Synthetic aperture: Using signal processing to get better images with smaller, more affordable hardware

What is synthetic aperture, and why is it a big deal?

In imaging systems such as telescopes or microscopes, how much detail you can see depends on the aperture (= the usable diameter) of the system (for technical details, see this Wikipedia article, for example).

It’s easy to see why you might want more detail. For example, with an earth-observing satellite you might want to see vehicles and people, not just houses. And with microscopes, you might be interested in seeing ever-smaller details of cells, for example.

But “more detail” means “you need bigger aperture”. “Bigger aperture” means “more expensive system”. And not just a bit more expensive–usually it’s exponentially more expensive.

Enter synthetic aperture. Synthetic aperture uses mathematical algorithms to combine signals from a smaller imaging system to create higher-resolution images. In other words, images that would otherwise require bigger, more expensive imaging systems.

For this article, I used Mergeflow software to discover companies, patents, and R&D in the area of synthetic aperture. Here is a snapshot of some of my results (click on the image to see the snapshot):

Snapshot of some Mergeflow data on "synthetic aperture".
Snapshot of some Mergeflow data on “synthetic aperture”.

Below are some results in more detail. For each category (venture-backed companies, patents, etc.) I had to select some examples. This is my subjective, and to an extent certainly arbitrary, selection.

Venture-backed companies

Asterra: Pipe leak detection from space

When you look at the Mergeflow data snapshot above, you’ll notice that most venture-backed synthetic aperture companies work on satellite-based imaging systems. Asterra, formerly Utilis, is an example of this category. They raised $6M from Beringea, and they use synthetic aperture radar to measure underground moisture levels. This way they can spot leaks in underground pipes, for example.

A burst pipe. Asterra's technology helps detect pipe leaks from space. Image by Photon-Photos from Getty Images Pro.
A burst pipe. Asterra’s technology helps detect pipe leaks from space. Image by Photon-Photos from Getty Images Pro.

Detecting pipe leaks quickly and continuously is a big deal. For example, according to this BBC report, London’s pipes alone burst over 36,000 times between 2011 and 2018. That’s more than 16 times per day, on average.

Asterra’s technology has an interesting origin: Lauren Guy, co-founder at Asterra, originally worked on using synthetic aperture radar for underground water detection on Mars.

Rebus Biosystems: Synthetic aperture optics for faster analyses of subcellular details

From space to microscopic structures: Rebus Biosystems is a biomedical imaging company. They have raised $20M Series B from Illumina Ventures, Lifecore Partners, Ncore Ventures, Xolon Invest, CTK Investments, Ray, Seegene Medical Foundation, LabGenomics, and Timefolio Asset Management.

Rebus Biosystems uses synthetic aperture optics so that you can get the same resolution from a 20x air microscope lens that would otherwise require a 100x oil immersion lens. Not only are oil immersion lenses a lot more expensive than air lenses. The oil immersion process also takes a lot longer. And this means that you can’t do high-throughput analyses. In other words, Rebus Biosystems enable you to use lenses that (1) are cheaper, and that (2) enable you to do high-throughput analyses of subcellular structures.

With Rebus Biosystems' synthetic aperture optics, you can use 20x air microscope lenses to get the same resolution as a 100x oil immersion lens. Image from Rebus Biosystems' website.
With Rebus Biosystems’ synthetic aperture optics, you can use 20x air microscope lenses to get the same resolution as a 100x oil immersion lens. Image from Rebus Biosystems’ website.

Patents: Synthetic aperture imaging for medical applications

Los Alamos National Laboratory

A group of scientists at Los Alamos National Laboratory holds patents for using synthetic aperture in ultrasound imaging. This one, for example:

SYSTEMS AND METHODS FOR SYNTHETIC APERTURE ULTRASOUND TOMOGRAPHY

One of the inventors listed on the patents, Lianjie Huang, is a geophysicist by training. I think this is worth noting because it hints at the interdisciplinary nature of this field of imaging (or imaging more generally).

Konica Minolta

Konica Minolta has substantial patenting activities in medical applications of synthetic aperture technology. You can see this from the Mergeflow screenshot below (larger font -> more patents; click on the image to see it in full size):

This screenshot from Mergeflow shows that Konica Minolta has substantial patenting activity in medical applications of synthetic aperture.
This screenshot from Mergeflow shows that Konica Minolta has substantial patenting activity in medical applications of synthetic aperture.

Similar to Los Alamos National Laboratory, these applications are mostly in the area of ultrasound imaging. Here’s one of their most recent patents:

ULTRASOUND SIGNAL PROCESSING APPARATUS, ULTRASOUND DIAGNOSTIC APPARATUS, AND ULTRASOUND SIGNAL PROCESSING METHOD

Science publications: Smaller satellites, smaller medical devices

New systems for dealing with the data volume generated by synthetic aperture imaging satellites

SpaceFibre is an on-board network technology for satellites. Remember how in the beginning I said that synthetic aperture combines many images from a system into one higher-resolution image. “Many images” means “more data”. And “more data” might mean “more expensive”–unless you come up with an alternative. And this is the goal of a group of scientists from Pisa, Italy:

Design of a Reduced SpaceFibre Interface: An Enabling Technology for Low-Cost Spacecraft High-Speed Data-Handling

As is often the case in space technologies, these scientists operate in a network of international collaborations. You can see the network (by organizations, not people) in the graph below, in this case centered around the European Space Agency (click on the image to see it in full size):

International collaboration network of organizations, in the areas of "synthetic aperture" and "miniaturized satellites". Screenshot from Mergeflow.
International collaboration network of organizations, in the areas of “synthetic aperture” and “miniaturized satellites”. Screenshot from Mergeflow.

Synthetic aperture for enabling portable ultrasound devices

Remember the patents above, In medical imaging, synthetic aperture plays an important role in ultrasound. Here is an example R&D publication from this field:

Comparison of synthetic aperture architectures for miniaturised ultrasound imaging front-ends

The goal here is to enable portable ultrasound devices, an area that has seen substantial growth in R&D over the past few years (click on the image to see it in full size):

Science publications on portable ultrasound devices are going up. Screenshot from Mergeflow.
Science publications on portable ultrasound devices are going up. Screenshot from Mergeflow.

Featured image by 3DSculptor from Getty Images Pro.

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