Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
1997-09-22
2001-02-20
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S224200, C359S298000
Reexamination Certificate
active
06191882
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to light valves, which are devices capable of selectively switching multiple light spots at the same time.
BACKGROUND OF THE INVENTION
Light valves, and in particular micromachined light valves, have been known for many years. There are two types of micromachined light valves. The first group are devices operating over a wide range of wavelengths, including white light. These devices typically require a large movement (several microns) of the active micromachined element. This large movement prevents a fast (sub-microsecond) response time. In the second group are devices working on the principle of diffraction gratings. These devices require only sub-micron movements, therefore permitting sub-microsecond response times. Devices in this second group have higher losses and lower contrast ratio than devices of the first group. They are wavelength specific, as the elements move about one quarter of one wavelength. It is an object of this invention to combine fast response time, high optical efficiency, high contrast ratio and a wide range of wavelengths in a single device.
SUMMARY OF THE INVENTION
The invention uses the fact that the diameter of the beam waist of a tightly focused laser beam can be below one micron. If a micromachined cantilever is placed to just cut off the beam at this point, the beam can be permitted to pass by moving the cantilever through distance of less than one micron. In order to get high optical efficiency an array of microlenses is used to break up the illuminating line into an array of spots. Since the spacing between the spots can exceed the spot diameter many times, only a small part of the cantilever width is used. This allows easy micromachining of a cantilever array with large spaces between cantilevers. The invention works particularly well in the U.V. part of the spectrum, as the spot size, therefore the cantilever movement, scales down with the wavelength. For a U.V. light valve, sub-micron cantilever movements are sufficient. Since each one of the cantilevers is individually actuated, typically by electrostatic action between the cantilever and an electrode placed in the air space under it, a multi-channel linear light valve is created.
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Creo SRL
Epps Georgia
Lester Evelyn A.
Oyen Wiggs Green & Mutala
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