Automated defect detection and mapping for optical filters

Patent metadata

Field	Value
Publication number	US-9927369-B2
Application number	US-201615172592-A
Country	US
Kind code	B2
Filing date	Jun 3, 2016
Priority date	Jun 3, 2015
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

Devices and methods are disclosed for characterizing point flaws (including pinholes and point defects) of an optical filter. A passband test is performed, including: illuminating the optical filter with passband illumination whose spectral range at least overlaps a passband of the optical filter; acquiring a passband map of the optical filter using a two-dimensional array of photodetectors while illuminating the optical filter with the passband illumination; and identifying point defects of the optical filter as low intensity locations of the passband map. A stopband test is performed, including: illuminating the optical filter with stopband illumination whose spectral range lies entirely outside of the passband of the optical filter; acquiring a stopband map of the optical filter using the two-dimensional array of photodetectors while illuminating the optical filter with the stopband illumination; and identifying pinholes of the optical filter as high intensity locations of the stopband map.

First claim

The invention claimed is:

1. A test device for characterizing point flaws of an optical filter under test including pinholes and point defects, the test device comprising:
a passband illumination source configured to illuminate the optical filter under test with passband illumination whose spectral range at least overlaps a passband of the optical filter under test;
a stopband illumination source configured to illuminate the optical filter under test with stopband illumination whose spectral range lies entirely outside of the passband of the optical filter under test;
a two-dimensional array of photodetectors arranged to detect the passband illumination after passing through the optical filter under test and to detect the stopband illumination after passing through the optical filter under test; and
an electronic controller configured to operate in conjunction with the passband illumination source, the stopband illumination source, and the two-dimensional array of photodetectors to:
perform a passband test including acquiring a passband map of the optical filter under test using the two-dimensional array of photodetectors while illuminating the optical filter under test with the passband illumination and not illuminating the optical filter under test with the stopband illumination, and
perform a stopband test including acquiring a stopband map of the optical filter under test using the two-dimensional array of photodetectors while illuminating the optical filter under test with the stopband illumination and not illuminating the optical filter under test with the passband illumination.

2. The test device of claim 1 wherein the test device is configured to not simultaneously illuminate the optical filter under test with both the passband illumination and the stopband illumination.

3. The test device of claim 1 wherein:
the electronic controller is configured to perform the passband test further including identifying point defects as locations of the passband map of the optical filter under test where the intensity is below a point defect threshold intensity; and
wherein the electronic controller is configured to perform the stopband test further including identifying pinholes as locations of the stopband map of the optical filter under test where the intensity is above a pinhole threshold intensity.

4. The test device of claim 3 further comprising:
a display component;
wherein the electronic controller configured to perform the passband test further including displaying one of the passband map and a map of the identified point defects on the display component; and
wherein the electronic controller configured to perform the stopband test further including displaying one of the stopband map and a map of the identified pinholes on the display component.

5. The test device of claim 3 wherein:
the electronic controller configured to perform the passband test further including computing statistics for the identified point defects and displaying the computed point defects statistics on a display component of the electronic controller; and
the electronic controller configured to perform the stopband test further including computing statistics for the identified pinholes and displaying the computed pinhole statistics on the display component of the electronic controller.

6. The test device of claim 3 wherein:
the identifying of point defects includes aggregating contiguous pixels of the passband map whose intensities are below the point defect threshold intensity to identify a point defect as the aggregation of contiguous pixels; and
the identifying of pinholes includes aggregating contiguous pixels of the stopband map whose intensities are above the pinhole threshold intensity to identify a pinhole as the aggregation of contiguous pixels.

7. The test device of claim 1 wherein:
the passband illumination source is configured to output only the passband illumination whose spectral range at least overlaps the passband of the optical filter under test;
the stopband illumination source is configured to output only the stopband illumination whose spectral range lies entirely outside of the passband of the optical filter under test;
the test device further includes an optical multiplexing component or sub-system configured to couple the passband illumination to illuminate the optical filter under test and to couple the stopband illumination to illuminate the optical filter under test;
the electronic controller is configured to perform the passband test including operating the passband illumination source to output the passband illumination and operating the stopband illumination source to not output the stopband illumination; and
the electronic controller is configured to perform the stopband test including operating the stopband illumination source to output the stopband illumination and operating the passband illumination source to not output the passband illumination.

8. The test device of claim 1 wherein:
the passband illumination source includes:
a broadband light source outputting a broadband illumination whose spectral range includes both the spectral range of the passband illumination and the spectral range of the stopband illumination; and
a passband filter configured to pass the passband illumination and block the stopband illumination;

the stopband illumination source includes:
the broadband light source; and
a stopband filter configured to pass the stopband illumination and block the passband illumination;

the electronic controller is configured to perform the passband test with the passband filter arranged to filter the broadband illumination output by the broadband light source to illuminate the optical filter under test with the passband illumination; and
the electronic controller is configured to perform the stopband test with the stopband filter arranged to filter the broadband illumination output by the broadband light source to illuminate the optical filter under test with the stopband illumination.

9. The test device of claim 1 wherein the test device is not configured to acquire any spectral data for the optical filter under test.

10. The test device of claim 1 wherein the test device does not include a spectrometer or spectrograph.

11. A test method for characterizing point flaws of an optical filter under test including pinholes and point defects, the test method comprising:
performing a passband test including:
illuminating the optical filter under test with passband illumination whose spectral range at least overlaps a passband of the optical filter under test and
acquiring a passband map of the optical filter under test using a two-dimensional array of photodetectors while illuminating the optical filter under test with the passband illumination and
using an electronic controller, identifying point defects of the optical filter under test as low intensity locations of the passband map; and

performing a stopband test including:
illuminating the optical filter under test with stopband illumination whose spectral range lies entirely outside of the passband of the optical filter under test and
acquiring a stopband map of the optical filter under test using the two-dimensional array of photodetectors while illuminating the optical filter under test with the stopband illumination and
using the electronic controller, identifying pinholes of the optical filter under test as high intensity locations of the stopband map.

12. The test method of claim 11 wherein:
the performing of the passband test does not include illuminating the optical filter under test with the stopband illumination; and
the performing of the st

Assignees

• Materion Corp

Inventors

• Sprague Robert

Classifications

• G01N2021/9511

  Optical elements other than lenses, e.g. mirrors · CPC title

• G01N21/255

  Details, e.g. use of specially adapted sources, lighting or optical systems · CPC title

• G01N21/8806 Primary

  Specially adapted optical and illumination features · CPC title

• G01N21/958 Primary

  Inspecting transparent materials {or objects, e.g. windscreens (for conveyed flat sheet or rod G01N21/896)} · CPC title

• G01M11/0285

  by measuring material or chromatic transmission properties (G01M11/0292 takes precedence) · CPC title