Electrostatic bimorph actuator
View Patent ↗An electrostatic bimorph actuator includes a cantilevered flexible bimorph arm that is secured and insulated at one end to a planar substrate. In an electrostatically activated state the bimorph arm is generally parallel to the planar substrate. In a relaxed state, residual stress in the bimorph arm causes its free end to extend out-of-plane from the planar substrate. The actuator includes a substrate electrode that is secured to and insulated from the substrate and positioned under and in alignment with the bimorph arm. An electrical potential difference applied between the bimorph arm and the substrate electrode imparts electrostatic attraction between the bimorph arm and the substrate electrode to activate the actuator. As an exemplary application in which such actuators could be used, a microelectrical mechanical optical display system is described.
1. A microelectrical mechanical structure (MEMS) optical display system, the system comprising:
a source of illumination;
a first lens to focus the illumination;
a beam splitter to direct the illumination towards an array of MEMS devices, wherein the MEMS devices are controlled to reflect portions of the illumination back to the beam splitter, and wherein the beam splitter passes the reflected portions of illumination in a direction away from the source of illumination; and
a display screen which displays the reflected portions of illumination;
wherein a MEMS device is formed on a planar semiconductor substrate and comprises:
a cantilevered flexible bimorph arm that is secured to the planar substrate, the bimorph arm being generally parallel to the planar substrate in the electrostatically activated state and extending out-of-plane from the planar substrate in the relaxed state;
plural spaced-apart substrate electrodes secured to the substrate and positioned under and in alignment with the bimorph arm; and
plural stand-off dimples extending between the bimorph arm and the substrate to hold the bimorph arm in spaced-apart relation to the substrate when the actuator is activated, the plural stand-off dimples being interdigitated with the plural substrate electrodes when the actuator is activated.
2. The system of claim 1 , where the illumination is one of polarized and non-polarized light.
3. The system of claim 1 , wherein the source of illumination is a three color light source that operates in a field-sequential manner with a MEMS device controller.
4. The system of claim 1 , wherein each MEMS device corresponds to a picture element and is separately controllable.
5. The system of claim 1 , further comprising a reflector to direct the illumination onto the first lens.
6. The system of claim 1 , wherein the first lens is a condenser lens.
7. The system of claim 1 , further comprising a lens array to focus illumination directed by the beam splitter onto an aperture array, the aperture array being in front of the array of MEMS devices.
8. The system of claim 7 , wherein the aperture array allows the illumination directed by the beam splitter to become incident upon the array of MEMS devices.
9. The system of claim 8 , wherein the aperture passes illumination reflected by a MEMS device when the MEMS device is at rest and blocks illumination reflected by a MEMS device when the MEMS device is activated.
10. A display engine for selectively modulating light from an illumination source, the engine comprising:
a MEMS reflective modulator assembly, the modulator assembly comprising:
an array of MEMS devices, each device having formed on one or more planar semiconductor substrates, each device comprising:
a cantilevered flexible bimorph arm that is secured to the planar substrate, the bimorph arm being generally parallel to the planar substrate in the electrostatically activated state and extending out-of-plane from the planar substrate in the relaxed state;
plural spaced-apart substrate electrodes secured to the substrate and positioned under and in alignment with the bimorph arm; and
plural stand-off dimples extending between the bimorph arm and the substrate to hold the bimorph arm in spaced-apart relation to the substrate when the actuator is activated, the plural stand-off dimples being interdigitated with the plural substrate electrodes when the actuator is activated; and
means for control of the array;
an aperture plate positioned such that illumination passes through before being reflected by a MEMS device; and
a lens array to focus illumination onto the array of MEMS devices.
11. The engine of claim 10 , wherein the lens array is formed of one of molded plastic, holographic lenses, and conventional glass lenses.
12. The engine of claim 10 , wherein each MEMS corresponds to a picture element and is separately controllable using the control means.