What is a Liquid Lens?

By changing the shape of the crescent-shaped surface at the junction of two different liquids with a thickness of only 8mm, the focal length was changed.

Liquid lens

By changing the shape of the crescent-shaped surface at the junction of two different liquids with a thickness of only 8mm, the focal length was changed.

Chinese name

Liquid lens

Thickness

8mm

Miniature liquid lens

Structural and low cost advantages

Application

Liquid reflecting mirror telescope

Liquid lenses can be classified in different ways, such as using one liquid, or using two liquids with different reflectances that cannot be fused at all. At present, liquid lenses can be divided into two types: conductive type and reflective type according to different implementation methods.

Before 2000, the cost of astronomical telescopes was as high as tens of millions of dollars, and it was almost impossible for individuals to own them and only share them. As many astronomers as there are so few astronomical telescopes. After 2000, for just over $ 1 million, scientists created a huge astronomical telescope. The key to cost reduction is the first use of liquid lenses, rather than the traditionally used polished metal, hard glass, and large mirrors. The mirror on the reflecting telescope is preferably parabolic, that is, the shape of the surface formed by the liquid in the rotating container. It takes a lot of hard work for the person making the telescope to make the mirror have such a surface. The work of polishing mirrors for telescopes often takes several years. In order to solve this difficulty, the American physicist Ude created a liquid mirror surface: he rotated mercury in a large container to obtain an ideal paraboloid. Since mercury can reflect light well, it can function as a mirror.

Reflective liquid lenses have been used in large telescopes to replace the glass reflective environment used in traditional telescopes. When a container filled with liquid (usually mercury) is rotated, the centripetal force creates a smooth reflective concave surface for the telescope. Usually such a smooth curved surface can completely replace the expensive glass lens that requires a lot of complicated technology, and the failure of the Hubble Space Telescope has also made us understand how fragile the glass lens is.

Reflective liquid lenses do not have the problem of fragility. By changing the rotation speed of the liquid container, emission surfaces with different curvatures can be formed. Scientists at the University of Columbia (UBC) in the UK have developed a 236-inch (6-meter) liquid-launching surface telescope (LMT). As the 13th largest telescope in the world, its reflection surface is formed by a container full of mercury rotating at a speed of 5RPM. The cost of this telescope is only about 1 million US dollars, and the traditional technology to build a telescope of the same size will cost about 100 million US dollars.

The conductive liquid lens uses two liquids that cannot be fused. Each liquid has a different refractive index, creating a variable focus lens that is the same as a traditional high-quality optical lens, but the lens size can be reduced to 10mm. Two liquids, one is a conductive aqueous solution and the other is a non-conductive oil. These two liquids are contained in a small tube with a spring device. The inside of the tube and the spring device are coated with a waterproof material. The spring device is used to pressurize and adjust the DC voltage at both ends of the tube to form an equivalent at one end of the tube. With the Crescent-shaped surface of the glass lens, the curvature of the surface is the focal length of the liquid lens. According to relevant tests, the energy consumed by each zoom process is only 0.1 microjoule (mJ), and the time it takes to zoom from the most extreme convex to concave takes only a few milliseconds. In addition, the boundary between the two liquids is very smooth and regular, making the liquid lens useful in medical endoscope imaging systems, but also in other areas where space is limited, such as microscope cameras.

This small liquid lens that mimics the function of a human eyeball has been introduced by Philips. Its two liquids are contained in a small tube with a diameter of 3 mm and a height of 2.2 mm. The lens can focus on an object as close as 5 cm away, and the focal distance can be adjusted within 10 microseconds.

The human eyeball also observes different objects near and far by changing the focal length. The difference is that humans adjust the focal length through the muscles around the eyeball. Therefore, it can be said that the electric field around this new lens is equivalent to the muscles around the human eyeball.

South Korea's Samsung Electro-Mechanics Co. announced at CeBIT 2004 that it will supply Liquid Lens camera modules for mobile phones, which are based on Varioptic's patents. According to reports, the camera module can be made thinner with a liquid lens, and the lens does not need to do physical movement, so it can greatly reduce power consumption. At present, the thickness of the module using this lens has only increased by 2mm, supports 5cm to infinity focus, the driving voltage is 0 to 40V, and the driving frequency is 1kHz.