Optical wavefront measuring device and measuring method thereof

1 . An optical wavefront measuring device for testing an optics under test, the optical wavefront measuring device comprising:

a rotational spindle rotating the optics under test in a plurality of different azimuthal directions;

a light source module emitting an incident light beam that propagates to the optics under test, from which testing light beam containing the measured wavefront of the optics under test is generated;

a wavefront sensor acquiring the testing light beam passing through the optics under test rotated in at least two of the plurality of different azimuthal directions; and

a computing device processing data associated with the testing light beam;

wherein the wavefront sensor captures a plurality of camera frames with different exposures for each of the plurality of different azimuthal directions to acquire the testing light beam; and

the camera frames with different exposures for each of the plurality of different azimuthal directions are synthesized into a measured wavefront corresponding to the respective azimuthal direction, the computing device is configured to receive the measured wavefronts obtained at the at least two azimuthal directions, determine, from the measured wavefronts, a fixed alignment error aberration (W DC ) attributable to misalignment of the optical wavefront measuring device, and subtract the fixed alignment error aberration (W DC ) from the measured wavefronts to obtain an angle-dependent aberration attributable to the optics under test.

2 . The optical wavefront measuring device as claimed in claim 1 , wherein the light source module comprises a light source beam and a converging lens, the converging lens is positioned between the light source beam and the optics under test, converging the incident light beam to a focal point, the relative distance between the focal point and the optics under test is predetermined by the design prescription of the optics under test.

3 . The optical wavefront measuring device as claimed in claim 2 , wherein a divergent light beam is collimated by a collimator forming the light source beam, the divergent light beam propagates from a point light source, the point light source is generated out of a fiber pigtail, and the collimator is placed between the converging lens and the fiber pigtail.

4 . The optical wavefront measuring device as claimed in claim 1 , further comprising a beam splitter module, wherein the beam splitter module is disposed between the optics under test and the wavefront sensor, and is located on a propagation path of the incident light beam, the beam splitter module redirects the incident light beam to the optics under test, and the incident light beam is reflected off the optics under test forming the testing light beam, the testing light beam is captured by the wavefront sensor after passing through the beam splitter module.

5 . The optical wavefront measuring device as claimed in claim 3 , wherein the light source module further comprises an aperture, the aperture is disposed between the collimator and the converging lens or between the converging lens and the optics under test, or the aperture is an opening of a lens holder of the rotational spindle, and the lens holder holds the optics under test.

6 . The optical wavefront measuring device as claimed in claim 1 , wherein the rotational spindle comprises a rotational stage, a translation stage and a lens holder, the translation stage is disposed on the rotational stage, the rotational stage has a rotation axis, the rotational stage rotates the translation stage to rotate along the rotation axis, the lens holder is disposed on the translation stage, and holds the optics under test, the translation stage moves the lens holder along a first direction and a second direction, the first direction and the second direction are perpendicular to the rotation axis and each other.

7 . The optical wavefront measuring device as claimed in claim 1 , further comprising at least one of a wavefront sensor translation stage and a light source module translation stage, wherein:

the wavefront sensor translation stage is connected to the wavefront sensor, and drives the wavefront sensor to move along a first direction, a second direction, and a third direction, wherein a rotation axis of the rotational spindle is parallel to the optical axis of the optics under test, the third direction is parallel to the rotation axis, the first direction and the second direction are orthogonal to the rotation axis and each other;

the light source module translation stage is connected to the light source module, and is adapted to drive the light source module to move along the first direction, the second direction, and the third direction.

8 . The optical wavefront measuring device as claimed in claim 6 , further comprising a robotic arm to pick and place the optics under test to the lens holder.

9 . An optical wavefront measuring method suitable for an optical wavefront measuring device to test optics under test, the optical wavefront measuring device comprising a rotational spindle rotating the optics under test, a light source module, a wavefront sensor, and a computing device, the optical wavefront measuring method comprising:

moving the light source module to a first pre-determined position, and moving the wavefront sensor to a second pre-determined position;

providing an incident light beam incident on the optics under test by the light source module, and a testing light beam containing measured wavefront of the optics under test propagates out of the optics under test;

when the optics under test is rotated to a plurality of different azimuthal directions by the rotational spindle, the testing light beam passing through the optics under test rotated in at least two of the plurality of different azimuthal directions is acquired by the wavefront sensor; and

capturing a plurality of camera frames with different exposures for each of the plurality of different azimuthal directions to acquire the testing light beam by the wavefront sensor;

wherein synthesizing the camera frames with different exposures for each of the plurality of different azimuthal directions into a measured wavefront corresponding to the respective azimuthal direction; and

receiving the measured wavefront corresponding to the respective azimuthal direction, by the computing device;

determining a fixed alignment error aberration (W DC ) attributable to misalignment of the optical wavefront measuring device from the measured wavefront, by the computing device; and

subtracting the fixed alignment error aberration (W DC ) from the measured wavefront to obtain an angle-dependent aberration component attributable to the optics under test, by the computing device.

10 . The optical wavefront measuring method as claimed in claim 9 , wherein the camera frames with different exposures are obtained by modulating a light intensity of the incident light beam of the light source module.

11 . The optical wavefront measuring method as claimed in claim 9 , wherein the camera frames with different exposures are obtained by configuring the wavefront sensor to capture the camera frames with different shutter times.

12 . The optical wavefront measuring method as claimed in claim 9 , wherein before the steps of when the optics under test is rotated to a plurality of different azimuthal directions by the rotational spindle, the testing light beam is acquired by the wavefront sensor at the plurality of different azimuthal directions, the optical wavefront measuring method further comprises aligning an optical axis of the optics under test with the rotation axis of the rotational spindle.

13 . The optical wavefront measuring method as claimed in claim 9 , the first pre-determined position and the second pre-determined position are determined by the method:

determining an optimum optical conjugate position according to a design prescription of the optics under test by ray tracing; and

determining the first pre-determined position and the second pre-determined position of the light source module and the wavefront sensor relative to the optics under test in a third direction parallel to the rotation axis according to the optimum optical conjugate position.

14 . The optical wavefront measuring method as claimed in claim 13 , wherein when determining the optimum optical conjugate position according to the design prescription of the optics under test by the ray tracing method, the optical wavefront measuring method comprises:

generating a reference wavefront phase or a reference ray slope in the micro lens array plane of the wavefront sensor; or

generating the reference wavefront phase or the reference ray slope according to the surface or elements decentration of the optics under test in the micro lens array plane of the wavefront sensor to quantify the decentration of surface or elements of the optics under test.

15 . The optical wavefront measuring method as claimed in claim 13 , wherein after the step of determining the optimum optical conjugate position according to the design prescription of the optics under test by the ray tracing method, the optical wavefront measuring method further comprises:

determining a numerical aperture of the incident light beam according to the optimum optical conjugate position of the optics under test, selecting an appropriate converging lens or an aperture to control the incident light beam convergence speed, and adjusting the first pre-determined position of the converging lens in the third direction parallel to the rotation axis according to the optimum optical conjugate position, using the computing device.

16 . The optical wavefront measuring method as claimed in claim 15 , wherein the rotational spindle comprises a lens holder, the lens holder holding the optics under test, the aperture is disposed between a collimator and the converging lens or between the converging lens and the optics under test, or the aperture is an opening of the lens holder.

17 . The optical wavefront measuring method as claimed in claim 12 , wherein the rotational spindle comprises a rotational stage, a translation stage and a lens holder, the translation stage is disposed on the rotational stage, the rotational stage has the rotation axis, and drives the translation stage to rotate along the rotation axis, the lens holder is disposed on the translation stage, and holding the optics under test, wherein the step of aligning the optical axis of the optics under test with the rotation axis of the rotational spindle comprises driving the lens holder to move along a first direction and a second direction by the translation stage, and the first direction and the second direction are perpendicular to the rotation axis and each other.