Inspection method, inspection device, and recording medium
An inspection method includes: obtaining a one-dimensional luminance profile by performing image processing of compressing a luminance of an inspection image of a pixel region of a display panel captured by an imaging device, into a one-dimensional luminance; generating a frequency spectrum intensity profile by performing Fourier transform on the one-dimensional luminance profile; calculating, based on a periodic structure of pixels shown in the pixel region, an imaging magnification of the imaging device from one or more peak positions included in the frequency spectrum intensity profile; and estimating a current focus position from the imaging magnification calculated and magnification information indicating a relationship between a focus position and an imaging magnification of the imaging device, the current focus position being a focus position of the imaging device in the inspection image.
1 . An inspection method, to be performed by a computer, for inspecting a display panel, the inspection method comprising:
obtaining a one-dimensional luminance profile by performing image processing of compressing a luminance of an inspection image of a pixel region of the display panel captured by an imaging device, into a one-dimensional luminance on an axis in a direction perpendicular to an arrangement direction of a plurality of subpixels included in one pixel of a plurality pixels each including a plurality of subpixels;
generating a frequency spectrum intensity profile by performing Fourier transform on the one-dimensional luminance profile;
calculating, based on a fact that the plurality of pixels are arranged in a periodic structure in the pixel region, an imaging magnification of the imaging device from one or more peak positions included in the frequency spectrum intensity profile; and
estimating a current focus position from the imaging magnification calculated and magnification information indicating a relationship between a focus position and an imaging magnification of the imaging device, the current focus position being a focus position of the imaging device in the inspection image.
2 . The inspection method according to claim 1 , wherein
in the calculating, among the one or more peak positions, a peak position of a fundamental frequency is estimated to be a peak position corresponding to a one-pixel unit structure of the pixel region shown in the inspection image, and the imaging magnification of the imaging device is calculated from the peak position of the fundamental frequency.
3 . The inspection method according to claim 2 , wherein
in the generating, the frequency spectrum intensity profile is generated by performing the Fourier transform twice on the one-dimensional luminance profile.
4 . The inspection method according to claim 2 , wherein
when an image of the pixel region of the display panel is captured by the imaging device at each of a plurality of focus positions of the imaging device, and a value of a fundamental frequency obtained by performing the Fourier transform on a one-dimensional luminance profile of the image captured at the focus position is used as the imaging magnification, the magnification information is information indicating a relationship between the value of the fundamental frequency and the focus position.
5 . The inspection method according to claim 1 , further comprising:
calculating, from the current focus position estimated and the magnification information, an amount of movement of the imaging device necessary for achieving focus, and adjusting a position of the imaging device using the amount of movement.
6 . An inspection device that inspects a display panel, the inspection device comprising:
an obtainer that obtains a one-dimensional luminance profile by performing image processing of compressing a luminance of an inspection image of a pixel region of the display panel captured by an imaging device, into a one-dimensional luminance on an axis in a direction perpendicular to an arrangement direction of a plurality of subpixels included in one pixel of a plurality pixels each including a plurality of subpixels;
a generator that generates a frequency spectrum intensity profile by performing Fourier transform on the one-dimensional luminance profile;
a calculator that calculates, based on a fact that the plurality of pixels are arranged in a periodic structure in the pixel region, an imaging magnification of the imaging device from one or more peak positions included in the frequency spectrum intensity profile; and
an estimator that estimates a current focus position from the imaging magnification calculated and magnification information indicating a relationship between a focus position and an imaging magnification of the imaging device, the current focus position being a focus position of the imaging device in the inspection image.
7 . A non-transitory computer-readable recording medium having recorded thereon a program for causing a computer to execute an inspection method for inspecting a display panel, the inspection method including:
obtaining a one-dimensional luminance profile by performing image processing of compressing a luminance of an inspection image of a pixel region of the display panel captured by an imaging device, into a one-dimensional luminance on an axis in a direction perpendicular to an arrangement direction of a plurality of subpixels included in one pixel of a plurality pixels each including a plurality of subpixels;
generating a frequency spectrum intensity profile by performing Fourier transform on the one-dimensional luminance profile;
calculating, based on a fact that the plurality of pixels are arranged in a periodic structure in the pixel region, an imaging magnification of the imaging device from one or more peak positions included in the frequency spectrum intensity profile; and
estimating a current focus position from the imaging magnification calculated and magnification information indicating a relationship between a focus position and an imaging magnification of the imaging device, the current focus position being a focus position of the imaging device in the inspection image.