Electrically controlled optical elements and method
The effective focal length of an optical system can be electronically controlled using switchable wave plates in conjunction with polarized light.
1. An electrically controlled optical system for controlling a focal length of an optical system in a light path between a lens and a display producing polarized light in a head mounted display comprising:
a quarter wave plate in the light path between the lens and the display;
a partially silvered mirror in the light path between the quarter wave plate and the display;
a switchable wave plate having two or more states, the switchable wave plate in the light path between the partially silvered mirror and the display;
electrical means for controlling the state of the switchable wave plate operably connected to the switchable wave plate;
an airspace between the partially silvered mirror and the switchable wave plate; and
a polarization dependent mirror in the light path between the switchable wave plate and the lens.
2. The electrically controlled optical system of claim 1 wherein the airspace is located between the switchable wave plate and the polarization dependent mirror.
3. The electrically controlled optical system of claim 2 further comprising:
a polarizer in the light path between the polarization dependent mirror and the display.
4. The electrically controlled optical system of claim 1 further comprising:
a polarizer in the light path between the polarization dependent mirror and the display.
5. An electrically controlled optical system for controlling a focal length of an optical system in a light path between a lens and a display producing polarized light in a near-to-eye display comprising:
a quarter wave plate in the light path between the lens and the display;
a partially silvered mirror in the light path between the quarter wave plate and the display;
a switchable wave plate having two or more states, the switchable wave plate in the light path between the partially silvered mirror and the display;
electrical means for controlling the state of the switchable wave plate operably connected to the switchable wave plate;
an airspace between the partially silvered mirror and the switchable wave plate; and
a polarization dependent mirror in the light path between the switchable wave plate and the lens.
6. The electrically controlled optical system of claim 5 wherein the airspace is located between the switchable wave plate and the polarization dependent mirror.
7. The electrically controlled optical system of claim 6 further comprising:
a polarizer in the light path between the polarization dependent mirror and the display.
8. The electrically controlled optical system of claim 5 further comprising:
a polarizer in the light path between the polarization dependent mirror and the display.
9. An electrically controlled optical system for controlling a focal length of an optical system in a light path between a lens and a display producing polarized light comprising:
a quarter wave plate in the light path between the lens and the display;
a partially silvered mirror in the light path between the quarter wave plate and the display;
a switchable wave plate having two or more states, the switchable wave plate in the light path between the partially silvered mirror and the display;
electrical means for controlling the state of the switchable wave plate operably connected to the switchable wave plate;
an airspace between the partially silvered mirror and the switchable wave plate; and
a polarization dependent mirror in the light path between the switchable wave plate and the lens.
10. The electrically controlled optical system of claim 9 wherein the airspace is located between the switchable wave plate and the polarization dependent mirror.
11. The electrically controlled optical system of claim 10 further comprising:
a polarizer in the light path between the polarization dependent mirror and the display.
12. The electrically controlled optical system of claim 9 further comprising:
a polarizer in the light path between the polarization dependent mirror and the display.