# US 8,570,514 B2 · Optical system polarizer calibration

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- Number: US 8,570,514 B2
- Document ID: US8570514B2
- Status: Granted
- Kind: B2
- Application number: 13/164,130
- Filed: 2011-06-20
- Published: 2012-12-20
- Granted: 2013-10-29
- Earliest claimed: 2011-06-20
- Assignees: KLA-Tencor Corporation
- Applicants: Johannes D. de Veer; Leonid Poslavsky; Guorong V. Zhuang; Shankar Krishnan
- Inventors: Johannes D. de Veer; Leonid Poslavsky; Guorong V. Zhuang; Shankar Krishnan
- Web page: https://patentgrep.com/patent/US8570514B2

## CPC

- G01N 21/21: Polarisation-affecting properties (G01N21/19 takes precedence)
- G01J 3/504: {Goniometric colour measurements, for example measurements of metallic or flake based paints}
- G01N 21/274: {Calibration, base line adjustment, drift correction}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)

## Abstract

A method to calibrate a polarizer in polarized optical system at any angle of incidence, by decoupling the calibration from a polarization effect of the system, by providing a calibration apparatus that includes a substrate having a polarizer disposed on a surface thereof, with an indicator on the substrate for indicating a polarization orientation of the polarizer, loading the calibration apparatus in the polarized optical system with the indicator in a desired position, determining an initial angle between the polarization orientation and a reference of the polarized optical system, acquiring spectra using the polarized optical system at a plurality of known angles between the polarization orientation and the reference of the polarized optical system, using the spectra to plot a curve indicating an angle of the polarizer in the polarized optical system, and when the angle of the polarizer is outside of a desired range, adjusting the angle of the polarizer, and repeating the steps of acquiring the spectra, and plotting a curve indicating the angle of the polarizer.

## Claims

### Claim 1

A method to calibrate a polarizer in a polarized optical system at any angle of incidence, by decoupling a polarization effect of the system from a polarization effect of a sample, the method comprising the steps of:
providing a calibration apparatus comprising a substrate with a polarizer, with an indicator on the substrate for indicating a polarization orientation of the polarizer,
loading the calibration apparatus in the polarized optical system with the indicator in a desired position,
determining an initial angle between the polarization orientation of the calibration apparatus and a reference of the polarized optical system,
acquiring signals based on optical readings of the calibration apparatus using the polarized optical system at a plurality of known angles between the polarization orientation of the calibration apparatus and the reference of the polarized optical system,
using the signals to plot a curve indicating an angle of a polarizer in the polarized optical system, and
when the angle of the polarizer in the polarized optical system is outside of a desired range, adjusting the angle of the polarizer in the polarized optical system, and repeating the steps of acquiring the signals, and plotting a curve indicating the angle of the polarizer in the polarized optical system.