JPH04110810A - Image pickup system - Google Patents

Abstract

PURPOSE:To shorten the total measurement time by activating an automatic focus control means at an image pickup position when a distance is larger than a specific positive threshold value and inactivating said control means at the image pickup position when the distance is smaller than the threshold value. CONSTITUTION:Once an image pickup optical device 170 is automatically focused, focusing is not performed again when the device 170 moves relatively in a range of a distance equal to the threshold value from the image pickup position, i.e. an encircled range wherein the radius centering on the image pickup position is equal to the threshold value to take a measurement. Then when the device 170 moves relatively to an image pickup position outside the range surrounded with the circle, the automatic focusing is performed again at the image pickup position. Further, the automatic focusing is not performed at an image pickup position in a range surrounded with a circle having the radius equal to the threshold value centering on the image pickup position where the focusing is performed newly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an imaging system used in a length measuring machine or the like that measures the dimensions of a precision pattern formed on a plane.

[Conventional technology]

Fine patterns are formed on liquid crystal panels, printed circuit boards, etc. and the masks used to manufacture them, and optical δ1 measurement is used to inspect whether or not these patterns are accurately formed. A long machine is used. In such a length measuring machine, an automatic focus control device is incorporated in an imaging optical device such as a television camera, and the focusing of the imaging optical device on the object to be imaged is automatically performed.

FIG. 11 is a diagram showing such a conventional measurement method. In the figure, first of all, the television camera 18 is moved to the first measurement point A on the object to be measured OB, and automatic focusing of the television camera 18 at the measurement point A is performed. This focusing is a necessary task before reading the image and performing image processing for length measurement. Thereafter, the image pig is read, and the button recognition process at the measurement point A is performed.

Next, the television camera 18 is moved to the second measurement point B, and automatic focusing and image data reading are similarly performed.

Thereafter, the television camera 18 moves to the next measurement point, and similar operations are performed one after another.

In order to perform such pattern recognition, based on the amount of movement of the TV camera] 8 and the pattern position within the field of view of the TV camera] 8, we calculate the distance between multiple slams and the pattern width. The law is calculated.

[Invention or problem to be solved]

Measuring precision patterns using conventional length measuring machines is carried out in duplicate, which poses the problem of having to focus on the measurement point, which increases the time required for measurement. Ta.

Such problems are not limited to the imaging system inside the length measuring machine, but also to imaging systems that intermittently capture images of the object while moving the imaging optical device and the object relative to each other. This has become a common problem.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an imaging system that can perform overall imaging processing at a series of imaging positions in a short time.

[Means to solve the problem]

This invention provides an object to be imaged and an imaging optical device to...
The object of the present invention is an imaging system that sequentially detects images of the object at each of a series of imaging positions set on the object while moving the object intermittently.

In a first configuration of the present invention, (a) automatic focus control means is coupled to the imaging optical device and automatically focuses the imaging optical device on the object to be imaged; b) Distance calculation for each of the series of imaging positions, calculating the distance between the imaging position and the position where focusing was last performed by the automatic focus control means among the imaging positions before the imaging position. (c) activating the autofocus control means at the imaging position when the distance is greater than a predetermined threshold having a positive value; and activating the autofocus control means at the imaging position when the distance is less than the threshold; selective activation means for disabling the control means.

Further, in the second configuration, a threshold value for the distance can be selectively inputted. If such selection is possible, both cello and positive values can be accepted as selection targets. In the second configuration, the "selective operation input" may be selected in a menu format or directly input a numerical value. In the third configuration, the above ( In addition to the automatic focus control means of a), (b) a rule holding means for holding as data a predetermined rule for dividing the imaged surface of the object to be imaged into a plurality of regions; and (c) the series of the above. For each of the imaging positions, which of the plurality of regions is the position where focusing was last performed by the automatic focus control means among the imaging positions before the imaging position concerned, and the position concerned? (d) an area specifying means for specifying whether the area belongs to the second area determined by the area specifying means;
determining whether the two positions belong to the same area; disabling the automatic focus control means when the two positions belong to the same area; and disabling the automatic focus control means when the two positions do not belong to the same area; selective activation means for activating the r1 dynamic focus control device.

Furthermore, in the fourth configuration, an operation input means for selectively inputting a rule for dividing the surface of the imaged object into regions as data is provided, so that the rule for region division can be selected. ing. The selective operation input in this means may also be either a menu-only method or a direct data input method. In this fourth configuration, "1" may also be selectable as the number of regions for dividing the surface to be imaged.

[Effect]

In the imaging system according to the first configuration, for each of the series of imaging positions set on the object to be imaged, the distance calculating means calculates the automatic focus between the imaging position and the imaging position before the imaging position. The distance to the position where focusing was last performed by the control means is determined. Next, selective activation means compares the distance determined by the distance calculation means with a predetermined threshold having a positive value, and activates the automatic focus control means if the distance is greater than the threshold. state, and when the distance is smaller than the threshold value, the automatic focus control means is disabled.

Therefore, at the imaging position where the selective activation means determines that the distance is smaller than the threshold, only the automatic focus control means performs new focusing.

Furthermore, since the imaging system according to the second configuration includes an operation input means that can selectively input one threshold value from among a plurality of threshold values including positive values, the selective activation means Comparing the distance determined by the calculation means with a threshold selectively input by the operation input means, and activating the automatic focus control means if the distance is greater than the selectively input threshold; If the distance is smaller than the selectively inputted threshold, the automatic focus control means is disabled. If zero is selected as the threshold value, autofocusing will occur at virtually all imaging positions. That is, in such an embodiment, it is only possible to switch between a mote for selectively focusing and a mode for hunting.

Further, in the imaging system according to the third configuration, the rule holding means holds a predetermined rule for dividing the surface of the object to be imaged into a plurality of regions. Then, for each of the series of imaging positions set on the object to be imaged, the area specifying means performs focusing by the automatic focus control means at the imaging position and the imaging position before the imaging position. 111 is determined based on the data held by the rule holding means, to which of the plurality of areas the held position belongs. In response to this determination result, the selective activation means determines whether the two imaging positions belong to the same area or not;
When the two imaging positions belong to different areas, the automatic focus control means is activated, and when the two imaging positions belong to the same area, the automatic focus control means is disabled. Therefore, at an imaging position belonging to the same area as an imaging position that has already been focused by the automatic focus control means, only the automatic focus control means will newly perform focusing.

In addition, in the imaging system according to the fourth aspect of the invention, since the operation input means selectively inputs a rule or data for dividing the surface of the object to be imaged into regions, area identification is performed based on the rule. means and selective activation means, or third
The same operations as the area determination means and the selective activation means in the imaging system according to the invention are performed. It is also possible to select “1” as the number of area divisions, and the parentheses “]”
When is actually selected, automatic focusing is performed only at the first imaging position.

〔Example〕

A. Configuration of Apparatus FIG. 1 is a perspective view showing a length measuring machine M incorporating an imaging system which is an embodiment of the present invention. In the figure, this length measuring machine M is roughly divided into a measuring section 1 and an operating section 2.

In the measurement unit 1, a base 2 is supported on four legs 11 via air butts (air springs) not shown, and a measurement table 3 is provided on the base 12. This measurement table 13 can be freely moved in the Y direction by a Y motor (not shown) provided on the back side of the M11 constant table 13. Further, on the back side of the measurement table 13, a linear encoder 8[]b extending in the Y direction is provided. Furthermore, a rail plate 15 is fixed to the front surface of the box body 14 erected on the rear end of the base 12.
5 is provided with a moving body 16, and the moving body 16 is moved by an X motor (not shown) attached to the opposite surface.
You can move freely in any direction. Also, rail board] 5
A linear encoder 80a extending in the X direction is provided on the back surface of the printer.

Furthermore, the moving body 16 includes a microscope 17 and a pulse motor 17.
a (not shown), coarse adjustment knob 17b and two-dimensional CCD
An imaging optics 170 consisting of a camera 18 is fixed. The operator moves the movable body 16 in the X direction by turning the X-axis movement knob 19a, and moves the moving body 16 in the Y direction by turning the Y-axis movement knob 19b.
You can also move it in any direction.

In addition, an electrical equipment box 10 installed below the base 2 has a built-in process counter to be described later, and an electrical equipment part 20 (not shown) below the operation part 2 includes a microcomputer and an NC device to be described later. There is a built-in device to control the measurement unit such as

On the other hand, in the operation unit 2, an operation panel 22 is provided at the front of the table 2, and a monitor CRT 2B and a personal computer 24 are provided at the rear for displaying images captured by the imaging optical device 70. is installed. The operation panel 22 includes a joystick 22a, a keyboard 22b, and the like.

By operating the joystick 22a, the operator can move the moving body [6] in the X direction and the measurement table [3] in the Y direction using the X motor and the Y motor, respectively. In addition, the operator uses the keyboard 22
By operating b, you can select various measurement modes and statistical processing methods for measurement data.
Using the personal computer 24, it is possible to create a measurement program for causing the measuring section 1 to automatically measure the length. The personal computer 24 is equipped with a keyboard 24a, a mouse 24b, a printer 24c, and a CRT 24d of a personal computer as peripheral devices.

2A and 2B are block diagrams showing part of the electrical configuration of the length measuring machine M shown in FIG. 1.

In the figure, the electrical equipment section 20 includes image data D of the object to be measured (object to be imaged) OB imaged by the imaging optical device 170.
Converter 30. Image data D1. which has been converted into a digital quantity by the A/D converter 30. An image memory 40 for storing .
Microcomputer 50. A pulse motor drive circuit 60 is provided to drive the pulse motor 17a. Further, a process counter 90 that receives output signals from the X linear encoder 80a and the Y linear encoder 80b and calculates the relative positional relationship between the table 21 and the imaging optical device 170 is provided in the electrical equipment box 10. An NC device 100 that drives and controls the X motor 110 and Y motor tacho 20 based on signals is connected to this electrical equipment section 20.
It is prepared for.

Further, the microcomputer 50 is composed of a CPU 51 and a memory section 53, and the CPU 51 includes automatic focus control means 510. Comparator 511. Distance calculation means 5121 has functions as image processing means 513 and measurement value calculation means 514. Here, the automatic focus control means 510
Image data D9. stored in the image memory 40. Based on this, the focusing conditions of the imaging optical device 170 are determined, and based on the determined focusing conditions, the pulse motor drive circuit 6
0 to control the pulse motor 17a.

On the other hand, the memory unit 53 includes a threshold value register 530 that stores the threshold value input through the keyboard 24a, and a
Measurement point position memory 531 stores the measurement coordinate values of the series of measurement points (imaging positions) set above; Among the measurement coordinate values of the series of measurement points stored in the measurement point position memory 531,
A register 5 that reads and registers the measurement coordinate values of the measurement point to be imaged and measured at that time from the measurement point position memory 531.
32, and a reference position memory 533 for storing a reference position, which will be described later. Note that the measurement coordinate values stored in the measurement point position memory 531 are values known in advance from CAD data, etc., and even though the position coordinates of each measurement point are specified by the measurement coordinate values, the process counter 9
The reason why the position coordinates of each measurement point are measured using 0 is that after the length measuring machine M moves to the specified measurement point, the value of the actual measurement of the position coordinates of that measurement point is stored in the measurement point position memory 531. This is because the measured coordinate values are shifted by a small distance, for example, several μm to several + μm, from the corresponding measured coordinate values.

Further, the measurement value calculation means 514 is a CRT for monitoring the operation section 2.
2B and printer 24c, and the measurement results are output to the monitor CRT 2B and printer 24C.

Operation of B9 Embodiment FIG. 3 is a flowchart showing the operation of this length measuring machine M.

In step S1, the object to be measured OB is manually placed on the measurement table 13. Here, the object to be measured OB is
For example, there is a pattern for a liquid crystal panel created on a glass substrate, and a mask used for printing the pattern.
Indicates KI.

In the figure, regions R1 to R4 surrounded by four broken lines are
A region where a pattern is formed on the mask MSKI is shown. Four points A, B, C, and D are measurement points for measuring the pattern, and the imaging optical device 170 moves in this order.

On the other hand, the measurement coordinate values of each measurement point A to D on the object to be measured OB are roughly input using the keyboard 24a and stored in the measurement point position memory 531. This operation is performed when the measurement coordinate values of each measurement point are known.
This operation is a preliminary step to controlling the motor tacho 20 to automatically move the movable body 16 and the measurement table 13 in the X direction and the Y direction, respectively. However, since the measurement coordinate values of each measurement point are not necessarily known, in such a case, the operator manually uses the X-axis movement knob Qa, the Y-axis movement knob IQb, and the joystick 22a. The imaging optical device] 70 is relatively moved between a series of measurement points on the object to be measured OB, and the position coordinates of each measurement point are measured. In the following steps, the operation will be explained in the case where the measurement coordinate values of each measurement point are known.

In step S2, at each measurement point, the imaging optical device 1
The operator decides whether or not to perform automatic focusing. Specifically, the personal computer 24 determines whether or not to perform automatic focusing on each measurement point.
Since the inquiry is made using RT 24 d l, the operator must respond with YES or NO information using the key fob 24a.

Here, if the operator answers YES, the length measuring machine M moves to the operation of step S20.

In step S20, at each measurement point, the automatic focus control means 510 automatically focuses the imaging optical device 70, reads image data at each imaging point, and calculates various measurement values.

That is, in step S20, the same operation as in the prior art is performed.

On the other hand, if the operator answers NO, the process moves to step S3.

In step S3, a threshold value having a zero or positive value is input into the threshold value register 530 using the keyboard 24a,
Make me remember. In this case, the operator
By operating a, it is possible to selectively input an appropriate threshold value depending on the situation. Specifically, since the personal computer 24 asks you to specify the threshold value on the CRT 24d of the personal computer, the operator uses the keyboard 24a.
You can specify the desired 0 or positive real value using .

In addition, multiple values can be displayed on the computer's CRT24 using one menu.
d, and one of them may be selected.

In step S4, rough focusing of the imaging optical device 170 is manually performed using the rough adjustment knob 17b.

In step S5, the length measuring machine that has been in standby mode starts measuring. The operator is Kiboto' 24
/IFI to the electrical equipment section 20 using the start key on a.
Enter the start information.

In step S6, upon receiving the information on the start of measurement in step S5, the imaging optical device 170 moves to the measurement point A (FIG. 4) on the object OB to be photographed, which is the first measurement point. This movement is performed by the following process.

First of all, the register 532 stores the measurement point A to be measured first from among the measurement coordinate values of all the measurement points A to D that have been input into the preliminary measurement point position memory 531 by the operator. Read and store the measured coordinate values.

The position data of this measurement point A is referred to as point A (X, Y).

Here, 01 old X and Y. 1 are the X component and Y component of the position coordinates of the measurement point A, respectively. Then, the coordinate values X and Y of the measurement point A are held in the register 532. 1 is converted into mechanical coordinate values by the coordinate conversion means 92, and then converted into the NCi device,
OC].

The NC device 100 receives the mechanical coordinate value from the first stage of coordinate conversion 92 as a LOAD signal of the up/down counter 101, and drives the X motor]]0 and Y motor]20.

As a result, the moving body] 6 starts moving in the X direction, and the measurement table 13 starts moving in the Y direction.

On the other hand, the X linear encoder 80a optically detects the moving distance of the moving body 16. And X linear encoder 8
The signal from 0a is input into the counter 90 after being shaped into a rectangular pulse wave by a waveform shaping circuit 93a in the process counter 90.

Similarly, the Y linear encoder 80b has a measurement table]3
The moving distance is optically detected, and the Y linear encoder 80
The signal from the counter 9 is shaped into a rectangular pulse wave by the waveform shaping circuit 93b in the process counter 90.
It is input to 0.

The output signals of the X linear encoder 80a and the Y linear encoder 80b input to the counter 9 are as follows:
After being multiplied in the counter 9], the signal is input to the amplifier down counter 01 in the NC device 100. Further, by counting the output pulses of these encoders 80a80b, the counter 91 holds the relative position between the imaging optical device 170 and the table 13 as mechanical coordinate values.

The up/down counter 101 decrements when these pulses are input, and when the held value reaches zero, the NC device 100 stops the operation of the X motor 1]0 and the Y motor 120, respectively. let Through the above process, the first measurement point A of the imaging optical device 170 is
Move to or complete.

In step S7, the current position of the imaging optical device 170 is stored as the reference position. That is, the counter 91 stores the mechanical coordinate value (Xl.

Y,) is stored in the reference position memory 5.
33, and the mechanical coordinate values (X, Y,
) as reference position data in this reference position memory 533.
write to.

In step S8, focusing of the imaging optical device 170 at the first measurement point A is automatically performed by the automatic focus control means 510. At this point, the comparator 5]1, which will be described later, is not operating, so the automatic focus control means 510 operates without being controlled by the comparator 5]1. Therefore,
Automatic focus control means 5]-○ analyzes the image data stored in the image memory 40, and controls the object to be measured of the imaging optical device 17θ by the pulse motor 17a via the pulse drive circuit 60 until the in-focus condition is met. Adjust the height from the OB and focus. The above analysis method for detecting the in-focus condition is, for example, disclosed in Japanese Patent Application Laid-Open No. 61-1226.
There is something like that disclosed in Publication No. 17.

In step S9, the focusing condition determined in step S8 is locked, and the automatic focus control means 510 enters a disabled state in which new operations are stopped.

In step S1-0, pattern recognition is performed in a state where focusing has been completed according to the procedure up to step S9, that is, image data on the screen of the CCD camera 18 is read. The image processing means 51 within the CPU 51
3 and the measured value calculation means 514 calculate the measured values according to a previously created program.

- As an example, consider a case where a liquid crystal pattern 620 exists within the field of view 18w (FIG. 6) of the CCD camera 18, and it is to be detected whether the center point 630 of this liquid crystal pattern exists at a position on the table 13. At this time, the position vector 1 from the origin on the table 13 to the center point 610 of the visual field 18W can be detected using the mechanical coordinate values given from the counter 9. Further, a position vector V2 from the center point 610 of the field of view 18W to the center point 630 of the button 620 is calculated by the image processing means 513. Therefore, by finding the sum of these vectors V 1 and (2), it is possible to know the vector V3 from the table origin to the pattern center point 630.

Returning to FIG. 3, in step S11, the imaging optical device 170 is moved to measurement point B, which is the next measurement position. Specifically, this movement is performed by the following process.

The register 532 again reads the measurement coordinate value (X, ¥) of the next measurement point B from the measurement point position memory 531 and holds it, and then sends the measurement point to the NC device 100 as a LOAD signal of the up/down counter 101 of the NC device 100. The measurement coordinate value (XYO2".2) of B is input via the coordinate conversion means 92. Upon receiving this signal, the NC device 100 drives the X motor 110 and Y motor 120, and the imaging optical device 170 performs the measurement. The series of processes up to moving to point B are similar to the process described above in step S6.

In step 31.2, the current position of the imaging optics 170 is stored. That is, the counter 91 holds the mechanical coordinate values (X, Y) of the measurement point B.

In step 313, the distance between the position of the measurement point currently being measured and the reference position is calculated. This operation is achieved by the following process.

That is, the counter 91 calculates the mechanical coordinate values (X, Y2) of the measurement point B held in the counter 91 by the distance calculation means 5.
Transfer to 12. Distance calculation stage 1 5] 2 is counter 9]
The mechanical coordinate values (X, Y2) of measurement point B from , and the reference position data read from the reference position memory 533, that is,
Based on the mechanical coordinate values (x, y) of the first measurement point A, a distance d12 between two points AB is calculated using the following equation.

d2=(X-X)+(Y2-Y,
) In step S14, the distance d obtained in step S14 and the threshold value d are determined. Make a comparison with That is, the comparator 51] reads the threshold value d from the threshold value register 530.

and the value of the output result d of the distance calculation means 5]2 are compared. Here, the threshold value d. is a zero or positive value given by the keyboard 24a, and is selectively given by the operator as described above. Therefore, the operator sets the threshold value d. It is also possible to input a value of zero, or it is also possible to input values corresponding to the length and width dimensions of the measurement table 13. Moreover, instead of selectively inputting the threshold value do using the key fob 24a as described above, the threshold value d having a positive value is used as a predetermined fixed value.

may be stored in the threshold register 530.

Then, when the comparator 511 determines that the distance d between the two points AB is smaller than or equal to the threshold do, the comparator 511 causes the automatic focus control means 510 to set the locked focus condition. Furthermore, a signal is issued to maintain the
The automatic focus control means 510 remains disabled. As a result, automatic focusing is not performed at the current imaging position, and the process moves to the next step 818.

On the other hand, if the comparator 51] determines that the distance d12 between the two points AB is greater than the threshold, the process moves to step S15, and then moves to step 318 via a series of steps S16 and S17.

In step S15, the current position of the imaging optical device 170 is stored as a new reference position. That is, counter 9
1 is the current imaging position held in the counter 91;
That is, the mechanical coordinate values (X, Y) of measurement point B are input into the reference position memory 533. Therefore, the reference position memory 533
Instead of the previous reference position data, that is, the mechanical coordinate values (X, Y) of measurement point A, which were already written in the memory 533, the mechanical coordinate values (X, Y) of measurement point B are written into the reference position memory 533. This means that

Next, in step S16, the automatic focus control means 510 focuses the imaging optical device 170 at the current imaging position.
This is done automatically. That is, the distance d1 between two points AB
The comparator 51 that determines that .degree. is greater than the threshold issues a control signal to the automatic focus control device 510 to unlock the previous focus condition. Upon receiving this signal, the automatic focus control means 5]0 becomes active and automatically focuses the imaging optical device 170. When the focusing of the imaging optical device] 70 is completed, the process moves to step S17, the focusing condition determined by the automatic focus control means 510 is locked, and the automatic focus control means 510 becomes disabled again.
Step S], move to 8.

In step S]8, pattern recognition and Ji calculation of measured values are performed by the same procedure as step s10.

In step S19, it is determined whether the current 7jllj fixed point is the last measurement point. If it is the last measurement point, the measurement ends; if it is not the last measurement point, the process returns to step s11, the imaging optical device 170 moves to the next measurement point C (X, Y3), and then The series of steps S], 2 to S18 are performed again.

Then, the imaging optical position 170 is moved to the last measurement point until the measurement at that measurement point is completed in step 31.
The operations from 1 to S18 continue to be performed.

When the pattern position is detected at each measurement point A to D in this manner, a length measurement result regarding the relative distance of each pattern area (FIG. 4) can be obtained, for example, based on the difference in these positions.

As shown in the operation described above, the imaging optical device 170
Once automatic focusing is performed by the automatic focusing control means 510, within a range that is a distance equal to the threshold value from the imaging position, that is, the 4' diameter centered at the 471 image position or the threshold value. When measuring by relatively moving the imaging optical device [7r] within a range surrounded by a circle equal to , only focusing is performed again. Then, when the imaging optical device 170 is relatively moved to an imaging position outside the range surrounded by the optical imaging device 170, automatic focusing is performed again at that imaging position.

Further, in the same way, only automatic focusing is performed at the imaging positions that belong to a range surrounded by a circle whose radius is equal to the threshold value and whose center is the imaging position where the focusing has been performed again. FIG. 5 illustrates the above operation. In the figure, four points A, B, C, and D indicate imaging positions (measurement points) to which the imaging optical device 170 moves in this order. However, for convenience of illustration, the four points A-D in FIG. 5 have a slightly different positional relationship from the four points A-D in FIG. 4. The imaging position B has a radius d (d
o is a threshold value), and therefore automatic focusing is not performed at the imaging position B. When the imaging optical device 170 relatively moves to the imaging position C, since the imaging position C is outside the circle c1 formed by the imaging position A, automatic focusing is performed at the imaging position C, and the radius around the imaging position C is A range surrounded by circle c2 of do is formed. Similarly, at the imaging position, a range surrounded by a circle c3 of radius d 2 centered on the imaging position is formed.

Note that when the threshold value is set to zero, automatic focusing is performed at all measurement points other than the same position.

C3 Other embodiments Other embodiments will be described below.

In this embodiment, first, the surface 13a of the measurement table 13 is conceptually divided into one or more regions. 7th
The figure is a plan view of the surface 13a of the measurement table 13 divided into regions in this manner, and shows a state in which the surface 13a is divided into m×n regions in a matrix. In the figure, the area located in the 1st row and the jth column is expressed as R3, and in the =J method, the vertical direction is p and the horizontal direction is W. Rules for dividing the surface 13a of the measurement table 3 into regions using the microcomputer 50 include a method for the operator to specify the number of divisions m and n in the X direction and Y direction, and a method for specifying the dimensions of each region R9. There is a method of specifying pj and W.

Further, a mask MS K 2, which is the object to be measured OB, is set on the area-divided measurement table]3.

Therefore, dividing the surfaces 1 and 3a of the measurement table]3 into regions is substantially equivalent to dividing the surface to be measured of the mask MSK2 into regions.

FIG. 8 shows the mask MSK2 shown in FIG. The mask MSK2 includes a region R22.

The entire range of R23, R32 and R33, and region R, RII
12 R13・R21・R24'R31'R34"R41
'R42' Contains a portion of R43 and R44.

Then, the imaging optical device 170 moves from the imaging position A belonging to the region R22 to the imaging position B also belonging to the region R22 above the mask MSK2, and then from the imaging position C belonging to the region R23 in red to the imaging position A belonging to the region R33. Measurements are taken at each position and then the robot moves sequentially.

FIG. 9 is a block diagram showing a portion corresponding to FIG. 2A of the electrical configuration of the length measuring machine M when performing a length measuring operation by performing such area division.

The configuration of FIG. 2B also applies to this embodiment. In the figure, the rule holding register 530a is the keyboard 2
The surface of the measurement table 13 designated by the operator using 4a], 3a is retained as data for dividing a into one or more regions. The area specifying means 512a specifies which area the measurement point belongs to based on the data held in the rule holding register 530a and the position information from the counter 9 (FIG. 2B), and the reference area register 533a specifies which area the measurement point belongs to. , as will be described later, stores information specifying the reference area. On the other hand, comparator 511
a is the area specifying means 512a and the reference area register 533
The outputs of both a are compared, and the autofocus control means 510 is enabled or disabled according to the comparison result. Other components are the same as those in FIG. 2A.

FIG. 10 is a flowchart showing the order of operation in this embodiment.

In step SEA, the object to be measured OB is placed in the measuring chamber 13, as shown in FIG. 8, for example.

Step S2 is the same as step S2 in FIG.

In step S3A, the operator selectively specifies a rule for area division using the keyboard 24a, and inputs the rule into the rule holding register 530a to hold it. Specifically, the personal computer 24 determines whether to divide the area according to the following rules.
The operator will ask the question on RT24 d.
For the area, a rule (for example, the number of divisions m, n) is input by a menu selection method using the keyboard 24a or a numerical input method. The division numbers m and n are usually integers of 2 or more, or may be 1.

If you want to always fix the rule for the area of surface 1.3a of the measurement table 13 when measuring, instead of inputting the rule for the area each time using the keyboard 24a as described above, you can enter the rule in advance. Rule holding register 5 for specific rules
Of course, it is also possible to store it in 30a.

Steps 84 to S6 are steps S4 to S6 in FIG.
It is the same as S6.

In step S7A, it is specified to which of the J regions R, , (i-1 to m, j-1 to n) the current position of the imaging optical device 170 belongs, and a coat representing that region is determined. It is stored as a reference area coat. That is, the area specifying means 512a receives the mechanical coordinate values (X, Y1) of the first measuring point A from the counter 91, and determines in which area the measuring point A falls based on the rule held in the rule holding means 530a. Identify whether it belongs. For example, in the example in Figure 8,
The code of the region R22 to which the imaging position A belongs is written into the reference region register 533a as the code of the reference region.

Step 88~S1. ] are the same as steps 88 to S1 in FIG.

In step 512A, the current position of the imaging optical device 170 and the area to which it belongs are specified by the area specifying means 5]2a as in step S7A, and the result is determined by the comparator 5].
1a.

In step 51.4A, a comparison is made to see if the area identified in step 512A matches the reference area. That is, the comparator 5]1a compares the code of the reference area read from the reference area register 533a with the area code specified at that time by the area specifying means 5]2a.

If the comparator 5 ] 1a determines that the area to which the measurement point belongs matches the reference area, the comparator 51
]a issues a signal to the autofocus control means 5]0 to still maintain the locked focus condition, leaving the autofocus control means 510 in a disabled state. As a result, automatic focusing is not performed at the current measurement point, and step 5
It will move to 18.

Therefore, comparator 5]]a determines whether the measurement point at that time belongs to the area or not! ? If it is determined that the regions do not match, the process moves to step S]5A, and then moves to steps S] and S8 through a series of steps S16 and S]7.

In step 515A, the coat of the area identified in step S1-2A is stored in the base/$ area register 533a as the coat of the new reference area.

Steps 51.6-S20 are the same as steps 316-S20 in FIG.

As understood from the above procedure, the imaging optical device 17
As long as the imaging optical device 1.70 moves within the range of the area belonging to the measurement point previously performed by the automatic focus control means 510, that is, within the reference area, and performs the measurement, the focusing is performed again. There will be no. When the imaging optical device] 7o moves by a measurement point outside the reference area, focusing is performed again at that measurement point, and the area to which this measurement point belongs becomes a new reference area.

For example, in the example shown in FIG. 8, since the area to which measurement point B belongs is the reference area R22, measurement is performed at imaging position B without refocusing. Further, since the imaging position C belongs to the region R23, the measurement is performed after the imaging position C is refocused, and the region R23 becomes the reference region. Similarly, since the imaging position belongs to region R33 and is not the reference region, the imaging position is again focused, and this time it becomes region R33 or the reference region.

Note that when m = n = 1, automatic focusing is performed only for the first measurement point, and automatic focusing is not performed for other measurement points.

D. Modification (1) The first embodiment in which the distance between measurement points is compared with a threshold value and the second embodiment in which the surface to be measured (surface to be imaged) is divided into regions can be combined with each other. It can also be implemented.

For example, (a) the first condition is that the distance between the last focused measurement point and the current measurement point is greater than a threshold, and (1) the last focused measurement point and the current measurement point. When one of (a) and (b) is satisfied, automatic focusing may be performed using the current measurement point. Alternatively, automatic focusing may be performed using the current measurement point only when both conditions (a) and (b) are satisfied at the same time.

(2) When selecting a threshold value in the first embodiment, it may also be possible to input a negative value. However, the quantity to be compared with this threshold is the distance between the measurement points, and the quantity expressing the distance is a positive value or zero. Therefore, if a negative value is used as the threshold value, automatic focusing will be performed at all measurement points, and the threshold value has no particular meaning.

In the second configuration of the present invention, the threshold value corresponds to "zero or a positive value".

(3) When the relative movement between the imaging optical device and the object to be imaged is performed at a substantially constant speed, the relative movement time may be counted and the counted value may be used as the mutual distance between the measurement points. . "Distance" in the first and second configurations of the present invention is a term that also includes a physical quantity proportional to distance.

(4) If the measurement coordinate values at each measurement point are known, compare the distance between the measurement points with a threshold value or compare the area to which the measurement point belongs with the reference area before or after moving the imaging optical device. You can also do it inside.

(5) The imaging system of the present invention can be used not only in a length measuring machine but also in a device that requires imaging at a plurality of measurement points, such as an automatic pattern inspection device for printed circuit boards.

〔Effect of the invention〕

As explained above, according to the invention of claim], once the focusing of the imaging optical device is automatically performed by the automatic focus control means, the imaging optical device is automatically focused from the imaging position where the focusing was performed. When the relative movement distance is smaller than the predetermined threshold value, automatic focusing of the imaging optical device by the automatic focusing control means is not performed again, thereby reducing the time required to complete all measurements. It has the effect of being able to do something.

Further, according to the invention of claim 2, since the threshold value can be appropriately selected by the operation input means depending on the planar accuracy of the object to be imaged, etc., efficient imaging corresponding to the object to be imaged can be achieved. This has the effect of shortening the time required to complete all measurements.

Furthermore, according to the third aspect of the invention, since automatic focusing is not repeated at imaging positions within the same area, the time required to complete all measurements can be shortened.

Furthermore, according to the fourth aspect of the invention, since the rules can be changed in various ways for each area, the same effect as the apparatus according to the second aspect can be obtained.

In addition, when this invention is used in a length measuring machine, it is possible not only to maintain focusing accuracy (closely related to measurement accuracy) and shorten measurement time, but also to reduce the threshold value. Depending on how it is taken, it is possible to use it differently, giving priority to accuracy or giving priority to time.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a 7111 long aircraft to which an embodiment of the second invention is applied, and Figs. 2A and 2B are electrical configurations of a j-long aircraft to which an embodiment of the second invention is applied. FIG. 3 is a flowchart showing the procedure of an embodiment of the present invention; FIG. 4 is a plan view showing an example of the object to be measured; FIG. An explanatory diagram showing the operation of the example; Fig. 6 is a plan view showing the screen of the object to be measured displayed on the monitor; Fig. 7 is a plan view of the measurement table divided into multiple regions; Fig. 8 is a plan view of the object to be measured, FIG. 9 is a block diagram showing part of the electrical configuration of a length measuring machine to which another embodiment of the present invention is applied, and FIG. 10 is another embodiment of the present invention. A flowchart showing an example procedure. FIG. 11 is a conceptual diagram showing a measuring method using a conventional length measuring machine. M...-length measuring machine, 170...imaging optical device, 51,0...automatic focus control means, OB...object to be measured (object to be imaged), 512...distance calculation means, 530... Threshold register, 24a...Keyboard, 511, . 511a... Comparator, 512a... Area specifying means, 530a... Rule holding FIG.

Claims (4)

[Claims] (1) Imaging that sequentially detects images of the object at each of a series of imaging positions set on the object while moving the object and the imaging optical device relatively and intermittently. A system comprising: (a) automatic focus control means coupled to the imaging optical device to automatically focus the imaging optical device on the imaged object; and (b) each of the series of imaging positions. (c) a positive value; and (c) a positive value. selective activation for activating the autofocus control means at the imaging position when the distance is greater than a predetermined threshold value having a value of An imaging system comprising: means for converting. (2) Imaging that sequentially detects images of the object at each of a series of imaging positions set on the object while moving the object and the imaging optical device relatively and intermittently. A system comprising: (a) automatic focus control means coupled to the imaging optical device to automatically focus the imaging optical device on the imaged object; and (b) having a value of zero or a positive value. (c) for each of the series of imaging positions, a position where focusing was last performed by the automatic focus control means among the imaging positions before the imaging position; and (d) activating the automatic focus control means at the imaging position when the distance is greater than the threshold, and the distance is smaller than the threshold. and selective activation means for disabling the automatic focus control means at the imaging position. (3) Imaging that sequentially detects images of the object at each of a series of imaging positions set on the object while moving the object and the imaging optical device relatively and intermittently. A system comprising: (a) automatic focus control means coupled to the imaging optical device to automatically focus the imaging optical device on the object to be imaged; (b) an image of the object to be imaged; (c) for each of the series of imaging positions, the automatic focusing means among the imaging positions before the imaging position; 2. The position where focusing was last performed by the control means and the relevant position.
(d) determining whether the areas to which the two positions determined by the area specifying means belong are the same area; selective activation means for determining and disabling the automatic focus control means when the two positions belong to the same area and activating the automatic focus control apparatus when the two positions do not belong to the same area; An imaging system comprising: (4) Imaging that sequentially detects images of the object at each of a series of imaging positions set on the object while moving the object and the imaging optical device relatively and intermittently. A system comprising: (a) automatic focus control means coupled to the imaging optical device to automatically focus the imaging optical device on the object to be imaged; (b) an image of the object to be imaged; (c) for each of the series of imaging positions, an operation input means for selectively inputting a rule for dividing the surface into one or more regions as data; 2 of which are the last position where focusing was performed by the automatic focus control means and the said position.
(d) determining whether the areas to which the two positions determined by the area specifying means belong are the same area; , selective activation means for disabling the automatic focus control device when the two positions belong to the same area and activating the automatic focus control device when the two positions do not belong to the same area. An imaging system characterized by: