JP2000056210A - Automatic focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic focusing device by which erroneous detection caused by noise is eliminated and stabilized focusing is made possible. SOLUTION: A featured amount extracted from an image picked up by a CCD camera 50 and the position information of the CCD camera 50 then are stored at a measured data storing part 23 as a pair of data, and the featured amount is roughly interpolated by taking the featured amount stored by a CPU 21 as an ordinate axis and the position information as an abscissa, and the searching direction of a focal position is decided based on the featured amount, and an accurate searching range out of the featured amount stored is specified in a decided direction, and the featured amount within a range is interpolated, so that the focal position is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus device, and more particularly to an autofocus device used for a defect repair device for repairing a defect of an electrode such as a liquid crystal display (LCD) or a plasma display (PDP). .

[0002]

2. Description of the Related Art Although LCDs and PDPs are becoming larger and larger, there is a drawback in that they are more expensive than CRT displays. One of the causes of the high price is that the yield in forming the electrodes is poor. When the electrodes are etched on the substrate, there is a problem that the electrode patterns are chipped or the electrode patterns are stuck together. In order to correct such a defect, a pattern correction device is used.

FIG. 6 is a diagram showing a configuration of a conventional pattern correction device. In FIG. 6, the pattern correction apparatus is roughly classified into a laser irradiation mechanism 5 including a laser and its optical system, an ink application mechanism 9 including a needle for applying defect correction ink or conductive paste or ink,
An image processing mechanism 2 for recognizing a defect, a host computer 1 for controlling the entire apparatus, and an XY table 6 on which a work is mounted, and a chuck table 7 for holding the work on the XY table 6 And a Z-axis table 4 for driving a laser irradiation mechanism 5 up and down, a drop lighting 10 for illuminating a work, a monitor 8 and the like.

The laser irradiation mechanism 5 has a CCD (not shown)
A camera is provided, and its image output is provided to the image processing mechanism 2 to recognize a pattern defect by image processing. In order to capture an image of a pattern with a CCD camera, an autofocus device for automatically performing focusing is provided.

In a conventional autofocus device, a CCD is used.
The grayscale image captured from the camera is processed, the absolute value of the differential value of the entire image is obtained, and the CCD camera is repeatedly moved up and down to search for the in-focus position. The measurement of the differential value is performed at every certain movement step, but in order to obtain an accurate differential value, the image is captured after the movement of the camera is stopped during the measurement.

The search direction of the in-focus position is determined by comparing the current differential value with the immediately preceding differential value. When the current differential value is larger than the previous differential value, it is assumed that a focus position exists in the current search direction. Otherwise, it is assumed that the in-focus position exists in the opposite direction, and the direction is changed.
By reducing the moving step of the camera after the direction change to 方向, the moving amount is reduced and the camera is focused on the in-focus position.

[0007]

However, the high-frequency component, which is a differential value, tends to emphasize electrical or optical noise, and therefore does not always change smoothly with the movement of the camera. For example, a local maximum point may be detected as a focus position due to noise. In addition, since the focus position is searched for by the reciprocating motion while narrowing the distance, it takes time for detection. Furthermore, since the camera is stopped before capturing the image in order to obtain the image data accurately, there is a disadvantage that the moving stop time of the camera decreases the average moving speed. Furthermore, the conditions for terminating the search were unclear.

[0008] Therefore, a main object of the present invention is to provide an auto-focusing apparatus which can reduce malfunctions due to noise, shorten the time required to detect a focus position, and clarify the conditions for terminating a search. is there.

[0009]

The invention according to claim 1 is
An auto-focusing device that determines a focus position based on a feature amount extracted from an image of a subject and position information of an imaging unit, wherein the feature amount extracted from the image and the position information of the imaging unit at that time are paired with data. A data storage means for sequentially storing the feature amounts, and a search for determining a focus direction search direction based on a plurality of feature amounts by coarsely interpolating the feature amounts using the stored feature amounts on the vertical axis and position information on the horizontal axis. A direction determining means, and specifying a fine search range among the feature amounts stored in the data storage means in response to the search direction being determined;
A focus position determining means for determining a focus position by interpolating a feature amount within the range.

In the invention according to claim 2, the search direction determining means determines the presence of the in-focus position based on the inclination of a straight line interpolated by roughly setting the position information on the horizontal axis.

In the invention according to claim 3, the search direction determining means according to claim 1 or 2 moves the imaging means based on a sampling cycle of the characteristic amount in order to obtain an image of the characteristic amount suitable for interpolation. Determine the speed.

In the invention according to claim 4, the in-focus position determining means in claim 1 uses a feature amount which is maximum or minimum at the in-focus position.

In the invention according to claim 5, the focus position determining means according to claim 1 or 4 fits a quadratic curve, Gaussian or Laplacian, and determines the position where the maximum or minimum is the focus position.

According to a sixth aspect of the present invention, the imaging means of the first aspect captures an image of the subject while moving while the feature amount extracted from the image of the subject is stored in the data storage means.

[0015]

FIG. 1 is a schematic block diagram of an embodiment of the present invention. In FIG. 1, a CCD camera 50 is shown.
Is attached to the laser irradiation mechanism 5 shown in FIG.
The image output is stored in the image memory 22 of the control unit 20. The CPU 21 measures the feature amount based on the image data stored in the image memory 22, acquires the position information, and stores it in the measurement data storage unit 23. CPU 21
Is supplied with position information from a position control unit 24 that controls the position of the Z table 4, and a movement command for moving the Z table 4 is given from the CPU 21 to the position control unit 24.

FIGS. 2 and 3 are flow charts for explaining the operation of the embodiment of the present invention. In particular, FIG. 2 shows a coarse search operation, and FIG. 3 shows a fine search operation.

FIG. 4 is a diagram showing the relationship between the coarse search range and the differential value, and FIG. 5 is a diagram showing the relationship between the position and the differential value.

Next, the operation of the embodiment of the present invention will be described with reference to FIGS. First, a coarse search shown in FIG. 2 is performed. This coarse search is to search within the coarse search range shown in FIG. 4 to determine whether or not the current position is the in-focus position. More specifically, the CPU 21 sets the moving speed of the Z table 4 in a step (abbreviated as SP in the drawing) SP1, and in step SP2, causes the position control unit 24 to move the Z table 4 to the initial observation direction shown in FIG. Move to In step SP3, wait until the Z table 4 reaches a constant speed.
In step P4, i = 1 is set. In step SP5, the image data from the CCD camera 50 is stored in the image memory 22, the feature amount is measured from the image data, and the position of the CCD camera 50 is synchronized with the image capture. Information to the position control unit 24
And accumulate them in the measurement data storage unit 23.

In step SP6, i is incremented by 1 and step S
At P7, it is determined whether i ≦ M, and at step SP8, it is determined whether the limit of the search range has been reached. If the limit has not been reached, the process returns to step SP5. When M pairs of feature amount and position information are accumulated in the measurement data storage unit 23, in step SP9, the feature amount is set on the vertical axis and the position is set on the horizontal axis with reference to the measurement data storage unit 23. To perform linear interpolation.

At step SP10, it is determined whether or not the inclination of the straight line is positive.
At step P11, the Z table 4 is stopped. At step SP12, the Z table 4 is moved in the opposite direction. At step SP13, the system waits until the Z table 4 reaches a constant speed.
At 14, i = 1 is set.

After the search direction is determined in this way,
In the rough search, it is determined whether or not the in-focus position exists. That is, of the N data stored in the measurement data storage unit 23 in step SP16, (i−N)
Using the data up to i, the vertical axis represents the feature amount, the horizontal axis represents the position, and linear interpolation is performed. When the inclination of the straight line is negative, it is determined that the in-focus position exists.

If the inclination is positive, the program proceeds to steps SP18 to SP18.
In SP20, the feature amount is continuously measured, and the feature amount is stored in the measurement data storage unit 23 together with the position. If it is determined in step SP20 that the search range has been reached, the XY table 6 is stopped, and the process is stopped. Through these processes, the coarse search measurement points indicated by ● in FIG. 4 are extracted.

Next, as described above, after the existence of the in-focus position is confirmed by the coarse search, the fine search is started based on the flowchart shown in FIG. In this process, the existence range of the focus position is determined based on the pair data measured in the coarse search,
The feature amount is more finely measured within the range, and the focus position is determined by interpolation. That is, step SP shown in FIG.
21, the data (i−N / 2) of the data measured in the coarse search is used as a reference, and the sum of the neighborhood ± K (2K
−1) data, and (i−N / 2−K) to (i−
N / 2), the position L at which the change in the feature amount is the maximum,
The position where the change of the feature amount becomes maximum between (i−N / 2) to (i−N / 2 + K) is R, and as shown in FIG.
Is the range of the fine search.

After the search range is determined in step SP22, the movement amount | L between the sampling period T of the feature amount and L to R so that S feature amounts can be measured between L and R. The table speed V is calculated from −R | according to the following equation.

V = | LR- / T When the setting is made so that S differential values can be measured, the moving direction of the Z table 4 is reversed in step SP23, and the Z table 4 is changed in step SP24. Be moved. Then, in step SP25, the process waits until the Z table 4 reaches a constant speed, and i is set to 1 in step SP26.

In step SP27, the Z table 4
Is moved at a constant speed, and the measured feature amount and the position information are accumulated as the next data in the measurement data storage unit 13 while measuring the feature amount and acquiring the position information. When S feature values are measured in step SP28, the process proceeds to step S28.
At P29, the Z table 4 is stopped. Then, in step SP30, the measurement data storage unit 23 is referred to, and a secondary interpolation is performed by taking the feature amount on the ordinate and the position on the abscissa.
In P31, a position where the maximum value is obtained is determined as the in-focus position. Finally, the amount of movement of the Z table 4 from the current position to the in-focus position is obtained, the Z table 4 is moved to the in-focus position, and the process ends.

The feature value used in the search is a differential value, and is calculated from the image as follows.

[0028]

(Equation 1)

Here, Δd represents a differential value at the image position (x, y). The relationship between the derivative value and the camera position is as shown in FIG. That is, it becomes maximum at the in-focus position and becomes smaller as the distance increases. In this embodiment,
The capture of an image and the acquisition of position information were performed using the vertical synchronization signal of the CCD camera 50 as a trigger. Therefore, the sampling period T is 1/60 second.

As for the interpolation, in this embodiment, the relation between the differential value and the position is approximated by a polynomial. Variable (x,
respect y), the y and the derivative value, as the position of x, as a model the polynomial that _{y = a 0 + a 1 x} + a 2 x 2 + ... + a n x n. Here, the linear interpolation is to approximate the relationship of (x, y) with a linear expression of y = a ₀ + a ₁ x and interpolate between (x, y) obtained discretely. . a ₁ corresponds to the slope of the straight line, a ₀ corresponds to the y-intercept. Coefficient (a
₀ , a ₁ ) was estimated using the least squares method.

Further, the quadratic _{interpolation, y = a 0 + a 1} x + a 2 x 2 of a quadratic equation (x, y) approximating the relationship, between the discretely obtained (x, y) Is to interpolate. Coefficient (a
₀ , a ₁ , a ₂ ) was estimated using the least squares method as in the case of the linear equation.

It is to be noted that a Gaussian or Laplacian may be fitted without using a quadratic straight line, and a position where a maximum or a minimum is obtained may be set as a focus position.

[0033]

As described above, according to the present invention, coarsely interpolated feature values are stored by using the stored feature values on the vertical axis and position information on the horizontal axis, and the in-focus position is searched based on these feature values. Since the direction is determined, the fine search range is specified among the stored feature amounts, and the focus position is determined by interpolating the feature amounts within the range, so that erroneous detection due to noise can be reduced, Stable focusing becomes possible. Moreover,
The conditions for terminating the search are clear, and the in-focus position can be accurately positioned. Further, while the feature amount is being measured, the movement is performed so as to capture the image of the subject without stopping the imaging unit, so that a decrease in the average moving speed due to the start and stop of the camera can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a flowchart for explaining the operation of the embodiment of the present invention, and particularly shows a coarse search operation.

FIG. 3 is a flowchart for explaining a specific operation of the embodiment of the present invention, and shows a fine search operation.

FIG. 4 is a diagram illustrating a relationship between a coarse search range and a differential value.

FIG. 5 is a diagram showing a relationship between a position and a differential value.

FIG. 6 is a diagram showing a configuration of a conventional pattern correction device.

[Explanation of symbols]

 4 Z table 20 control unit 21 CPU 22 image memory 23 data storage unit 24 position control unit 50 CCD camera

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G051 AA73 AB02 BA10 CA03 DA07 EA08 EA11 EA12 EA14 EA23 EC02 EC10 2G086 EE03 EE04 EE11 HH01 2H051 AA00 BA47 CE08 CE10 CE16 CE20 CE26 FA49 GB12 2H088 EA22 FA16 FA16

Claims (6)

[Claims] 1. An auto-focusing device that determines a focus position based on a feature amount extracted from an image of a subject and position information of an imaging unit, wherein the feature amount extracted from the image and the imaging at that time Data storage means for sequentially storing the position information of the means as paired data, wherein the vertical axis represents the feature amount stored in the data storage means,
Search direction determining means for coarsely interpolating the feature amount using the position information as the horizontal axis and determining a search direction of the in-focus position based on the plurality of feature amounts, and according to the search direction being determined by the search direction determining means. An auto-focusing device, comprising: a focus position determining unit that specifies a fine search range among the feature amounts stored in the data storage unit and determines a focus position by interpolating the feature amount within the range. apparatus. 2. The search direction determining means sets coarsely the position information of the horizontal axis,
2. The method according to claim 1, wherein the presence of the in-focus position is determined.
An autofocus device according to item 1. 3. The search direction determining means determines a moving speed of the image pickup means based on a feature value sampling cycle in order to obtain an image of a feature quantity suitable for the interpolation. The autofocus device according to claim 1. 4. The method according to claim 1, wherein the in-focus position determining means uses a feature amount that is maximum or minimum at the in-focus position.
The autofocus device according to claim 1. 5. The focusing position determining unit according to claim 1, wherein the focusing position determination unit fits a quadratic curve, Gaussian, or Laplacian, and determines the maximum or minimum position as a focusing position. Auto focus device. 6. The imaging device according to claim 1, wherein the imaging unit captures the image of the subject while moving the feature amount extracted from the image of the subject in the data storage unit. An autofocus device according to item 1.