JPH0711831B2 - Pattern elasticity calculator - Google Patents

Description

The present invention relates to a pattern expansion / contraction degree calculating device, and more particularly to a pattern expansion / contraction for highly accurate positioning when performing a comparative inspection between patterns accompanied by expansion / contraction. Degree calculator.

[Conventional technology]

As conventional techniques, for example, Hara, Esaki, and Utsu "Automation of appearance inspection of printed circuit board pattern", Theory J67-C, 8, P43
As shown in 5 (Sho 59-05), when performing comparison inspection between stretchable patterns, alignment error occurs,
For example, as seen in this example, other means or local features are used to avoid registration errors.

[Problems to be solved by the invention]

The above-described conventional technique has a problem in that it is impossible to perform a comparative inspection between patterns having a large degree of expansion and contraction, and it is also impossible to perform a high-precision comparative inspection due to high density. An elasticity calculation device is required.

[Means for solving problems]

The pattern elasticity calculation device of the present invention is an A / D conversion circuit for converting a standard pattern image signal read by scanning with a photoelectric conversion scanner into a digital image of a multi-value level,
A density distribution calculating circuit for calculating an average value in each of the horizontal and vertical directions of the digital image to obtain a density distribution in each of the vertical direction and the horizontal direction, and an autocorrelation function for each direction using the calculated density distribution. And an autocorrelation function calculating circuit for calculating a value of a plurality of points in the vicinity of the calculated amount of deviation of the autocorrelation function of 0, and a linear approximation is performed to obtain an approximate autocorrelation line. An equivalent pulse width calculation circuit for calculating the position of the shift amount as an equivalent pulse width, an equivalent pulse width storage circuit for storing the calculated equivalent pulse width for each of the vertical direction and the horizontal direction, and an expansion / contraction pattern image. By performing the same processing as described above, the equivalent pulse width is calculated for each of the vertical direction and the horizontal direction, and the calculated equivalent pulse width and the Configured to include a stretchable calculating circuit for calculating the ratio of the equivalent pulse width for the standard patterns stored in the valence pulse width memory circuit for the vertical and horizontal directions, respectively.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

Input image 2 scanned and read by photoelectric conversion scanner 1
Is converted into a digital image 4 of multilevel by the A / D conversion circuit 3.

The density distribution calculation circuit 9 calculates an average value in each of the horizontal and vertical directions of the digital image 4 to obtain a vertical and horizontal density distribution, and outputs a density distribution signal 10.

An autocorrelation function calculation circuit 11 uses the concentration distribution signal 10 to calculate an autocorrelation function 12 for each of the vertical and horizontal directions.

Further, in the equivalent pulse width calculation circuit 13, the above-mentioned autocorrelation function
A linear approximation is performed by using the values of a plurality of points near the deviation amount 0 of 12 to obtain an approximate autocorrelation value straight line, and the position of the deviation amount at which the value of the approximate autocorrelation straight line is 0 is equivalent pulse width 14
Calculate as

The equivalent pulse width storage circuit 15 stores the equivalent pulse width 14 in the vertical direction and the horizontal direction, which is obtained as a result of performing the above-described processing on the standard pattern.

In the expansion / contraction degree calculation circuit 17, the equivalent pulse width 14 in the vertical direction and the horizontal direction obtained as a result of performing the above-described processing on the expansion / contraction pattern, and the equivalent to the standard pattern output from the equivalent pulse width storage circuit 15 described above. The ratio with the pulse width storage signal is calculated in each of the vertical direction and the horizontal direction, and the value of the calculated ratio is output as the elasticity signal 18.

Next, details of each unit will be described.

2A to 2C are schematic diagrams showing a method of calculating the pattern expansion / contraction degree only in the horizontal direction.

FIG. 2A shows the digital images of the standard pattern 22 and the expansion / contraction pattern 21 superimposed on each other in order to explain the difference between them.

In FIG. 2B, the digital image shown in FIG. 2A is calculated as a horizontal density distribution by calculating an average value only in the vertical direction using the density distribution calculation circuit 9 described above. These are shown as a standard pattern density distribution 23 and a stretch pattern density distribution 24, respectively.

FIG. 2C shows the standard pattern autocorrelation function 25 and the expansion / contraction pattern autocorrelation function 26 obtained for the standard pattern density distribution 23 and the expansion / contraction pattern density distribution 24 shown in FIG. 2B.

Generally, the autocorrelation function of the concentration distribution signal as shown in FIG. 2 (b) is as shown in FIG. 2 (c), and the shape of this autocorrelation function is the same as that of a single rectangular pulse. Becomes (Mikio Hino "Spectral Analysis" Asakura Shoten).

Therefore, the pulse widths b and b ′ of the equivalent rectangular pulses corresponding to the standard pattern autocorrelation function 25 and the expansion / contraction pattern autocorrelation function 26 are obtained as the equivalent pulse widths, and the ratio γx of both is obtained. Obtained by the equation (1), this value becomes the expansion / contraction degree of the expansion / contraction pattern with respect to the standard pattern.

FIG. 3 is a schematic diagram showing an equivalent pulse width calculation method.

Approximation by linear approximation by the least squares method using the value of the autocorrelation function value C (k) (where k = 0, ± 1, ± 2 ... ± N) calculated by the autocorrelation function calculation circuit 11 described above. Find the autocorrelation line 27 (K1 and K2). Furthermore, the positions b1 and b2 of the shift amount at which the value of the approximate autocorrelation line 27 (K1 and K2) becomes 0 are obtained, and the equivalent pulse width b described above is calculated. It is calculated from the equation (2).

〔The invention's effect〕

Since the pattern expansion / contraction degree calculation device of the present invention can calculate the expansion / contraction degree of a pattern with large expansion / contraction, it is possible to correct the input image using the calculated expansion / contraction degree. There is an effect that inspection and highly accurate comparison inspection can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 (a) to 2 (c) are schematic diagrams showing a pattern expansion / contraction degree calculation method only in the horizontal direction, and FIG. 3 is an equivalent pulse width calculation method. It is a schematic diagram which shows. 1 ... Photoelectric conversion scanner, 2 ... Input image, 3 ... A / D
Conversion circuit, 4 ... Digital image, 9 ... Density distribution calculation circuit, 10 ... Density distribution signal, 11 ... Autocorrelation function calculation circuit, 12 ... Autocorrelation function, 13 ... Equivalent pulse width calculation circuit, 14 ...... Equivalent pulse width, 15 …… Equivalent pulse width memory circuit, 16 …… Equivalent pulse width memory signal, 17 …… Scaling factor calculation circuit, 18 …… Scaling factor signal, 20 …… Digital image, 21 ……
Stretching pattern, 22 …… Standard pattern, 23 …… Standard pattern density distribution, 24 …… Stretching pattern density distribution, 25 …… Standard pattern autocorrelation function, 26 …… Stretching pattern autocorrelation function, 27 …… Approximate autocorrelation line .

Claims (1)

[Claims] 1. An A / D conversion circuit for converting a standard pattern image signal scanned and read by a photoelectric conversion scanner into a multi-valued digital image, and an average for each of the horizontal and vertical directions of the digital image. A density distribution calculation circuit that calculates values and obtains vertical and horizontal density distributions, an autocorrelation function calculation circuit that calculates an autocorrelation function for each direction using the calculated density distributions, and a calculated self Equivalent to calculate the position of the deviation amount where the value of the approximate autocorrelation line becomes 0 by performing linear approximation using the values of a plurality of points near the deviation amount 0 of the correlation function as the equivalent pulse width A pulse width calculation circuit, an equivalent pulse width storage circuit for storing the calculated equivalent pulse width in each of the vertical direction and the horizontal direction, and an expansion / contraction pattern image. The equivalent pulse width is calculated for each of the vertical direction and the horizontal direction by performing the same process as described above, and the calculated equivalent pulse width and the equivalent pulse for the standard pattern stored in the equivalent pulse width storage circuit are calculated. An expansion / contraction degree calculating device, comprising: an expansion / contraction degree calculating circuit for calculating a ratio to a width in each of the vertical direction and the horizontal direction.