Precision non-contact core imaging of fiber optic assemblies
A method, system, and computer program product for determining a core-to-ferrule offset of a ferrule for a fiber optic connector. A reference ferrule is physically aligned with a core imager by positioning the reference ferrule so that edges of the reference ferrule in a plurality of profile images are aligned with fiducial markers in the images. The reference ferrule is incrementally rotated about its longitudinal center access, a core image captured at each rotational angle, and a reference core-to-ferrule offset determined based on the core images. A test ferrule is physically aligned with the core imager by positioning the test ferrule so that edges of the test ferule are aligned with the edges of the reference ferrule in a plurality of profile images. The core-to-ferrule offset of the test ferrule is then determined based on an offset between the test and reference cores in a composite core image.
1. A method of focusing a core image of a test ferrule that has an optical fiber coupled thereto, wherein the optical fiber includes a core for the core image, the method comprising:
positioning the test ferrule relative to a core imager including an optical sensor and a lens to achieve a rough focus of an image element in the core image;
positioning the lens of the core imager at each of a plurality of lens focus settings each corresponding to a different position of the lens in the core imager relative to the optical sensor of the core imager;
at each of the plurality of lens focus settings:
capturing another core image including the image element, and
determining a width of the image element in the core image;
identifying the lens focus setting having a smallest width of the image element; and
setting the position of the lens in the core imager to the lens focus setting having the smallest width.
2. The method of claim 1 , wherein identifying the lens focus setting having the smallest width of the image element comprises:
plotting the width of each image element verses the lens focus setting;
fitting the plotted widths to a curve; and
identifying a minimum of the curve as the lens focus setting having the smallest width.
3. The method of claim 2 , wherein the curve is a polynomial curve.
4. The method of claim 3 , wherein the curve is a parabola.
5. The method of claim 1 , wherein determining the width of the image element comprises:
fitting a Gaussian function to the image element;
determining a standard deviation of the fitted Gaussian function; and
determining the width of the image element based on the standard deviation.
6. The method of claim 5 , wherein the width of the image element is twice the standard deviation.
7. The method of claim 1 , further comprising:
comparing the smallest width of the image element to a maximum allowable width;
in response to the smallest width of the image element exceeding the maximum allowable width:
repositioning the test ferrule; and
repeating the positioning the lens, the capturing another core image, the determining the width of the image element, the identifying the lens focus setting, and the setting the position of the lens steps.
8. A system for focusing a core image of a test ferrule that has an optical fiber coupled thereto, wherein the optical fiber includes a core for the core image, the system comprising:
a core imager including an optical sensor and a lens having a lens focus setting corresponding to a position of the lens in the core imager relative to the optical sensor of the core imager;
a positioner configured to position the test ferrule relative to the core imager;
one or more processors in communication with the core imager and the positioner; and
a memory coupled to the one or more processors and including program code that, when executed by the one or more processors, causes the system to:
position the test ferrule relative to the core imager to achieve a rough focus of an image element in the core image;
position the lens of the core imager at each of a plurality of lens focus settings each corresponding to a different position of the lens in the core imager relative to the optical sensor of the core imager;
at each of the plurality of lens focus settings:
capture another core image including the image element, and
determine a width of the image element of the core image;
identify the lens focus setting having a smallest width of the image element; and
set the position of the lens in the core imager to the lens focus setting having the smallest width.
9. The system of claim 8 , wherein the program code causes the system to identify the lens focus setting having the smallest width of the image element by:
plotting the width of each image element verses the lens focus setting;
fitting the plotted widths to a curve; and
identifying a minimum of the curve as the lens focus setting having the smallest width.
10. The system of claim 9 , wherein the curve is a polynomial curve.
11. The system of claim 10 , wherein the polynomial curve is a parabola.
12. The system of claim 8 , wherein the program code causes the system to determine the width of the image element by:
fitting a Gaussian function to the image element;
determining a standard deviation of the fitted Gaussian function; and
determining the width of the image element based on the standard deviation.
13. The system of claim 12 , wherein the width of the image element is twice the standard deviation.
14. The system of claim 8 , wherein the program code further causes the system to:
compare the smallest width of the image element to a maximum allowable width;
in response to the smallest width of the image element exceeding the maximum allowable width:
reposition the test ferrule; and
repeat the positioning the lens, the capturing another core image, the determining the width of the image element, the identifying the lens focus setting, and the setting the position of the lens steps.
15. A computer program product for focusing a core image of a test ferrule that has an optical fiber coupled thereto, wherein the optical fiber includes a core for the core image, the computer program product comprising:
a non-transitory computer-readable storage medium; and
program code stored on the non-transitory computer-readable storage medium that, when executed by one or more processors, causes the one or more processors to:
position the test ferrule relative to a core imager including an optical sensor and a lens to achieve a rough focus of an image element in the core image;
positioning the lens of the core imager at each of a plurality of lens focus settings each corresponding to a different position of the lens in the core imager relative to the optical sensor of the core imager;
at each of the plurality of lens focus settings:
capture another core image including the image element, and
determine a width of the image element of the core image;
identify the lens focus setting having a smallest width of the image element; and
set the position of the lens to the lens focus setting in the core imager having the smallest width.