# US 2016/0252425 A1 · Apparatus and method for evaluation of optical elements

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- Number: US 2016/0252425 A1
- Document ID: US20160252425A1
- Status: Published application
- Kind: A1
- Application number: 15/154,454
- Filed: 2016-05-13
- Published: 2016-09-01
- Earliest claimed: 2013-03-11
- Assignees: Lumetrics, Inc.
- Applicants: Lumetrics, Inc.
- Inventors: Filipp V. IGNATOVICH; Donald S. GIBSON; Michael A. MARCUS
- Web page: https://patentgrep.com/patent/US20160252425A1

## CPC

- G01M 11/0271: {by using interferometric methods}
- G01M 11/02: Testing optical properties
- G01M 11/0207: {Details of measuring devices}
- G01M 11/0235: {by measuring multiple properties of lenses, automatic lens meters}
- G01M 11/025: {by determining the shape of the object to be tested (measuring contours or curvatures by optical means G01B11/24)}
- G01M 11/0278: {Detecting defects of the object to be tested, e.g. scratches or dust (investigating the presence of flaws or contamination on materials by optical means G01N21/88)}
- G01M 11/0285: {by measuring material or chromatic transmission properties (G01M11/0292 takes precedence)}
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR

## Abstract

An apparatus for measuring the optical performance characteristics and dimensions of an optical element comprising a low coherence interferometer and a Shack-Hartmann wavefront sensor comprising a light source, a plurality of lenslets, and a sensor array is disclosed. The low coherence interferometer is configured to direct a measurement beam along a central axis of the optical element, and to measure the thickness of the center of the optical element. The light source of the Shack-Hartmann wavefront sensor is configured to emit a waveform directed parallel to and surrounding the measurement beam of the interferometer, through the plurality of lenslets, and to the sensor array. A method for measuring the optical performance characteristics and dimensions of a lens using the apparatus is also disclosed.

## Claims

### Claim 1

A method for measuring a lens having a focal length and comprising a first surface and a second surface defining a lens thickness therebetween, the method comprising the steps of:
a) measuring the thickness of the lens at a center of the lens with a low coherence interferometer;
b) measuring the focal length of the lens with a wavefront sensor;
c) communicating the thickness of the lens and the focal length of the lens to an analyzer computer;
d) calculating a radius of curvature of the first surface of the lens and a radius of curvature of the second surface of the lens using an algorithm executed by the computer to obtain dimensions of the lens; and
e) performing at least one of storing in a non-transitory computer storage medium, communicating externally, or displaying the dimensions of the lens.

### Claim 2 (depends on 1)

The method of claim 1, wherein the low coherence interferometer is configured to direct a first beam of light along a defined axis of the lens and wherein the wavefront sensor is a Shack-Hartmann wavefront sensor further comprising a light source configured to emit a second beam of light and a plurality of lenslets placed in front of a sensor array.

### Claim 3 (depends on 2)

The method of claim 2, wherein the diameter and location of the center of the lens is measured with an image sensor which receives a portion of the second beam of light.

### Claim 4 (depends on 1)

The method of claim 1, further comprising the step of calculating at least one optical performance parameter of the lens.

### Claim 5 (depends on 4)

The method of claim 4, wherein the at least one optical performance parameter of the lens is selected from optical power, spherical aberration, chromatic aberration, astigmatism, coma, field curvature, prism, and distortion.

### Claim 6 (depends on 1)

The method of claim 1, wherein measuring the thickness of the lens at the center of the lens further comprises measuring the optical thickness of the lens and calculating the thickness and index of refraction of the lens.

### Claim at position 7

7-17. (canceled)

### Claim 18 (depends on 6)

The method of claim 6 wherein the step of measuring the thickness of the lens at the center of the lens with a low coherence interferometer further comprises installing the lens in the inner volume of a cuvette and measuring the optical thickness of the lens.

### Claim 19 (depends on 18)

The method of claim 18, wherein measuring the optical thickness of the center of the lens with the low coherence interferometer further comprises measuring an optical path from a top inner surface of the cuvette to a top of the center of the lens and an optical path from a bottom of the center of the lens to a bottom inner surface of the cuvette, and calculating the thickness and index of refraction of the lens.

### Claim 20 (depends on 19)

The method of claim 19, further comprising measuring the optical path from the top inner surface of the cuvette to the bottom inner surface of the cuvette at the location of the center of the lens measurement location with the lens absent from the cuvette.

### Claim 21 (depends on 18)

The method of claim 18 wherein the inner volume of the cuvette contains a liquid medium.