Terms of use
Version 2026-09-20 · applies to the REX-Optics Coating Designer (designer.rex-optics.com), REX Analyze (analyze.rex-optics.com) and the related pages on rex-optics.com
The Coating Designer and REX Analyze (each a "Tool") are provided by REX-Optics B.V., Drienerlolaan 5, 7522 NB Enschede, The Netherlands (KvK 97561029). By using either Tool you agree to these terms. If you do not agree, please do not use it. Sections 1 to 9, 11 and 12 apply to both; section 10 adds terms specific to REX Analyze.
1. Public beta
The Tool is published as a public beta. Features, material datasets, example designs and results may change or be withdrawn at any time, and the Tool may be unavailable without notice. We may modify or discontinue it, in whole or in part, at our discretion.
2. Permitted use
You may use the Tool free of charge for academic, research and commercial engineering purposes, including designs you go on to have manufactured elsewhere. You may export and reuse the results of your own simulations, including in reports and publications. An acknowledgement of the Tool is appreciated but not required.
Sections 2 and 9 describe the Tool as it is supplied today, without charge. If we later offer paid access, that supply will be governed by separate terms presented before purchase, which will state the price, the applicable VAT, the right of withdrawal where one applies and a liability regime appropriate to a paid service.
You may not: attempt to gain unauthorised access to the Tool or its underlying data; systematically extract or mirror the material datasets or any substantial part of them; interfere with or overload the service, including through automated querying at a rate that degrades it for others; or remove or obscure attributions in exported material.
3. Results are simulations, not guarantees
The Tool computes the optical response of an idealised planar layer model using published optical constants. Results are indicative engineering estimates. They are not a measurement, a specification, a manufacturing guarantee, or a prediction of what any particular deposited coating will achieve.
Agreement with a real coating depends on optical constants, film density and composition, interface structure, roughness, substrate quality, deposition process and measurement conditions — several of which the model does not represent.
The Tool is provided "as is" and "as available", without warranty of any kind, whether express or implied, including any warranty of accuracy, completeness, merchantability, fitness for a particular purpose, or non-infringement.
Do not rely on results from the Tool, without independent verification by a qualified engineer, for any application where failure could cause injury, loss of life, environmental harm or significant financial loss. This includes medical, aerospace, nuclear, automotive-safety and other safety-critical uses.
4. Your designs and your data
You keep all rights in the coating designs and parameters you enter. We do not claim ownership of them, we do not store them in a database, and we do not use them to train models or publish them. Parameters are transmitted to our server only in order to compute the result you asked for; see the privacy notice for detail.
You confirm that you are entitled to submit the information you enter — in particular that doing so does not breach an obligation of confidentiality owed to a third party, such as a customer or employer.
5. Confidentiality of shared links
The Tool can encode a complete design into a shareable link. The design travels in the fragment of the address (after the #), which browsers do not send to our server — so we never receive it. However, anyone holding the link can open the design, and links commonly persist in browser history, corporate proxies, email and messaging systems.
Do not use shareable links for confidential, customer-owned or export-controlled designs. For those, use the export file, or contact us to agree a non-disclosure arrangement first.
6. Our intellectual property
The Tool's software, interface, documentation and the selection, compilation and arrangement of its material database remain the property of REX-Optics B.V. and its licensors. Nothing in these terms transfers those rights to you.
The underlying optical-constant data originate from third-party sources under their own terms, including the CC0 public-domain refractiveindex.info database and published atomic scattering-factor tabulations. Each dataset displays its source, type, valid range and licence within the Tool. If you redistribute data obtained through the Tool, you are responsible for complying with the terms of the original source.
7. Quotations and technical assistance
Sending a design through the Request this coating function is a request for information, not an order, and does not create a contract. Any quotation we issue is subject to our separate terms of sale, and manufacturability, tolerances and final specifications are always confirmed by our engineers before we commit to supply.
8. Export control and sanctions
Use of the Tool, and any technical assistance, quotation or supply that follows, is subject to applicable European Union and Netherlands export-control and sanctions law. Where a request involves a controlled item, a restricted destination or a sensitive end use, REX-Optics may request end-use and end-user information, and may decline or suspend the request pending classification, verification or authorisation. You may not use the Tool if you are subject to applicable sanctions.
9. Limitation of liability
To the fullest extent permitted by law, REX-Optics B.V. is not liable for any indirect or consequential loss arising from use of the Tool — including lost profits, lost production, scrapped material or batches, delay, loss of data, or the cost of rework — whether or not we were advised such loss was possible.
Because the Tool is supplied free of charge, our total aggregate liability arising from or in connection with its use is limited to EUR 500. Nothing in these terms excludes or limits liability for intent, wilful recklessness or gross negligence, for death or personal injury caused by our negligence, or for any other liability that cannot lawfully be excluded. Liability arising from a paid supply contract is governed by that contract, not by these terms.
If you are using the Tool as a consumer rather than for a trade, business or profession, the exclusions and the cap in this section apply only so far as Dutch consumer law permits; your statutory rights are unaffected, and you keep the right to bring proceedings in the courts of your own country of residence.
10. REX Analyze
REX Analyze is a separate, access-controlled beta service for analysing measurement data. Everything above applies to it, with the following additions.
10.1 Access and allowance
Access is granted to approved, verified email addresses. Trial or sponsored allowances are shown in your account. We fund the underlying model usage ourselves and may pause, reduce or withdraw the free allowance at any time, including before your allowance is used up. Allowances are personal and not transferable. Monthly allowances reset each month; trial allowances apply to the total number of trial analyses.
10.2 What one analysis covers
One analysis covers one measurement file: the numerical search, the clarifying questions the service asks you within that same analysis, and the resulting report. The free curve and Fourier preview never consumes an analysis. If the service fails for a technical reason on our side, the analysis is returned to your allowance. A scientifically sound outcome that concludes the data cannot determine a parameter is a result and uses the analysis.
10.3 Results are model-dependent estimates
An analysis returns the parameters of a model fitted to your data. It is not an independent measurement, a calibration, a certificate, or proof that the structure you described is the one that exists. The report does not quote ± uncertainties or confidence intervals, because none are validated for this analysis: treat every digit shown as a fitted value, not as a stated precision.
X-ray reflectivity responds to electron density, not composition: converting it to a mass density or a chemical identity always rests on an assumption, which the report names. Different structures can reproduce the same curve. Check any result that matters against an independent method before you publish it or accept material on the strength of it.
The interpretation section of a report is written by a language model from numbers computed by our own code. It can describe sound numbers wrongly. Read the parts the code produces — the layer table, in which every value is marked fitted, fixed or poorly constrained; the plot of your data against the fitted curve; the density profile; and the plaque reading either "Fit supports this structure" or "Use with caution" — and treat the prose as commentary.
Reports are AI-assisted. Do not present them as reviewed or certified by a human expert.
10.4 Your files
You keep all rights in the data you upload. We do not use it to train models, publish it or share it with other users. To run an analysis we transmit numerical evidence from your file and the description you write to our language-model provider, as set out in the privacy notice. Files and reports are deleted automatically after 30 days and you can delete them sooner. Keep your own copy of anything you need; the service is not a data archive and we give no guarantee against loss.
You confirm that you are entitled to upload the measurement and the description — in particular that doing so breaches no obligation of confidentiality to a customer, employer or funder, and that the data is not export-controlled or otherwise restricted from disclosure.
Do not include personal data in uploads or descriptions. Instrument files can carry operator names, user accounts and machine identifiers in their metadata; remove them if this matters to you.
10.5 Account and fair use
Sign-in codes and sessions are personal. Do not share them, do not create accounts for people who cannot verify their own address, and do not use automated means to submit analyses. We may suspend access that exhausts shared funding, circumvents the allowance, or degrades the service for others.
11. Governing law
These terms are governed by the laws of the Netherlands. Disputes will be submitted to the competent court in Overijssel, the Netherlands, without prejudice to any mandatory right you may have to bring proceedings elsewhere.
12. Contact
Questions about these terms: info@rex-optics.com.
This address is also our single point of contact for users and for authorities in connection with the Tool, including notices about content stored in it. We answer in English and Dutch. Postal address: REX-Optics B.V., Drienerlolaan 5, 7522 NB Enschede, The Netherlands (KvK 97561029).