JP2000092350A - Method and apparatus for imaging an object having a periodic light and dark pattern and inspection method and apparatus using the same - Google Patents

Abstract

(57) Abstract: An imaging moire generated by a relative positional relationship between a periodic light / dark pattern of an imaging target and imaging pixels of a solid-state imaging device is removed. SOLUTION: A solid-state imaging device 2 of an imaging system A and a solid-state imaging device 6 of an imaging system B image an imaging field of view 16 of an imaging object 16 having a periodic light and dark pattern via a half mirror 10. The arithmetic processing unit 15 calculates a pixel shift amount according to the light and dark pattern of the imaging target 16 and calculates the z, y direction movement signal S
The position of the imaging system B is shifted in the z and y directions by generating z and Sy so that a video signal VB that is pixel-shifted with respect to the video signal VA of the imaging system A is obtained. This video signal VB
Are processed by the pixel unit shift correction processing unit 13 and the video signal V
A video signal VB ′ having a pixel shift amount equal to or smaller than the imaging pixel size for A is generated. These video signals VA and VB ′ are subjected to arithmetic addition processing of gradation values for each pixel in the arithmetic processing unit 15 to obtain a video signal V from which imaging moire has been removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup method using a solid-state image pickup device for an object having a periodic light and dark pattern and an apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, when an image is picked up by a solid-state image sensor of a target having a periodic light-dark pattern, the relative brightness of the target light-dark pattern and a pixel on an image-capturing surface of the solid-state image sensor (hereinafter, referred to as an image pickup pixel). As a method for eliminating the imaging moiré caused by the positional relationship, it has been effective to separate the resolution of the imaging pixels from the resolution created by the cycle of the target pattern by one or more digits.

However, as the information to be detected becomes weak or minute, the resolution often cannot be realized on the imaging side, so that the imaging characteristic of the imaging system may be degraded and the imaging system may be defocused. It is done routinely. However, when the image is defocused,
Since weak and minute information that should be originally detected other than the imaging moiré (hereinafter, referred to as original information) is also defocused, there is a problem that the information becomes weaker and minute information and cannot be detected.

[0004]

In order to avoid such a problem, attempts have been made to detect weak and minute original information from imaging moiré. Originally, it is impossible to stably detect information having a brightness value equal to or less than the brightness of the screen (light and dark of the screen are repeated due to the imaging moire).

The present invention solves such a problem, and removes image moiré caused by the relative positional relationship between a light / dark pattern of an object and image pixels of a solid-state image sensor, so that information can be easily detected originally. And a device using the same.

[0006]

In order to achieve the above object, the present invention provides a solid-state imaging device for changing a declination formed by real and imaginary values of a spatial frequency spectrum of an imaging moire by 180 degrees. The imaging position shift amount in the imaging plane of the element is calculated, and an image to which the imaging position shift amount is added and an image to which the imaging position shift amount is not added are arithmetically combined for each gradation value in imaging pixel units. I do. As a result, a captured image having the same resolution and the same number of pixels as the image to which the imaging position shift amount is not applied can be obtained.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of an image pickup method and an apparatus using the same according to the present invention.
1 is a pixel shift unit, 2 is a solid-state imaging device, 3 is an optical system, 4 is an imaging lens, 5 is a numerical aperture adjustment mechanism, 6 is a solid-state imaging device, 7 is an optical system, 8 is an imaging lens, and 9 is an aperture. Number adjusting mechanism, 10 is a half mirror, 11 is a z-direction moving mechanism, 1
2 is a y-direction moving mechanism, 13 is a pixel unit shift correction processing unit,
14 is an imaging moiré reduction processing unit, 15 is an arithmetic processing unit, 16
Is an imaging target, A and B are imaging systems, and CE is an imaging field of view.

In FIG. 1, a pixel shift unit 1 comprises:
The imaging system 16 includes two imaging systems A and B, a pixel unit shift correction processing unit 13 and an imaging moiré reduction processing unit 14. B, and the output video signals VA and VB of the imaging systems A and B are processed to generate and output a video signal V after the reduction of image moire.

An imaging system A includes a solid-state imaging device 2 and an imaging lens 4.
The imaging system B includes a solid-state imaging device 6 and an optical system 7 having a built-in imaging lens 8, and a numerical aperture adjusting mechanism (for example, a diaphragm). Mechanism 9). Light from the imaging field of view CE of the imaging target 16 having the periodic light-dark pattern is split into two by the half mirror 10, and in the imaging system A, the light transmitted through the half mirror 10 is imaged by the numerical aperture adjusting mechanism 5 and the optical system 3. By receiving light on the imaging surface of the solid-state imaging device 2 via the lens 4, a video signal VA is output from the solid-state imaging device 2. In the imaging system B, the light reflected by the half mirror 10 is reflected by the numerical aperture adjustment mechanism 9 and By receiving light on the imaging surface of the solid-state imaging device 6 via the imaging lens 8 of the optical system 7, the solid-state imaging device 6 outputs a video signal VB. In other words, in each of the imaging systems A and B, the same imaging field of view C of the imaging target 16 is provided at the same imaging magnification via the half mirror 10.
E will be imaged.

An imaging system B includes a z-direction moving mechanism 11.
And a y-direction moving mechanism 12, which are used to move the imaging system B in the z direction (the direction perpendicular to the pattern formation surface of the imaging target 16) and the y direction (the direction parallel to the pattern formation surface of the imaging target 16). ). The imaging system B is formed by the z-direction moving mechanism 11 and the y-direction moving mechanism 12.
Is moved in the z and y directions, since the imaging system B receives the reflected light of the half mirror 10, the imaging visual field CE of the imaging system 16 with respect to the imaging system B is changed to the imaging visual field CE of the imaging system A. It will be shifted in the x and y directions parallel to the plane with respect to CE. the moving amount by the z-direction moving mechanism 11,
The direction of movement, the amount of movement by the y-direction moving mechanism 12, and the direction of movement are controlled by the z-direction drive signal Sz and the y-direction drive signal Sy supplied from the arithmetic processing unit 15, respectively.
The moving amount is set with an accuracy of less than one pixel in the solid-state imaging device 6 (hereinafter, a pixel of the solid-state imaging device is referred to as an imaging pixel). Further, shifting the imaging field of view CE by displacing the imaging system B in the z and y directions in this manner is hereinafter referred to as “pixel shifting”.

The output video signal VA of the imaging system A is directly supplied to the imaging moiré reduction processing unit 14, and the output video signal Vb of the imaging system B is processed by the pixel unit shift correction processing unit 13 and then subjected to the imaging moiré reduction processing. It is supplied to the unit 14. The pixel unit shift correction processing unit 13 outputs the output video signal VB of the image sensor B.
Is converted into a video signal VB ′ for the imaging visual field CE obtained by shifting the imaging visual field CE of the imaging system A by less than one imaging pixel in the x and y directions.
For example, the imaging direction CE of the imaging system A of the imaging system A of the imaging system B is controlled by the z-direction moving mechanism 11 and the y-direction moving mechanism 12.
In the case where the pixel shift amount with respect to is 3.5 image pixels in both the z and y directions, the pixel unit shift correction processing unit 13 corrects an integer image pixel of 3 image pixels among them,
It is assumed that the pixel signal is converted into a video signal VB 'when the pixel shift amount is shifted by 0.5 image pickup pixel in both the z and y directions. The pixel unit shift correction processing unit 13 can be realized by a circuit based on a combination of shift registers, or can be realized by software processing on digitized and stored image data.

The video signal VB ′ output from the pixel unit shift correction processing unit 13 is an image signal when the imaging visual field CE is shifted by less than one imaging pixel with respect to the video signal VA output from the imaging system A. Signal. The video signals VA and VB ′ contain imaging moire components having the same period and amplitude. The pixel shift amount is determined by the phase difference between the video moire components in the video signals VA and VB ′. The angle is set to be approximately 180 °.

The imaging moiré reduction processing unit 14 processes these video signals VA and VB ', thereby
A video signal V having the same resolution and the same number of pixels as the pixels A and VB and from which image moire has been removed is obtained. This imaging moiré reduction processing unit 1
The processing of No. 4 is for arithmetically synthesizing these video signals VA and VB ′ in pixel units. The arithmetic synthesis processing is a weighted average processing of the gradation values in pixel units, and the arithmetic processing of the gradation values in pixel units. One of a simple averaging process, a process of selecting the maximum value of tone values in pixel units, and a process of selecting the minimum value of tone values in pixel units.

Now, the gradation value of the pixel at the i-th row and j-th column on the screen of the video signal VA is f (i, j), and the gradation value of the pixel of the video signal VB 'corresponding to this pixel is g (i , j), and assuming that the gray level of the same pixel of the video signal V in which the imaging moire has been reduced is h (i, j), the above-described arithmetic synthesis processing is expressed as follows, respectively. That is, weighted averaging processing: h (i, j) = ｛α · f (i, j) + β
G (i, j)｝ / 2 (where 0 ≦ α, β and α + β = 2) Simple averaging processing: h (i, j) = ｛f (i, j) + g (i,
j)｝ / 2 MAX (x, y) is the larger of x and y,
MIN (x, y) is set to the smaller value of x and y, and the maximum value selection processing is performed: h (i, j) = MAX ｛f (i, j),
g (i, j)｝ Minimum value selection processing: h (i, j) = MIN ｛f (i, j),
g (i, j)｝.

The arithmetic processing unit 15 calculates the above-mentioned pixel shift amount such that the image signal VA and VB 'can be obtained from the video signals VA and VB' by the above-described arithmetic processing so that the image signal V with reduced imaging moire is obtained. Is generated and supplied to the z-direction moving mechanism 11 and the y-direction moving mechanism 12 of the imaging system B.

Here, the principle of occurrence of image pickup moire and the principle of operation of this embodiment will be described with reference to FIG. 2 using a one-dimensional periodic pattern as an example.

FIG. 2B shows a sinusoidal high-frequency component of the spatial frequency of a one-dimensional periodic pattern.
Assuming that the spatial period of the periodic pattern is L, the spatial frequency is proportional to N / L (where N is an integer) by Fourier transform. N = 1 is proportional to the fundamental spatial frequency of this periodic pattern.

Assuming that such a periodic pattern is imaged by a solid-state image sensor having a resolution (pixel size) p, FIG.
This high frequency component is sampled at the timing of the period p indicated by the white circle in (b), and when p ≠ (１ period of the high frequency component) × (integer), the sampling value f ( 1), f (2), f (3), signals S ₁ of amplitude change represented by the curve connecting the ...... is obtained. This is the imaging moire based on the spatial frequency of the periodic pattern.

The occurrence of a spatial frequency component different from the high-frequency component due to sampling of the high-frequency component is called "spatial frequency folding". In this case, the spatial frequency of the high-frequency component is referred to as a "folding source". The spatial frequency and the spatial frequency generated by the return are referred to as the "return spatial frequency". Therefore, a spatial frequency aliasing original frequency in FIG. 2 (b), the frequency of the signals S ₁ shown in FIG. 2 (a) is folded away frequency.

On the other hand, when the high frequency component shown in FIG. 2B is sampled at the timing indicated by a black circle shifted by γp (where 0 <γ <1) from the sampling point of the white circle (this means that the white circle is sampled). In contrast to the imaging with a point, the imaging with a black circle as a sampling point is a pixel shift with a pixel shift amount of γp.)
FIG. 2A shows the sampling values g (1), g (2),
g (3), the signal S ₂ of the amplitude change represented by the curve connecting the ...... is obtained. Here, although the i-th sampling point of the i-th sampling point and the signal S ₂ of the signals S ₁ are shifted by .gamma.p, sampled values f (i thereof corresponding sampling points (and associated with an arrow) ) And g (i), if f (i) + g (i) = substantially constant, then the above-described simple averaging processing can reduce the imaging moire. In order to match the timings of the sampling values f (i) and g (i) so that this simple averaging process can be performed, the pixel unit shift amount correction processing unit 13 adjusts the phase of the video signal VB. Note that FIG.
In the case of (a), the signal S ₂ lags the signal S _1, although pixel shift amount correcting unit 13 is forwarding the phase of the video signal VB, this is, on the contrary, pixel shift The image signal V from the imaging system A is output by the amount correction processing unit 13.
This delays the phase of A.

In FIG. 1, the imaging moiré reduction processing unit 14
When the imaging moiré is reduced by the simple averaging process, the processing operation unit 1 performs the simple averaging process.
5 sets the above-mentioned pixel shift amount γp. In this case, the arrangement relationship of the periodic pattern, the resolution of the solid-state imaging device, and the like are known, and the pixel shift amount γp can be calculated from these. Further, the pixel unit shift correction processing unit 13 corrects the timing shift of the sampling values f (i) and g (i).

The same applies to the case where the imaging moiré reduction processing unit 14 uses processing other than the simple averaging processing in the above-described arithmetic synthesis processing, but it goes without saying that the pixel shift amount γp differs for each processing. .

When the pixel shift amount γp is an integral multiple of the resolution p, as is apparent from FIG. 2, the sampling points of the white circle and the black circle coincide with each other, and FIG.
The signals S ₁ and S ₂ shown in ( ₁₎ and ( ₂₎ cannot be matched to perform the imaging moiré reduction processing. However, when the required pixel shift amount is γp, the actual pixel shift amount is mp ± γp, where m is an integer, and a black circle shifted by (mp ± γp) from the sampling value of the white circle sampling point. The sampling moiré reduction processing can be performed by associating the sampling values at the sampling points of.

Therefore, in the first embodiment shown in FIG. 1, as described above, the imaging system A of the imaging visual field CE of the imaging system B
Even if the pixel shift amount with respect to the imaging field of view CE is 3.5 imaging pixels (= 3.5p) in both the z and y directions, the pixel unit shift correction processing unit 13 uses the three imaging pixels (=
3p) is corrected so that the pixel shift amount is converted into a video signal VB 'when the pixel shift amount is shifted by 0.5 image pickup pixel (= 0.5p) in both the z and y directions. I just need. In this case, the output video signal VA of the imaging system A
2A (that is, the gradation value of the pixel)
, The gradation value of the pixel of the video signal VB ′ becomes a black circle in FIG. 2A, and the corresponding pixel value f
The processing of the pixel unit shift correction processing unit 13 is performed so that the timings of (i) and g (i) match.

FIG. 2 (c) shows the signals S ₁ and S ₂ by (3p + γp) pixel shift separately, and the corresponding sampling as shown by connecting the signals S ₁ and S ₂ by arrows. The pixel unit shift correction processing unit 13 sets the pixel shift amount (3) so that the timings of the points f (i) and g (i) match.
(p + γp).

When an object having a different periodic pattern is used as the imaging target 16, the arithmetic processing unit 20 calculates a pixel shift amount corresponding to the periodic pattern every time the periodic pattern is changed. The amount of movement of the imaging system B in the z and y directions is set in accordance with the calculation result. If the periodic pattern is different in this way, the pixel shift amount γp is also different. The correction amount in the unit 13 must also be different. For this reason, although not shown, this pixel unit shift correction processing unit 13
In the z-direction movement signal S from the arithmetic processing unit 15.
It is controlled according to the z, y direction movement signal Sy.

FIG. 3 is a diagram showing a specific example of the imaging target 16 in FIG. 1. Here, the fluorescent surface of a color cathode ray tube (color CRT) and the light emitting surface of a liquid crystal display panel or a plasma display panel are exemplified. .

FIGS. 3A and 3B show a phosphor screen of a color CRT in which pixels are arranged in a hexagonal lattice pattern.
The shape of the pixel is elliptical or circular. FIG.
(A) shows an imaging target 16 in a single-color light emission state by, for example, R pixels among the three color phosphor pixels of R (red), G (green), and B (blue). This is referred to as an imaging target 16-1 (elliptical / circular aperture, hexagonal lattice arrangement, single color). FIG. 3B shows the imaging target 16 in a light emitting state of three colors (that is, white) by the R, G, and B pixels. Hexagonal lattice arrangement, three colors). In this case, the light emission intensities of the R, G, and B pixels are not always equal. The pixel pitch of phosphors of the same color in the horizontal direction is referred to as a horizontal pitch, and the pixel pitch of phosphors of the same color in the vertical direction is referred to as a vertical pitch.

FIGS. 3C and 3D show the light emitting surface of a liquid crystal display panel or a plasma display panel in which cells (pixels) are arranged in a square lattice, and the shape of the pixel is rectangular. ing. FIG. 3C shows R (red),
Among the three color pixels of G (green) and B (blue), for example, the pixel 16 indicates the imaging target 16 in a single-color light emission state by the R pixel, which is referred to as an imaging target 16-3 (rectangular aperture, square lattice (Array, single color). FIG. 3B shows the imaging target 16 in a light emitting state of three colors (that is, white) by the R, G, and B pixels, and the imaging target 16-4 (rectangular aperture, square lattice array) is shown. , Three colors). Again, R,
The emission intensities of the G and B pixels are not always equal. The pixel pitch of phosphors of the same color in the horizontal direction is referred to as a horizontal pitch, and the pixel pitch of phosphors of the same color in the vertical direction is referred to as a vertical pitch.

FIG. 4A shows an image pickup moire when the image pickup object 16-1 shown in FIG. 3A is picked up by the solid-state image pickup device 2. In this case, the solid-state image pickup device 2 The imaging pixel size p on the imaging surface is determined by the imaging target 16-1.
Are close to the arrangement pitches Hp and Vp of the phosphors on this imaging surface. FIG. 4B shows the condition of the imaging target 16-2 shown in FIG. 3B under the condition that the imaging pixel size p is slightly changed.
2 shows an image pickup moire when the image is picked up by the solid-state image pickup device 2. When such imaging moire occurs, it becomes difficult to detect display unevenness, pixel defects, and the like occurring in the imaging targets 16-1 and 16-2.

FIG. 5 shows an imaging target 16-1 (FIG. 3A) or an imaging target 16-in which the arrangement of the phosphors is a hexagonal lattice.
FIG. 3 is a diagram showing a distribution of a spatial frequency spectrum when the solid-state imaging device 2 having an imaging pixel resolution of p [mm / pixel] is imaged at 2 (FIG. 3B).

In the figure, the spatial frequency spectrum has a real value and an imaginary value. The spatial frequency in the H (horizontal) direction is defined as u, and the spatial frequency in the V (vertical) direction is defined as v, and the coordinate system of the spatial frequency is represented by a plane of a uv coordinate system. These u and v coordinate axes are defined by the number of pixels per unit length, and the unit is [mm ^-1 ].

In the uv plane, the object 16-
The spectrum in which the power of the phosphor array at 1, 16-2 is concentrated (hereinafter referred to as the phosphor array spatial frequency spectrum) is also distributed in a hexagonal lattice shape in the uv plane as indicated by a black circle. . Here, Hp and Vp are shown in FIG.
The horizontal and vertical pitches (mm) of the arrangement of the phosphors shown in (b). Further, each phosphor array spatial frequency spectrum is expressed as a phosphor array spatial frequency spectrum [i, j], with the phosphor array spatial frequency spectrum at the origin 0 on the uv plane being [0, 0]. The phosphor array spatial frequency spectrum [0, 0] is a DC (direct current) component, and other phosphor array spatial frequency spectra [i, 0] are used.
j] is the variable component.

In the uv plane, the solid-state image sensor 2
Is 1 / side depending on the imaging pixel resolution (pixel size) p of
An area surrounded by a square frame of p (hereinafter, referred to as a square area) is defined. A square area centered on the origin 0 of the uv plane is defined as a square area (0, 0), and the other square areas are expressed as square areas (m, n). The area where u ≧ 0, v ≧ 0 of the square area (0, 0), that is, the hatched upper right quarter area is the spatial frequency area (visible spatial frequency area A) that can be seen on the screen. Now, assuming that the number of pixels on the imaging surface of the solid-state imaging device 2 is, for example, 500 in the horizontal and vertical directions, 1 / p in the horizontal and vertical directions is 250 pixels. Therefore, one side of the visible space frequency region A in the u and v axis directions is 250.

The other area in this square area (0,0) is
At least one of the values of u and v becomes negative, and is an area that appears mathematically and cannot be seen with the eyes. Also, a square area (m, n) other than the square area (0, 0)
Is a harmonic region of the square region (0,0) with respect to the basic spatial frequency region.

The imaging moire is generated in principle as described with reference to FIG. 2, but when this is applied to FIG. 5, the fluorescence in the square region (m, n) which is a harmonic region is obtained. This is caused by folding the body arrangement spatial frequency spectrum [i, j] into the visible spatial frequency area A in the square area (0, 0). This return (aliasing)
Are the square area (0,0) and the square area (m,
n) and when the square area (0,0) is moved to a position symmetrical to the square area (m, n) with respect to the square area (m, n) while maintaining the arrangement relationship of these square areas. Means that the spatial frequency spectrum [i, j] of the phosphor array in the square area (m, n) that moves with this becomes the spatial frequency spectrum on the uv plane where the phosphor array is located.
Here, the spatial frequency of the phosphor array spatial frequency spectrum [i, j] in the square area (m, n) at the original position is folded back to the original spatial frequency, and the shifted square area (m, n)
The spatial frequency of the same phosphor array spatial frequency spectrum [i, j] at is referred to as the return spatial frequency. When the return spatial frequency enters the visible spatial frequency region A of the square area (0,0), the fluorescence becomes The body arrangement spatial frequency spectrum will appear as imaging moire.

Therefore, in FIG. 5, the square area (1,
Regarding -2), while maintaining the arrangement relationship between the square area (0,0) and the square area (0,0), the square area (0,0) is defined as a square area (1, -2) with respect to the origin 0 of the uv plane. Is moved symmetrically with respect to the origin, this square area (0,0) coincides with the square area (−1,2).
The square area (1, -2) coincides with the position of the square area (0, 0), and the phosphor array spatial frequency spectrum [3, -2] in the upper right quarter of the square area (1, -2).
3] is folded back into the visible spatial frequency region A in the square region (0, 0) at the original position. Accordingly, the phosphor array spatial frequency spectrum [3, -3] is folded at the imaging pixel resolution p, thereby causing imaging moire.

The phosphor array spatial frequency spectrum [-2, 2] in the upper right quarter of the square area (-1, 1)
The same applies to the case in which the imaging pixel resolution p is turned back to enter the visible spatial frequency region A, thereby causing imaging moire. In general, as shown by hatching, the upper right area (that is, one side of each square area (m, n)) is 1 /
The phosphor array spatial frequency spectrum existing within the (2p) square area generates imaging moire due to the folding of the imaging pixel resolution p.

Here, when imaging moire occurs due to folding of the phosphor array spatial frequency spectrum [i, j] in the square area (m, n), δ = MAX (m, n) (this is an absolute value). Indicates that the larger is selected),
This turn is referred to as ± δ / p turn. Therefore, in FIG. 5, the return from the square area (1, -2) is ± 2 / p, and the return from the square area (-1, 1) is ± 2.
1 / p folding.

Since the return range of the phosphor array spatial frequency spectrum that causes imaging moire is ± ∞ / p, the sum of the infinite number of return destination (moire) spatial frequency spectra is the imaging moire spectrum. The moiré spectrum of interest is in the range of 0 to + 1 / (2p) indicated by hatching in each square area (m, n).

FIG. 6 shows the imaging target 16-3 (FIG. 3C) or the imaging target 16-in which the arrangement of the phosphors is a square lattice.
4 is a diagram showing a distribution of a spatial frequency spectrum when the solid-state imaging device 2 having an imaging pixel resolution of p [mm / pixel] is imaged at 4 (FIG. 3D).

In the figure, the spatial frequency spectrum has a real value and an imaginary value. Similarly to FIG. 5, the spatial frequency in the H (horizontal) direction is defined as u, and the spatial frequency in the V (vertical) direction is defined as v, and the coordinate system of the spatial frequency is represented by a plane of a uv coordinate system. The u and v coordinate axes are defined by the number of pixels per unit length, and the unit is [mm ^-1 ].

In the uv plane, the object 16-
The phosphor array spatial frequency spectrum in which the power of the phosphor array at 3, 16-4 is concentrated is also distributed in a square lattice shape in the uv plane, as indicated by (black circles). Where H
p and Vp are the horizontal and vertical pitches (mm) of the arrangement of the phosphors shown in FIGS. 3 (c) and 3 (d). Further, each phosphor array spatial frequency spectrum is expressed as a phosphor array spatial frequency spectrum [i, j], with the phosphor array spatial frequency spectrum at the origin 0 on the uv plane being [0, 0]. Phosphor array spatial frequency spectrum [0,0]
Is a DC component, and the other phosphor array spatial frequency spectrum [i, j] is a variable component.

In this case, the distribution of the phosphor array spatial frequency spectrum [i, j] is different from the distribution of the phosphor array spatial frequency spectrum [i, j] shown in FIG. , I + j≡1 (mod2), that is, i + j
= Odd-numbered phosphor array spatial frequency spectrum [i,
j] is added. In other words, in the distribution shown in FIG. 6, i + j≡0 (mod2), that is, i + j =
The phosphor array spatial frequency spectrum [i,
j] is the distribution shown in FIG.

Also, in this case, on this uv plane, one side is 1 / p due to the imaging pixel resolution p of the solid-state imaging device 2.
Are defined, a square area centered on the origin 0 of the uv plane is defined as a square area (0, 0), and the other square areas are defined as square areas (m, n). The region where u ≧ 0, v ≧ 0 of this square region (0, 0), that is, the hatched upper right quarter region is the visible spatial frequency region A, and the number of pixels on the imaging surface of the solid-state imaging device 2 is , 500 in the horizontal and vertical directions, respectively, the 1 / p in the horizontal and vertical directions is 250 pixels.
Therefore, one side of the visible space frequency region A in the u and v axis directions is 250.

Other areas in this square area (0,0) are:
At least one of the values of u and v becomes negative, and is an area that appears mathematically and cannot be seen with the eyes. Also, a square area (m, n) other than the square area (0, 0)
Is a harmonic region of the square region (0,0) with respect to the basic spatial frequency region.

When the phosphor array spatial spectrum [i, j] in the square area (m, n) is folded back to the visible spatial frequency area A in the square area (0, 0), imaging moire occurs. In this case, similarly to the case of FIG. 5, the phosphor array spatial spectrum in the upper right quarter area (range of 0 to + 1 / (2p)) indicated by hatching in each square area (m, n). [I, j] is an image that causes imaging moire due to folding. For example, as shown in the figure, the phosphor array spatial frequency spectrum [3, -3] existing in the hatched area of the square area (1, -2) is square area.
It is folded back into the visible spatial frequency region A of (0,0) and imaging moire occurs. The turn in this case is ± 2 / p turn. The same applies to the phosphor array spatial frequency spectrum [−2, 2] in the hatched area of the square area (−1, 1), which enters the visible spatial frequency area A by ± 1 / p folding to generate imaging moire. Will be.

As in the case of FIG. 5, the return range of the spatial frequency spectrum of the phosphor array which causes imaging moire is ±
Since ∞ / p, an infinite number of return-destination (moire) spatial frequency spectra are generated in the visible spatial frequency region A, and the sum of these becomes the imaging moire spectrum.

As described above, the reflection of the phosphor array spatial frequency spectrum causes imaging moire. Next, a method of calculating the pixel shift amount γp in the arithmetic processing unit 15 in FIG. 1 will be described.

FIG. 7 is a flowchart showing a method of calculating the absolute value (moiré power spectrum) of the imaging moiré spectrum in the arithmetic processing unit 15.

In this method, the spatial frequency of the spatial frequency spectrum [i, j] of the phosphor array (i, j) for each square area (m, n) in FIG. 5 or FIG.
And the frequency of the imaging moiré when this is folded back into the visible spatial frequency region A (FIGS. 5 and 6) (the return spatial frequency), and the moiré power spectrum is found based on this. Therefore, a moiré power spectrum is obtained for each phosphor array spatial frequency spectrum [i, j]. The moiré power spectrum is represented by the sum of the square of the real value and the square of the imaginary value of the imaging moiré spectrum or the square root of the sum.

In the figure, the target range (turning range) on the uv plane shown in FIGS. 5 and 6 is limited. This is because, as described above, the phosphor array spatial spectrum [i, j] that causes imaging moire has a folding range of ± ∞ / p on the uv plane.
In general, as the phosphor array spatial spectrum [i, j] farther from the origin 0 on the uv plane becomes smaller, the moire power spectrum due to the return becomes smaller and the imaging moire becomes less conspicuous. This is not a separate problem. So, first,
When this return range is ± k / p (where k ≧ 1), k
Is set to a predetermined value. Usually, k is set to 10 or less (step 100). When the range illustrated in FIGS. 5 and 6 is targeted, k = 2.

Then, first, n = -k is set (step 1).
01), and m = −k (step 102). this is,
First, as a square area (m, n) in FIGS.
Square area farthest in the − direction from the origin 0 of the v plane (−k,
−k).

Next, an integer value of i _min = m × Hp / p or more,
i _max = (m + 0.5) × Hp / p or an integer, j _min = n
Integer value equal to or more than × Vp / p, j _max = (n + 0.5) × Vp / p
The following integer value is calculated (step 103). here,
As shown in FIGS. 5 and 6, the phosphor array spatial frequency spectrum [i, j] is distributed at an interval of 1 / Hp in the u-axis direction and at an interval of 1 / Vp in the v-axis direction. The square areas (m, n) are arranged at 1 / p intervals in the u and v axis directions. 5 and 6 in this square area (m, n).
And the ranges of the hatched areas in the u and v axis directions are m / p ≦ u ≦ (m / p + 1 / (2p)) and n / p ≦ v ≦ (n
/ p + 1 / (2p)), and the phosphor array spatial frequency spectrum falls within this range.
In order for [i, j] to exist, m / p ≦ i / Hp ≦ (m / p + 1 / (2p)) n / p ≦ j / Vp ≦ (n / p + 1 / (2p)) No. Then, when these expressions are modified, m × Hp / p ≦ i ≦ (m + 0.5) × Hp / pn × Vp / p ≦ j ≦ (n + 0.5) × Vp / p (where i , J are integers). Therefore, in step 103, the phosphor array spatial frequency spectrum [i, j] existing in the hatched area of the target square area (m, n) is searched.

When i _min and j _min are determined in step 103, j = j _min (step 104) and i = i _min (step 105), and the phosphor existing in the hatched area of the square area (m, n) is set. Array spatial frequency spectrum [i,
j]. In step 103, i _min
≤ i _max , j _min ≤ j _max , but when there are no integer values i _min , i _max , j _min , j _max that satisfy this,
Although not shown, the process proceeds to step 113.

When the phosphor array spatial frequency spectrum [i, j] satisfying the above conditions is obtained, if the spectrum is distributed in a square lattice shown in FIG. A moire power spectrum obtained by folding the body arrangement spatial frequency spectrum [i, j] is obtained. When the spectrum is distributed in a hexagonal lattice shape shown in FIG. 5, i + j≡0 (mod2), that is, i + j =
Even-numbered phosphor array spatial frequency spectrum [i, j]
Only the moire power spectrum is calculated in step 108 (step 107). i + j≡1 (mod
2) Phosphor array spatial frequency spectrum [i, j]
If this is the case, it is determined that this is not the object and the process proceeds to step 109.

When the processing in step 108 for one phosphor array spatial frequency spectrum [i, j] in the square area (m, n) is completed and the moiré power spectrum is obtained,
Next, i = i + 1 is set (step 109). In this case, if another phosphor array spatial frequency spectrum [i + 1, j] exists in the hatched area of the same square area (m, n), i + 1 ≦ _imax is satisfied (step 1).
10), this phosphor array spatial frequency spectrum [i +
[J], the processing from step 106 is performed. This corresponds to, for example, the square area (0,
As in 1), there is a case where two or more phosphor array spatial frequency spectra [i, j] exist in the u-axis direction in the hatched area. In the case of the distribution shown in FIG. 5, this phosphor array spatial frequency spectrum [i + 1, j] is (i +
1) Since + j≡1 (mod 2), step 107
And the process immediately goes to step 109.

If i + 1> _imax (step 110), there is no other phosphor array spatial frequency spectrum [i, j] in the u-axis direction in the hatched area of the same square area (m, n). Then, j = j + 1 is set (step 111). If j + 1 ≦ _jmax (step 112), another phosphor array spatial frequency spectrum [i, j + 1] exists in the v-axis direction in the same hatched area, and i = i. _{As min} (step 105), the processing from step 106 is performed on the phosphor array spatial frequency spectrum [i, j + 1].

In this way, the same square area (m,
When the moiré power spectra of all the phosphor array spatial spectra [i, j] in the hatched area n) are obtained in step 108, i> i _max (step 110),
As j> j _max (step 112), one square area (m, n) (in this case, square area (-k, -k))
Is completed.

Therefore, m = m + 1 (step 11
3) When this m + 1 satisfies m + 1 ≦ + k (step 11)
4), a square area (m
(+1, n), and the processing from step 103 is performed. Thus, m> k, and u-axis direction 1
When the similar processing for the square areas (−k, −k) to (+ k, −k) in the column is completed, then n = n + 1 (step 115), and when n ≦ + k (step 116), step 102 And the above processing operation is repeated. this is,
A row of square areas one adjacent to each other in the v-axis direction on the uv plane, that is, square areas (-k, -k + 1) to (+ k, -k +
1) is to be processed.

In this way, m> + k (step 11)
3), when n> + k (step 116), it means that a moiré power spectrum has been obtained for all the target phosphor array spatial frequency spectra [i, j].

FIG. 8 is a flowchart showing a specific example of step 108 in FIG.

In the figure, the square area obtained as a processing target in steps 103 to 107 of FIG.
Phosphor array spatial frequency spectrum [i, j] at (m, n)
For, first, the u, v is the axial direction of the spatial frequency aliasing original spatial frequency U _m, V _n [units mm ^-1] and, folded destination frequency u _m is the spatial frequency of the imaging moire due to the folding, v _n [unit is mm ^-1 ] (step 200). Here, a _{U m = i / Hp V n} = j / Vp u m = i / Hp-m / p v n = j / Vp-n / p.

Here, in the case of the color CRT, the liquid crystal display, and the plasma display shown in FIG. 3, the periodic pattern of the object 16 is one pixel of R, G, and B.
It has not two points but a shape and dimensions (ie, openings). For this reason, each phosphor array spatial frequency spectrum [i, j] also has a spread of power, and the spread method also differs depending on the shape and size of the pixel. Accordingly, upon obtaining the moire power spectrum, it is necessary to determine the spectrum S _{2, 4} folding the spread of such power (u _m, v _n).

Therefore, if the aperture (cell) of the pattern of the object 16 is rectangular as shown in FIGS. 3C and 3D (step 201), the folded spectrum S _2,4 ( u _m , v _n ) is determined by the following equation 1 (step 202).

[0067]

(Equation 1)

In the above equation 1, the sinc of the first item on the right side is
(dh · U _m , dv · V _n ) represents the aperture shape spectrum of the phosphor when the cell is rectangular. As for the primary function sinc (x), FIG. The waveform is as shown. The second item on the right side indicates the aperture shape spectrum of the imaging pixel. The multiplication of the first item and the second item is a phosphor array spatial frequency spectrum [i,
j] represents the power of the folded spectrum.

The opening (pixel) of the pattern of the object 16 to be imaged
But, as shown in FIG. 3 (a), (b), in the case of the elliptical shape (step 201), the folded spectrum S _{2, 4} (u _m
, v _n ) by the following equation (step 20):
3).

[0070]

(Equation 2)

In the above equation (2), the first item on the right-hand side represents the aperture shape spectrum of the phosphor when the pixel is elliptical, and the primary function besinc (x) is the waveform shown in FIG. Becomes Also in this case, the second item on the right side indicates the aperture shape spectrum of the imaging pixel.

As described above, the return spectrum when the pixel has a finite aperture is obtained.
(A), (c), the if only one type of pixel monochromatic luminescence emitted (step 204), S (u _{m,
v n) = S 2,4 (u} m, as v _n) (step 206), obtaining the moire power spectrum (step 207). However, in the case of 3-color light emitting three types of pixels emit light (step _{204), S (u m,} v n) = S 2,4 (u m, v n) × f (i, g, b, r) becomes performs calculation to obtain the moiré power spectrum by using the _{S (u m, v n)} ( step 207). Note that f
(i, g, b, r) is expressed by f (i, g, b, r) = g + b + ri≡0 (mod3) = g- (b + r) / 2i≡1,2 (mod3). When g = b = r, i≡0 (mod 3),
That is, only the phosphor array spatial frequency spectrum [i, j] where i is a multiple of 3 (including i = 0) is f (i, g, b,
r) ≠ 0, and in the other phosphor array spatial frequency spectrum [i, j], f (i, g, b, r) = g− (b +
Since r) / 2 = 0, the distribution of the phosphor array spatial frequency spectrum [i, j] is 1/3 that of a single color.

[0073] At step 207, the moiré power spectrum _{P m (u m, v n} ) is,

[0074]

(Equation 3)

Is obtained.

FIG. 10 is a flowchart showing a method for calculating the pixel shift amount from the moiré power spectrum P _m (u _m , v _n ) obtained as described above.

In the figure, first, a pixel shift degree of freedom N
(≧ 1) is set (step 300). This is set to の of the number of moire spectra to be removed. Next, the moiré power spectrum P _m (u _m ,
v _n ), the moire power spectrum P ₀ of m = n = ₀
(u ₀ , v ₀ ) is excluded (step 301). This is for the non-folded phosphor array spatial frequency spectrum [0,0], and this phosphor array spatial frequency spectrum
[0,0] is generated in the visible spatial frequency area A in the basic square area (0,0), and does not cause imaging moire.

Then, the remaining moire power spectrum P
_m (u _m, v _n) arranged in descending order (step 302), i
= 1 and the i-th largest moiré power spectrum is P
_mi (u _m , v _n ) (step 303), the original spatial frequencies U _mi , V _ni for the i-th largest moiré power spectrum P _mi (u _m , v _n ) and the next (i + 1) -th largest moiré The return source spatial frequencies U _{m (i + 1)} and V _{n (i + 1)} for the power spectrum P _{m (i + 1)} (u _m , v _n ) are selected (step 304. Note that, for the moire power spectrum, folding original spatial frequency has been obtained in the processing shown in FIG. 8), the stiff 305, using these folded original spatial frequencies, these moiré power spectrum P _mi (u _m
, v _n ) and P _{m (i + 1)} (u _m , v _n ) are calculated.

The spatial frequency spectrum of the imaging moiré has a real value and an imaginary value, and the spatial frequency of the imaging moiré whose angle differs by 180 ° with respect to the angle between them, that is, the argument (also called phase). By generating the spectrum, the spatial frequency spectrum of the original imaging moiré can be canceled out by this. In order to obtain an imaging moiré spatial frequency spectrum having a declination of 180 ° with respect to the original imaging moiré spatial frequency spectrum, -1 = exp (jn
π) (where j is an imaginary number and n is an odd number), but this is realized by shifting the imaging range of the solid-state imaging device by an amount smaller than the pixel size.

Now, if the imaging range of the solid-state imaging device is shifted from the state shown in FIG. 3 by α pixels in the horizontal direction and β pixels in the vertical direction (however, pixel shift amounts α, β <p) The imaging moiré spatial frequency spectrum generated when the phosphor array spatial converging frequency spectrum of the same spatial frequency is folded is expressed as exp ｛j2πp in the original imaging moiré spatial frequency spectrum generated when there is no such shift.
(ΑU _m + βV _n )}. In order for this to have a declination of 180 ° with respect to the original imaging moiré spatial frequency spectrum, n = 1,

[0081]

(Equation 4)

Therefore, the pixel shift amounts α and β are

[0083]

(Equation 5)

This satisfies the following.

[0085] Step 305 in FIG. 10 is intended to make this calculation, two moiré power spectrum P _mi sequentially larger _{(u m, v n),} P m (i + 1) (u m, v n) for Return source spatial frequencies _Umi , _Vni , _{Um (i + 1)} , V
_{Using n (i + 1)} , the pixel shift amounts for these are α _{i / 2} ,
As β _{i / 2} ,

[0086]

(Equation 6)

The simultaneous equations should be satisfied.

Next, assuming that i = i + 2 (step 30)
6) Thereafter, the processing of steps 304 and 305 is sequentially performed on two moiré power spectra in descending order, and the pixel shift amounts α _{i / 2} and β _{i / 2} are obtained for each, and these are set to i ≧ 2N. This is repeated until it becomes (step 307).

The arithmetic processing unit 15 shown in FIG. 1 performs the above arithmetic processing to obtain the pixel shift amounts α _{i / 2} and β _{i / 2}
Is calculated, and the z-direction movement signal Sz and the y-direction movement signal Sy are generated in accordance with the above. The effect of the pixel shift will be described below based on an experimental example.

Here, as the imaging target 16, FIG.
Using the imaging targets 16-1 and 16-2 shown in (a) and (b), as shown in FIG. 11A, it is assumed that a defective pixel PE exists in the imaging visual field CE. The effect of reducing imaging moiré is examined by making the pixel shift amount different from CE. In addition, such an imaging target 16
Then, Hp = 0.221 mm, Vp = 0.292 mm,
It is assumed that the minor axis of the pixel is 0.1 mm and the major axis of the pixel is 0.12 mm.

The size of the image pickup pixel is 0.15 mm in both the horizontal and vertical directions, and 16 reference points 0, 1, and 1 at regular intervals (1/4 pixel intervals in the horizontal and vertical directions) are included therein.
2, 3, ..., 15 are set. Such a reference point is determined by setting the first imaging pixel VE in the upper left corner of the imaging screen to the imaging visual field CE.
Is determined with respect to the point B at the upper left corner of the table, and there are 16 ways of positioning.

That is, the image pickup pixel VE in FIG.
Indicates a case where the reference point 0 is coincident with the point B at the upper left corner of the imaging visual field CE. In the imaging visual field CE, it is assumed that other imaging pixels are arrayed based on the imaging pixel VE. Become. FIG. 12 schematically shows an arrangement relationship of the imaging pixels VE with respect to the imaging visual field CE at that time, and one surrounded by a broken line frame is one imaging pixel VE.
In FIG. 11A, the reference point 1 is set to the imaging visual field CE.
12 is shifted to the left from the illustrated imaging pixel VE by 1/4 pixel, and the imaging pixels in this case are the same as those in FIG. Are shifted by −１ pixel in the horizontal direction and by 0 pixel in the vertical direction from the imaging pixel indicated by. Similarly, in FIG. 11A, when the reference point 4 is coincident with the point B at the upper left corner of the imaging visual field CE, the imaging pixel is shifted by １ ／ pixel above the illustrated imaging pixel VE. In this case, the respective imaging pixels are shifted from the imaging pixels shown in FIG. 12 by 0 pixels in the horizontal direction and by ＋１ pixel in the vertical direction. Therefore, in FIG.
Is matched with the point B in the upper left corner of the imaging visual field CE,
The imaging pixel is shifted by 3/4 pixel to the left and 3/4 pixel upward from the illustrated imaging pixel VE,
In this case, each imaging pixel is shifted from the imaging pixel shown in FIG. 12 by -3/4 pixel in the horizontal direction and by +3/4 pixel in the vertical direction.

FIG. 13A shows the brightness of the image pickup moire and the pixel defect P when the image pickup pixel VE is shifted 16 times as described above with respect to the image pickup visual field CE shown in FIG. 11A.
FIG. 9 is a diagram showing a relationship between the brightness of E and the brightness of the brightest part of the captured image, where the brightest value is 100%, and the brightness of the captured moiré is the ratio of the brightness of the darkest part to the brightest value. Moiré darkest value [%] and pixel defect PE
Is plotted for each of the reference points 0, 1, 2, 3,..., 15 of the imaging pixels that match the imaging field of view CE, with the ratio of the darkest portion to the brightness maximum value being the darkest value [%]. are doing.

In FIG. 13A, the moire darkest value is almost constant at 50% regardless of the arrangement of the image pickup pixels with respect to the image pickup visual field CE. On the other hand, the darkest value of the defect is determined by changing the arrangement relationship of the imaging pixels with respect to the imaging visual field CE by changing the reference point of the imaging pixels to be coincident with the point B at the left corner of the imaging visual field CE. Has a different value because the positional relationship changes.

According to FIG. 13A, the reference point of the image pickup pixel to be coincident with the point B at the left corner of the image pickup visual field CE is shown in FIG.
, The darkest value of the defect is approximately 50%
And almost match the Moire darkest value. This indicates that, when the arrangement relationship of the imaging pixels with respect to the imaging visual field is set in this way, it is very difficult to identify the defective pixel PE by the imaging moiré. That is, FIG.
In the case where the imaging moiré reduction processing as in the embodiment shown in FIG. 1 is not performed, a pixel defect may not be detected depending on the positional relationship between the imaging field of view CE and the imaging pixels.

On the other hand, FIG.
As in the case of (a), imaging is performed by shifting the imaging pixel VE in 16 ways with respect to the imaging visual field CE as described above. However, the embodiment shown in FIG. 1 is used. For each image pickup, the calculation unit 15 also performs image pickup of pixel shift, and the image signal when pixel shift is not performed and the image signal when pixel shift is performed are processed by the image pickup moiré reduction processing unit 14 to reduce image pickup moiré. Was performed. In this case, the pixel shift amount is set to +0.7 in the horizontal direction.
Four pixels and -49 pixels in the vertical direction. Otherwise, it is the same as the case of FIG.

According to FIG. 13 (b), the darkest value of moire rises to almost 70%, and the effect of reducing image moiré appears, and the reference point 6 of the image pixel is located at point B at the upper left corner of the image field CE.
Are matched, the darkest value of the defect becomes close to the darkest value of the moire, but there is still a difference of 10% or more, and the detection of the pixel defect PE becomes easier than in the case of FIG.

As described above, by performing the imaging moiré reduction processing according to the embodiment shown in FIG. 1, the imaging visual field C is obtained regardless of the positional relationship between the imaging visual field CE and the imaging pixels.
The pixel defect PE at E can be reliably detected.

In this example, it is assumed that the two moire power spectra are shifted from the largest one, and that the greater the moire power spectrum is subjected to pixel shift, a greater effect can be obtained. Become.

In this embodiment, the image pickup moiré is reduced to detect a pixel defect. However, the present invention is not limited to this, and image quality such as color shift, color purity, resolution, sharpness, image distortion, image inclination, etc. Needless to say, the inspection is effective as a means for reducing image moire.

As described above, in this embodiment, a video signal with effectively reduced imaging moire can be obtained from an imaging target having a periodic light / dark pattern. The influence of the imaging moiré on the fluctuation is greatly suppressed, and such a light-dark fluctuation can be easily and accurately detected. For this purpose, a method of quantifying and inspecting the superiority and inferiority of the imaging target, for example, when the display screen of a display device which is one of the imaging targets having a periodic light and dark pattern such as pixels is set as the imaging target, this display is performed. Quantitative analysis of at least one of color unevenness, luminance unevenness, particle unevenness, pixel defect, color shift, color purity, resolution, sharpness, image distortion, image inclination, etc., which are particularly important among screen image quality items In the inspection method, the imaging method for eliminating moiré imaging according to this embodiment is very effective, and is an inevitable means for realizing a product quality inspection device and achieving stable product quality at a high level with this device. is there.

FIG. 14 is a diagram showing an image pickup system B according to a second embodiment of the method for picking up an image of an object having a periodic light and dark pattern according to the present invention and an apparatus using the method.
Reference numeral 7 denotes a glass plate unit, and parts corresponding to those in FIG.

The second embodiment has the same overall configuration as the embodiment shown in FIG. 1, but as shown in FIG.
In the imaging system B, a glass plate unit 17 is provided between the solid-state imaging device 6 and the optical system 7. The imaging lens 8 incorporated in the optical system 7 is an image-side telecentric lens, and makes light rays contributing to imaging on the image side parallel to the optical axis. The glass plate unit 17 changes the optical path of the parallel light from the imaging lens 8 according to the rotation drive signals Sθ1 and Sθ2 from the processing unit 15 (FIG. 1). Is equivalent to the displacement of the imaging system B in the z and y directions, and the same effect as in the embodiment shown in FIG. 1 can be obtained.

FIG. 15 is a view showing a specific example of the glass plate unit 17 in FIG. 14. Numerals 18 and 19 are glass plates, and portions corresponding to those in FIG.

In FIG. 15A, a glass plate unit 17 is composed of two glass plates 18 and 19.
These glass plates 18 and 19 are provided before and after in the optical path of the parallel light L from the imaging lens 8, and the glass plate 18 is perpendicular to the optical axis of the parallel light L (the optical axis of the imaging lens 8). The glass plate 19 is rotatable about a rotation axis RP1, and the glass plate 19 is provided so as to be rotatable about a rotation axis RP2 perpendicular to the optical axis of the parallel light L and the rotation axis RP1 of the glass plate 18. Have been.
When the glass plate 18 rotates, the optical path of the parallel light L is displaced in the z direction by an amount corresponding to the amount of rotation, and when the glass plate 19 rotates, the optical path of the parallel light L is displaced in the y direction. Therefore,
For example, the glass plate 18 is rotated according to the rotation drive signal Sθ1 from the arithmetic processing unit 15 (FIG. 14),
Is the rotational drive signal Sθ2 from the arithmetic processing unit 15 (FIG. 14)
By rotating the imaging system B in accordance with, the same effect as when the imaging system B is displaced in the z and y directions as in the first embodiment shown in FIG. 1 can be obtained.

As shown in FIG. 15B, the arrangement order of the glass plates 18 and 19 may be reversed, and it goes without saying that the same effect can be obtained.

FIG. 16 is a block diagram showing a third embodiment of the method for picking up an image of an object having a periodic light-dark pattern and an apparatus using the same according to the present invention. This is a y-direction moving mechanism, and portions corresponding to FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted. In the third embodiment, a single imaging system can be used to obtain a video signal without pixel shift and a video signal with pixel shift as described above.

In the figure, the imaging system is provided with an x-direction movement mechanism 20 and a y-direction movement mechanism 21, and responds to the x-direction movement signal Sx and the y-direction movement signal Sy from the arithmetic processing unit 15. X, y in a plane parallel to the plane of the imaging target 16
It is configured to be movable in the direction.

In such a configuration, the solid-state imaging device 2 captures an image of the field of view CE of the imaging target 16 through the optical system 3 in a state where the x-direction movement signal Sx and the y-direction movement signal Sy are not supplied from the arithmetic processing unit 15. The output video signal of the solid-state imaging device 2 at that time is supplied to the arithmetic processing unit 14 and the pixel unit shift correction processing unit 13, but is captured by the imaging moiré reduction processing unit 14 as a video signal VA without pixel shift. Will be retained.

Next, an x-direction movement signal Sx and a y-direction movement signal Sy corresponding to the pixel shift amount calculated therefrom are supplied from the arithmetic processing unit 15, and accordingly, the x-direction movement mechanism 20, the y-direction movement signal The mechanism 21 operates and the imaging system is displaced in the x and y directions. At this time, the output video signal of the solid-state imaging device 2 is directly supplied to the imaging moiré reduction processing unit 14 and the pixel unit deviation correction processing unit 13. Captures the video signal VB 'corrected.

Here, the imaging moiré reduction processing unit 14
The video signals VA and VB 'are fetched, respectively, and temporarily stored in a built-in memory. Thereafter, these video signals are read out from the memory and subjected to the above-described arithmetic synthesis processing to obtain a video signal V with reduced imaging moire. To generate,
By correcting the pixel shift amount of the video signal VB shifted by the pixel in the pixel unit shift correction processing unit 13 as described above, the imaging moiré reduction processing unit 14 converts the captured video signal VB ′ regardless of the pixel shift amount. Need only be written mechanically to the memory. If the pixel unit shift correction processing unit 1
3, the video signal VB shifted in pixels
The write start position (address) in the memory, or the read start position and read start timing of the video signal VB 'in the memory must be changed according to the pixel shift amount.

In the third embodiment, the x direction movement signal Sx and the y direction movement signal Sy
Although the imaging system is moved in the x and y directions according to the above, the imaging system is fixed and the imaging target 16 is similarly moved.
According to the x direction movement signal Sx and the y direction movement signal Sy, x,
It may be moved in the y direction.

FIG. 17 is a block diagram showing a fourth embodiment of the method for picking up an image of an object having a periodic light and dark pattern and an apparatus using the same according to the present invention, wherein reference numeral 22 denotes an optical low-pass filter; Parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted. This fourth embodiment also uses one imaging system. However, the imaging system is fixed, and the captured image of the imaging field of the imaging target on the imaging surface of the solid-state imaging device is optically moved. It was done.

In the figure, the image pickup system is provided with an optical low-pass filter 22, and an image of the field of view CE of the object 16 is picked up by the solid-state image sensor 2 via the optical low-pass filter 22. The optical low-pass filter 22 receives the rotation drive signal Sθ from the arithmetic processing unit 15.
18, as shown in FIG. 18, which shows a cross section along the dividing line CC ′ in FIG.

The optical low-pass filter 22 is a birefringent plate having a birefringent characteristic such as a quartz plate.
As shown in (1), the incident light beam L from the imaging lens 4 is split into two light beams L1 and L2. Here, one of the light beams L2 is a part of the incident light beam L as it is as the optical low-pass filter 2.
2, the other light beam L2 has a constant amount Δ determined by the thickness of the optical low-pass filter 22 in the constant shift direction θ (FIG. 18) in which the rest of the incident light beam L is shifted in the optical low-pass filter 22. Only the light beam L1.

In this case, the divided light amount ratio of the two light beams L1 and L2 is not always 1: 1. However, in the solid-state imaging device 2 close to the optical low-pass filter 22, an image having no pixel shift amount is provided. This is equivalent to performing weighted averaging of gradation values on a pixel-by-pixel basis.

Therefore, in FIG. 17, the amount of pixel shift that can reduce the image moiré is determined according to the periodic light / dark pattern of the object 16 to be imaged.
2 is used, which generates a shift amount Δ (FIG. 19) between the light beams L1 and L2 equal to the pixel shift amount.
Calculates a pixel position shift direction θ capable of reducing imaging moiré by weighted averaging of gradation values in pixel units to generate a rotation drive signal Sθ, and the rotation drive signal Sθ generates a rotation amount of the optical low-pass filter 22 according to the rotation drive signal Sθ. By controlling the
From the solid-state imaging device 2, a video signal V with reduced imaging moire is obtained. The pixel shift direction θ is obtained from α _{i / 2} and β _{i / 2} obtained in step 305 in FIG.

[0118]

(Equation 7)

Is the angle θ.

Since the displacement Δ of the optical low-pass filter 22 is proportional to the thickness of the optical low-pass filter 22, when the imaging target 16 having a different periodic light-dark pattern is imaged, the pixel shift determined by the periodic light-dark pattern is performed. Optical low-pass filter 2 having a plate thickness that produces the above-mentioned shift amount Δ according to the amount
2 may be used. Accordingly, by making the optical low-pass filters 22 of various thicknesses replaceable, even when the imaging target 16 of various different periodic light and dark patterns is imaged, the imaging moire is effectively performed as in the above embodiments. A reduced video signal can be obtained.

[0121]

As described above, according to the present invention,
By capturing an image of an imaging target having a periodic light-dark pattern, it is possible to obtain a video signal in which imaging moire is effectively reduced, and the accuracy of such a light-dark pattern inspection is greatly improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a method for capturing an image of an object having a periodic light-dark pattern and an apparatus using the same according to the present invention.

FIG. 2 is a diagram showing a cause of occurrence of imaging moiré and a principle of the present invention.

FIG. 3 is a diagram showing a specific example of an imaging target according to the first embodiment shown in FIG. 1;

FIG. 4 is a diagram illustrating an example of imaging moiré obtained when imaging the imaging target illustrated in FIG. 3;

FIG. 5 is a diagram showing a process of generating image moiré when an image of the image capturing target shown in FIGS. 3A and 3B is captured.

FIG. 6 is a diagram illustrating a generation process of an imaging moiré when the imaging target illustrated in FIGS. 3C and 3D is imaged.

FIG. 7 is a flowchart illustrating a specific example of a process of calculating a moiré power spectrum in the arithmetic processing unit in FIG. 1;

FIG. 8 is a flowchart showing a specific process of step 108 in FIG. 7;

FIG. 9 is a diagram showing waveforms of functions used in steps 202 and 203 in FIG. 8;

10 is a flowchart showing a specific example of a calculation process of a pixel shift amount based on the moiré power spectrum obtained in FIG. 7 in the arithmetic processing unit in FIG. 1;

FIG. 11 is a diagram illustrating an imaging target having a pixel defect and imaging pixels.

FIG. 12 is a diagram illustrating an example of an arrangement relationship of imaging pixels with respect to an imaging target having a pixel defect.

13 is a diagram showing a comparison between the relationship between the imaging moiré and the pixel defect when the imaging target shown in FIG. 12 is imaged by a conventional method and in the first embodiment shown in FIG. 1;

FIG. 14 is a configuration diagram showing one image pickup system in a second embodiment of an image pickup method of an object having a periodic light and dark pattern according to the present invention and an apparatus using the method.

FIG. 15 is a configuration diagram showing a second embodiment of a method for capturing an image of an object having a periodic light-dark pattern and an apparatus using the same according to the present invention.

FIG. 16 is a configuration diagram showing a third embodiment of a method for capturing an image of an object having a periodic light-dark pattern and an apparatus using the same according to the present invention.

FIG. 17 is a configuration diagram showing a fourth embodiment of a method for capturing an image of an object having a periodic light-dark pattern and an apparatus using the same according to the present invention.

FIG. 18 is a sectional view taken along the line CC ′ of FIG. 17;

FIG. 19 is a diagram showing the operation of the optical low-pass filter in FIGS. 17 and 18.

[Description of Signs] 1 Pixel shift correction unit 2 Solid-state imaging device 3 Optical system 4 Imaging lens 5 Numerical aperture adjustment mechanism 6 Solid-state imaging element 7 Optical system 8 Imaging lens 9 Numerical aperture adjustment mechanism 10 Half mirror 11 Z-direction moving mechanism 12 y-direction moving mechanism 13 pixel unit shift correction processing unit 14 imaging moiré reduction processing unit 15 arithmetic processing unit 16, 16-1 to 16-4 imaging target 17 glass plate unit 18, 19 glass plate 20 x-direction moving mechanism 21 y direction Moving mechanism 22 Optical low-pass filter A, B Imaging system CE Imaging field of view

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Kawaguchi 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside of Hitachi, Ltd. F-term in the Electronic Device Division of Manufacturing (reference) 5C021 PA66 YA01 5C024 AA01 CA00 CA02 FA01 FA14 HA17

Claims (17)

[Claims] 1. A method for capturing an image of an object having a periodic light-dark pattern, comprising: obtaining a pixel shift amount corresponding to the light-dark pattern; An image of the light and dark pattern shifted by the pixel shift amount is obtained to obtain a second video signal having a pixel shift, and the first and second video signals are subjected to arithmetic synthesis processing of a gradation value for each pixel. And obtaining a third video signal having the same resolution and the same number of pixels as the first video signal and having a reduced number of image capturing moire. 2. The image pickup apparatus according to claim 1, wherein the imaging moire component included in the first video signal is
The pixel shift is performed so that the imaging moire component having a spatial frequency spectrum having a declination angle 180 ° different from the declination of the real frequency and the imaginary value of the spatial frequency spectrum of the imaging moiré component is included in the second video signal. A method for imaging an object having a periodic light and dark pattern, characterized by setting an amount. 3. The imaging moiré component according to claim 2, wherein the imaging moiré components included in the first and second video signals are one or more imaging moiré components in order from the largest absolute value of the spectrum in the spatial frequency domain. An image capturing method for an object having a periodic light and dark pattern. 4. A method for inspecting an object using an image capturing method for an object having a periodic light and dark pattern according to claim 1, wherein the object is a display screen on a display device, By capturing the display screen by the imaging means and obtaining a video signal in which imaging moire is suppressed, color unevenness, luminance unevenness, particle unevenness, pixel defect, pixel defect among image quality items of the display screen are obtained.
An inspection method characterized by quantitatively inspecting at least one of color shift, color purity, resolution, sharpness, image distortion, and image inclination. 5. A video signal in which moiré is suppressed by using the image capturing method of any one of claims 1 to 3 to capture an image of the display screen by the image capturing means. An inspection method comprising: detecting light / dark variations other than the periodic light / dark pattern in the object; and quantitatively inspecting the quality of the object. 6. An apparatus for picking up an image of an object having a periodic light-dark pattern, comprising: an arithmetic processing means for obtaining a pixel shift amount corresponding to the light-dark pattern; Imaging means for imaging the video signal and the light and dark pattern shifted by the pixel shift amount and outputting a second video signal with pixel shift, and converting the first and second video signals into pixel units. Imaging moiré reduction processing means for arithmetically synthesizing the tone value, wherein the imaging moiré reduction processing means obtains a video signal having the same resolution and the same number of pixels as the first video signal and having image moire suppressed. An image pickup device for a target having a periodic light and dark pattern, characterized in that it is configured. 7. The arithmetic processing unit according to claim 6, wherein the image processing moiré component included in the first video signal has an argument based on a real value and an imaginary value of a spatial frequency spectrum of the moiré component. Wherein the pixel shift amount is set so that the second video signal includes a moiré component having a spatial frequency spectrum having a declination angle different by 180 °. . 8. The moire power spectrum according to claim 6, wherein the arithmetic processing means calculates a moire power spectrum which is the power of the imaging moire generated by the return of the spatial frequency spectrum in a finite region of the spatial frequency. An image pickup apparatus for a target having a periodic light and dark pattern, wherein a spatial frequency before turning back of one or more imaging moire is obtained in order, and the pixel shift amount is calculated from the obtained spatial frequency. 9. The (i + 1) -th imaging method according to claim 8, wherein the return frequency of the spectrum in the spatial frequency domain in which the i-th imaging moiré is generated in the descending order of the moiré power spectrum is U _mi and V _ni. Assuming that the return spatial frequencies of the spectrum in the spatial frequency domain where moiré occurs are U _{m (i + 1)} and V _{n (i + 1)} , α _i × U _mi + β _i × V _ni = 1 / (2p) α _i × U _{m (i + 1)} + β _i × V _{n (i + 1)} = 1 / (2p) where α _i and β _i satisfying p = resolution of the image pickup means are the pixel shift amounts. An image pickup apparatus for an object having a characteristic periodic light and dark pattern. 10. The arithmetic synthesis of tone values for each pixel by the imaging moiré reduction processing means according to any one of claims 6 to 9, wherein weighting of tone values for each pixel unit, Periodic light / dark pattern characterized by one of simple average processing of gradation values for each pixel, maximum gradation value selection processing for each pixel unit, and minimum gradation value selection processing for each pixel unit An image pickup apparatus for a target having: 11. The imaging device according to claim 6, wherein the imaging unit includes first and second solid-state imaging devices for imaging a periodic light-dark pattern of the same object. An object having a periodic light and dark pattern, characterized in that the solid-state imaging device captures a visual field range shifted by an amount corresponding to the pixel shift amount from the visual field range of the target by the first solid-state imaging device. Image pickup device. 12. The optical sensor according to claim 11, wherein an optical path changing unit is provided in the second solid-state imaging device, and the visual field range of the target of the second solid-state imaging device is changed by the optical path changing unit. An object image pickup apparatus having a periodic light and dark pattern, wherein the object is shifted from the object view range of the one solid-state image sensor by an amount corresponding to the pixel shift amount. 13. The imaging device according to claim 6, wherein the imaging device has one solid-state imaging device including a moving device that can move in parallel with the surface of the object. The output video signal of the solid-state image sensor when not operating is set as the first video signal, and the output of the image sensor when the moving unit is operated according to the pixel shift amount obtained by the arithmetic processing unit. An image pickup apparatus for a target having a periodic light and dark pattern, wherein a video signal is the second video signal. 14. The apparatus according to claim 6, further comprising: means for moving the object in accordance with the pixel shift amount obtained by the arithmetic processing means, wherein the imaging is performed when the object is not moved. A periodic video signal, wherein an output video signal of the means is the first video signal, and an output video signal of the imaging means when the object is moved by the means is the second video signal. An image pickup device of a target having a pattern. 15. An apparatus for picking up an image of a target having a periodic light-dark pattern with one solid-state imaging device, wherein the solid-state imaging device determines an optical path of a part of image light from the target by the light-dark pattern. Optical means for optically changing the amount by the pixel shift amount is provided, and a pixel shift direction according to the light / dark pattern is calculated, and a direction of an optical path of a part of the image light by the optical means is calculated. Arithmetic processing means for controlling the optical means so as to match the direction of pixel shift, so as to obtain a video signal in which imaging moire is suppressed from the solid-state imaging device. An image pickup device of a target having a pattern. 16. An inspection apparatus for an object using an image capturing apparatus for an object having a periodic light and dark pattern according to any one of claims 6 to 15, wherein the object is a display screen on a display device, By capturing the display screen by the imaging means and obtaining a video signal in which imaging moire is suppressed, color unevenness, luminance unevenness, particle unevenness, pixel defect, pixel defect among image quality items of the display screen are obtained.
An inspection apparatus characterized by quantitatively inspecting at least one of color shift, color purity, resolution, sharpness, image distortion, and image inclination. 17. An object imaging apparatus having a periodic light and dark pattern according to any one of claims 6 to 15, wherein
By capturing the display screen by the imaging unit and obtaining a video signal in which imaging moire is suppressed, a light-dark variation other than the periodic light-dark pattern in the object is detected, and the quality of the object is quantitatively determined. An inspection method apparatus characterized by performing an inspection.