More Pixels or More Eyes? SCD's Mini Blackbird 1280 vs the Boson 640

Why compare these two

Two thermal cores sit at opposite ends of the counter-drone design space. Teledyne FLIR's Boson 640 is a small, low-power uncooled long-wave core, widely used in fixed and staring cameras; with its 14 mm lens it covers a 32° horizontal field of view with 640 × 512 pixels at up to 60 Hz. SCD (SemiConductor Devices) makes one of the most compact cooled, high-definition mid-wave cores: the Mini Blackbird 1280, a 1280 × 1024 MWIR detector that weighs under 350 g with its cooler. The question this post asks is what each one actually buys you when the target is a small drone.

Every number on either core comes from the manufacturer's own published material, listed at the end. Where arithmetic is involved, the assumptions are stated next to each table.

The two cores on paper

SCD publishes two Mini Blackbird 1280 variants. The product page and its linked datasheet describe a HOT XBn version. A separate 2024 datasheet describes an HFM ("Hot Full Mid-wave") version with a wider band and a higher frame rate. Both are shown below.

Two cautions about this table. First, a Mini Blackbird is not a camera. SCD supplies the detector, dewar and cooler with optional proximity electronics. An integrator still has to add the lens, the enclosure and the video pipeline. A Boson ships as a complete core with a lens. Second, the NETD figures are measured at different f-numbers: F/4 for the Blackbird and f/1.0 for the Boson. Each figure is fair to its own sensor, but they are not one test.

What each band actually sees

A small quadcopter is not a jet. Its heat comes from motors, speed controllers and the battery, and most of the airframe sits near ambient temperature. Wien's law puts the emission peak of a 300 K (27 °C) object at about 9.7 µm. Even at 340 K (67 °C), a hot motor housing, the peak is about 8.5 µm. Both fall inside the Boson's 8–14 µm band and well outside the Blackbird's 3.6–4.2 µm band.

Blackbody arithmetic makes the gap concrete. A 300 K surface emits about 147 times more radiance in 8–14 µm than in 3.6–4.2 µm, and about 405 times more photons. Against the HFM variant's 3.6–4.9 µm band, the ratios are about 36 and 89. The mid-wave band compensates in two ways. Its radiance changes faster with temperature: about 4% per kelvin at 300 K, against about 1.5% for 8–14 µm. And a cooled photon detector is far more sensitive per photon than a microbolometer. This is why cooled MWIR cores still reach lower NETDs than uncooled LWIR, despite seeing fewer photons from room-temperature objects. Teledyne FLIR's own guidance places uncooled cameras in the long-wave band because that is where ambient-temperature targets emit most of their energy.

The atmosphere also matters. In Teledyne FLIR's fog-modelling article, LWIR penetrated fog better than MWIR in every case they studied: about four times the range in Category II fog. MWIR did best in the hot conditions of summer or tropical climates, and was more affected by pollutants. In rain the two bands performed similarly. The article's own conclusion is that sensitivity and target signature still have to be weighed for each application. Field signature work on small rotorcraft has compared the two bands directly. Fudala et al. (2019) measured a DJI Phantom 4 and a DJI Inspire in both bands, against clear sky, cloud and land, at three aspect angles. Results like these depend on the scene, so neither band can be declared the winner from them.

Some things are clear. Against a clear sky, a drone in LWIR is a warm object on a cold background. Teledyne FLIR notes that, against the cold sky, an infrared camera can often detect a moving drone as a cluster as small as 2 × 2 pixels. Neither band removes the hard cases, such as warm cloud edges, birds and sun glints. Those are an algorithm problem whichever band you pick.

Pixels on target: the Blackbird's real advantage

Here is the geometry. Assumptions: a 0.35 m quadcopter, a square target, and pixels across the target = size ÷ (range × IFOV), where IFOV = pixel pitch ÷ focal length. The Boson lenses are FLIR catalogue lenses. SCD publishes no lens, so every Blackbird focal length below is an assumption, chosen either to match the Boson's field of view or to represent a typical long cooled zoom.

*Computed from pitch, array width and focal length. FLIR publishes 32.0° for this lens, about 20 pixels per degree, which changes these counts by about 4%.

Read the table in three ways.

At the same field of view, the Blackbird has twice the linear resolution. That means twice the pixels across the target at every range, and in pure geometry a sub-pixel drone fills four times as much of each pixel. Add a published NETD of 25 mK, against 20–60 mK across the Boson family, and the Blackbird has the lower noise floor. Sensitivity is its first clear win.

There is a catch at wide fields. Diffraction blurs a point into a spot with an angular diameter of about 2.44 × wavelength × f-number ÷ focal length. For the Boson's 14 mm f/1.0 lens at 10 µm, that spot is about 1.7 mrad. For a Blackbird at F/4 with a matched 23 mm lens at 3.9 µm, it is about 1.6 mrad, nearly the same. At matched wide fields, the Blackbird's extra pixels sample almost the same blur more finely. They do not separate detail twice as well, and the four-fold geometric fill gain shrinks, because the blur spreads the drone's signal over several of the smaller pixels. This simple model leaves out aberrations and turbulence.

The cooled core earns its keep at long focal lengths. This is the second clear win, and the bigger one. A cooled detector is sensitive enough to work behind slow optics. Teledyne FLIR notes that cooled MWIR can use lenses as slow as f/5.5, allowing focal lengths beyond 1,000 mm at a manageable lens size and cost. It also puts the cost crossover from uncooled LWIR to cooled MWIR at focal lengths above about 250 mm. An uncooled core needs f/1-class optics, so its aperture grows with focal length. Behind a 300 mm lens, the Blackbird resolves a 0.35 m drone at 2 km with about five pixels, while the 14 mm Boson sees a fifth of a pixel. If you need to identify a small drone at long range, this is the right tool.

Independent commentary by GOTEAM. Not affiliated with or endorsed by SCD or Teledyne FLIR. Specifications are quoted from each manufacturer's published material and have not been independently tested by us. Pixel counts, diffraction spots, blackbody ratios and ring sizes are our own arithmetic, and every Blackbird focal length in them is an assumption, not an SCD product.