# US 2018/0024008 A1 · Optical system phase acquisition method and optical system evaluation method

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- Number: US 2018/0024008 A1
- Document ID: US20180024008A1
- Status: Published application
- Kind: A1
- Application number: 15/651,915
- Filed: 2017-07-17
- Published: 2018-01-25
- Earliest claimed: 2016-07-20
- Assignees: Ushio Denki Kabushiki Kaisha
- Applicants: Ushio Denki Kabushiki Kaisha
- Inventors: Masashi OKAMOTO; Tsukasa MATSUO
- Web page: https://patentgrep.com/patent/US20180024008A1

## CPC

- G01J 9/02: by interferometric methods (using interferometers for measuring optically the linear dimensions of objects G01B9/02)
- G01B 9/02032: {generating a spatial carrier frequency, e.g. by creating lateral or angular offset between reference and object beam (shearing interferometers G01B9/02098)}
- G01B 9/02047: {using digital holographic imaging, e.g. lensless phase imaging without hologram in the reference path}
- G01B 9/021: using holographic techniques
- G01M 11/0271: {by using interferometric methods}
- 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}
- G03H 2001/0445: {Off-axis recording arrangement (G03H2001/0456 takes precedence)}
- G03H 2001/045: {Fourier or lensless Fourier arrangement}
- 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)
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- 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})

## Abstract

When an optical system is illuminated with illumination light fluxes emitted from respective input image points, an interference image generated by superimposing output light fluxes output from the optical system and a reference light flux coherent with the output light fluxes is imaged to acquire interference image data collectively including information of an interference image about all input image points. Diffractive optical light propagation simulation is performed to acquire a phase distribution associated with only light emitted from a single input image point at a position where reconstructed light fluxes to the respective output light fluxes are separated into each light flux. In each input image point, this simulation is performed to acquire a phase distribution on an exit pupil plane.

## Claims

### Claim 1

An optical system phase acquisition method of acquiring a phase of an optical system (Ot) comprising one or more image forming optical elements, this method comprising:
when the optical system (Ot) is illuminated with illumination light fluxes (Fs1, Fs2, . . . ) emitted from respective input image points (Ps1, Ps2, . . . ) with respect to an input side of the optical system (Ot), imaging, with an imaging element (Uf), an interference image generated by superimposing output light fluxes (Fo1, Fo2, . . . ) output from the optical system (Ot) and a reference light flux (Fr) coherent with the output light fluxes to acquire interference image data (Df) collectively including information of an interference image about the input image points (Ps1, Ps2, . . . );
performing diffractive optical light propagation simulation based on the interference image data (Df) to acquire a broad sense phase distribution Ψgj(u″, v″) associated with only light emitted from the input image point (Psj) of the input image points (Ps1, Ps2, . . . ), at a position where reconstructed light fluxes to the respective output light fluxes (Fo1, Fo2, . . . ) are separated into each light flux; and
performing diffractive optical light propagation simulation based on the broad sense phase distribution Ψgj(u″, v″) to acquire a broad sense phase distribution Ψsj(u, v) belonging to the input image point (Psj) on a phase defining plane (T) located at a prescribed relative position with respect to an output side of the optical system (Ot).

### Claim 2 (depends on 1)

The optical system phase acquisition method according to claim 1, wherein a relay optical system (Oq) is inserted between the optical system (Ot) and the imaging element (Uf) so that output light fluxes (Fo1, Fo2, . . . ) output from the optical system (Ot) are input to the relay optical system (Oq), and the relay optical system (Oq) outputs a relay output light flux which is an output light flux from the relay optical system (Oq), and a target in which an interference image generated by superimposing the reference light flux (Fr) is imaged by the imaging element (Uf) is replaced with the output light fluxes (Fo1, Fo2, . . . ) output from the optical system (Ot) to provide the relay output light flux.

### Claim 3 (depends on 1)

An optical system evaluation method of evaluating the optical system (Ot), this method comprising:
determining a broad sense phase distribution Ψsj(u, v) on the phase defining plane (T) with respect to the input image point (Psj) of the input image points (Ps1, Ps2, . . . ) to the optical system (Ot), by the method according to claim 1;
determining an optical path length aberration distribution H(U, V) on an aberration defining virtual plane arbitrarily provided, based on an optical path length extending from a position of coordinates (U, V) on the aberration defining virtual plane to an ideal output image point conjugate to the input image point (Psj) and the broad sense phase distribution Ψsj(u, v); and
evaluating the optical system (Ot) based on the optical path length aberration distribution H(U, V).