Reflective fourier ptychography imaging of large surfaces
Various embodiments include reflective-mode Fourier ptychographic microscope (RFPM) apparatuses and methods for using the RFPM. In one example, the RFPM includes a multiple-component light source configured to direct radiation to a surface. The multiple-component light source has a number of individual-light sources, each of which is configured to be activated individually. The RFPM further includes collection optics to receive radiation reflected and scattered or otherwise redirected from the surface, and a sensor element to convert received light-energy from the collection optics into an electrical-signal output. Other apparatuses, designs, and methods are disclosed.
1 . A method of operating a reflective-mode Fourier ptychographic microscope (RFPM) to detect defects on a surface of a part, the method comprising:
loading the part onto a holding fixture of the RFPM;
generating, by using a programmable controller, at least one predetermined lighting pattern from a multiple-component light source configured to direct radiation on the surface, the multiple-component light source having a plurality of individual-light sources, each of which is configured to be activated individually, the at least one generated predetermined lighting pattern being selected from a plurality of patterns including temporal patterns and spatial patterns, the temporal patterns and the spatial patterns of the predetermined lighting pattern being computationally combined to increase a resolution of the detected defects over a Rayleigh limit-of-resolution for a given numerical aperture and wavelength of light;
collecting radiation redirected from the surface in a sensor element, the plurality of patterns of the temporal patterns and the spatial patterns to be generated by selecting individual ones of the multiple-component light source to be activated to illuminate the part at a range of predefined angles-of-incidence;
obtaining phase-derivative measurements by differential-phase contrast (DPC) techniques from the radiation collected by the sensor element;
determining an angle between an imaging axis from the surface to the sensor element; and
determining at least a height characteristic of one or more defects on the surface.
2 . The method of claim 1 , further comprising raster scanning the at least one generated predetermined lighting pattern over an area of the surface.
3 . The method of claim 1 , further comprising performing a raster scan over an area of the surface by moving the part under the at least one generated predetermined lighting pattern.
4 . The method of claim 1 , further comprising performing a raster scan over an area of the surface by:
scanning the at least one generated predetermined lighting pattern over the area of the surface; and moving the part under the at least one generated predetermined lighting pattern.
5 . The method of claim 1 , wherein an area over an area of the surface to be inspected is selected to be at least about 0.25 square meters over the surface.
6 . The method of claim 1 , further comprising determining at least one wavelength for selected ones of the plurality of individual-light sources.
7 . The method of claim 1 , wherein the at least one predetermined lighting pattern is selected to illuminate the surface at a number of incidence angles.
8 . The method of claim 1 , wherein the temporal patterns and the spatial patterns are pre-determined.
9 . The method of claim 1 , wherein selecting the temporal pattern includes:
selecting which of the plurality of individual-light sources to activate; and
determining which of the selected plurality of individual-light sources are activated, in time, relative to remaining ones of the selected plurality of individual-light sources.
10 . The method of claim 1 , wherein selecting the spatial pattern comprises selecting which of the plurality of individual-light sources to activate during a substantially-uniform time period.
11 . The method of claim 1 , further comprising setting an angle from which a midpoint of the at least one generated predetermined lighting pattern is offset from normal by a pre-determined number of degrees from vertical with reference to the surface, the angle being an angle-of-incidence of at least a portion of the at least one generated predetermined lighting pattern.
12 . The method of claim 1 , further comprising combining computationally at least one of radiation collected that is redirected from the surface to increase the resolution of the detected defects over the Rayleigh limit-of-resolution for the given numerical aperture and wavelength of light of the plurality of individual-lighting sources.
13 . The method of claim 1 , further comprising selecting collection optics to focus the collected radiation onto the sensor element from a pre-determined numerical aperture.
14 . The method of claim 1 , wherein the multiple-component light source comprises an LED array.
15 . The method of claim 14 , wherein the generating of at least one predetermined lighting pattern comprises selecting ones of the plurality of individual-light sources to include a group of LEDs from the LED array.
16 . The method of claim 1 , wherein each of the plurality of individual-light sources comprises an LED.
17 . A method of operating a reflective-mode Fourier ptychographic microscope (RFPM), the method comprising:
loading a non-biological part to be inspected onto a fixture; and
selecting a program to run and control one or more predetermined aspects of the RFPM, the predetermined aspects being selectable from aspects including a spatial pattern of a multiple-component light source, a temporal pattern of the multiple-component light source, a range of defect sizes to be detected, an area of the part to be inspected, at least one height characteristic for one or more detected defects, and a number of images of the non-biological part to record, the spatial patterns and the temporal patterns to be generated by selecting individual ones of the multiple-component light source to be activated to illuminate the part at a range of predefined angles-of-incidence, the temporal patterns and the spatial patterns of further being computationally combined to increase a resolution of the detected defects over a Rayleigh limit-of-resolution for a given numerical aperture and wavelength of light; and
obtaining phase-derivative measurements by differential-phase contrast (DPC) techniques from the radiation collected by the sensor element.
18 . The method of claim 17 , further comprising determining a level of roughness of at least a portion of the area of the part based on the recorded images.
19 . The method of claim 17 , further comprising selecting a size range of defects to be detected.
20 . The method of claim 17 , further comprising selecting a range of angles at which the multiple-component light source directs radiation to the part.
21 . The method of claim 17 , wherein the non-biological part includes at least one material selected from materials including metallic surfaces, ceramic surfaces, ceramic-coated surfaces, elemental semiconductor substrate surfaces, compound semiconductor substrate surfaces, glass surfaces, anodized surfaces, plastics, and oxidized surfaces.
22 . The method of claim 17 , wherein the size range of defects to be detected includes a range from about 50 nm to about 50 mm of a characteristic dimension of the detected defect.
23 . A method of operating a reflective-mode Fourier ptychographic microscope (RFPM) to detect defects on a surface of a part, the method comprising:
generating, by using a programmable controller, at least one predetermined lighting pattern from a multiple-component light source configured to direct radiation on the surface, the multiple-component light source having a plurality of individual-light sources, each of the plurality of individual-light sources is configured to be activated individually, the at least one predetermined lighting pattern being selected from temporal patterns and spatial patterns, the temporal patterns and the spatial patterns to be generated by selecting individual ones of the multiple-component light source to be activated to illuminate the part at a range of predefined angles-of-incidence, the temporal patterns and the spatial patterns of the predetermined lighting pattern further being computationally combined to increase a resolution of the detected defects over a Rayleigh limit-of-resolution for a given numerical aperture and wavelength of light;
using both brightfield-imaging and darkfield-imaging to sample a Fourier space of an image of the surface;
collecting radiation redirected from the surface in a sensor;
obtaining phase-derivative measurements by differential-phase contrast (DPC) techniques in an area proximate the defect from the redirected radiation collected by the sensor;
determining an angle between an imaging axis from the surface to the sensor; and
determining at least a height characteristic of one or more defects on the surface.
24 . The method of claim 23 , wherein a characteristic dimension of the detected defects is about 5 μm and larger in size over an area of up to several square meters.
25 . The method of claim 23 , wherein the part is a non-biological part.
26 . The method of claim 25 , wherein the non-biological part includes at least one material selected from materials including metallic surfaces, ceramic surfaces, ceramic-coated surfaces, elemental semiconductor substrate surfaces, compound semiconductor substrate surfaces, glass surfaces, anodized surfaces, plastics, and oxidized surfaces.
27 . The method of claim 23 , wherein the spatial pattern is selected to illuminate the surface at a number of incidence angles substantially simultaneously during a time period for a selected spatial pattern.
28 . The method of claim 23 , wherein selecting the temporal pattern comprises:
selecting which of the plurality of individual-light sources to activate; and
determining which of the selected plurality of individual-light sources are activated, in time, relative to remaining ones of the selected plurality of individual-light sources.
29 . The method of claim 23 , wherein selecting the spatial pattern comprises selecting which of the plurality of individual-light sources to activate during a substantially-uniform time period.