JPS6219684B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an outer diameter measuring device for measuring the outer diameter of an object, and in particular, it uses a light emitting source and a light receiving means to determine the outer diameter of the object to be measured without contact. This invention relates to an optical outer diameter measuring machine.

Since the optical outer diameter measuring machine basically measures changes in the optical image in the light receiving means, it has the advantage that the direct measuring section including the optical system does not come into contact with the object to be measured at all. Therefore, it is possible to perform continuous measurements of many types of objects efficiently and quickly, such as detecting holes in sheet-like objects and detecting the outer diameter of tubular objects. It's starting to look like this.

This type of optical outer diameter measuring machine can be classified very roughly into those that use a light source side scanning method that scans the light source side, and those that use a light receiving side scan method that scans the light receiving side. I can do it. The main measuring device for the former is a laser outer diameter measuring device using a laser device, and the main measuring device for the latter is an outer diameter measuring device using an image sensor.

However, since the laser outer diameter measuring machine must scan the measurement surface with a laser beam, the scanning mechanism is mechanical and complex, resulting in larger size, higher price, and a higher failure rate, which are the essential drawbacks. have. On the other hand, an outer diameter measuring device using an image sensor performs scanning electrically, so it is possible to reduce the size, cost, and failure rate of the device. Therefore, many outer diameter measuring machines using this image sensor are in practical use, but most of the conventional measuring machines illuminate the object to be measured with diffused light and illuminate the object on the image sensor through an imaging lens. By forming an image of the object to be measured and measuring the dark part of the image, the outer diameter of the object was known or identified. Obviously, in such a measuring device, the object to be measured must be imaged on the image sensor, so care must be taken to ensure that the object to be measured always falls within the depth of focus of the imaging lens, and This has the disadvantage that the imaging magnification varies depending on the focus position of the object.

In other words, conventional outer diameter measuring machines using image sensors are limited by constraints on the spatial measurement position of the object to be measured and the variability of the optical image on the image sensor due to variations in imaging magnification, in other words, quantitative measurement of the outer diameter. It had the disadvantage of being difficult.

Therefore, the main purpose of the present invention is to provide an optical measuring device that retains the advantages of an external diameter measuring device using an image sensor, while also being able to quantitatively measure the external diameter of an object regardless of its position. The purpose of the present invention is to provide an outer diameter measuring machine.

To summarize this invention, while an image sensor is used as a light receiving means, a line light source and a collimator lens are used to extremely easily form a parallel light beam with no optical unevenness, and the object to be measured is placed within this parallel light beam. It is designed to measure an optical image that sometimes appears on an image sensor.

FIG. 1 shows a schematic diagram of the optical system portion of an outer diameter measuring machine, which is the premise of this invention. Moreover, FIG. 2 shows a light intensity distribution diagram on the image sensor of the same measuring device.

In Figure 1, 1 is an infinitesimal point light source, 2 is a collimator lens, 3 is an aperture stop, and 4 is a screen 6.
The upper image sensor 5 indicates a bar material which is the object to be measured. Note that the point light source 1 is placed at the focal point of the collimator lens 2.

As shown in FIG. 2, in the optical image formed on the image sensor 4 with the above configuration, the portion illuminated by the rod 5 appears as a dark portion. Therefore, by measuring the length of this dark part, the diameter φd of the bar 5 can be determined.

In this way, the outer diameter of the object to be measured placed within the parallel light beam can be easily determined by measuring the length of the shadow part (dark part) projected on the image sensor. It is very simple and the measurement results are always accurate regardless of the position of the object to be measured.

However, in this device, which uses an infinitesimal point light source as a light emitting source, it is difficult to obtain an optical image with sufficient contrast due to the insufficient amount of light because the point light source is a point light source.

FIG. 3 shows a schematic diagram of the optical system portion of the outer diameter measuring machine according to the present invention. Moreover, FIG. 4 shows a light intensity distribution diagram on the image sensor of the same measuring device.

The difference in configuration from FIG. 1 is that the light source is a finite array of point light sources 1, that is, a line light source 1'.

By doing this, the image sensor 4
The optical image formed above is represented by the superposition of the optical images in the y' direction from each point light source constituting the linear light source 1', and the dark and bright parts of the bar (object to be measured) 5. The contrast will be sufficiently improved. 5A and 5B show the range of the light source that enters the image sensor 4 in the configuration shown in FIG. 3. Figure A shows the case where the image sensor 4 is located at the focal point of the lens 2, and Figure B shows the case where the image sensor 4 is located outside the focal point. In the same figure A, as shown in the figure, if there is no aperture diaphragm 3, light up to the point light source at position A enters the image sensor 4, and if there is an aperture diaphragm 3, the point light source at position A' The light reaches the image sensor 4. In addition, in Figure B, if there is no aperture stop 3, light up to the point light source at position B enters the image sensor 4, and if there is an aperture stop 3, light up to the point light source at position B' enters the image sensor 4. The light enters at 4. From this figure, the farther the image sensor 4 is located, and the smaller the range of the light source that reaches the image sensor 4 is with an aperture stop than without it. However, even if the range of the light source is reduced, the amount of light reaching the image sensor 4 is considerably larger than when the light source is a point light source.
That is, the light from each point light source is superimposed on the image sensor 4, thereby forming an image of the object to be measured with high contrast.

By the way, as a device for forming the line light source shown above, the light source is made into a collection of point light sources (a normal light source having a constant area), and a slit parallel to the y-axis is interposed between the light source and the collimator lens. I can think of things that would cause it. However, when an equivalent linear light source is formed in this way, light unevenness occurs in the slit and a real image of the light source is formed on the image sensor, resulting in a decrease in resolution and resulting in undesirable results. Don't let it happen. In order to solve this problem, a device in which a condenser lens for aberration correction is placed between the collimator lens and the slit may be considered, but this would be large and expensive, and it would also have the disadvantage of greatly reducing the efficiency of light source use. be.

That is, in order to form a line light source, it is necessary to use an actual line light source body without using a slit.

FIG. 6 shows a schematic diagram of the most preferred embodiment of the outer diameter measuring device according to the present invention, and shows one using a linear filament tube 10 as the linear light source.

As is clear from the figure, the optical system consists of only the collimator lens 2 and the linear filament tube 10, and its configuration is very simple. Furthermore, since no slit is used, no light unevenness occurs, and there is no need to correct aberrations using an intermediate optical system such as a condenser lens.

Therefore, it is possible to obtain an outer diameter measuring device that is small and inexpensive and has high light utilization efficiency.

The image sensor 4 is generally composed of a photodiode array, and the length of the dark part of the optical image is measured by scanning the photodiode array and identifying the photodiode corresponding to the dark part. Then, multiply the number of diodes by the array pitch.

As described in detail above, according to the present invention, the optical system can be made extremely compact, and mechanical elements unlike laser outside diameter measuring machines are not required, resulting in highly reliable and low cost outside diameter measurement. It can be used as a measuring device. Furthermore, since a parallel beam of light is used as the light to irradiate the object to be measured, the outer diameter can always be accurately measured without being restricted by the position of the object. Furthermore, since a line light source is used as the light source, accurate measurement with high contrast is possible even in a measurement environment with high illuminance.

Therefore, the optical outer diameter measuring device according to the present invention can be fully applied not only to the field of qualitative measurement but also to the field of quantitative measurement.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the main parts of the outer diameter measuring machine which is the premise of this invention, Fig. 2 is a light intensity distribution diagram on the image sensor of the measuring machine, and Fig. 3 is a diagram of the outer diameter measuring machine according to the present invention. A schematic diagram of the main parts, Fig. 4 is a light intensity distribution diagram on the image sensor of the same measuring device, Figs. The most desirable embodiment schematic diagram of such an outer diameter measuring machine is shown, respectively. DESCRIPTION OF SYMBOLS 1... Point light source, 1'... Line light source, 2... Collimator lens, 3... Aperture stop, 4... Image sensor, 5... Bar material, 10... Line-shaped filament tube.

Claims (1)

[Claims] 1 A linear light source is placed at the focal point of a collimator lens to form a parallel light beam, an image sensor is placed at the irradiation part of this parallel light beam, and an object is placed between the collimator lens and the image sensor. An optical outer diameter measuring machine that measures the outer diameter of an object by measuring the length of the dark area on the image sensor.