JPH10332340A - Length measuring method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure length for a long period by measuring an article to be measured after it is automatically set up in a high contrast state. SOLUTION: An image taken in by an image taking up means 7 in a state of an object W to be measured loaded on a measuring base 1 with the variation of the supply voltage Vs1 of a transmitted illumination part 13 is stored in an image memory part 51, and a computing section 53 obtains a high contrast image out of the image group. After supply voltage Vs1 corresponding to the above image is supplied to the transmitted illumination part 13 to set up it into the high contrast conditions, the measurement is carrier out. Since setting up in the high contrast state, when the image of the object W to be measured is taken in, the image excellent in a contrast ratio can be obtained, and the deterioration of the transmitted illumination part 13 can be absorbed, thereby improving the measurement accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an original plate for producing a printed circuit board, an original plate for producing a glass mask for printing a predetermined pattern on a liquid crystal display device, a semiconductor wafer, or the like, and a printed material requiring high precision. The present invention relates to a method and apparatus for measuring the size and coordinates of figures such as figures, and more particularly, to a technique for measuring a length of an object to be measured while the object is illuminated by illumination means.

[0002]

2. Description of the Related Art As a conventional length measuring method of this type, for example, an object to be measured is placed on a measuring table, illuminated by an illumination unit, and an image capturing unit arranged above the moving unit is moved. , And a length measurement method for measuring the coordinates and dimensions of a specific location on the measured object based on the coordinates of the field of view of the image capturing unit.

[0003] The setting of the illuminating section performed before the measurement is performed, for example, by moving the image capturing section to a specific location on the measured object where the operator wants to measure coordinates, dimensions, and the like. Adjust the illumination adjustment volume manually while observing. This is performed by fixing the illumination adjustment volume in a state in which the image is considered to be the clearest.

When the start of measurement is instructed after the setting of the illumination unit as described above, the image reading unit is moved to a preset location by the moving mechanism and is illuminated by the illumination unit so as to be clear. The length measurement is performed while displaying the image of the measured object on the CRT.

[0005]

However, such a conventional method has the following problems. That is, in the state where the illumination unit is set in advance as described above, the object to be measured is captured by the image capturing unit in a clear state, so that it is possible to perform the measurement with high accuracy, while the cause of the change over time or the like is possible. Therefore, when the luminous intensity of the illumination unit fluctuates, the image of the object to be measured becomes unclear, so that there is a problem that accurate measurement cannot be performed over a long period of time.

In addition, the adjustment of the illuminating section that becomes clear depends on the pattern formed on the object to be measured, and therefore generally differs for each object to be measured. Therefore, a lighting adjustment volume that is clear for each DUT is set / adjusted and marked for each DUT. When measuring a different DUT, the illumination adjustment volume is adjusted to the corresponding position. It is necessary to adjust the volume, and the work becomes complicated. In addition, even if such a complicated operation is performed, a setting error by the operator may occur, and the above-described variation factor of the illumination unit cannot be absorbed, so that accurate measurement cannot be performed.

[0007] The present invention has been made in view of such circumstances, and by performing measurement after automatically setting a condition under which an object to be measured has a high contrast, measurement can be accurately performed over a long period of time. An object of the present invention is to provide a length measuring method and an apparatus thereof that can be performed.

[0008]

The present invention has the following configuration in order to achieve the above object. That is, in the length measuring method according to claim 1, the measuring table on which the object to be measured is mounted and the image capturing means for capturing an image of the object to be measured are relatively moved by the moving means in a plane parallel to the measuring table. In the length measurement method for measuring the length and coordinates of the specific portion of the object to be measured illuminated by the illumination means,
(A) changing the supply voltage of the illumination means while the object to be measured is placed on the measurement table, and capturing an image of the object to be measured for each supply voltage; and (b) the object to be measured. And (c) supplying the supply voltage corresponding to the high-contrast image to the illuminating unit, and then measuring the object to be measured. It is a feature.

According to a second aspect of the present invention, in the length measuring method, the measuring table on which the object to be measured is mounted and the image capturing means for capturing an image of the object to be measured are moved in a plane parallel to the measuring table. In the length measurement method for measuring the length and coordinates of a specific portion of the object to be measured illuminated by illumination means, wherein (a) the image of the object to be measured is placed on the measuring table. Varying the gain of the capturing means, capturing an image of the device under test for each gain;
(B) obtaining the image with the highest contrast from the images of the object to be measured as a high-contrast image;
(C) The object to be measured is measured after adjusting the image capturing means to a gain corresponding to the high contrast image.

According to a third aspect of the present invention, in the length measuring apparatus, the measuring table on which the object to be measured is mounted and the image capturing means for capturing an image of the object to be measured are moved in a plane parallel to the measuring table. In a length measuring device for measuring relative length and coordinates of a specific portion of the object to be measured illuminated by an illuminating unit, the supply of the illuminating unit is performed while the object to be measured is mounted on the measuring table. An image storage unit that stores an image for each supply voltage captured by the image capturing unit while varying a voltage; and an arithmetic unit that obtains, as a high-contrast image, the image with the highest contrast among the images of the device under test. Along with supplying a supply voltage corresponding to the high contrast image to the illumination means,
The measurement of the object to be measured is performed.

According to a fourth aspect of the present invention, there is provided the length measuring apparatus according to the third aspect, wherein the calculating means is configured to determine each pixel value of the image for each supply voltage and the vicinity of each pixel value. A high-contrast image is obtained from a contrast ratio based on a difference from a pixel value of a part.

According to a fifth aspect of the present invention, in the length measuring apparatus, the measuring table on which the object to be measured is mounted and the image capturing means for capturing an image of the object to be measured are moved in a plane parallel to the measuring table. In a length measuring device for relative movement by measuring the length and coordinates of a specific portion of the object illuminated by the illuminating means, in a state where the object to be measured is placed on the measuring table, the image capturing means Image storage means for storing an image for each gain captured by the image capturing means while varying the gain, and arithmetic means for obtaining the highest contrast image from among the images of the device under test as a high contrast image. After adjusting the image capturing means with a gain corresponding to the high-contrast image, the measurement of the object to be measured is performed.

According to a sixth aspect of the present invention, in the length measuring apparatus according to the fifth aspect, the calculating means comprises: an individual pixel value of an image for each gain; and a peripheral portion of the individual pixel value. A high-contrast image is obtained from a contrast ratio based on the difference between the pixel value and the pixel value.

[0014]

The operation of the method according to the first aspect is as follows. The image capturing means and the measuring table are relatively moved by the moving means, and the image capturing means is positioned at a specific location of the object to be measured illuminated by the illuminating means. Then, the illumination voltage on the DUT is varied by varying the supply voltage of the illumination means,
An image of the device under test is captured by the image capturing means for each supply voltage (step (a)). Next, an image having the highest contrast among the captured images is determined as a high-contrast image (step (b)), and a supply voltage corresponding to the high-contrast image is supplied to the illumination means (step (c)). Then, the image of the object to be measured captured by the image capturing means can be made such that the pattern on the object to be measured can be very clearly identified. Since the optimum supply voltage of the lighting means is automatically set based on the contrast of the image taken in this way, there is no variation or erroneous setting as in the manual setting based on the operator's observation, and it is caused by the temporal change of the lighting means. Fluctuations can also be absorbed.

The operation of the method according to the present invention is as follows. The image capturing means and the measuring table are relatively moved by the moving means, and the image capturing means is positioned at a specific location of the object to be measured illuminated by the illuminating means. Then, the apparent illuminance on the DUT is changed by varying the gain of the image capturing means, and an image of the DUT is captured for each gain by the image capturing means (step (a)). Next, an image having the highest contrast among the captured images is determined as a high-contrast image (step (b)), and the image capturing means is adjusted with a gain corresponding to the high-contrast image (step (c)). Then
The image of the object to be measured captured by the image capturing means can be formed so that the pattern on the object to be measured can be very clearly identified. Since the optimum gain of the image capturing means is automatically set based on the contrast of the captured image in this way, there is no variation or erroneous setting as in the manual setting of the lighting means based on the operator's observation, and the time generated in the lighting means does not change. Variations due to changes can also be absorbed.

The operation of the device invention according to claim 3 is as follows. The image capturing means and the measuring table are relatively moved by the moving means, and the image capturing means is positioned at a specific location of the object to be measured illuminated by the illuminating means. Then, the illuminance on the object to be measured is varied by varying the supply voltage of the illumination means, and an image of the object to be measured is captured by the image capturing means for each supply voltage and stored in the storage means. next,
The image with the highest contrast among the captured images is obtained as a high-contrast image by the calculation means, and a supply voltage corresponding to the high-contrast image is supplied to the illumination means before measurement. Since the optimum supply voltage of the lighting means is automatically set based on the contrast of the image taken in this way, there is no variation or erroneous setting as in the manual setting based on the operator's observation, and it is caused by the temporal change of the lighting means. Fluctuations can also be absorbed.

Further, according to the present invention, each pixel value of an image photographed while varying the supply voltage of the illuminating means and a pixel value located in the periphery of each pixel value are obtained. Since the difference changes depending on the illuminance on the object to be measured, the shape of the pattern, the material, and the like, the calculation means can obtain a high contrast image by obtaining a contrast ratio based on the difference.

The operation of the device invention according to claim 5 is as follows. The image capturing means and the measuring table are relatively moved by the moving means, and the image capturing means is positioned at a specific location of the object to be measured illuminated by the illuminating means. Then, the apparent illuminance on the DUT is changed by changing the gain of the image capturing means, and the image of the DUT is captured by the image capturing means for each gain and stored in the storage means. Next, among the captured images, the one having the highest contrast is obtained as a high-contrast image by the calculating means, and the measurement is performed after adjusting the image capturing means with a gain corresponding to the high-contrast image. Since the optimum gain of the image capturing means is automatically set based on the contrast of the captured image in this way, there is no variation or erroneous setting as in the manual setting of the lighting means based on the observation of the operator, which may occur in the lighting means. Variations due to aging can also be absorbed.

According to the apparatus described in claim 6, the individual pixel values of an image photographed while varying the gain of the image capturing means and the pixel values located around the individual pixel values. Since the difference changes depending on the apparent illuminance on the object to be measured, the shape of the pattern, the material, and the like, the calculation means can obtain a high contrast image by obtaining a contrast ratio based on the difference.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 is an external perspective view showing a schematic configuration of a length measuring apparatus according to an embodiment, and FIG. 2 is a block diagram thereof. In the following description, an original plate or a printed material for producing a printed wiring board is simply referred to as an object to be measured.

A measurement table 1 formed of a light-transmitting material such as glass and having a plate-like shape on which an object to be measured W is placed has an operation panel 3 including various switches for operating the apparatus. It is arranged on the upper surface of the body 5 in a horizontal posture. Above the measuring table 1, an image capturing means 7 is attached via an X-direction drive base 9, and the image capturing means 7 can be moved in the X direction on the upper part. The X-direction drive gantry 9 is moved in the Y-direction by the Y-direction drive unit 11 built in the upper part of the apparatus housing 5 together with the image capturing means 7. The driving unit 11 moves the image capturing unit 7 in an XY plane parallel to the measuring table 1. The X-direction drive base 9 and the Y-direction drive unit 11
Correspond to the moving means of the present invention.

Below the measuring table 1, as shown in FIG.
A transmission illumination unit 13 having a reflection mirror 13a is provided at a position facing the image capturing unit 7. The transmission lamp 13 has a halogen lamp 1 via an optical fiber 15.
Light from the light source 9 is guided to illuminate the object W from below while moving in a state of always facing the image capturing means 7. The supply voltage Vs1 for adjusting the luminous intensity of the halogen lamp 19 is controlled by a control unit 39 described later.
Is supplied from a lamp power supply 21 controlled by the

It should be noted that, as in the above configuration, the transmission illumination unit 13
Thus, instead of illuminating only the area immediately below the image capturing means 7, illumination such as a fluorescent lamp may be provided on the entire lower surface of the measuring table 1 to illuminate the entire area.

The image capturing means 7 is provided with a ring-shaped reflection illuminating section 25 below the lens barrel section 23 having a built-in autofocus mechanism including an objective lens. The light from the halogen lamp 29 is led out to the reflection illumination unit 25 through the optical fiber 27, and illuminates the object W from above and around the lens barrel 23. A supply voltage Vs2 is supplied to the halogen lamp 29 from a lamp power supply 31 controlled by a control unit 39 described later, and the luminous intensity is adjusted.

Note that the above-described transmission illumination section 13 and reflection illumination section 25 correspond to illumination means in the present invention. Further, in addition to the above-described illuminations, the object W is disposed coaxially with an optical system built in the lens barrel 23 of the image capturing means 7.
May be provided with a coaxial epi-illumination unit that illuminates from above.

A CCD camera 33 is provided above the lens barrel 23.
Has been deployed. The gain of the CCD camera 33 is controlled by a gain signal G output from a camera control unit 35, and the image capturing unit 37
To output an image signal. The captured image signal is subjected to appropriate processing by the control unit 39 via the bus, and the CRT 4 mounted above the measurement table 1
1 and an image of the object W to be measured (in-field image) within the field of view of the image capturing means 7 is projected.

The image capturing means 7 is driven in each of the X / Y directions by the two X / Y axis servo motors 43a controlled by the servo motor controller 43 and the X direction drive base 9 and the Y direction drive unit 11 described above. It is supposed to be. The moving distance corresponding to the rotation amount of the X / Y axis servo motor 43a is detected by the encoder 45 and read by the X / Y coordinate reading unit 47 as the XY coordinates on the measuring table 1.

As will be described in detail later, in the "high contrast condition measurement process" performed prior to the "length measurement process", the supply voltage Vs1 to the halogen lamp 19 and / or the supply voltage Vs2 to the halogen lamp 29 are changed. The image (in-field image) of the device under test W is captured by the image capturing unit 7 and the image capturing unit 37 while being associated with each of the supply voltages Vs1 and Vs2.
(Image storage means). The calculation unit 53 corresponding to the calculation means of the present invention has a function of obtaining an image with the highest contrast as a high-contrast image from the in-view images stored in the image storage unit 51. The supply voltages Vs1 and Vs2 corresponding to the high-contrast image obtained by the calculation unit 53 in this manner are supplied in association with a measurement program stored in a memory (not shown) incorporated in the control unit 39 as necessary. It is stored in the voltage storage unit 55.

Next, the "high contrast condition measuring process" performed by the length measuring device having the above configuration prior to the "length measuring process" will be described with reference to FIGS. FIG. 3 is a flowchart showing “high-contrast condition measurement processing”, and FIG. 4 is a flowchart showing “high-contrast image calculation processing”.
FIG. 6 and FIG. 6 are schematic diagrams used to explain a region of interest and a pixel of interest.

Step S1 (setting the object to be measured) The operator places the object to be measured W to be subjected to the length measurement process on the upper surface of the measuring table 1. The measurement object W may be the measurement object W to be actually measured, or may be the same material and have the same pattern or the like. At the time of this measurement, the camera control unit 35
Is maintained constant.

Step S2 (movement of the image capturing means) The entire surface of the apparatus housing 5 is arranged so that a specific portion on the DUT placed on the measuring table 1 is located within the field of view of the image capturing means 7. By operating the operation panel 3 provided, the image capturing means 7 is moved.

Step S3 (Set Supply Voltage to Initial Value) The controller 39 outputs a control signal to the lamp power supply 21 to set the supply voltage Vs1 to the halogen lamp 19 to the initial value. Therefore, the illuminance on the object W is relatively low. In this case, the lamp power supply 3
1 is instructed to stop the power supply to the halogen lamp 29, and first, the illumination is performed only by the transmission illumination unit 13.

Step S4 (capturing the image of the object to be measured) The image in the field of view on the object W to be measured is referred to as an "in-field image" through the image capturing means 7 and the image capturing section 37.
And stored in the image storage unit 51 in association with the supply voltage Vs1.

Step S5 (supply voltage = maximum value) The current supply voltage Vs1 is compared with the maximum value that can be supplied by the lamp power supply 21, and the process branches depending on whether they match. Here, it is determined that the value is less than the maximum value (No), and the process branches to step S6.

Step S6 (increase the supply voltage) The supply voltage Vs of the lamp power supply 21 set to the initial value
Increment 1 by a predetermined step. As a result, the luminous intensity of the halogen lamp 19 increases, and the illuminance on the workpiece W increases according to the predetermined number of steps. Note that the predetermined step may be set appropriately in accordance with the specification of the lamp power supply 21 while taking into account the adjustment level at the time of actual measurement.

After the supply voltage Vs1 of the lamp power supply 21 is increased by a predetermined step in this manner, the supply voltage Vs1 is increased.
Steps S4 through S until the value reaches the maximum value.
Step 6 is repeated. Thus, the image storage unit 51 stores a plurality of sets of one in-field image corresponding to one supply voltage Vs1. Steps S4 to S6 described above correspond to the process (a) of the present invention.

In the above description, the image in the visual field is stored for each supply voltage Vs1 while varying the supply voltage Vs1 to the transmission illumination unit 13, but subsequently, only the reflection illumination unit 25 is supplied as described above. The in-field image is stored for each supply voltage Vs2 while varying the supply voltage Vs2, and the transmission illumination unit 13 and the reflection illumination unit 25 are combined to supply the supply voltage Vs2.
The image in the visual field is stored for each combination of the supply voltages Vs1 and Vs2 while varying the values of Vs1 and Vs2. That is, a plurality of sets of one in-view image corresponding to one supply voltage Vs1 are stored in the image storage unit 51 and stored as a first in-view image group, and one view corresponding to one supply voltage Vs2 is stored. A plurality of sets of internal images are stored and stored as a second in-field image group, and a plurality of sets of one in-field image corresponding to a combination of two supply voltages Vs1 and Vs2 are stored as a third in-field image group. Is stored. Therefore, the image storage unit 51 stores three types of in-view image groups.

Step S7 (Calculation of High Contrast Image) From the plurality of in-field images stored in the image storage unit 51 as described above, the calculation unit 53 obtains the image with the highest contrast. The following steps T1 to T5, which are specific processes of step S7, correspond to the process (b) of the present invention.

Referring to the flowchart of FIG. In addition,
In the following description, only the first in-view image group, which is the in-view image captured for each supply voltage Vs1, will be described. However, other second / third in-view image groups are similarly processed. You. In other words, the processing described below is performed on all three types of in-view image groups.

Step T1 (Calculation of Luminance Difference Data) First, a target area is set for one in-field image corresponding to one supply voltage Vs1, and a pixel located at the center thereof is set as a target pixel. The luminance difference data is calculated based on the pixel value and the pixel value of the pixel adjacent thereto.

For example, as shown in FIG.
Assuming that V is composed of a square pixel group (for example, 512 × 512 pixels), the upper left pixel is defined as a pixel P (1,
1), a pixel adjacent to the right is referred to as a pixel P (2, 1), a right end pixel is referred to as a pixel P (i, 1), and a lower right pixel is referred to as a pixel P (i, j). I do. In such an in-view image FV, for example, first, a rectangular pixel group composed of an odd number of pixel groups located near the upper left (in this example,
A region of 3 × 3 pixels) is set as a region of interest R, and a pixel P (2, 2) located at the center of the region is focused on, and this is set as a pixel of interest NP (indicated by hatching in the figure). In the case of this example, the target pixel NP can be adopted only in a region formed by a group of pixels that are two pixels inside from the outermost periphery of the in-field image FV (the rectangular region indicated by a dotted line in FIG. 5). (In).

For convenience of explanation, each pixel located in the region of interest R is denoted by a symbol as shown in FIG. That is, the target pixel NP (= pixel P) located at the center of the target region R
(2, 2)) is P0, and the pixel P adjacent to the right
(= P (3,2)) is set to P1, and P2 to P8 are set counterclockwise around the target pixel NP.

When each pixel in the region of interest R is given a code, the luminance difference data DV can be calculated as follows. Luminance difference data DV (i, j) = MAX | Pk-P0
However, in this example, k = 1 to 8, i = 2 to 511,
j = 2 to 511.

Note that the luminance difference data DV corresponds to the pixel of interest NP in the region of interest R set in the in-view image FV.
= P0 and the pixels P1 adjacent to the pixel value
The absolute value of the difference from the pixel value of .about.P8 is taken, and the absolute value of the difference is the maximum value, indicating the contrast in the focused area R.

The above-mentioned luminance difference data DV is obtained by setting one region of interest R in one in-field image FV as described above, and all the pixels within the above-mentioned rectangular dotted line (see FIG. 5) are obtained. Is obtained while switching the region of interest R such that the target pixel NP becomes the pixel of interest NP.

Step T2 (Calculation of Contrast Data) After calculating the luminance difference data DV for one in-field image FV, the contrast data CV representing the contrast of one in-field image FV is obtained from the luminance difference data DV.
Ask for.

Specifically, it was determined as described above.
The sum of the luminance difference data DV (i, j) of each region of interest R set in one in-field-of-view image FV is calculated by the following equation. Contrast data CV = SUM (DV (i, j))

Incidentally, in this example, since the in-view image FV is composed of 512 × 512 pixels, 26,010 luminance difference data DV are obtained for one in-view image FV. Will be calculated.

By determining the sum of the luminance difference data DV of each region of interest R set in one in-field image FV in this way, it is possible to determine the contrast of the in-field image FV.

Step T3 (processing end determination) As described above, the contrast data CV is calculated for one in-field image FV, and the processing branches depending on whether or not the processing has been completed for all the in-field images FV.
That is, until the contrast data CV is obtained for all the in-field images FV of the first, second, and third in-field images, the processing target is set to the next in-field image via step T4, and steps T1 and on are repeatedly executed. I do.

Step T5 (Determination of High Contrast Image) All the in-view images F of the first, second, and third in-view image groups
Based on the contrast data CV relating to V, an in-view image FV having the highest contrast is obtained.

More specifically, all the contrast data C
The largest one among V is obtained, and the in-view image FV corresponding to the contrast data CV is set as a high contrast image. This high-contrast image is the one in which the contrast data CV is the largest, the contrast of the in-field image FV is the largest, and the pattern on the workpiece W is the clearest.

When there are a plurality of maximum contrast data CV, the corresponding supply voltages Vs1, Vs2
Is selected, the power saving and halogen lamp 19,
It is preferable to extend the life of 29.

As described above, a small region of interest R is set in the in-view image FV, and the contrast is determined based on the contrast data, which is the sum of the luminance difference data obtained for the entire region in the in-view image FV while switching the small region. Is determined, an appropriate image can be determined as a high-contrast image even if the pattern in the in-view image FV is biased. Further, it is possible to prevent the inconsistency in which the contrast criterion fluctuates due to, for example, the shape of a pattern that differs depending on the image capturing position (specific portion) on the workpiece W.

After converting the in-field image FV having the maximum contrast into a high-contrast image as described above, FIG.
The process returns to step S8.

Step S8 (Storing Corresponding Supply Voltage) The supply voltage Vs1 or the supply voltage Vs2 corresponding to the high-contrast image or a combination of these supply voltages Vs1 and Vs2 is stored in the supply voltage storage unit 55. here,
It is assumed that the high-contrast image is the supply voltage Vs1 that defines the illumination of the transmission illumination unit 13, and this is stored in the supply voltage storage unit 55. When storing, it is preferable to associate the measurement program with the measurement program for the object to be measured W so that the above condition is read out only by selecting the measurement program in the “length measurement processing”.

Next, the "length measurement process" performed after the "high contrast condition measurement process" is completed will be described with reference to the flowchart of FIG.

Since this "length measurement process" is performed under the high contrast condition determined by the above process,
In order to prevent the halogen lamps 19 and 29 from deteriorating and deviating from the conditions, it is preferable to shorten the elapsed time from the execution point of the “high contrast condition measurement process”. That is, it is preferable to perform the above processing immediately before the “length measurement processing”. On the other hand, when it is not possible to carry out immediately before, for example, the halogen lamp 1
The lighting times of 9, 29 may be counted, and the above processing may be performed again when a certain time has elapsed.

Step S10 (Instruction) The operator operates the operation panel 3 to set a measurement program for automatic measurement including a preset measurement location on the DUT W and the high contrast condition measured by the above processing. Instruct. Here, the supply voltage Vs1 stored in the above-described processing is read out instructed by the operator. When a high-contrast condition is associated with the specified measurement program, the high-contrast condition is automatically read from the supply voltage storage unit 55 together with an instruction from the operator.

Step S11 (set to high contrast condition) The above-described high contrast condition (here, the supply voltage Vs
1) is output from the control unit 39 to the lamp power supply 21, and the lamp power supply 21 turns on the halogen lamp 19 under the conditions. The lamp power supply 21 outputs a status signal to the control unit 39. The status signal includes completion indicating that the setting has been completed and impossibility indicating that the setting cannot be performed.

Step S12 (cannot be set?) If the status signal output from the lamp power supply 21 to the control unit 39 cannot be set or if no status signal is output, the halogen lamp 19 or the lamp power 21
Then, it is determined that some inconvenience has occurred, and the process proceeds to step S13. Then, information indicating this is output to the monitor 41 and the apparatus is stopped. Therefore, it is possible to prevent the measurement from being performed continuously even though the high contrast condition has not been set.

Step S14 (measurement processing) When it is determined that the setting in step S12 has been normally performed, the measurement processing is performed according to the measurement program. At this time, since the contrast of the illumination of the object to be measured W by the transmission illumination unit 13 is the maximum, the pattern in the field of view captured by the image capturing unit 7 is extremely clear. The measurement of coordinates and dimensions can be performed with high accuracy.

Moreover, since the measurement is performed under the high-contrast conditions determined by the “high-contrast-condition measurement process” performed immediately before the “length-measurement process”, the measurement is performed for a long time without being adversely affected by deterioration of illumination or the like. Measurement can be performed with high accuracy over a wide range.

Steps S11 to S14 described above correspond to step (c) in the present invention.

<Second Embodiment> In the first embodiment, the "supply voltage of the illumination means of the transmissive illumination unit 13 and the reflection illumination unit 25 is controlled while the gain of the image capturing unit 7 is kept constant." The contrast is adjusted by directly changing the illuminance on the object to be measured W by "variable". However, in the second embodiment, the image capturing means 7 is controlled while the "supply voltage of the illumination means is kept constant". The contrast is adjusted by changing the apparent illuminance of the device under test W by changing the gain.

The apparatus according to the second embodiment is shown in FIG.
The supply voltage storage unit 5 is the same as that of the first embodiment shown in FIG. 2 and has a block diagram in the configuration of the first embodiment shown in FIG.
5 in that a gain storage unit 61 (dotted line in the figure) is provided in place of 5.

First, the "high contrast condition measuring process" will be described with reference to the flowchart of FIG.
Only the steps different from the same processing in the above-described <first embodiment> (portions shown in bold in FIG. 8) will be described, and detailed description of the other steps will be omitted.

Step S22 (gain is set to an initial value) The controller 39 sends a CC signal to the camera controller 35.
An instruction is given to set the gain of the D camera 33 to an initial value. Specifically, the camera control unit 35 receiving the instruction outputs the gain signal G set to the initial value to the CCD camera 33. Then, the image of the device under test W is captured by the image capturing unit 7 and stored in the image storage unit 51 (step S23).

Step S24 (gain = maximum value?) The controller 39 branches the processing depending on whether or not the gain of the CCD camera 33 is the maximum value. That is, when the maximum value has been reached, the above-described “high contrast image calculation processing” is performed (step S26), and when the maximum value has not been reached, the gain signal G is increased by a predetermined step (step S25). .

The above steps S23 to S25
Is repeatedly executed, the image storage unit 51 stores
An in-field image for each gain signal G is stored. Steps S23 to S25 correspond to the process (a) in the present invention.

Step S27 (Storing the Corresponding Gain) The gain signal G corresponding to the high-contrast image determined by the above-described “high-contrast image calculating process” is stored in the gain storage unit 61. Note that it is preferable to store the program in association with the measurement program for the reason described above.

After the above processing, the above-mentioned “length measurement processing”
(See FIG. 7). In this case, the high contrast condition is the gain signal G in step S11. At this time, since the gain of the image capturing means 7 is set to a high contrast condition, the captured image in the visual field has a very clear pattern and the like on the workpiece W, and the coordinates and dimensions can be measured with high precision. Can be done with

It is needless to say that the same effect as in the above-described <first embodiment> can be obtained even when the gain of the image capturing means 7 is changed to a high contrast condition instead of changing the illumination means.

In the first and second embodiments described above, the image capturing means 7 is moved, but the measuring table 1 may be moved while the image capturing means 7 is fixed.

[0075]

As is apparent from the above description, according to the method of the present invention, the illumination means is supplied so that the image of the object to be measured has a high contrast based on the contrast of the captured image. Since the voltage is automatically set to an optimum value, there is no variation or erroneous setting as in the manual setting based on the operator's observation, and it is possible to absorb the fluctuation due to the aging of the lighting means. Therefore, it is possible to prevent inconveniences such as a decrease in measurement accuracy due to an operator's setting error or deterioration of the illumination means, and it is possible to easily manage illuminance, which has a large effect on measurement accuracy, and to perform accurate measurement over a long period of time. .

According to the second aspect of the present invention, the gain of the image capturing means is automatically set to an optimum value so that the image of the object to be measured has a high contrast. There is no variation or erroneous setting as in the manual setting of the illuminating means, and the fluctuation caused by the aging of the illuminating means can be absorbed. Therefore, the same effect as the method of the first aspect can be obtained.

According to the third aspect of the present invention, the method of the first aspect can be suitably implemented.

According to the apparatus of the fourth aspect, a high-contrast image is determined based on the pixel value of the image captured by the image capturing means. It is possible to perform a practical calculation including the influence of the optical system of the image capturing means as compared with the method based on the above. Therefore, a high-contrast image can be obtained with high accuracy.

According to the apparatus described in claim 5, the method described in claim 2 can be suitably implemented.

Further, according to the device invention of the sixth aspect, the same effect as that of the device invention of the fourth aspect can be obtained.

[Brief description of the drawings]

FIG. 1 is an external perspective view illustrating a schematic configuration of a length measuring device according to a first embodiment.

FIG. 2 is a block diagram showing a schematic configuration.

FIG. 3 is a flowchart showing “high contrast condition measurement processing”.

FIG. 4 is a flowchart illustrating “high contrast image calculation processing”.

FIG. 5 is a diagram provided to explain an in-view image and a region of interest.

FIG. 6 is a diagram provided for explaining a region of interest.

FIG. 7 is a flowchart showing “length measurement processing”.

FIG. 8 is a flowchart illustrating “high contrast condition measurement processing” according to the second embodiment.

[Explanation of symbols]

 W: object to be measured 1: measuring table 7: image capturing means 9: X-direction driving gantry (moving means) 11: Y-direction driving section (moving means) 13: transmission illumination section (illuminating means) 15: optical fiber 19: halogen lamp 21 ... lamp power supply 23 ... lens barrel 25 ... reflection illumination unit (illumination means) 27 ... optical fiber 29 ... halogen lamp 31 ... lamp power supply 51 ... image storage unit (storage means) 53 ... calculation unit (calculation means) FV ... Image P ... Pixel R ... Area of interest NP ... Pixel of interest

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // H05K 3/00 G06F 15/64 325G

Claims (6)

[Claims] 1. A measuring table on which an object to be measured is mounted and an image capturing means for capturing an image of the object to be measured are relatively moved by a moving means in a plane parallel to the measuring table, and illuminated by an illuminating means. In the length measuring method for measuring the length and coordinates of a specific portion of the object to be measured, (a) changing a supply voltage of the illumination means while the object to be measured is placed on the measuring table, (B) obtaining an image of the object under test having the highest contrast as a high-contrast image; and (c) supply voltage corresponding to the high-contrast image. The measurement of the object to be measured is performed after the measurement is supplied to the illumination means. 2. A measuring table on which an object to be measured is mounted and an image capturing means for capturing an image of the object to be measured are relatively moved by a moving means in a plane parallel to the measuring table and illuminated by an illuminating means. In the length measuring method for measuring the length and coordinates of a specific portion of the object to be measured, (a) changing a gain of the image capturing means while the object to be measured is placed on the measuring table, and A step of capturing an image of the object to be measured; (b) a step of obtaining an image of the object to be measured having the highest contrast as a high-contrast image; and (c) a gain corresponding to the high-contrast image. A length measuring method, wherein the object to be measured is measured after adjusting the image capturing means. 3. A measuring table on which an object to be measured is mounted and an image capturing means for capturing an image of the object to be measured are relatively moved by a moving means in a plane parallel to the measuring table and illuminated by an illuminating means. In a length measuring device for measuring the length and coordinates of a specific portion of the object to be measured, in a state where the object to be measured is placed on the measuring table, the image capturing unit captures the image while varying the supply voltage of the illumination unit. Image storage means for storing an image for each supply voltage, and calculation means for obtaining the highest contrast image from the images of the device under test as a high contrast image, and a supply voltage corresponding to the high contrast image. A measuring device for measuring the object to be measured after supplying the measuring device to the illumination means. 4. The length measuring device according to claim 3, wherein said calculating means calculates a pixel value of each pixel in an image for each supply voltage and a pixel value of a pixel corresponding to a peripheral portion of each pixel. A length measuring apparatus characterized in that a high contrast image is obtained from contrast data based on a difference. 5. A measuring table on which an object to be measured is mounted and an image capturing means for capturing an image of the object to be measured are relatively moved by a moving means in a plane parallel to the measuring table and illuminated by an illuminating means. In the length measuring device for measuring the length and coordinates of a specific portion of the object to be measured, in a state where the object to be measured is placed on the measuring table, the image capturing unit captures the image while changing the gain of the image capturing unit. Image storing means for storing an image for each gain, and calculating means for obtaining the image with the highest contrast among the images of the device under test as a high-contrast image; and A length measuring device for measuring the object to be measured after adjusting an image capturing means. 6. The length measuring device according to claim 5, wherein the calculating means calculates a difference between a pixel value of each pixel in an image for each gain and a pixel value of a pixel corresponding to a peripheral portion of each pixel. A high-contrast image is obtained from contrast data based on a length measurement device.