Tuesday, June 25, 2024

New U.S. Technology Makes More Powerful Thermal Imagers At Lower Cost

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Thermal imaging has been a critical technology in the war in Ukraine, spotting warm targets like vehicles and soldiers in the darkest nights. Military-grade thermal imagers used on big Baba Yaga night bombers are far too expensive for drone makers assembling $400 FPV kamikaze drones who have to rely on lower-cost devices. But a new technology developed by U.S company Obsidian Sensors Inc could transform the thermal imaging market with affordable high-resolution sensors.

Thermal Imaging For Drones

While digital cameras developed rapidly after they were introduced, thermal imaging is stuck in the doldrums. This is because with no mass market, there is no incentive for manufacturers to invest in the next generation. The resulting difference in development has been dramatic.

Apple’s 1994 Quicktake camera offered 640x 480 pixel resolution for $1000. By 1999 Nikon’s Coolpix 800 was giving six times the resolution and cost less. Now even a $10 kids’ camera boasts far higher resolution.

By contrast the Seek Thermal imager for consumers was launched in 2015 with 206 x 156 pixel imaging for around $200. The same product is a market leader at the same price today. More powerful thermal imagers —– like this $8,000 military-type system with 1024×768 pixels — sell in tiny numbers.

This makes it difficult to make a low-cost drone for night operations. A drone maker who goes by FPVDronesUA on Twitter/X and builds FPVs for Ukraine and told me about the compromise between price and performance in the imagers they have worked with, invariably from Chinese companies.

The minimum viable sensor is a 256×192 pixel imager. This costs around $200 but gives a very grainy picture.

“256 offer you quite bad image quality, compared to better thermals and are very dependent on weather factors such as humidity, cloudiness and how cold it is outside,” FPVDronesUA told me. “256 is really hard to fly.”

The next level is 388 x 254 pixels, which is significantly better but three times the price at around $600.

“They are less dependent on weather because they catch more pixels, their Spectral Band and NETD are about the same as with 256,” says FPVDronesUA. “These are much more comfortable to use on a drone.”

But his preferred sensor is 640 x 480 (VGA resolution), starting at $800 if bought in batches of 50 or more but typically well over $1,000 if bought individually.

“640 thermals are great, but very expensive,” says FPVDronesUA. “These are very comfortable thermals, very similar to the ones we see in Mavic 3T [an industrial drone for thermal mapping]. Also thermals with higher resolution have higher Field of View.“ This means that the bigger imagers provide a much wider view; it’s less like seeing through a drinking straw and piloting is easier. “256 thermal with 9mm lens would be pretty narrow, while 640 thermal with 9mm offers you more than twice the Field of View.”

Ideally the imager would have higher resolution to spot targets (and obstacles) at longer ranges and make piloting less challenging. A $15 FPV daylight camera has a resolution of 1280 x 960, four times as much as VGA.

Adding an $800 imager turns a $400 drone into a $1200 one, so it cuts the number of drones he can afford to build by factor of three. That’s extremely important in a conflict where drone makers like FPVDronesUA are still funded by charitable donations, and the Russians, with more funding, initially fielded more thermal-imaging FPVs.

Thermal Imaging Technology

Older digital cameras were based on CCDs (charge coupled devices), the current generation use more affordable CMOS imaging sensors which produce an electrical charge in response to light. The vast majority of thermal imagers use a different technology: an array of microbolometers, miniature devices whose pixels absorb infrared energy and measure the resulting change in resistance. The conventional design neatly integrates the microbolometers and the circuits which read them on the same silicon chip.

Scaling up this technology would be possible but would take a multi-billion-dollar ‘fab’ (chip fabrication plant) as happened with digital cameras. There is no incentive to invest that sort of money,

John Hong, CEO of Obsidian Sensors based in San Diego believes he has a better approach, which can scale up to high resolution at low cost and, crucially, high volume, at established foundries. The new design does not integrate everything in one unit but separates the bolometer array from the readout circuits. This is more complex but allows a different manufacturing technique to be used.

The readout circuits are still on silicon, but the sensor array is produced on a sheet of glass, leveraging technology perfected for flat-screen TVs and mobile phone displays. Large sheets of glass are far cheaper to process than small wafers of silicon and bolometers made on glass cost about a hundred times less than on silicon.

Hong says the process can easily produce multi-megapixel arrays. Obsidian are already producing test batches of VGA sensors, and plan to move to 1280×1024 this year and 1920×1080 in 2025.

Obsidian has been quietly developing their technology for six years and are now able to produce units for evaluation at a price three to four times lower than comparable models. Further evolution of the manufacturing process will bring prices even lower.

Cars And Drones

Obsidian’s first target market is automotive safety and self-driving cars. At present these typically use LIDAR (laser-based radar) sensors to keep to the road and avoid accidents. But LIDAR cannot easily distinguish pedestrians from the background, which thermal imagers can.

Last month the U.S. National Highway Traffic Administration issued a new safety standard for automatic emergency braking for all new passenger cars from September 2029. This must automatically detect pedestrians and apply the brakes, and the requirement to work in darkness will strongly favor thermal imaging systems. Millions of new cars sold every year represent a huge potential market and this week Obsidian announced a partnership with Quanta Computer Inc to producer thermal imagers for automobiles

Delivery drones are another potential market. These are currently at the stage of small-scale trials, but large-scale operations will likely require high-resolution thermal imagers for safety and again demand could run to millions.

Meanwhile Ukraine is planning to build over two million drones this year, and import a million more, and their drone makers have already expressed an interest in the technology. Other nations will likely follow suit, creating even more demand for small, low-cost thermal imagers.

The Future of Thermal Imaging

Hong says they plan to sell a thousand VGA cameras this year on a pilot production run, and are currently raising a series B to hit much larger volumes in 2025 and beyond. That should be just about right to surf the wave of demand in the next few years.

The emerging market will attract new suppliers. Many are likely to be based in China and will simply scale up existing production techniques. But the advantages for cost and scaling, and the desire for greater supply chain security, may favor the new approach of building sensors on glass in the U.S.

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