FIELD OF THE INVENTION

This invention relates generally to the adjustment of the optical path length of light passing through a media, and in particular, to a tunable optical phase shifter with a transmissive and wide aperture medium.

BACKGROUND AND SUMMARY OF THE INVENTION

When light propagates through a media, the optical path length of the light depends on the effective index of refraction of the media. As is known, the optical phase may be adjusted when light propagates through a media having a desired optical path length. Optical phase tuning is highly desired in various precision and imaging tools used for applications in industry and scientific research. Among various optical phase shifters (OPS), electro-optic modulators are frequently used, though mainly in communication systems.

Electro-optics are comprised of components, devices (e.g., lasers, light-emitting diodes (LEDs), waveguides, etc.) and systems which operate by the propagation and interaction of light with various tailored materials. Other phase shift methods employ fiber-optic based modulators, which suffer light loss, liquid crystal phase shifters, which can be slow, or mirror based systems, which require complex, precise mechanical controls.

With the advancement of imaging systems, such as optical coherence tomography, these imaging systems require optical path length modulation in one arm of an interferometer setup to produce noninvasive cross-sectional imaging in biological systems. In phase shifting interferometry (PSI), an OPS with a wide aperture and a linear medium is required. Other optical imaging systems, such as phase contrast microscopy, rely on a static OPS. Existing optical phase shift solutions each come with certain drawbacks. A tunable optical phase shifter with a transmissive and wide aperture medium is desirable for the simplification and miniaturization of optical systems.

Therefore, it is a primary object and feature of the present invention to provide a tunable optical phase shifter with a transmissive and wide aperture medium.

It is a further object and feature of the present invention to provide an optical phase shifter that simply and easily adjusts the optical phase of light propagating through a media having a desired optical path length.

It is a still further object and feature of the present invention to provide an optical phase shifter that is compatible with current imaging tools and is inexpensive to manufacture.

In accordance with the present invention, a tunable optical phase shifter is provided for adjusting an optical phase of light propagating therethrough along an optical axis. The tunable optical phase shifter includes a sheet having first and second sides and including a rigid outer portion interconnect to a rigid inner portion alignable with the optical axis by a complaint ring. The rigid inner portion is moveable along the optical axis between a first position and a second position. A fluid is provided on the second side of the sheet and is engageable with the rigid inner portion of the sheet for exerting a pressure thereon. A pressure generator is operable to selectively vary the pressure of the fluid against the rigid inner portion of the sheet to move the rigid inner portion of the sheet along the optical axis so as to adjust the optical phase of light propagates through the optical phase shifter.

The rigid inner portion of the sheet may be fabricated from a negative photoresist and the fluid may be non-conductive. The pressure generator also includes a conductive fluid extending about at least a portion of the non-conductive fluid. The pressure generator also includes a plurality of interdigitated electrodes positioned in spaced relation to the second side of the sheet. The plurality of interdigitated electrodes are operatively connectable to a voltage source. The voltage source supplies an adjustable voltage such that the pressure of the fluid against the rigid inner portion of the sheet varies in response to a magnitude of the voltage supplied to the plurality of interdigitated electrodes by the voltage source. At least one spacer may be positioned between the plurality of interdigitated electrodes and the second side of the sheet for spacing the sheet from the plurality of interdigitated electrodes.

In accordance with a further aspect of the present invention, an optical phase shifter is provided for adjusting an optical phase of light propagating therethrough along an optical axis. The optical phase shifter includes first and second transparent slides defining a cavity therebetween. A sheet is received in the cavity and has first and second sides. The sheet includes a rigid inner portion alignable with the optical axis and is moveable along the optical axis between a first position and a second position. A tuning structure is operatively engageable with the rigid inner portion of the sheet to selectively move the rigid inner portion of the sheet along the optical axis so as to adjust the optical phase of light propagating through the optical phase shifter.

The sheet includes a rigid outer portion interconnect to the rigid inner portion by a complaint ring. The compliant ring urges the rigid inner portion toward the first position. At least one spacer spaces the sheet from the second slide. The rigid inner portion of the sheet is fabricated from a negative photoresist. The tuning structure includes a first fluid on the second side of the sheet that is engageable with the rigid inner portion of the sheet for exerting a pressure thereon. The first fluid is non-conductive. The tuning structure also includes a second fluid extending about at least a portion of the first fluid. The second fluid is conductive. A plurality of interdigitated electrodes are spaced from the second side of the sheet. The plurality of interdigitated electrodes are operatively connectable to a voltage source. The voltage source supplies an adjustable voltage such that the pressure of the first fluid against the rigid inner portion of the sheet varies in response to a magnitude of the voltage supplied to the plurality of interdigitated electrodes by the voltage source.

In accordance with a still further aspect of the present invention, an optical phase shifter is provided for adjusting an optical phase of light propagating therethrough along an optical axis. The optical phase shifter includes first and second transparent slides defining a cavity therebetween. A sheet is received in the cavity and has first and second sides. The sheet includes a rigid inner portion alignable with the optical axis and moveable along the optical axis between a first position and a second position. A tuning structure is operatively engageable with the rigid inner portion of the sheet to selectively move the rigid inner portion of the sheet along the optical axis so as to adjust the optical phase of light propagating through the optical phase shifter. The tuning structure includes a first fluid on the second side of the sheet and engageable with the rigid inner portion of the sheet for exerting a pressure thereon. The first fluid is non-conductive. A second fluid extends about at least a portion of the first fluid. The second fluid is conductive. At least one electrode is spaced from the second side of the sheet and communicates with the conductive fluid. The electrode is operatively connectable to a voltage source. The voltage source supplies an adjustable voltage. The pressure of the first fluid against the rigid inner portion of the sheet varies in response to a magnitude of the voltage supplied to the electrode by the voltage source.

The sheet includes a rigid outer portion interconnect to the rigid inner portion by a complaint ring. The compliant ring urges the rigid inner portion toward the first position. At least one spacer spaces the sheet from the second slide. The rigid inner portion of the sheet is fabricated from a negative photoresist and the at least one electrode is one of a plurality of interdigitated electrodes.

