We have found three errors in our paper [1], and thus would like to make the following corrections to this paper:On page 302, in the second paragraph, line 12, "tenabiliby" should be changed to "tunability". On page 302, in the fourth paragraph, "In a typical cell, LC passing the cell, where d is the cell gap. When a sufficiently high voltage is applied to the indium tin oxide (ITO) electrodes, the LC directors will be reoriented material is sandwiched between two substrates coated with electrodes (e.g., indium tin oxide, ITO) and surface alignment layers (e.g., polyimide, PI) [53]" should be changed to "In a typical cell, LC material is sandwiched between two substrates coated with electrodes (e.g., indium tin oxide, ITO) and surface alignment layers (e.g., polyimide, PI) [53]".On page 303, in the first paragraph, "It will experience an optical path of L = dne after in vertical direction and the optical path becomes L = dno (Figure 1b)" should be changed to "It will experience an optical path of L = dne after passing the cell, where d is the cell gap. When a sufficiently high voltage is applied to the ITO electrodes, the LC directors will be reoriented in vertical direction and the optical path becomes L = dno (Figure 1b)." OPEN ACCESS

A tunable-focus liquid lens using dielectrophoretic effect is demonstrated. When a voltage is applied to a dielectric liquid droplet, the generated electric field inside the droplet is inhomogeneous. As a result, the liquid bears a dielectric force and its surface profile can be reshaped which causes the focal length to change. Adaptive lenses with different apertures are fabricated and their performances evaluated. In comparison to the patterned-electrode liquid lenses, our lens uses continuous electrode which is much simpler for fabrication.

We demonstrated a liquid lens whose focal length can be controlled by an actuator. The lens cell is composed of elastic membrane, planar glass plate, a periphery sealing ring, and a liquid with a fixed volume in the lens chamber. Part of the periphery sealing ring is excavated to form a hollow chamber which functions as a reservoir. This hollowed periphery is surrounded by an exterior rubber membrane. The shaft of an actuator is used to deform the elastic rubber. Squeezing the liquid contained in the reservoir into the lens chamber. Excess liquid in the lens chamber will push the lens membrane to outward, resulting in a lens shape change. Due to the compact structure and easy operation, this liquid lens has potential applications in zoom lenses, auto beam steering, and eyeglasses.

A variable-focus liquid lens using a transparent flat cell is demonstrated. The top substrate has an aperture which is sealed with a thin elastic membrane on the outer surface and the bottom aperture is sealed on the inner surface of the bottom substrate. By applying a pressure to the outer membrane inward causes the liquid to redistribute and swell the inner membrane outward which, in turn, forms a plano-convex lens. To prove principles, a water lens with 5 mm aperture was fabricated. The resolution is better than 25 lp/mm and the response time is approximately 40 ms. Potential applications of such a lens for real-time active imaging are emphasized.

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High-efficiency and economical solar-energy-pumped laser with Fresnel lens and chromium codoped laser medium

We demonstrate a tunable focus liquid crystal (LC) lens by sandwiching a homogeneous LC layer between a planar electrode and a curved electrode. The curved electrode which is made of conductive polymer has parabolic shape with a large apex distance. Such design dramatically reduces the phase loss which leads to a short focal length (~15 cm). By using a thin top glass substrate on the curved electrode side, the operating voltage of the lens cell is reduced to ~23 V(rms). This LC lens has advantages in wide focal length tunability, low operating voltage, and good mechanical stability.

A tunable-focus spherical lens using two flat substrates and inhomogeneous electric field over a homogeneous liquid crystal ͑LC͒ layer is demonstrated. The top flat substrate has an imbedded spherical indium-tin-oxide ͑ITO͒ electrode and the bottom has a planar ITO electrode on its inner surface. The inhomogeneous electric field generates a centrosymmetric gradient refractive index profile within the LC layer which causes the focusing behavior. The focal length of the LC lens can be tuned continuously from infinity to 0.6 m by the applied voltage.