# US 11,896,303 B2 · Optical apparatus

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,896,303 B2
- Document ID: US11896303B2
- Status: Granted
- Kind: B2
- Application number: 16/630,217
- Filed: 2018-07-03
- Published: 2020-05-14
- Granted: 2024-02-13
- Earliest claimed: 2017-07-14
- Assignees: Wavesense Engineering GmbH
- Applicants: Wavesense Engineering GmbH
- Inventors: Abhishek Kumar
- Web page: https://patentgrep.com/patent/US11896303B2

## CPC

- A61B 3/0025: {characterised by electronic signal processing, e.g. eye models}
- A61B 3/1015: {for wavefront analysis}
- A61B 3/102: {for optical coherence tomography [OCT]}
- G01B 9/02091: Tomographic interferometers, e.g. based on optical coherence
- G01J 9/02: by interferometric methods (using interferometers for measuring optically the linear dimensions of objects G01B9/02)
- G03H 1/0443: {Digital holography, i.e. recording holograms with digital recording means (holobject computation G03H1/0866)}
- G03H 1/0866: {Digital holographic imaging, i.e. synthesizing holobjects from holograms}
- G06T 12/30: Image post-processing, e.g. metal artefact correction
- A61B 3/12: for looking at the eye fundus, e.g. ophthalmoscopes (A61B3/13 takes precedence)
- A61B 3/1225: {using coherent radiation}
- A61B 3/13: Ophthalmic microscopes
- A61B 5/0066: {Optical coherence imaging}
- A61B 5/7257: {using Fourier transforms}
- G01J 2009/002: {Wavefront phase distribution}
- G01J 2009/0226: {Fibres}
- G03H 2001/0883: {Reconstruction aspect, e.g. numerical focusing}
- G06T 2207/10101: Optical tomography; Optical coherence tomography [OCT]
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- 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)
- G03H: HOLOGRAPHIC PROCESSES OR APPARATUS (holograms, e.g. point holograms, used as ordinary optical elements G02B5/32; producing stereoscopic or other three-dimensional effects G02B30/00; diffraction-grating systems G02B27/44; systems using moiré fringes G02B27/60; optical logic elements G02F3/00; stereo-photography G03B35/00; photosensitive materials or processes for photographic purposes G03C; {stereo-photographic or similar processes G03C9/00}; apparatus for processing exposed photographic materials G03D; analogue computers performing mathematical operations with the aid of optical elements G06E3/00; authentication by radiation, of concealed information carried by holograms or diffraction gratings G06K19/16; holographic storage G11B7/0065, G11C13/04; {stereoscopic or other three dimensional effects in television systems H04N13/00})
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

An optical apparatus is comprising an optical imaging arrangement generating either an image of the original object field or the field of the original sample at the pupil plane which consist of both amplitude and phase information. The apparatus is further comprising a digital adaptive optics arrangement with a wave front sensor and a computing unit, which is adapted to generate at least one orthogonally translated digital copy of the original sample object field at the spatial Fourier or pupil plane and to analytically calculate a wave front error based on the phase difference between the original sample wave front and its digital copy or copies.

## Claims

### Claim 1

An interferometric apparatus to image a point on a sample, comprising:
an optical arrangement configured to produce a sample beam and a reference beam and to produce either 1) an image of an original object field of the point at an image plane illuminated by the sample beam, the field including both amplitude information and phase information or 2) a field of the point at a pupil plane when the point is illuminated by the sample beam, the field including both amplitude information and phase information, the optical arrangement configured to produce a combination of the sample beam after illumination of the point and the reference beam;
a scanner located to receive the combination of the sample beam and reference beam and to direct the combination through focusing optics and onto a pinhole filter, the scanner and focusing optics being arranged to translate overlapping spots corresponding to the reference beam and the sample beam across the pinhole filter,
a photodetector located to receive light from the combination passing through the pinhole filter as the overlapping spots translate across the pinhole filter thereby determining a point spread function of the apparatus; and
a digital adaptive optics arrangement comprising:
(i.) a wavefront sensor configured to calculate (1) a sampled wavefront of the original object field of the point at the image plane or (2) a sampled wavefront of the object field of the point at the pupil plane, using the point spread function; and
(ii.) a computing unit adapted to:
A) generate at least one digital shifted copy of the sampled wavefront of the object at the pupil plane by
(1) using the image of the original object field of the point at the image plane to calculate the field at the pupil plane and shifting the calculated field along a horizontal or a vertical direction or an axis of a defined coordinate system of the pupil plane or
(2) using the field of the point at the pupil plane and shifting the field along a horizontal or a vertical direction or an axis of a defined coordinate system of the pupil plane and
B) determine a wavefront error in the original object field based on a phase difference between (1) a sampled wavefront of the calculated and the at least one digital shifted copy at the pupil plane or (2) the sampled wavefront of the object field of the point at the pupil plane and the at least one digital shifted copy at the pupil plane.

### Claim 2 (depends on 1)

The optical apparatus according to claim 1, wherein the computing unit is adapted to generate the at least one digital shifted copy of the original object field at the pupil plane by performing, digitally, a 2-D fast Fourier transformation on the image of the original object field and then shifting the transformation of the image by at least one pixel along the horizontal direction or the vertical direction or the axis of the defined coordinate system of the pupil plane.

### Claim 3 (depends on 1)

The optical apparatus according to claim 1, wherein the optical apparatus constitutes at least a portion of a digital holography system, phase sensing interferometric system or optical coherence tomography system.

### Claim 4 (depends on 3)

The optical apparatus according to claim 3, further comprising:
a source of laser light or a broad band partially coherent source of light,
collimation optics for the light from the source of laser light or the broad band partially coherent source of light,
a beam splitter arrangement configured to direct a part of the light from the source of laser light or the broad band partially coherent source of light to the sample beam in a sample arm and another part of the light from the source of laser light or the broad band partially coherent source of light to the reference beam in a reference arm,
the scanner placed at a Fourier plane of the focusing optics in the sample arm,
a three-dimensional translation stage arranged as a carrier of the sample, and
the photodetector configured to detect recombined light from the sample arm and the reference arm after the beam splitter, said photodetector connected with the computing unit, the computing unit configured to digitize and process a signal corresponding to the combination of the sample beam and the reference beam to produce the phase information and amplitude information of the combination.

### Claim 5 (depends on 4)

The optical apparatus according to claim 4, wherein the reference arm includes an element that matches dispersion caused by the focusing optics in the sample arm.

### Claim 6 (depends on 5)

The optical apparatus according to claim 5, further comprising a phase shifting device or a frequency shifting device in the reference arm to introduce a phase shift between light in the reference arm and light in the sample arm.

### Claim 7 (depends on 4)

The optical apparatus according to claim 4, further comprising a pixelated phase mask placed at a plane conjugate to the sample where the light from the source of laser light or the broad band partially coherent source of light is focused using second focusing optics and collimation optics, the second focusing optics and the collimation optics placed between the phase mask and the photodetector.

### Claim 8 (depends on 4)

The optical apparatus according to claim 4, further comprising a second optical arrangement to receive light that has passed through the pinhole filter, the arrangement comprising: (1) a diffraction grating or prism, and (2) a one-dimensional array of photodetectors to receive the light from the diffraction grating or prism.

### Claim 9 (depends on 1)

The optical apparatus according to claim 1, wherein the optical arrangement further comprises a light source, collimation optics and a linear polarizer for the light from the light source, a reflective polarizing beam splitter to direct the sample beam along a sample path, toward the sample,
the sample beam directed through a quarter wave plate toward the sample, a three dimensional translation stage configured to maintain the sample in the sample beam, such that the sample path after reflection from the sample includes the quarter wave plate, a first telescope arrangement, a second beam splitter located after the first telescope to separate the reference beam from the sample beam, followed by a second telescope arrangement with the pinhole filter placed at an intermediate focal plane of the first telescope for one of the beams produced by the second beam splitter, and the photodetector disposed at the back focal plane of the second telescope, said photodetector connected with the computing unit.

### Claim 10 (depends on 9)

The optical apparatus according to claim 9, further comprising a pixelated phase mask placed at the intermediate focal plane of the second telescope to focus one of the beams produced by the second beam splitter, and the pinhole filter disposed to filter another of the beams produced by the second beam splitter.

### Claim 11 (depends on 1)

The optical apparatus according to claim 1, wherein the optical arrangement further comprises a light source, collimation optics and a linear polarized for the light from the light source, a reflective polarizing beam splitter to direct the sample beam along a sample path,
the sample beam directed through a quarter wave plate, a mirror to reflect the sample beam, such that the sample path after reflection from the mirror includes the quarter wave plate, a first telescope arrangement, a second beam splitter located after the first telescope to separate a reference beam from the sample beam, followed by a second telescope arrangement with the pinhole filter placed at an intermediate focal plane of the first telescope for the reference beam produced by the second beam splitter and a support for placing a transmissive sample in the sample beam at the intermediate focal plane of the first telescope, and the photodetector disposed at the back focal plane of the second telescope, said photodetector connected with the computing unit.

### Claim 12 (depends on 1)

The optical apparatus according to claim 1, further comprising a swept source laser or a tunable frequency laser to produce light for the sample beam and the reference beam, and wherein the photodetector comprises a single element photodetector.

### Claim 13 (depends on 1)

The optical apparatus according to claim 1, further comprising a broad-band light source to produce light for the sample beam and the reference beam and wherein the photodetector comprises a spectrometer.

### Claim 14 (depends on 1)

The optical apparatus according to claim 1, further comprising a light source including a monochromatic coherent continuous wave (CW) or pulsed laser, a frequency tuneable laser source or a broad band partially coherent light source to produce the sample beam and the reference beam, the light source followed by a linear polarizer and a non-polarizing beam-splitter arranged to receive light from the light source,
the path of the sample beam containing a first telescope and an aperture, a first quarter wave plate at 45° with respect to an optical axis of the sample beam, and a non-polarizing beam splitter, and
the path for light after illumination of the point containing the non-polarizing beam splitter, a second and third telescopes with an X-Y galvo scanner system intermediate the second and third telescopes, and the first quarter wave plate, and
the reference path containing an adjustable reference mirror, a second quarter wave plate and a dispersion compensation glass.

### Claim 15 (depends on 14)

The optical apparatus according to claim 14, further comprising a polarizing beam splitter disposed between the non-polarizing beam splitter and the second telescope of the sample path, said polarizing beam splitter or the non-polarizing beam splitter placed before the sample, the polarizing beam splitting of the sample path of the non-polarizing beam splitter of the sample path being pivotable in and out of the path of the sample beam.

### Claim 16 (depends on 1)

The optical apparatus according to claim 1, further comprising a swept source laser as a light source, a fiber coupler branching to direct light from the light source into the sample beam in a sample light path and to direct light into the reference beam in a reference light path, the reference light path containing a collimator, an adjustable reference mirror and a second collimator, the sample light path containing a third collimator, at least one deflection mirror and a beam splitter,
the apparatus further comprising a telescope disposed to receive light from the beam splitter after the light traverses the sample location, followed by a X-Y galvo scanner, a second telescope and a fourth collimator, the light in the sample path and the light in the reference light path aligned to combine together into a second fiber coupler, the output side of the second fiber coupler connected to a dual balance detector.

### Claim 17 (depends on 1)

The optical apparatus according to claim 1, wherein the pinhole filter comprises a pinhole aperture or a tip of a single mode fiber.

### Claim 18

A non-transitory computer readable medium having executable programming instructions stored thereon comprising program code for:
generating at least one laterally translated digital copy of an original object field of an optical apparatus at a spatial Fourier plane along the horizontal or vertical direction or axis of a defined coordinate system of the pupil plane; and
determining a wavefront error based on a phase difference between an original wavefront and a digital copy or copies of the original wavefront.

### Claim 19 (depends on 18)

The non-transitory computer readable medium having executable programming instructions stored thereon according to claim 18, wherein the code is adapted to generate the translated digital copy of the original object field as an original object field at the pupil plane, by performing digitally a 2-D fast Fourier transformation on an image field and then shifting the original object field by at least one pixel along the horizontal or vertical direction or axis of a defined coordinate system of the spatial Fourier or pupil plane.

### Claim 20 (depends on 18)

The non-transitory computer readable medium having executable programming instructions stored thereon according to claim 18, wherein the step of determining the wavefront comprises multiplying pixel-by-pixel the original wavefront with a complex conjugate of the translated digital copy and calculating slope per pixel of the wavefront error.