filled with a value copied from another product.
Make the transmission requirement comparable
Two quotations can use the same percentage while describing different measurements. One may describe a coated surface at a single wavelength; another may describe the finished window over a band. The incidence angle, orientation and test arrangement may also differ.
Ask the supplier to identify the measured item, wavelength interval, angular conditions and whether the figure is a minimum or an average. Keep the measurement method and report with the drawing revision. A coating statement alone does not describe every loss in a finished optical stack.
Transmission is also only one acceptance item. A window can transmit useful light while creating an unwanted near reflection or clipping one optical path. Conversely, a change in reported distance is not enough to identify the window’s transmission as the cause. Geometry, mounting and target conditions need to remain controlled during the comparison.
Compare three assembly states
- Document the baseline. Record the bare module in a stable fixture, using the selected operating mode, supply, target and reference method. Preserve individual results and unsuccessful attempts.
- Add the proposed window. Repeat with its specified orientation and mounting relationship. Keep the target, module position and other settings unchanged where practical; record any unavoidable difference.
- Complete the enclosure. Repeat after installing the actual bezel, seal and retention features. This is the assembly the customer will use, so evidence from the loose window alone cannot replace this step.
Set the acceptance criteria before reviewing the results. The application should define the distances, target materials, viewing angles, environmental conditions and allowable outcomes. This article supplies no universal sample count, optical tolerance or allowable error.
| Observation | Record alongside it |
|---|---|
| Distance error or offset change | The reference method, its uncertainty, assembly state and individual readings. |
| Valid and unavailable results | The total attempts, validity definition and reasons for rejection where available. |
| Unexpected near or background readings | Target geometry, nearby surfaces, window state and unchanged raw reports. |
| Changed update behavior | The operating mode, host reception intervals and known buffering limits. |
| Environmental dependence | The observed illumination, temperature, contamination and other conditions relevant to the intended use. |
Keep the comparison diagnostic
If behavior changes, vary one suspected cause at a time where practical. Check for aperture obstruction, incorrect orientation, assembly movement and contamination before interpreting the result as a change in sensor accuracy. A smoothed display can hide intermittent failures, so preserve the underlying records.
Repeat the relevant comparisons at the application’s required environmental conditions and across its working distances. A successful indoor comparison establishes evidence for that configuration and scene; it does not demonstrate performance in direct sunlight, condensation or another untested condition.
Retain the window lot, drawing, coating and assembly revisions. A later substitution can change the optical path even when the part still fits. Decide which acceptance checks must be repeated whenever the window or enclosure changes.
The 905 nm integration guide explains the broader optical and mechanical context. Use the model pages for published module conditions, then send ERDILRF the proposed window drawing, enclosure sketch and required target conditions for a model-specific review.