JPH0829129A - Length measuring apparatus - Google Patents

Abstract

PURPOSE:To provide a highly reliable noncontact type length measuring apparatus at a low cost so that the measurement can be performed at high accuracy all the time. CONSTITUTION:A liquid-crystal display panel 11 is utilized, graduation values are patterned and a scale 1 is provided. The scale 1 is photographed with a camera 2, and a substance to be measured 15 is photographed with another camera 3. The substance to be measured 15 and the scale l are moved as a unitary body with a moving stage 10. Two measuring positions of the substance to be measured 15 are sequentially aligned with cursor on a monitor 5. The graduation value of the scale corresponding to the position of the respective cursor is computed by processing the image of the scale 1 with a CPU 9. Thus, the difference between two values is obtained. That is, the absolute values corresponding to two measured positions are read from the image of the scale 1 respectively in this apparatus, and the length is obtained from the difference between two absolute values. Therefore, even if the stage is moved at any speed between two measuring positions, the measured value is not affected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a length measuring device for contactlessly measuring the length of an object, particularly the size of a precision part or the like requiring high dimensional accuracy.

[0002]

2. Description of the Related Art In recent years, a non-contact high-precision length measuring device has been developed in order to measure dimensions of precision parts and the like which cannot directly contact calipers or micrometers.
Widely used.

As a conventional non-contact type length measuring device of this type, there is one using a magnet scale. In this measuring device, an object to be measured placed on a moving table is moved from one measurement position to the other measurement position along the magnescale, and at the time of the movement, the magnetic flux with a fine pitch, which is the scale of the magnescale, is Changes are detected and converted into pulse signals,
By counting the number of the pulse signals, the movement amount, that is, the length between the two measurement positions is calculated. Also,
The measurement position of the object to be measured is magnified with an optical device such as a microscope so that it is accurately aligned with the reference line in the field of view.

[0004]

However, in the conventional non-contact type length measuring device using the above-mentioned magnescale, as described above, when the object to be measured is moved, the fine pitch which is the scale of the magnescale is adjusted. Since the length is measured by detecting the magnetic change, erroneous detection may occur when the moving speed is increased too much or the moving direction is changed, resulting in a measurement error.

Further, since the magnet scale itself is expensive, there is a problem that the length measuring device is also expensive.

The present invention has been proposed in order to solve such a problem, and is a non-contact type length measuring apparatus which is highly reliable and inexpensive, which can always measure with high accuracy. The purpose is to provide.

[0007]

The length measuring device according to the present invention has the following structure.

That is, the scale (1) in which the scale values are shown as a pattern, the scale photographing means (2) for photographing the scale (1) and electrically outputting the image, and the object to be measured (15) ) Is photographed and the image of the object to be measured is electrically output, and the object to be measured is photographed (3).
An image display means (5) for displaying an image of the object to be measured photographed by and the image of the scale (1) photographed by the scale photographing means (2), and a scale (1) photographed by the scale photographing means (2). Image is stored at every predetermined sampling time, and a cursor (2
3) is displayed on the image display means (5), an image storage means (6), a measurement command input means (7) for inputting a measurement start position determination command and a measurement end position determination command, and the image storage means (6). By processing the image of the scale (1) stored by 6), the scale (1) corresponding to the position of the cursor (23) displayed on the image display means (5) by the image storage means (6). The scale value above is calculated for each of the predetermined sampling times, and among the scale values calculated for each sampling time, a measurement start position determination command and a measurement end position determination command from the measurement command input means (7). And image processing calculation means (9) for calculating the difference between the two scale values at the time of inputting each of the commands and displaying the numbers on the image display means (5), and the scale photographing means (2).
And the object to be measured photographing means (3) integrally, or the scale (1) and the object to be measured (15) integrally moved in parallel to the length direction of the scale (1). And a moving means (10).

[0009]

In the length measuring device having the above structure, the object to be measured (1
The absolute values for the two measurement positions of 5) are read by processing the image of the scale (1), and the length is obtained from the difference between the two absolute values. Therefore, no matter what speed the object to be measured (15) is moved between the two measurement positions or the moving direction is changed, the measured value is not affected.

The reference numerals in the above parentheses are for comparison with the drawings and do not limit the structure of the present invention.

[0011]

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

FIG. 1 is a block diagram showing the basic structure of a length measuring device according to the present invention. Further, FIG. 2 is a plan view showing the configuration of the scale in the length measuring device,
Is an overall view, and (b) is a partially enlarged view.

As shown in the figure, this length measuring device comprises a scale 1, a scale photographing camera (scale photographing means) 2,
Object to be measured photographing camera (object to be measured photographing means) 3, monitor (image display means) 5, image memory (image storage means) 6
A measurement command input unit (measurement command input means) 7 and a CPU
(Image processing calculation means) 9 and moving base (moving means) 10
And Below, each of these components will be described together with other components.

The scale 1 is a pattern of scale values, and is constructed by using a liquid crystal display panel 11 as shown in FIG. 2A, for example. That is, the liquid crystal display panel 11 is driven by the liquid crystal drive circuit 11 in accordance with the control signal from the CPU 9, so that the display panel 11 is driven.
The scale values are displayed as a pattern using the dots that make up the.

For example, as shown in FIG. 2B, in the longitudinal direction of the liquid crystal display panel 11, the marker dots M are set as a scale for every 3 dot rows, and the scale value of each marker dot M is set for each marker. By a dot pattern (a range indicated by an alternate long and short dash line in the figure) using a 4 dot row following the dot M and a 3 dot row up to the next marker dot
Display in hexadecimal.

The dots of the liquid crystal display panel 11 are regularly arranged with a very high accuracy, and if the dot pitch in the longitudinal direction is 0.3 mm, the marker dot M is formed.
Is a scale every 0.9 mm. Then, in order to calibrate the scale value indicated by this dot pattern to a true value, calibration data for a standard gauge such as a block gauge is stored in the CPU 9 in advance.

The scale photographing camera 2 and the object to be measured camera 3 have a scale 1 and an object to be measured 1, respectively.
5 is provided with lenses 2a and 3a capable of partially enlarging and photographing, and electrically outputs the photographed image in real time. For example, a small TV camera using a CCD can be used. .

The monitor 5 displays an image of the scale 1 photographed by the scale photographing camera 2 and an image of the DUT 15 photographed by the DUT photographing camera 3, and a CRT is used. An image changeover switch SW is provided on the monitor 5 so as to select and display the image of the scale 1 and the image of the DUT 15.

The image memory 6 stores the image of the scale 1 photographed by the scale photographing camera 2 at every predetermined sampling time and displays a cursor indicating a measurement position on the monitor 5. The image of the scale 1 displayed on the monitor 5 is also sent from the image memory 6. When the monitor 5 displays either the image of the scale 1 or the image of the DUT 15 according to the switching of the image switching switch SW, the image memory 6 displays the images. The cursor is displayed over again.

The measurement command input unit 7 is used by the user to input a measurement start position determination command and a measurement end position determination command at the time of measurement, as will be described later, and is operated by operating a push button switch or the like. It has become.

The CPU 9 processes the image of the scale 1 stored in the image memory 6 to set the scale value on the scale 1 corresponding to the position of the cursor displayed on the monitor 5 by the image memory 6 to the predetermined value. It is calculated for each sampling time. At that time, adjacent two on the scale 1
Values between two scale values are calculated by proportional calculation. Further, the calculated scale value is calibrated to a true value according to the calibration data stored inside. further,
Of the scale values calculated and calibrated for each sampling time, the difference between the two scale values at the time of each command input of the measurement start position determination command and the measurement end position determination command from the measurement command input unit 7 is calculated. , Display on the monitor 5 by numbers.

The moving table 10 is for moving the scale 1 and the object to be measured 15 integrally in parallel with the length direction of the scale 1. It is designed to be moved by operation. Instead of moving the scale 1 and the DUT 15 in this way, the scale photographing camera 2 and the DUT photographing camera 3 are used.
May be integrally supported, and may be configured to move in parallel to the length direction of the scale 1. Further, in FIG. 1, the moving table 10 is shown to be moved in the arrangement direction of the two cameras 2 and 3, but it may be moved in a direction perpendicular to the moving direction.

FIG. 3 is a side view showing a concrete configuration example of the length measuring device.

As shown in the figure, in this configuration example, the object-to-be-photographed camera 3 is exposed on the front side of the case 20 and is supported with its optical axis directed vertically downward. Is supported in parallel with the DUT camera 3 while being housed in the case 20. A zoom lens is used as the lens 3a of the DUT camera 3.

At the lower part of the case 20, a movable table 10 is horizontally provided so as to move in the left-right direction (the direction perpendicular to the paper surface in FIG. 3).
The mounting portion 10a on which the 5 is mounted is exposed on the front side of the case 20 corresponding to the object photographing camera 3, and the case 2
It can be moved in the vertical direction by operating the focus adjustment knob 21 arranged on the side surface of the No. 0. Further, the rear end of the movable table 10 is located inside the case 20, and at the rear end thereof, the liquid crystal display panel 11 serving as the scale 1 is horizontal and the scale 1 is left and right corresponding to the scale photographing camera 2. It is fixed so that it faces the direction.

As for the optical system such as the focal lengths of the lenses 2a and 3a of the cameras 2 and 3 and the positional relationship with the movable table 10, the appropriate range of the scale 1 and the object to be measured 15 is expanded as described later. In addition, it is set so that an in-focus image can be obtained accurately.

On the side surface of the case 20, an operating section 16 for horizontally moving the movable table 10 together with the focus adjusting knob 21.
And the monitor 5 is attached to the upper surface of the case 20. Further, although not shown, Case 2
A power switch, the above-described image changeover switch SW, the measurement command input unit 7, and the like are provided on the front surface of 0, and the above-described other components are housed inside.

As in this configuration example, the scale photographing camera 2 and the liquid crystal display panel 11 are housed in the case 20 because these components do not need to be touched by the user. This is also because the liquid crystal display panel 11 serving as the scale 1 is shielded from ambient light to improve the contrast of the image of the scale 1 and thereby maintain high measurement accuracy.

Next, the measurement operation of the length measuring device having the structure shown in FIG. 3 will be described, together with the measuring method, in plan view of the movable table of FIG. 4 and FIGS. 5 (a), 5 (b) and 5 (c). This will be described with reference to the monitor screen of FIG. Note that FIG. 1 will be referred to for components not shown in FIG.

After turning on the power supply of the measuring apparatus, the user sets the object 15 to be measured on the mount portion 10a of the moving table 10 as shown in FIG. At this time, the length of the object to be measured 15 to be measured is precisely in the left-right direction, that is, parallel to the length direction of the scale 1, and the range of the length to be measured is the scale. Set it so that it is within the range of 1 scale. In order to set the object 15 to be measured accurately and quickly, when a reference line is provided on the upper surface of the mounting part 10a or when the parts having the same shape are continuously measured, FIG. As shown therein, it is preferable to provide a holder 22 on which the object to be measured 15 can be set with one touch.

Then, the user causes the monitor 5 to display an image of the object 15 to be measured by the object photographing camera 3.
Then, while observing the image of the object to be measured 15 displayed on the monitor 5, the operation unit 16 is operated to move the movable table 10, and as shown in FIG. One of the measurement positions (here, the left end) of the DUT 15 on the same screen is accurately aligned with the cursor 23 displayed on the screen.

At this time, the focus adjustment knob 21 is operated to move the stage 10a of the movable table 10 up and down.
The focus position of the DUT camera 3 is accurately aligned with the measurement position of the DUT 15. That is, the measurement position of the DUT 15 is displayed on the monitor 5 as sharply as possible. In addition, the photographing magnification of the DUT camera 3 is increased,
Monitor 5 with the measurement position of DUT 15 enlarged as much as possible
If this is displayed, the alignment with the cursor 23 will be more accurate and the measurement accuracy will be improved. However, when the photographing magnification of the DUT camera 3 is high before the measurement is started, it becomes difficult to determine which part of the DUT 15 is displayed on the monitor 5, and thus it is difficult to determine the configuration example. To
The lens 3a of the DUT camera 3 may be a zoom lens so that the photographing magnification can be changed as necessary. Further, an illumination device that illuminates the measurement position of the DUT 15 may be provided.

Here, when the image changeover switch SW is operated to display the image of the scale 1 by the scale photographing camera 2 on the monitor 5, as shown in FIG. The image is displayed together with the cursor 23 in a state in which the image is enlarged in a predetermined range and is in focus accurately. The position of the scale 1 where the cursor 23 overlaps corresponds to the measurement position of the DUT 15.

The CPU 9 processes the scale 1 image as described above to calculate the scale value on the scale 1 corresponding to the position of the cursor 23, and
Calibrate to true value. That is, the absolute value indicating the measurement position of the DUT 15 is read from the image of the scale 1.

Regarding the photographing magnification of the scale photographing camera 2, the CPU 9 can calculate the scale value on the scale 1 corresponding to the position of the cursor 23, that is, one or more markers at least on both sides of the cursor 23. It is set as large as possible within a range including the dot M and the dot pattern indicating the scale value thereof. The larger the photographing magnification of the scale photographing camera 2, the higher the measurement accuracy. The reference point of the scale value is the center point of each marker dot M. The user does not need to display the image of the scale 1 on the monitor 5 during the actual measurement.

Thus, the DUT 1 is displayed on the screen of the monitor 5.
After aligning the measurement position of 5 with the cursor 23, the user inputs a measurement start position determination command from the measurement command input unit 7. Then, the CPU 9 stores the calculated scale value at the time of inputting the measurement start position determination command.

Next, the user operates the operation unit 16 to move the movable table 10 while looking at the image of the object 15 to be measured displayed on the monitor 5, and as shown in FIG. The other measurement position (here, the right end) of the object to be measured 15 is accurately aligned with the cursor 23 on the screen, and then the measurement end position determination command is input from the measurement command input unit 7.

Then, the CPU 9 processes the image of the scale 1 by the scale photographing camera 2 stored in the image memory 6 at the time of inputting the measurement end position determination command, so that the measured object 15 with respect to the other measurement position. The scale value of the scale 1 is calculated and calibrated to a true value, and the difference between the calibrated calculated scale value and the scale value at the time when the previously stored measurement start position determination command is input is calculated. The difference between the two scale values thus calculated becomes the measured value. Then, the CPU 9 causes the measured value to be displayed numerically at a predetermined measured value display position 5a on the screen of the monitor 5.

As described above, in the length measuring device according to the present invention, the absolute values for the two measurement positions of the DUT 15 are
Since the length of each object is read from the image of the scale 1 and the length is determined from the difference between the two absolute values, the object to be measured 15 can be moved at any speed between the two measurement positions or the moving direction can be changed. However, it does not affect the measured value. Furthermore, since the measurement position is aligned by looking at the image of the DUT 15 displayed on the monitor 5 and the cursor, the measurement error due to the position viewed by the user does not occur. That is, accurate and highly reliable measurement values can always be obtained. The measurement accuracy can be set to about several microns by appropriately setting the measurement conditions such as the photographing magnification of each of the cameras 2 and 3.

Further, by using the liquid crystal display panel 11 as the scale 1, it is possible to easily form a fine and accurate pattern representing a scale value by an electric signal and the scale 1 itself emits light. To
It is possible to obtain a high-contrast image of the scale 1 without illuminating the scale 1.

Although the length of the DUT 15 in one direction (X direction) is measured in the above embodiment, the direction of the scale 1 (X direction) is displayed on the liquid crystal display panel 11.
In addition to switching and displaying the scale in the direction (Y direction) orthogonal to, a movable table 10 that can be moved in the X and Y directions is used, and two orthogonal cursors are displayed on the monitor 5. This makes it possible to measure the lengths of the measured object 15 in two directions (X and Y directions) without changing the orientation of the measured object 15 on the moving table.

In addition to the liquid crystal display panel 11, it is also possible to use, as the scale 1, for example, a glass plate on which scale values are patterned and carved.

Further, the color T is set on the object photographing camera 3.
If a V camera is used and a color monitor is used as the monitor 5 to display the image of the DUT 15 in color on the monitor 5, it becomes easier to confirm the measurement position of the DUT 15 on the monitor 5. Therefore, the measurement position can be aligned with the cursor more quickly and accurately, and the efficiency of the measurement work is further improved.

[0044]

As described above, according to the length measuring apparatus of the present invention, it is possible to always perform highly accurate and highly reliable measurement based on the images of the object to be measured and the scale. It can be realized at low cost without using expensive parts such as Magnescale.

Further, by using the liquid crystal display panel, the scale used in the length measuring apparatus according to the present invention can be easily formed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a basic configuration of a length measuring device according to the present invention.

FIG. 2 is a plan view showing a configuration of a scale in the length measuring device, (a) is an overall view, and (b) is a partially enlarged view.

FIG. 3 is a side view showing a specific configuration example of the length measuring device according to the present invention.

FIG. 4 is a plan view of a moving table for explaining a measuring operation and a measuring method of the length measuring device.

5 (a), (b) and (c) are diagrams of monitor screens for explaining a measuring operation and a measuring method of the same length measuring device.

[Explanation of symbols]

 1 scale 2 scale photographing camera (scale photographing means) 3 measured object photographing camera (measured object photographing means) 5 monitor (image display means) 6 image memory (image storage means) 7 measurement command input section (measurement command input means) 9 CPU (image processing calculation means) 10 Moving stand (moving means) 11 Liquid crystal display panel

Claims (2)

[Claims] 1. A scale having a pattern of scale values, a scale photographing means for photographing the scale and electrically outputting the image, and a scale for photographing an object to be measured and electrically measuring the image. Outputting means for photographing the measured object, image display means for displaying the image of the measured object photographed by the measured object photographing means and the image of the scale photographed by the scale photographing means, and the scale photographed by the scale photographing means Image for each predetermined sampling time, and an image storage means for displaying a cursor indicating the measurement position on the image display means, and a measurement command input means for inputting a measurement start position determination command and a measurement end position determination command. And processing the scale image stored by the image storage means to bring the image storage means to the position of the cursor displayed on the image display means. A scale value on the corresponding scale is calculated for each of the predetermined sampling times, and among the scale values calculated for each sampling time,
An image processing calculation means for calculating a difference between two scale values at the time of inputting each of the measurement start position determination command and the measurement end position determination command from the measurement command input means and displaying the difference on the image display means by numbers. A moving unit that moves the scale photographing unit and the DUT photographing unit integrally, or moves the scale and the DUT integrally in parallel to the length direction of the scale. A length measuring device. 2. The length measuring device according to claim 1, wherein the scale is configured by displaying scale values in a pattern on a liquid crystal display panel.