In machine vision, historically there is a preponderance of fixed focal length (FFL) lenses, also know optically as a prime lens. They are less complex to design and manufacture, and are high-performance in terms of image sharpness and ability to accept wide aperture options for low-light applications. FFL lenses are typically are set for a designed FOV and WD and don’t have flexibility on focal lengths. If your application is like that, lucky you.
But my application isn’t like that!
You may have a factory production monitory project, for example. You know the general dimensions of the layout and the approximate camera mounting position. But you have limited time to configure and deliver proof of concept or acceptance testing. so you want to show up with everything you need to achieve good outcomes, instead of guessing wrong on a fixed focal length lens and having to exchange it.
Whatever your planned application, you know the optical “neighborhood” but need the flexibility to fine-tune in the field.
Zoom lens
A zoom lens remains in focus across a range of focal lengths, and is often remotely controlled. Likewise it’s also often motorized. So they tend to be large(ish), heavier, more complex to design, and are more expensive than a fixed-focal length lens.
In the illustration above, notice how the light rays entering from the right range from a wide field of view (FOV) at the top to a narrow FOV at the bottom. That’s a consequence of the changing focal length. It’s an asset if you need that behavior. Or a liability if you don’t
This blog is about varifocal lenses, so that’s all we’ll say about zoom lenses here. But the “different focal lengths” and “different FOV” concepts also apply to varifocal lenses, so it’s worth noting points of overlap.
Varifocal lens
A varifocal lens is designed to hit the sweet spot between fixed focal length vs. zoom. By spanning a (modest) range of focal lengths, a varifocal lens can be adapted in the field to optimize for observed conditions.
You might not know at design time exactly what final focal length you’ll choose, so a range of coverage lets you tune as you deploy and run acceptance tests. It also means the same lens could be used for a year or more in one setting – then loosen a set screw, refocus, and tighten the set screw and the same lens performs great in the new context.
But unlike a big motorized zoom, the varifocal lens is often* manually adjusted. And it’s typically modest in size, weight, design complexity, and cost.
(*) EXCEPTION! The Optotune electrically tunable series describe below uses liquid lens technology for autofocus within milliseconds.
Enough concept already – what varifocal lenses are available?
Below we present and link to three different varifocal product lines carried by 1stVision. We sequence by alphabetical order, but each series has its own value proposition, depending on your application needs:
Kowa LMVZ Varifocal Lenses
Kowa’s LMVZ varifocal lenses are designed for machine vision, industrial inspection, and surveillance applications. Their adjustable focal length design allows integrators to fine-tune field of view without changing lenses.
Optotune Focus Tunable Lenses
Optotune is an industry leader in focus tunable lenses. Many are electrically tunable, utilizing liquid lens technology. They also offer a manually tunable lens.
– Courtesy Optotune
Unlike manually tunable varifocals, the EL series offers fast, precise autofocus in milliseconds with no moving mechanics.
Tamron Vari-Focal Lens Series
The Tamron vari-focal series is designed for high-resolution IP and security surveillance cameras. These lenses offer flexible focal length adjustment for both wide-area coverage and detailed zoom.
Select IR-corrected models enable true day/night performance, while compact, durable construction ensures dependable operation in commercial, industrial, and municipal security installations.
Optics is partly physics and science…
But it’s also engineering, and performance requirements, and budget, and experiential knowledge. If you’ve got a lot of all that in your wheelhouse, just call for a quote at 978-474-0044. Or if you’d like some help in choosing, call that same number and tell us a little about your application. Either way, we’re here for you. For lenses, cameras, and more.
1st Vision’s sales engineers have over 100 years of combined experience to assist in your camera and components selection. With a large portfolio of cameras, lenses, cables, NIC cards and industrial computers, we can provide a full vision solution!
About you: We want to hear from you! We’ve built our brand on our know-how and like to educate the marketplace on imaging technology topics… What would you like to hear about?… Drop a line to info@1stvision.com with what topics you’d like to know more about.
#varifocalmachinevisionlens
#zoommachinevisionlens
#optotune
#kowa
#tamron