Technology | Corning® Varioptic® Lenses | Adjustable Lenses | Corning

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Varioptic Lenses Technology

For centuries, scientists have combined lenses of very different optical powers, from diverging lenses to highly converging ones to design and manufacture complex optical instruments. Until now, the optical properties of these types of glass or plastic lenses were fixed.

Corning® Varioptic® Lenses has created a programmable lens that can be reconfigured on demand by a voltage change. The lens can adapt rapidly and continuously from diverging to converging and be modeled to support demanding variable focus applications.

Advantages

The traditional way to perform the auto focus function is to mechanically move the lens module to adjust the back focal length (distance to the image sensor) depending on object distance. This method presents several drawbacks:

    - Requires bulky and fragile motors
    - Friction of small parts that can lead to damage and malfunction
    - Noise and high power consumption
    - Slow focus speed

The unique characteristics of Corning Varioptic Lenses bring an ideal competitive advantage to the market that enables:

    - No moving parts, significantly increasing the lens lifespan compared to a mechanical actuator
    - Hundreds of millions of cycles endurance
    - Faster speed
    - Robustness and unmatched vibration and mechanical shock resistance
    - Close focus ability
    - Low power consumption
    - Silent operation

Electrowetting

Electrowetting is the key principle behind Varioptic Lenses technology. Electrowetting occurs when a drop of insulating liquid (e.g., oil drop) is deposited on a flat surface made of a conductive material covered with an insulating and hydrophobic layer, and then both the drop and surface are immersed in a conductive liquid (e.g., electrolyte). Voltage is then applied between the conductive substrate and the conductive liquid, causing the insulating liquid drop to change shape.

Check out our Electrowetting Demonstration video to see what's happening inside a Varioptic Lens.

Watch Now

Lens Structure

The design of the adjustable lens structure ensures:

  - Stable optical axis, by a conical centering of the drop
  - Non sensitivity to orientation, by using two liquids of equal density
  - High shock resistance, by a simple mechanical structure and equal density

Depending on the voltage applied, the lens can be a divergent lens, a flat lens, or a convergent lens.

electrowetting varioptic diagram

      

Product Performance

Optical Power vs. Voltage

The optical power (ability of a lens to converge or diverge light) of Corning® Varioptic® Lenses is a linear response versus voltage. See graph on the right.

The relation between optical power (OP, in diopters) and focusing distance (d, in meters) is given by: OP = 1/d

Optical Quality

The optical quality of each adjustable lens is specified by the Wave Front Error (WFE). The WFE characterizes the deviation of the actual shape of the lens compared to a perfectly spherical lens (aberrations)  – and measured in nanometers rms. The typical WFE of the lens is in the range of 50 nm rms, which is the equivalent of a lambda/10 lens for visible light, commonly accepted as a high-quality grade lens.

Transmission

The standard version of each lens comes with an anti-reflective coating which is optimized in the visible range. Therefore, the transmission drops slightly in the near infrared. The loss of transmission below 400 nm is linked both to the anti-reflective coating and to the glass that is used in the lenses, which is a standard borosilicate glass.

With an anti-reflective coating optimized in the near infrared, the transmission curve flattens from 700 nm to 1100 nm.

System Integration

Varioptic Lenses can be used in several types of systems:

    - Manual focus: the user adjusts the focus manually, with a knob for example
    - Closed-loop: this is the standard auto focus method, where a processor runs a contrast optimization loop to maximize the 
      sharpness of the image
    - Open-loop: this is a mode where the focus command is directly sent to the lens, from an external distance measurement
      for instance
    - Mixed mode: a combination of open loop for coarse search, and closed loop for fine tuning of the focus

 

For more information on system integration for your application click here.