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Years ago, taking high-quality, in-focus photographs required expensive high-end cameras with equally expensive and fragile lenses. But that wasn’t enough. You also needed the skills and know-how to bring that bulky gear into focus on your subject. If your subject moved, your focus was ruined, and you had to re-focus the entire device.
As cameras have improved and become an increasingly present part of our lives, they’ve become easier to use and autofocus has taken over the camera world. But you’re still limited by the shape and focal length of your lens. Professional photographers still carry around multiple lenses with different focal lengths to capture images of closer or farther objects. Cell phones have multiple sets of lenses to achieve the same effect.
But what if new technology could make it possible to get multiple focal lengths and lens shapes from a single lens? Well, with liquid lenses, you can do precisely that.
Liquid lenses are unique in that there are no mechanical parts inside. In a mechanical lens setup, glass lenses are moved closer or farther from the camera sensor to achieve different focal lengths. This will drastically alter the field of view and the distance the camera appears to be from the subject.
At shorter focal lengths, you’ll get a very wide field of view and the image will appear to be zoomed out. With longer focal lengths, you’ll have a much narrower field of view and an image that’s zoomed in. To achieve different focal lengths, you must either use a zoom lens that lets you move the lens closer to or further from the image sensor, or you must switch to another lens with a different focal length.
What’s so special about liquid lenses is that they can change shape and drastically alter their focal length with no mechanical parts. Even better, this can be done in mere milliseconds—so fast that you won’t even notice it happening. In theory, this means you could replace multiple lenses of different focal lengths with a single liquid lens.
Since the liquid lens need not change its distance relative to the image sensor to change its focal length, it can also be made much smaller than the bulky mechanical lenses that we’re used to. But just how does a liquid lens alter its shape and change its focal length?
The speed at which a liquid lens can change its shape may seem like magic, but it’s actually very scientific. If a drop of liquid is placed on a hydrophobic surface (something that repels liquids), then the molecules in the liquid will bond together and form a bead since they are repelled by the hydrophobic nature of the surface.
When an electric field is applied to that liquid and another conductive material such as aluminum that’s on the opposite side of the hydrophobic barrier, the liquid becomes electrostatically attracted to the aluminum. The molecules that make up the liquid will spread out as they try to reach the aluminum, resulting in the water droplet drastically changing shapes. This process is called electrowetting, and it’s the basis of liquid lens technology.
The stronger the electric field that’s applied, the more attracted the liquid is to the conductive material. This means the water will spread out farther as it tries harder to reach the conductive material across the barrier. By varying the amounts of electricity used, the liquid can be forced to take many shapes. If that liquid is used as a lens, then the different shapes it changes into each have a different focal length that can drastically alter the image that the sensor picks up.
The concept of electrowetting was first discussed back in the late 1800s. It was then studied again later in the mid and late 1900s, but it wasn’t until 1993 that an insulating layer (the hydrophobic material) was placed between the conductive metal and the liquid. Technically, this is called electrowetting-on-dielectric (EWOD) but it can still be referred to as electrowetting.
The first person to add the insulating layer was Bruno Berge, and he’s pioneered the use of this technology in liquid lenses. After discovering this technology, Berge founded the company Varioptic in 2002 and started creating the first liquid lenses for cameras.
For a camera lens, some changes had to be made with electrowetting that would be viable for taking images. The shape-changing liquid was suspended in another liquid that would repel it, similar to how oil and water repel each other. The conductive metal is around the body of the lens, with glass on either side to hold the liquids in. The hydrophobic insulator covers the metal so you can create the same reactions as before. This means that the suspended liquid is now being repelled on all sides by the repellent liquid and the hydrophobic insulating layer. Repelled on all sides, the conductive liquid is forced to keep shape, even negating the effects of gravity. With this advancement, the technology became usable in cameras.
Now that we’ve discussed how liquid lenses work, you may wonder if they’re worth all the trouble that went into forming the technology. Varioptic liquid lenses pose quite a few benefits over the mechanical lenses that we all know, so let’s dive into some of those advantages.
We’ve already touched on focal length, and it’s one of the big benefits of liquid lenses. Traditionally, if you wanted multiple focal lengths from the same lens, you needed a zoom lens that allowed the lens inside to move mechanically. This resulted in bulky and heavy lenses that are very costly and fragile.
Liquid lenses can provide multiple focal lengths without moving parts by introducing a small amount of electrical current to the lens. This means that lenses can be much smaller but still provide images with drastically different fields of view and zoom levels.
While changing focal lengths is great, what’s most impressive about how a liquid lens does it is the incredible speed at which the change takes place. With a zoom lens, you have to wait for motors to move the lens or move it yourself by turning a ring on the outside of a lens. This takes more time. But with a liquid lens, the change is nearly instant, requiring only a few milliseconds to get a completely different image. This also allows a liquid lens to get a clear focus rapidly on subjects that are different distances away.
A liquid lens can take a focused picture of a close subject, and a fraction of a second later, get an equally well-focused image of a distant subject.
Varioptic liquid lenses have no moving parts and no mechanical parts. This means there’s a lot less inside that can get damaged. The result is a robust lens that’s no longer as fragile as the lenses we’ve all grown accustomed to. If you drop an expensive high-end lens, you’ve likely caused irreversible damage. Traditional lenses have so many parts that can be knocked out of place, and the slightest variation can ruin the lens permanently as the image will no longer focus properly. But with a liquid lens from Varioptic, there are no moving or mechanical parts to damage. This results in shock-resistant lenses, so if they get dropped, it doesn’t mean the end of their usable life.
Mechanical systems wear out. Everyone knows it. Because of this, mechanical lenses have a certain expected lifespan of how many times they can cycle. For an industrial-use camera in an automated factory that cycles millions of times, traditional lenses only last a few weeks before starting to wear out. Liquid lenses have a much longer lifespan because they don’t have any mechanical parts to go bad. This means that they can perform hundreds of millions of cycles without getting damaged or starting to break down.
To get multiple focal points in a single lens, zoom lenses had to grow to an unruly size. They stick way out in front of the camera and contribute a significant amount of weight. All this room is needed so that the glass inside can be moved closer to and farther from the sensor to change the focal length. But since a liquid lens can change focal lengths without any moving parts, the total lens size can be a fraction of the large lenses that dominate the market at the moment.
Professional photographers often carry around cumbersome tripods to hold their cameras steady and negate the shake of human hands. No matter how stable you are, a camera will pick up the tiny movements of your hands. This can cause images to appear unfocused and blurry, even if the focus was dead on. But liquid lenses can counterbalance this movement and provide stable images despite human error. This could usher in a new world of handheld photography where tripods become obsolete.
Traditional lenses are limited in how close they can be to a subject and still stay in focus. But liquid lenses can focus at extremely close distances. This makes them very useful for the medical field where cameras may be inserted inside the body and there isn’t much room for the lens to have focusing distance.
Liquid lenses use only a tiny bit of electricity to change their shape and focal length. Mechanical lenses use many times more power to make adjustments, especially if it’s controlled by a motor.
Where are Liquid Lenses Being Used Now?
Because of their incredibly fast focus time and their ability to survive hundreds of millions of cycles, liquid lenses were first introduced for industrial applications. Automated manufacturing equipment needs to focus on different sized items quickly and do it millions of times each week. These liquid lenses can survive many years of this constant cycling, whereas traditional mechanical lenses typically failed in just a few months or even weeks. This saves manufacturers time and money by eliminating the need to replace failed lenses.
Barcode scanners have been using liquid lenses for quite some time. They need to focus quickly on barcodes from varying distances. Liquid lenses make this easy since they can refocus near-instantly at any distance from the target.
Thanks to their close-focusing abilities and low power consumption, liquid lenses have made their way into the medical field. Laparoscopic cameras are using liquid lenses that can focus on very close-up subjects. They need instant focus inside of the body so that doctors and surgeons can clearly see what’s going on, and the tolerances are very tight. Three-dimensional microscopes have also begun integrating this technology for an excellent focus on subjects of varying sizes.
Liquid lenses are also used with lasers since they can redirect the beam in many directions without any movement. This keeps the laser stable but allows the user to aim it where they need.
Liquid lenses are making their way into consumer cameras, but this is a pretty recent development. However, the technology was initially invented in 2002 by Varioptic. Even as far back as 2005, Samsung was working with Varioptic to introduce the technology into smartphone cameras.
Smartphones are a perfect platform for this technology since they have such limited space. Nowadays, these phones are implementing more and more separate lenses to provide users with powerful cameras. But those lenses take up a lot of space inside the phone, and we still don’t have good optical zoom technology that can fit in these devices. But liquid lenses, like the ones Varioptic makes, can provide incredible zoom capabilities in a package that’s small enough to fit inside our modern smartphones.
Varioptic has sold over 2 million liquid lenses to date. With so many of them on the market, the technology is becoming available in more consumer-oriented forms. In fact, some USB cameras are even made with a liquid lens now, bringing the technology into our homes for the first time. But this is just the start. As the technology continues to improve and expand, we’ll likely begin seeing it used in regular cameras, even replacing the mechanical lenses we’ve gotten used to over the years.
Liquid lenses are the future of image technology. With cameras becoming a daily part of our lives, the demand for improvements in the technology used to build them has resulted in increasingly smaller cameras with continually growing capabilities. But mechanical parts can only be made so small, and to achieve multiple focal lengths from a single lens requires too many moving parts with traditional lens technology.
As liquid lenses become more common, companies like Varioptic will continue working to make them smaller and more capable. Soon, you’ll likely carry a liquid lens in your pocket, inside of a smartphone. Most people may not even realize it when it happens, but when the capabilities of your smartphone camera make a sudden leap forward, you’ll know that the age of liquid lenses has arrived.
In other news, here are some of the equipment we recently reviewed:
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Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.
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