Method and device for modulating light
Light in the visible spectrum is modulated using an array of modulation elements, and control circuitry connected to the array for controlling each of the modulation elements independently, each of the modulation elements having a surface which is caused to exhibit a predetermined impedance characteristic to particular frequencies of light. The amplitude of light delivered by each of the modulation elements is controlled independently by pulse code modulation. Each modulation element has a deformable portion held under tensile stress, and the control circuitry controls the deformation of the deformable portion. Each deformable element has a deformation mechanism and an optical portion, the deformation mechanism and the optical portion independently imparting to the element respectively a controlled deformation characteristic and a controlled modulation characteristic. The deformable modulation element may be a non-metal. The elements are made by forming a sandwich of two layers and a sacrificial layer between them, the sacrificial layer having a thickness related to the final cavity dimension, and using water or an oxygen based plasma to remove the sacrificial layer.
1. A device for modulating light comprising:
a light modulating element having a first wall and a second wall defining a cavity, wherein at least one of the walls is movable relative to the other; and
a circuit configured to periodically apply a plurality of pulses having varying widths across the first and second layers, the plurality of pulses being configured to control the relative movement of the first and second walls.
2. The device of claim 1 , wherein at least one of the pulses has a duty cycle of less than 100 percent.
3. The device of claim 1 , wherein at least one of the pulses has a duty cycle of less than 50 percent.
4. The device of claim 1 , wherein the intensity of modulated light is controlled at least in part by duty cycle.
5. The device of claim 4 , wherein the light modulating element is a pixel in a display.
6. The device of claim 5 , wherein the pixel is activated by one of the plurality of pulses.
7. The device of claim 6 , wherein the pixel remains activated for a remainder of the period.
8. A device for modulating light comprising:
first and second layers separated by a space, wherein a dimension of the space is changeable from a first value to a second value in response to a voltage applied across the first and second layers, and wherein the first and second layers are substantially parallel when the dimension of the space is the first and second value; and
a control circuit configured to apply a continuous voltage across the first and second lays to maintain the dimension of the space at a prescribed height.
9. A device for modulating light, comprising:
first and second substantially non-absorptive layers separated by a space, wherein a dimension of the space is changeable in response to a voltage applied across the first and second layers; and
a control circuit configured to apply a continuous voltage across the first and second layers to maintain the dimension of the space at a prescribed height.