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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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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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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VCSEL LASER source for electro-optical testing

Electro-optical test benches for imaging sensors usually use LEDs.

For our client, the operating frequency requirements were such that only LASER diode-type sources – in particular VCSELs – had the necessary temporal dynamics to meet them.

With the help of our partner, Yole Group, PISÉO’s experts were able to quickly identify the VCSEL die suppliers in the United States and Asia that were likely to meet the client’s needs. The selected component was assembled by our partner, Serma Microelectronics, using microelectronics techniques, and then extensively tested by PISÉO in our optical laboratory.

Finally, since these components are generally used for optical fiber telecommunications links, our choice to control them quickly fell to a telecom-type driver.

Optical design and engineering

LASER sources, which are used for their dynamic temporal response, have very specific emission profiles requiring the design of a specific optical system to meet the needs of the application. To this end, our engineers, specializing in optical design and engineering, have defined a very precise multi-stage system that enables PISÉO to create controlled lighting from the point-of-view of spatial and incidence characteristics.

To do this, we first characterized the source beam using a beam profiler in the PISÉO optical laboratory.

Based on the measurement results, we then specified a system integrating optical geometry and materials to achieve the desired objectives. Our engineers also used Zemax Optics Studio software to perform this work.

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Creation and validation of modules in several copies

Several electro-optical test modules were thus assembled in a clean room, and then calibrated and tested in the PISÉO optical laboratory according to a rigorous protocol and test plan. Numerous R&R, reliability, and lifespan tests were carried out to allow us, in agreement with the customer, to fully validate the design and manufacturing of the modules.

PISÉO’s customers trust our experts for the development and manufacturing of complex, innovative, and robust optical test benches.

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Assembly & validation of the bench

The characterization bench was entirely assembled at the PISÉO optical laboratory. Numerous electro-optical tests were rigorously carried out to verify the reproducibility and repeatability (R&R) of the measurements. Uncertainty calculations were also carried out to assess the precision achieved by the measurements. The results of this work enabled the validation of the bench in the laboratory.

Because this characterization bench must be integrated into a wafer tester, PISÉO’s engineers ensured the assembly and validation of the bench in a clean room at the client’s site. We also trained their engineers in the use of the bench.

PISÉO’s customers trust our experts for the development and manufacture of complex, ultra-precise optical characterization benches.

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ntegrating an intraoral scanner, combined with cutting-edge equipment, simplifies the manufacturing of prostheses and orthodontic devices, reduces delays, improves patient comfort and optimizes practitioner ergonomics.

Here you will discover how the advanced optical technologies integrated by PISÉO guarantee images of exceptional quality.

High-Resolution Imaging Sensor

After an in-depth study of their optical and electrical characteristics, PISÉO experts chose and integrated very small, high-resolution imaging sensors. To this end, the PISÉO imaging laboratory evaluated the performance of these advanced sensors by carrying out measurements of MTF 50 on the object side, SNR and distortion. The tests also made it possible to assess the deformations generated by the rolling-sutter of the sensors. The results of these evaluations were taken into account to size and develop the LED lighting, as well as the electronics and on-board software. These characterizations associated with the development work ultimately made it possible to produce images of unrivaled quality for the client’s application.

LED lighting

In order to be able to produce optimal quality images in the oral environment, an efficient lighting system is required. For this project, PISÉO engineers, specialized in LED lighting, therefore designed specific lighting which provides, in all circumstances, all the illumination, colorimetry and contrasts necessary for the image sensor. In addition, to overcome the problems of image distortion linked to the use of rolling-shutter CMOS sensors, LED control electronics have been designed specifically for this product.

Development of the Intraoral Scanner

PISÉO’s structured innovation process made it possible to resolve the technical challenges of the project, with risk analyzes and action plans.

Calculations, optical simulations, and models and prototypes were carried out to test the functions of the scanner before industrialization, paying particular attention to performance, waterproofing, “manufacturability”, and compliance with CE medical regulations.

The results of this project highlight the importance of a tailor-made approach in close collaboration with the Client. Opt for a personalized and efficient solution and trust the expertise of PISÉO and its valued partners for the development and manufacturing of your dental or medical devices.

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