How PISÉO transforms a laboratory setup into reliable industrial equipment for Non-Destructive Testing

In the semiconductor and integrated photonics industries, a component’s final performance depends directly on the quality of the material used. When a crystal defect is detected too late, after costly manufacturing steps, the industrial losses become irrecoverable.

Identifying these defects early on is therefore a major strategic challenge. However, this requires a measurement system capable of moving beyond the experimental framework to become a reliable, reproducible and usable tool in an industrial environment.

It is precisely at this critical juncture, the transition from scientific proof to industrial equipment, that PISÉO adds value.

Metrology based on nonlinear reflectometry

The solution is based on an advanced nonlinear reflectometry technique that utilizes second harmonic generation (SHG).

The material is illuminated with an infrared femtosecond laser and the optical response generated at twice the fundamental frequency is analyzed. The observed variations, combined with the analysis of polarization states, reveal signatures directly linked to the crystalline structure.

Unlike conventional optical approaches, this method allows for the detection of invisible structural defects while remaining completely non-destructive.

PISÉO, a partner in the industrialization of photonic technologies

Transforming a scientific innovation into a sustainable industrial advantage requires much more than just optical expertise. It requires a combined mastery of optics, precision mechanics, and systems engineering.

This is precisely the role that PISÉO plays for its industrial partners: designing, securing, and industrializing complex optical systems capable of operating reliably in demanding environments.

Choosing PISÉO means relying on a partner capable of transforming laboratory-based technology into operational, robust, and durable industrial equipment.

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Developing a multispectral optical zoom covering the visible (VIS), near-infrared (NIR) and short-wave infrared (SWIR) is a major technological challenge. Few companies are able to combine optical performance, mechanical robustness and industrial viability over such a broad spectrum.

PISÉO has demonstrated this with a multispectral continuous zoom project, illustrating its unique know-how in the design of complex optical systems, while meeting demanding specifications: precise numerical aperture, continuous x15 zoom factor, strict control of maximum authorized distortion, high MTF (Modulation Transfer Function: the system’s ability to reproduce fine details with contrast), while respecting constraints on size and field-of-view (FOV/DOV, i.e. the extent and depth of field of the observable scene).

PISÉO is a recognized partner for the development of complex optical systems, able to intervene at every stage: from initial idea to market-ready product. Working with PISÉO means benefiting from rigorous support, cutting-edge expertise and the ability to transform technical challenges into concrete, reliable solutions.

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The device in question used an optical concept based on the projection of an image via two curved mirrors and an output window, which was then reflected onto the windshield. This system had to meet strict criteria imposed by the customer, such as overall size and visibility characteristics, while maintaining high image quality. In order to meet the car manufacturer’s objectives, the customer called on PISÉO to optimize its head-up display. After a critical analysis of the existing system (performance and construction), PISÉO’s engineers developed an optical design that solved the problems identified.

Optical design of the HUD system

To meet the customer’s specific needs, PISÉO engineers used Zemax OpticStudio optical design and simulation software. The main focus was on the mirrors, a key factor in meeting space constraints while maintaining high image quality.

PISÉO engineers modeled the optical system in Zemax, optimized the design using their extensive experience in the field, and simulated the achievable performance. This work also made it possible to anticipate and correct recurring problems in augmented reality systems, such as ghost images, luminance management for day and night visibility, and distortion minimization. This optical design was carried out taking into account the industrial feasibility of the optics and the target cost.

Head-up display (HUD) systems are complex optical devices that must meet numerous technical constraints, particularly when used in vehicles.

Thanks to its expertise and technical resources, PISÉO supported this customer from the feasibility study to industrialization, demonstrating its ability to design low-cost, optimized, and industrializable embedded optical systems. These solutions meet the strict requirements of automotive manufacturers.

Please do not hesitate to contact us for any optical system design and optimization project. We will meet your needs and expectations from concept to manufacture.

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Entrusting laser risk management to PISÉO means choosing technical excellence, maximum safety for your products, and regulatory compliance.

Please do not hesitate to contact us with any questions you may have about the LASER safety of your devices.

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A concrete demonstration of this is our collaboration with an industry leader in the development of a large, flexible fingerprint sensor based on organic technology. This new-generation sensor paves the way for critical applications such as multi-fingerprint identity control in sensitive environments, and enhanced authentication on mobile devices.

For this sensor to live up to all its promises, it was necessary to take up a challenge that went far beyond simple lighting: to design a custom optical system adapted to particularly severe mechanical and electronic constraints. PISÉO was chosen to solve this demanding equation.

A highly technical optical challenge

Unlike conventional sensors, this device had to operate in a confined space, without a frontal light source, while ensuring a sharp, homogeneous image, whatever the conditions.

The project presented several major technical constraints:

• Large surface area to be illuminated: As the sensor is much larger than a standard fingerprint sensor, uniform illumination had to be guaranteed from the center to the edges, without shadow zones or excessive variations.
• Thickness and integration: The flexible sensor had to fit into a compact device. The illumination system could not use sources above the finger (no front LEDs), but had to illuminate from the side or in the background, in the same way as e-reader screens, which are backlit from the edge.
• Organic technology and optical stacking: The sensor is made up of innovative optical and electronic layers (organic polymers, thin films, etc.). A light guide had to be integrated to distribute the LED light under the footprint. The guide, in direct contact with other layers with no air space, radically altered light propagation and extraction. In addition, an angular filter was added above the sensor to allow only near-perpendicular light rays to pass through – a prerequisite for obtaining a clear image of the impression.
• Demanding operating conditions: The system had to operate in a variety of environments (e.g. variable ambient light) while maintaining high contrast between the ridges and valleys of the print. Stray light and unwanted reflections also had to be prevented from blurring the image.

Faced with such complexity, an empirical approach would have been time-consuming and uncertain. What was needed was a detailed understanding of the optical phenomena involved, in order to arrive at a reliable, optimized solution. This is where PISÉO made the difference, mobilizing its expertise in optical design and advanced modeling to meet the technical requirement.

A tailor-made lighting solution

PISÉO’s approach was to break down the problem into optical sub-systems and optimize each of them, while ensuring their overall smooth operation.

The main elements of the illumination system were:

• Lateral LEDs: chosen for their angle of emission and lens-free efficiency. The coupling with the light guide was carefully adjusted to limit losses.
• Integrated light guide: featuring microstructures just a few microns in size, inspired by flat-screen backlighting. Objective: to distribute light uniformly and at a precise angle.
• Multi-layer angular filter: modeled to block rays that are too inclined, allowing only light reflected directly from the ridges of the footprint to pass through.

3D modeling of the complete system: One of PISÉO’s strengths in this project was to use advanced optical simulation tools to create a digital twin of the biometric sensor. Each element – LED, light guide with its micro-structures, angular filter, and even the finger – was modeled to predict the system’s behavior. This approach made it possible to virtually test numerous configurations and identify optimal solutions even before physical prototypes were produced.

Integrating the human finger into the model

Modeling a human finger involves more than simply reproducing a 2D pattern: its complex topography (ridges and valleys) and optical properties (scattering through skin layers) must also be taken into account. To this end, PISÉO conducted a photometric measurement campaign, using an optical goniometer to analyze light reflection on real fingers.

The data collected revealed a dual response: a reflection due to the skin’s natural moisture, and a wider diffusion. These characteristics were translated into BRDF (Bidirectional Reflectance Distribution Function) and integrated into the optical model.

The result: the simulation generated imprint images very close to reality. Compared with the physical images, they confirmed the accuracy of the model. Even the customer’s own image processing (by reference subtraction) was successfully simulated, revealing the details of the impression.

This advanced modeling, validated experimentally, strengthened the customer’s confidence and made development more reliable right from the start.

Thanks to its expertise in optical modeling, its rigorous approach to design and its close collaboration with customers, PISÉO doesn’t just solve problems: it provides a complete understanding of the system, accelerates development and secures technical choices.

In a world where technological superiority is a strategic issue, PISÉO transforms operational constraints into concrete solutions. For your optical detection systems, your authentication systems or your on-board optronic devices, PISÉO is a committed partner in the service of performance and security.

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Use of materials in optical design

The optical design of high-performance systems requires perfect mastery of the optical properties of materials.
A large percentage of the engineering projects conducted by PISÉO involves optical design. Our experts design systems that meet our customers’ most demanding requirements, then model and evaluate their performance using optical simulation software that integrates the materials’ optical properties. The skills and resources they mobilize allow them to consider a variety of materials and quickly offer their clients appropriate choices for their optical systems.

For each project, we can offer you perfectly adapted materials for your optical systems, taking into account your technical needs, industrial constraints, and the regulatory requirements specific to your application.
Whether it is to develop precision optical systems, guarantee maximum luminous efficiency, or meet strict performance and safety standards, PISÉO is committed to providing you with tailor-made and optimal solutions.

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In this context, the main objective of the mission entrusted to PISÉO was to use our exprertise and advanced simulation tools to identify the different sources of stray light, quantify their influence, and propose actions for reduction.

The VEM space system: sensitivity to stray light presents an optical challenge

The VEM instrument (called VenSpec-M for the EnVision mission) is a multispectral imager designed to map the surface of Venus and its lower atmosphere. Mapping is accomplished by observation through narrow atmospheric windows in the near-infrared spectral range. This allows the VEM to detect thermal emissions such as volcanic activity, surface rock composition, and water and cloud formation.
To image the surface of Venus, the instrument features an optical design consisting of a single lens on a filter assembly composed of 14 individual spectral bands, and a two-lens relay optical system to reform the spectrally-filtered image on an InGaAs detector.
Given the low intensity of the scientific signal that the instrument must detect, any external contribution to the effective signal-to-noise ratio must be studied, and if possible, mitigated. As with most optical instruments, one of the main sources of interference is stray light.

Stray light can create undesirable effects such as :
 
• veiling effect : a reduction of image contrast,
• light halo : parasitic dispersion around intense sources,
• ghost images : uncontrolled internal reflections,
• star effects : light artifacts distorting the interpretation of data.
 
Stray light control is crucial for ensuring the reliability of the images produced by the sensor and avoiding any scientific interpretation errors. By combining mechanical engineering, advanced optics, and simulation strategies, the VEM system represents a cutting-edge approach that meets the challenges associated with space environments and the mapping of planetary surfaces.

VEM : sources of stray light

In collaboration with LESIA and DLR, PISÉO identified multiple sources of stray light that could potentially affect the quality of detection provided by the VEM. We then quantified the impact of these sources to assess the performance achievable by the VEM under its intended operating conditions.
 
These are the different sources of stray light identified by PISÉO :
 
• Reflections on the lenses : even treated lenses can generate stray radiation that is detected by the sensor.
• Reflections on mechanical elements : despite the use of a baffle, internal mechanical elements can generate unwanted radiation, depending on their geometries.
• Reflections on the sensor : InGaAs sensors like the one used in the VEM can reflect up to 30% of infrared radiation.
• Interference (“crosstalk”) between filters : the location of the 14 IR spectral bands is crucial for minimizing crosstalk.
• Materials and treatments : the optical properties and treatments (in particular, their diffusion) of the materials used significantly influence the propagation of light in optical systems.
• Dust contamination : particles generated during takeoff increase the diffusion of radiation..
• Solar influence : sun glare can saturate the sensor, depending on the orientation and launch date.
 
In order to precisely quantify these sources contribution to stray light, the VEM optical system was modeled in a powerful ray-tracing tool, and simulations were performed.

System modeling and simulation

LESIA used Zemax to design an imaging optical system that optimizes image formation on the sensor while minimizing optical aberrations. However, although PISÉO also has Zemax, our analysis of stray rays outside the main image was done with LightTools – a more suitable non-sequential simulation software. LightTools allows the modeling of sources and surfaces to study irradiance maps and intensity indicators, thus identifying the contributions of stray rays, including “ghost images”.
PISÉO exploited LightTools to its limits. In doing so, we determined the origin of the stray rays, evaluated their energy in relation to the main image, and proposed corrective actions. Moreover, the LightTools “imaging module”, used in beta version, made it possible to isolate the critical paths of stray light and optimize the results by focusing on the most relevant trajectories, thus guaranteeing a good signal-to-noise ratio.
 
The optical simulation used a far-field source to represent the instrument’s field of view (FoV). An approach combining an ideal lens and a point source, positioned at three strategic locations (optical axis, horizontal edge, and vertical edge), allowed for accurate analysis of stray rays relative to the main image. These analyses highlighted distortions and aberrations due to an excessively wide FoV, causing artifacts and asymmetries on the sensor. An optimization of the optical design then corrected these defects, aligning the simulated performance with the system’s real-world requirements.
 
The lenses were accurately modeled in LightTools by integrating material characteristics and optical properties, including Fresnel losses and internal reflections. The filters were simulated from a mechanical model, with specific surface treatments based on the spectral transmittance data provided by CILAS. The surfaces of the filters and spectral bands were modeled with distinct treatments to ensure high accuracy. The diaphragm, treated with a black absorbent paint validated by CNES, was designed to absorb non-reflected rays.
 
Ultimately, the analysis of stray light, with a precise threshold, revealed that the main sources of disturbance were internal reflections in the sapphire window and lenses, and interference between filters. Anti-reflective coatings were subsequently optimized to reduce these reflections, and studies were conducted to evaluate the impact of dust and surface roughness. Moreover, irradiance maps were used to identify critical areas and refine treatments to minimize stray light.
 
Analysis of the impact of the mechanical system on stray light revealed that internal reflections can cause ghost images. To counteract this, PISÉO used and then adjusted a mathematical diffusion model, supplemented by BRDF measurements at 850 nm and 1550 nm. These data made it possible to precisely evaluate the absorbing materials and select the most suitable one to reduce stray light.
 
Finally, the analysis evaluated the “off-axis” stray light caused by the contribution of the Sun. The asymmetric deflector used for the VERITAS mission was modeled to simulate the interactions between visible and infrared rays. A uniform planar source was adopted to improve the efficiency of the simulations, reducing the detection threshold and the computation times. These optimizations made it possible to choose a suitable material and design for effectively reducing stray light.

PISÉO’s in-depth stray light analysis for LESIA demonstrates the importance of optical design expertise and advanced simulation and modeling tools to ensure the performance of optical instruments in extreme space environments. By identifying critical sources of stray light and proposing innovative solutions, e.g., optimizing coatings, absorbing materials, and mechanical elements such as the baffle and deflector, PISÉO has ensured the reliability of scientific measurements for the VERITAS and EnVision missions.

If you are developing advanced optical systems or are facing stray light challenges, contact PISÉO today. We will ensure you benefit from customized solutions that ensure the performance of your optical systems even in the most demanding conditions.

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Thanks to the expertise of its optical design engineers and its advanced simulation and characterization resources, PISÉO successfully met the technical challenge. The team quickly provided results that met the manufacturer’s expectations, helping the customer win its contract.

If you want to design and produce a high-quality image projection solution while taking into account your industrial and economic constraints, do not hesitate to contact us to tell us about your project.

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Thanks to the recognized expertise of its engineers in optical design and the use of advanced laboratory simulation and characterization methods, PISÉO successfully met this technical challenge. The team was able not only to meet the customer’s rigorous requirements but also to produce results that exceeded expectations. The optical systems designed and validated by PISÉO offer superior performance in terms of luminance, contrast, and chromatic precision, thus contributing significantly to the perceived quality of the car manufacturer’s vehicles.

If, like this satisfied customer, you wish to design and produce a high-quality image projection solution, whilst taking into account your industrial constraints, do not hesitate to contact us to tell us about your project.

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PISÉO stands out for its expertise in designing custom LED-based UV-C sources adapted to the specific needs of its customers in various application areas. This expertise has proven particularly valuable during the COVID-19 epidemic, which generated a significant increase in the need for disinfection solutions. At the same time, the performance of UV-C LEDs has improved considerably in recent years, as shown in our UVC LED report.

Mercury-based UV tubes, historically used for disinfection applications, will be gradually withdrawn from the market by 2027. This deadline encourages users to review their strategies and look for alternative solutions. LED-based UVC sources now offer a viable and more environmentally friendly alternative. However, in order to reap all the benefits, the transition to this new technology requires specific know-how, which PISÉO has developed over the years.

UVC LEDs

The design of an appropriate UVC LED source takes into account the optical, electrical, and dimensional characteristics of the components available on the market. As the COVID-19 epidemic has sparked a strong craze for disinfection devices, many manufacturers have developed a portfolio of more or less effective UVC LEDs. It is, therefore, essential to have a good knowledge of the broad range of these components in order to make informed choices. Performance tests in an optical laboratory, such as PISÉO’s, can be useful for discriminating between products and ensuring the correct characteristics.

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Design of UVC Sources

The specific application cases of UVC LED sources require a design approach that draws on a knowledge of physics, as well as biology and chemistry. For a disinfection source, for example, it is crucial to know the sensitivity of microorganisms to ultraviolet radiation in order to determine the dose and spectrum required to deactivate the DNA and RNA molecules of these microorganisms. This is the germicidal effect of the UVC source. Examples of doses for air disinfection are given in the International Commission on Illumination document CIE 155:2003.

Once the dose and spectrum have been determined, it is necessary to consider the environment in or on where the biological or chemical reaction will occur. Indeed, characteristics such as the geometry and materials of the exposed or fluidic surfaces must be considered during the design to guarantee the efficacy  and durability of the systems developed.

Finally, LED system design know-how is required to ensure product performance and reliability. Once the component has been chosen, the integration of UVC LEDs requires in-depth work to provide the right level of energy illumination and maintain it over time, thanks to a precise optical design, suitable electronics, and efficient thermal management. The latter aspect is particularly crucial given the heat dissipation requirements of UVC LED components.

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In conclusion, the transition to UV-C sources represents an opportunity to improve disinfection and environmental protection practices. Thanks to our expertise and commitment to innovation, PISÉO is positioned as a partner of choice for all companies wishing to adopt this cutting-edge technology. To learn more about our UVC source design services and discover how we can support you in your projects, do not hesitate to contact us.

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