What Are M12 Lenses?
M12 lenses are the most usually encountered size of a whole class of small, fixed-focus, screw-mount lenses. They are also called “board mount lenses”, because they screw into a small mounting bracket that is attached directly to the same printed circuit board that holds the image sensor in a camera. They are also sometimes called “S-Mount lenses”, with the “S” standing for short, or small board-mount lens.
The “12” in M12 lenses comes from the fact that the lens barrel has a 12mm outer diameter thread on it. Board mount lenses are actually made in a variety of sizes with thread diameters ranging from 4mm to 16mm, all of which are identified by their thread size as “M4”, “M6” – and so on.
While all of these lenses have their uses, 12mm board mount lenses are by far the most common, because the size of the image circle they produce makes them suitable for use with a broad range of image sensors.
What Makes M12 Lenses so Useful?
At first glance, M12 lenses initially don’t seem all that exciting. They are usually fixed aperture, fixed-focus lenses with simple optical designs, and no moving elements in the lens. (Variable focus and variable iris M12 lenses do exist, but they’re less common). They are simply screwed into the mount until the image circle is correctly focused on the image sensor, and then locked in place with UV-cured glue.
However, their small size, relatively low cost and simple, durable construction make them tremendously useful for a wide range of applications. They are well-suited for creating compact, low power camera systems.
M12 lenses are produced in an almost bewildering variety of focal lengths from super-wide fisheye lenses through to telephoto lenses. They are also available with special optics optimized for SWIR (short-wave infrared), and ToF (Time-of-Flight) image sensors. There are even telecentric M12 lenses for machine vision applications that require things to be precisely aligned without perspective errors. (Telecentric lenses keep all chief rays parallel to the optical axis – creating an essentially flat, orthographic projection of the scene.)
For this reason, you’ll find M12 lenses in all kinds of devices, ranging from webcams to automotive systems. These lenses are also available in ruggedized formats for high-impact applications, like compact sports cameras.
The humble M12 lens is quite literally the “little lens that could”. They just happen to hit a sweet spot in terms of cost, utility, and size that makes them a universally popular choice for small cameras.
Board Mount Lenses in Consumer Devices
Board mount lenses are so ubiquitous that you probably have several around your home that you aren’t even aware of. They’re widely used camera systems for consumer products, ranging from the backup camera or dashboard camera in your car – to the webcam sitting on your computer monitor. Board mount cameras are found in GoPro sports cameras, in doorbell cameras and in baby monitors.
If you have a VR controller for your game console, there will be one or more board mount lenses in the motion tracker on top of your television. The latest generation of robot vacuum cleaners even use these lenses for their guidance systems. Some of these may be smaller diameter M6 or M8 lenses, but most of them will be M12 lenses.
The simplicity and small size of these lenses makes it inexpensive to incorporate them into a wide range of consumer devices. As a result, manufacturers have been quietly adding more and more camera systems to their products over the past few years. Backup cameras in cars were a novelty only a few years ago, but it’s now commonplace for cars to have at least two cameras – mounted on both the front and rear bumpers.
M12 Lenses for Embedded Vision Systems
Because these systems are required to be small, they often use M12 board-mount lenses.
In addition to visible light cameras, embedded vision systems often employ various depth-sensing technologies, including stereo depth cameras, LiDAR sensor, and Time-of-Flight (ToF) cameras. All of these can be built with M12 lenses, which are available with optics that are optimized for sensitivity to the wavelengths of light these systems use.
Stereo depth cameras, which need to “see” both visible light and the light from an infrared laser pattern projector may require special hyperspectral lenses. There are also specialized lenses for LiDAR sensors and ToF cameras, which use different wavelengths of infrared laser light.
Choosing the Right M12 Lens
Because of the ubiquity and popularity of the M12 lens format, there are literally thousands of M12 lenses available, including a wide assortment of very specialized lenses. This means that if you’re developing a camera system for a specific application, choosing the right lens can be a challenge.
First, you need to consider the type of camera you are building: Is this a visible light camera, or depth-sensing camera that uses infra-red illumination? This will dictate the range of image sensors and optics you have to choose from.
Then you need to consider the optical characteristics required by the image sensor you are using, including the optimal size of the image circle required to properly cover all of the effective pixels on the sensor.
You will you need to take into account the details of interest the lens must be able to resolve at the intended working distance and the desired field of view.
Finally, you need to consider the environmental and operating requirements for the camera system. These include factors that your vision system will be exposed to such as the lighting conditions, ambient temperature, and mechanical vibrations.
If you are going to need to choose a lens for a vision system, we’ve drafted a whitepaper called “How to Choose the Right Lens: Capturing What Matters”, which examines some of the factors that have to be considered when selecting a lens.
This paper focuses primarily on the optical parameters of lens selection and doesn’t delve too deeply into the non-optical factors that still have to be taken into account. However, it’s still a great starting point to understanding how to find the right M12 lens for your project.