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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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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These inspections require heavy equipment and put workers at risk

This is the way visual inspection procedures have been performed since the beginnings of civil aviation.

DONECLE, a French company, has strong expertise in aircraft maintenance processes, drone robotics, automation and “deep learning” computer vision algorithms.

This company has, therefore, seized this opportunity to revolutionize the way inspections have been carried out over the past 40 years.

It was for this ambitious project that DONECLE turned to the experts at PISEO for assistance in the design of the on-board inspection camera illuminator.

Design of the on-board inspection camera illuminator

Machine vision systems are more and more widespread. Indeed, cameras and ready-to-use lenses are readily available on the market.

However, software to process the captured images, even very sophisticated ones, does not always succeed in sufficiently discriminating between the scenes. This is often due to poorly adapted lighting.

Well-designed LED lighting can compensate for problems with lens vignetting, colorimetry, and scene uniformity.

PISEO, therefore, supported this company in the design of a particularly efficient lighting system.

The aim was to help compensate for vignetting and colorimetry issues due to the camera lens and thus the overall performance of the inspection system.

Thanks to this product and PISEO’s support, DONECLE is now the worldwide leader of automated aircraft visual inspection based on drone technology. The company offers a unique solution combining a 100% automated drone with advanced image analysis algorithms for the detection of damage to the exterior surface of aircraft.

The illuminator developed with PISEO now allows it to guarantee consistent image quality, regardless of exterior light conditions.

on-board inspection camera illuminator

· Search for suitable LED components.

· Optical design of potential solutions.

. Simulation performance comparisons with Light Tools software

· Prototyping of the chosen solution.

· Characterization of the optical performance of the prototype in the PISEO lab.

Illuminator for on-board inspection camera

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With their skills in the implementation of IR LEDs and optical design, PISEO experts have designed and qualified an innovative illumination system using pulsed IR LEDs and specific lenses to illuminate a scene at long distance witha light invisible to the naked eye. The main objective was Tt design and prototype a brand new illuminator for SWIR cameras.

Performed services

• Definition of application requirements (use cases, performance & regulations) and cost objectives.
• State of the art analysis of available IR LED technologies and proposal of optical and electronic concepts.
• Evaluation of the achievable performances of the different concepts by calculation and simulation with LightTools 8.7.
• Specification of the chosen optical and electronic architectures.
• Thermal design.
• Detailed design of the optical and electronic systems.
• Realization of mock-ups and prototypes.
• Performance assesment by means of IR goniophotometry.
• Prototype qualification.

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