Method and Apparatus for Improvement of Spectrometer Stability, and Multivariate Calibration Transfer

• US 20080120052A1
• Filed: 11/16/2006
• Published: 05/22/2008
• Est. Priority Date: 11/16/2006
• Status: Active Grant

• Current Assignee: Rockley Photonics Limited
• Original Assignee: TruTouch Technologies, Inc.
• Inventors: ver Steeg, Ben, Maynard, John D., Benz, Zachary, Ridder, Trent
• Granted Patent: US 7,446,878 B2
• Time in Patent Office: Days
• US Class Current: 702/75
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/027 Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation
• CPC Class Codes: G01J 3/45 Interferometric spectrometry

Abstract

The present invention provides methods and apparatuses that can improve measurement accuracy in interferometers. The invention provides methods for determining digital compensation filters that measure a frequency response or responses to be compensated, and then determining a filter target response from the inverse of the frequency response or responses. A digital compensation filter can be determined from the filter target response using a discrete sum of cosines with a phase argument. The invention also allows other desired filter responses to be integrated into the filter target response before determining the digital compensation filter.

Claims

1. A method for determining a digital compensation fitter comprising:

a. Measuring the frequency response or responses to be compensated;

b. Determining a filter target response from the inverse of the responses measured in step a;

c. Determining a digital compensation filter from the filter target response using a discrete sum of cosines with a phase argument.

2. A method as in claim 1, wherein determining a fitter target response further comprises combining the frequency responses of one or more band pass, low pass, or high pass frequency fitters with the inverse of the responses measured in step a.

3. A method as in claim 1 further comprising apodization truncation or both of the digital compensation filter.

6. A method for dynamically updating the compensation filter for changes in the interferometric system environment or operating conditions comprising

a. Determining the frequency response to be compensated by:

i. Measuring double-sided interferograms of a polychromatic light source in both directions of optical component travel;

ii. Determining the frequency response difference substantially related to the difference between interferograms obtained from the two directions of optical travel;

b. Determining a compensation filter from the response of (a) using the method of claim 1.

c. Implementing the compensation filter of (b)

d. Determining the frequency response at a subsequent time by;

i. Measuring double-sided interferograms of the polychromatic light source in both directions of optical component travel;

ii. Determining the frequency response difference substantially related to the difference between interferograms obtained from the two directions of optical travel;

e. Updating the frequency response from (a) with the frequency response in (d);

f. Determining a new compensation filter from the response of (e) using the method of claim 1.

g. Implementing the compensation filter of (f)

h. Repeat steps d-g at a subsequent time.

4. A method for determining a frequency response to be compensated comprising:

a. Measuring double-sided interferograms of a polychromatic tight source in both directions of optical component travel;

b. Determining the frequency response difference substantially related to the difference between interferograms obtained from the two directions of optical travel.

5. A method as in claim 4 comprising repeating steps a and b white inducing different velocities on optical component travel, and combining the frequency responses obtained from the different velocities.

7. A method for determining a digital compensation filter comprising:

a. Measuring the frequency response or responses to be compensated using the method of claim 4;

b. Determining a filter target response from the inverse of the responses measured in step a;

c. Determining a digital compensation filter from the filter target response using a discrete sum of cosines with a phase argument.