Broadband, common-path, interferometric wavefront sensor
Hybrid sensors comprising Shack-Hartmann Wavefront Sensor (S-HWFS) and Zernike Wavefront Sensor (Z-WFS) capabilities are presented. The hybrid sensor includes a Z-WFS optically arranged in-line with a S-HWFS such that the combined wavefront sensor operates across a wide dynamic range and noise conditions. The Z-WFS may include the ability to introduce a dynamic phase shift in both transmissive and reflective modes.
1. A hybrid wavefront sensor comprising:
a Shack-Hartmann wavefront sensor having a SH-input pupil and a re-imaged SH-output pupil comprising at its distal end a lenslet array for dicing an incident image wavefront into separate segments;
a Zernike wavefront sensor having a Z-input pupil and a Z-output pupil, the Zernike wavefront sensor being capable of dynamically shifting the phase of a portion of the image wavefront having a diameter on the order of λ/D, where D is the SH-input pupil diameter;
a relay optical system disposed proximal to the lenslet array and designed such that the image wavefront from the SH-input pupil is relayed one-to-one to the Z-input pupil and the Z-output pupil is relayed one-to-one to the lenslet array of the SH-output pupil;
a detector in optical alignment with the distal side of the lenslet array for imaging the incident image wavefront; and
an electronic controller in signal communication between the Zernike wavefront sensor and the detector for correlating the phase shift imposed on the imaged wavefront.
2. The hybrid wavefront sensor of claim 1 wherein the optical path of the wavefront sensor is arranged such that the Zernike wavefront sensor may be bypassed.
3. The hybrid wavefront sensor of claim 1 wherein the phase shift may be dynamically adjusted over a range of from +λA/2 and −λ/2.
4. The hybrid wavefront sensor of claim 1 wherein the relay optical system includes a parabolic mirror.
5. The hybrid wavefront sensor of claim 1 wherein the Zernike wavefront sensor is transmissive.
6. The hybrid wavefront sensor of claim 5 wherein the Zernike wavefront sensor comprises a plurality of transmissive phase plates movable into and out of the optical path of the Zernike wavefront sensor, each of said transmissive plates capable of producing a different phase shift in the image wavefront.
7. The hybrid wavefront sensor of claim 1 wherein the Zernike wavefront sensor is one of either reflective or refractive.
8. The hybrid wavefront sensor of claim 7 wherein the Zernike wavefront sensor includes a reflective mechanical capillary device.
9. The hybrid wavefront sensor of claim 8 wherein the reflective mechanical capillary device comprises:
a ceramic ferrule defining a central longitudinal hollow passage and having a reflective end; and
a fiber having a reflective end, said fiber being positioned within the central hollow passage and movable therein such that the reflective end of the fiber can be offset relative to the horizontal plane of the reflective end of the ceramic ferrule.
10. The hybrid wavefront sensor of claim 9 further comprising a piezoelectric transducer mechanically coupled to the fiber and disposed to translate said fiber within said ferrule.
11. The hybrid wavefront sensor of claim 9 further comprising a quad cell detector to determine the position of the image wavefront with respect to the reflective mechanical capillary device.
12. The hybrid wavefront sensor of claim 1 wherein the relay optical system comprises both a parabolic and elliptical reflector, and wherein the optical path of the sensor is switchable therebetween.
13. The hybrid wavefront sensor of claim 1 wherein the relay optical system includes a refractive element.