Pacala is careful to note that his flash lidar differs from conventional flash lidar (this shouldn’t surprise you, at this point). Traditional flash lidar uses “flood” illumination, which sends out a flood of light, some of which is wasted on parts of the scene where the detectors don’t measure. In contrast, Pacala says, Ouster’s solution illuminates the scene “with precision points of light,” or multiple beams.
The simplest way to explain the VCSEL is to contrast it against other solid-state laser technologies.
Ouster has packed 64 lasers into the single custom VCSEL chip used in its OM-1 lidar, which is about the size a grain of rice. One expert interviewed by Ars speculated that it could be possible to fit millions of lasers on a single chip, just as Intel has done with billions of transistors.
Ouster’s OS-1 lidar
Pacala, for his part, believes that VCSEL arrays could very well develop along similar lines as the digital camera sensor, which has seen designers continuously “pack more pixels in the same space” over the years. He says that Ouster is “going to be able to double, quadruple, 10x the resolution, without any change [in size or cost].”
The VCSEL has a bunch of other benefits. In his blog post, Pacala says that they are smaller, lighter, more durable, faster, simpler to make, and more power efficient than existing laser technologies. They also cost an order of magnitude less. Perhaps most importantly, he believes the technology is on a Moore’s Law-esque trajectory because VCSELs are not only being developed for commercial applications, but also widely used in consumer technology like smartphone cameras and computer mice. That means huge improvements to performance, volume, and cost are coming in the future as hundreds of billions of these chips are built.
A single-photon avalanche diode is a low noise detector that is sensitive enough to pick up a single photon (as the name indicates). When you think of single-photon lidar, you probably imagine the giant devices that hang off of airplanes for extremely wide area mapping, but SPADs offer a lot of advantages for smaller, ground-based lidar, too.
In his blog post, Pacala focuses most energy on the benefits to be gained from the SPAD’s potential for on-chip processing. He writes that Ouster has built SPADs directly into a semiconductor wafer, which enabled them to incorporate “massive amounts of signal processing” on the silicon “right next to the detectors.”
Essentially, that makes each chip a hybrid of a laser detector and a processor. The one in the OS-1 64-channel lidar counts and stores one trillion photons per second to its memory, and includes processing signal logic to handle over 100 billion operations per second. As anyone who works with 3D data knows, processing requirements are only going to increase in the future, so this kind of integrated chip could turn out to be very useful.
Pacala estimates that these SPAD detectors are going to improve about as quickly as the VCSELs they’re paired with. The SPADs we’re working with, he says, are currently about 2-5% efficient. They will soon hit 20-30% efficiency, and may one day scrape out 80% efficiency. This “makes an OS-1 with 640 lines of resolution not just possible, but extremely likely.”
(What I’ve outlined above is fairly surface level compared to Pacala’s blog, which I recommend you read if you’re interested in more technical detail. He also includes a bunch of information about why Ouster selected an uncommon wavelength for their lasers, and the benefits that wavelength brings.)
Ambient data at top, depth data at bottom, gathered simultaneously by one Ouster lidar.
Hopes and speculation
When I caught up with a few 3D-tech veterans to hash out the consequences of this technology, a few speculated that VCSEL-based lidar like Ouster’s could be a “game-changer” for the handheld 3D-capture market once it shows up in 2D arrays (currently, Ouster builds 1D arrays that they spin to achieve coverage of a scene).
One of my contacts speculated that if you could put a 2D array with thousands of these VCSELs on a low-cost, low-power, and light-weight chip, you could come close to the long-held dream of a “credit-card sizes lidar sensor that could be slapped onto any surface.” That means high-quality 3D scanning anywhere, the kind of ease of capture hinted at by Apple’s 3D depth camera/face sensor. He also wondered if it could be possible to combine data from a number of VCSEL chips, each one configured to sense a different defined range, or particular bands of light (thermal, RGB, etc) to offer the equivalent of multi-sensor capabilities in a small package.
A common sentiment in my conversations: 3D tech is overdue for a sea change, and VCSEL-based technology like Ouster’s represents a chance to get away from the spinning mirror and finally go solid-state. Of course, time will tell, and most are waiting to get their hands on the technology before they make up their minds about the potential.
For more information about Ouster’s lidar, I recommend checking out other SPAR articles, especially our article about Ouster’s ability to capture ambient data without a camera, and what that means for AI, SLAM, and sensor fusion problems. After that, dig into CEO Angus Pacala’s blog post here, and getting in touch with Ouster through their official website.