SILINA’s Sensor Curving Technology Hopes to Speed up Industry Usage

·8 min read

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“SILINA does not reinvent the wheel of sensor design and manufacturing”, states SILINA’S CTO Wilfred Jahn, “but is developing technological solutions to curve existing (flat) imaging sensors.” A PhD holder in Electro-optical System Design, Wilfred forms one half of SILINA’s co-founding team with CEO Michael Bally. Seeing a potential increase in demand among technological sectors, the duo formed SILINA in 2020 with a vision to reform the existing sensor ‘curving process’.

Technological innovation and R&D has been driving the digital camera industry over the last two decades. At the heart of this have been the developments in imaging sensor quality. We’ve gone from when ISO 800 at night was almost unusable to an era where images at ISO 12,800 are almost noise-free under the right conditions. The global CMOS (complementary metal-oxide-semiconductor) sales peaked at close to USD 19 billion in 2019. Hitting a speed bump last year due to Covid-19’s impact on the industry, the figures are expected to rise again this year.

Apart from the differences in sizes (micro 4/3rds, Full-Frame, Medium format etc.), the shape of an imaging sensor has mostly remained flat and rectangular. However, images produced by lenses are still susceptible to the phenomenon known as Petzval field curvature.

Simply put, this results in lenses creating images in a slightly curved plane rather than a flat one. Light rays that are closer to the center of the lens fall directly on the sensor. Those that are farther away from the center do not fall directly on it (due to the curvature). As a result, sharpness can drop, especially in the corners. Manufacturers introduce various elements inside modern lenses to mitigate the effect of the curvature. This, in turn, makes lenses larger and more complex than they need be.

One of the solutions to this problem is the usage of curved sensors in place of flat ones. SILINA hopes to make the process of curving a sensor more widespread with the introduction of its bulk curving process. We asked Wilfried what his thoughts were about their future in the camera industry and how SILINA hopes to change things for the better.

The Phoblographer: While not yet incorporated into mainstream electronics, curved sensor technology has been around for a few years. What makes SILINA’s sensors different?

Wilfried Jahn: For the last few years, curved sensor technology has mainly been developed by labs for research purposes. Various curving processes have been developed for a few years by different players. These curving processes are all “single-chip curving process”, meaning that only one sensor can be curved at a time. These single-chip curving processes create strong limitations, such as a very low volume of production and a very expensive unit price. Thus, a single-chip curving process is not economically viable for consumer applications, which is why you have not seen any compact camera using a curved imaging sensor yet. Up to now, technological developments have only been limited to niche markets (astro-instrumentation, scientific).

SILINA has developed a “multi-chip curving process” to curve thousands of sensors at the same time. This makes the process scalable and economically viable for high volume markets. We have proven our claims with a demonstrator: starting from a wafer of 275 imaging sensors, we have curved all of them at the same time. This is more sensors than have ever been curved during the past 20 years. SILINA plans to automate this manufacturing process, transfer the technology to large sensor manufacturers and reach high volume markets.

Note that SILINA does not manufacture any imaging sensor with foundries. SILINA only develops curving solutions for existing sensors that will be transferred to image sensor manufacturers for the mass market. For high-end markets and custom requests requiring specific technical features, SILINA will curve its clients’ sensors in-house.

The Phoblographer: SILINA is a recently founded startup, but how long have you been working on this technology?

Wilfried Jahn: SILINA has been created in February 2021 through the incubation program Entrepreneur First in Paris, but we have been developing the technology for the past 7 years through simulation studies, prototyping and lab testing. Our invention, the multi-chip curving process, comes from multiple professional experiences around the world in various fields such as aerospace.

The Phoblographer: When was the exact moment that you realized this could be a real game-changer for imaging companies?

Wilfried Jahn: At the very beginning, we realized the potential of that technology by simulating cameras and optical systems, comparing the simulated performance of flat sensor-based imaging systems VS curved sensor-based imaging systems. The improvement in terms of image quality, mass, volume and cost reduction were significant whatever the application we considered. Then, we have spent quite a lot of time discussing with potential customers and end-users from various market segments to understand their needs and investigate if curved imaging sensors may help solve their problems. We discovered that this is the case for most applications, the product market-fit was there, so we decided to move on by creating SILINA. Today, the biggest players in this industry are showing strong signs of interest. We are on the verge of a new standard of imaging systems.

The Phoblographer: Flat sensors have been around for some decades, and their performance has been improving every year. Is SILINA trying to reinvent the wheel with their curved sensor idea?

Wilfried Jahn: Curved sensors bring a real paradigm shift to this industry, and SILINA provides solutions to OEMs to reinvent the way their cameras are designed. SILINA does not reinvent the wheel of sensor design and manufacturing but is developing technological solutions to curve existing (flat) imaging sensors. This greatly improves the overall imaging system/camera. The intrinsic performance of the sensor itself remains the same, but the performance and cost of the overall camera is significantly improved since the lenses are way more performant.

The Phoblographer: Does sensor housing and processor-to-sensor communication technology have to change much to accommodate this?

Wilfried Jahn: No, the sensor housing, electronic board, processor or anything connected to the sensor remain unchanged. The curving process has been thought to avoid disrupting any other step of sensor manufacturing & packaging. Only the optics have to be specifically designed for a curved sensor.

The Phoblographer: Currently, flat sensors work with lenses that have multiple optical elements. How (if at all) will this change with curved sensors?

Wilfried Jahn: Curved sensors improve the overall system design, enabling [the removal of] numerous optical elements from the lens, making it simpler, smaller and lighter while improving the manufacturing cost. This simplification is accompanied by an increase in image quality.

The Phoblographer: How much of an image quality improvement are we talking about here? Will the difference be visible across the entire image or just display sharper corners?

Wilfried Jahn: The improvement really depends on the lens characteristics (FoV, aperture, focal length). We will publish results of comparative studies for various imaging systems on our website (once it has been created).In general, the sharpness, contrast and chromatic aberration will mainly be improved across the field of view, providing a much more uniform image quality all over the field. The vignetting can partially or totally be removed, increasing the illumination at the corners.

The Phoblographer: What sectors (commercial, industrial, consumer, or otherwise) do you see most benefiting from this technology?

Wilfried Jahn: So far, the traction mainly comes from smartphone, autonomous vehicle, aerospace and photography companies. Photography companies (through their sensor manufacturers) are showing a real interest. We know that leading photography companies are patenting many camera lens designs to prepare the next generation of cameras. They are waiting for the curved sensor technology to be ready for production.

The Phoblographer: Have you had any significant interest from leading photography or smartphone brands so far?

Wilfried Jahn: Yes, we are in the process of signing business deals with several smartphone and sensor manufacturers that are really proactive to be the first to benefit from our capabilities

The Phoblographer: What technological barriers do curved sensors aim to overcome in consumer cameras?

Wilfried Jahn: Companies doing consumer cameras want larger aperture lenses for low light imaging, better off-axis image quality, more compactness and a lower cost. For smartphone cameras, they are also looking for real optical zoom.

The Phoblographer: If curved sensors become widely adopted, are we looking at larger aperture lenses manufactured at lower prices and smaller physical sizes?

Wilfried Jahn: Exactly, curved sensors enable a gain on all of these parameters. Recent[ly] patented lens designs using curved imaging sensors consider large apertures with fewer optical elements.

The Phoblographer: Are there any limitations to the types of sensors that can be curved – CMOS / CCD, FSI / BSI, infrared, etc.? Any size limitations (m43 / APS-C, Full Frame, Medium)?

Wilfried Jahn: Our curving process is independent [of] the sensor characteristics. CMOS, CCD, FSI, BSI, visible or infrared have already been demonstrated. Today, we are discussing with various sensor manufacturers to perform testing on their last generation of sensors.

The Phoblographer: Any comparative images from your prototype that clearly demonstrate the advantages?

Wilfried Jahn: We provide curved sensors, not imaging systems, so we cannot provide comparative images from a fully integrated camera. You will have to wait for comparative pictures from the OEMs we are working with.

All images supplied by SILINA. Used with permission. Visit their website for more information about their technology.