JPS61218905A - Gap measuring instrument - Google Patents

Abstract

PURPOSE:To measure a gap with good accuracy by sampling and binarizing a stored video signal every bit and calculating a gap from a difference between the number of bits included in a prescribed period and the number of bits of the next prescribed period. CONSTITUTION:The shape of an optical beam from a light source 30 is converted with the 1st optical element group 31. The optical beam from this element group 31 is irradiated on a word 32 to be measured and for instance, the magnification or the like of optical information on the light and darkness corresponding to the shape of the transmitted work 32 is converted and photodetected with for instance, a CCD type image sensor 34 of an unidimensional line sensor with 4096 bits via the 2nd optical element group 33. The photoelectric conversion of photodetected optical information is performed with a video signal making circuit 35 to obtain the analog voltage. The A/D conversion is performed with a conversion circuit 36 and the analog voltage is converted into the digital voltage with the resolving power of about 10 bits and the output of the A/D conversion circuit 36 is stored with a memory circuit 37 and this video signal is sampled and binarized every integral number (n) bits (n>=2) and a leading edge and a trailing edge are calculated 40 accurately after the correction processing 39 of the noise is performed to calculate 41 the dimensions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for detecting minute gaps between a plurality of minute members, such as the hands of a clock, with high precision.

[Background of the invention]

In recent years, various automatic assembly technologies have advanced, and the need to automate the setting of hands on watches has increased in watch manufacturing. Automatic measurement of whether the gap between the two is the appropriate amount is also an important element.

[Prior art and problems]

With recent advances in electronic technology, solid-state image sensors are increasingly used in the field of optical measurement.

Particularly in the field of dimension measurement, the image of the object to be measured is magnified using a lens system and formed on a solid-state image sensor.
The light intensity of each element bit on the sensor is measured and the brightness and darkness are determined.
Dimensions are obtained by converting into values.

FIG. 2 is a principle diagram showing a conventional gap measurement method using an image sensor.

10 is a light source, 11 is an object to be measured, and 110 is a gap to be measured. 12 is a lens system, and 13 is a one-dimensionally arranged image sensor.

If the object to be measured 11 is minute and the gap 110 is also minute, it is necessary to enlarge the image of the object using the lens system 12 in order to improve the measurement accuracy of the gap.

At this time, the distance a between the lens system 12 and the image sensor 13 is fixed, and if it is not very long, the distance a between the object to be measured 11 and the lens system 120 needs to be as short as possible. In such a case, the tolerance for the distance a becomes small, and if the installation location of the object to be measured 11 changes, the magnification of the image changes and a measurement error occurs. In addition, the light that irradiates the object to be measured 11 is often incoherent light with a spherical spread, and because the light intensity distribution is uneven, the photoelectric conversion at the image sensor 13 decreases as the gap becomes smaller. The S/N ratio of the voltage data obtained is poor, and minute gaps cannot be measured.

Furthermore, as shown in the waveform diagram of Fig. 3, the image sensor 1
When calculating the gap from the portion 21 corresponding to the gap in the photoelectrically converted voltage data 20 in step 3, the amount of gap varies depending on the threshold level value as shown in 22 and 23, and there are various cases in which the dimension cannot be calculated uniquely. It has the following disadvantages.

[Purpose of the invention]

The present invention solves these drawbacks, and has a wide dynamic range (with no image magnification fluctuations), a good S/N ratio (and a fine gap that can be accurately detected without depending on the threshold level value). The purpose is to make it possible to measure

The configuration of the present invention includes a light source, a first optical element group that converts the shape of a light beam from the light source, and a workpiece to be measured is irradiated with the light beam from the first optical element group. a second optical element group for converting information; an image sensor for receiving optical information from the second optical element group; and a video signal generation circuit for photoelectrically converting optical information from the image sensor. , an A/D conversion circuit for the video signal, and the A/D conversion circuit for the video signal.
A memory circuit for the D conversion circuit output signal and the video signal held in the memory circuit are sampled and binarized every n bits where n≧2, and the bits of the change in brightness of the binarized data are a first binarization processing unit that calculates a number; a noise correction geography unit that changes the data island content of the stored video signal based on the data of the first binarization processing unit; The first binarization processing unit and the noise correction processing unit sample the stored video signal bit by bit and binarize it, and the rising and falling edges of the binarized data change in brightness and darkness. a second binarization processing unit that calculates a falling bit number;
The number of bits included in the first period from the rising edge to the next rising edge or from the falling edge to the next falling edge of the binarized data computed by the binarization processing unit of ', and the bits included in the first period. and a dimension calculation processing section that calculates the gap from the difference between the number of bits included in the second period from the falling edge to the rising edge.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a system block diagram of the present invention.

60 is a light source, and 61 is a first optical element group that converts the shape of the light beam emitted from the light source 6o.

32 is a workpiece to be measured, 66 is a second optical element group,
The light beam emitted from the first optical element group 31 is irradiated onto the workpiece 32 to be measured, and the magnification of bright and dark optical information according to the shape of the transmitted workpiece is converted, for example. 34 is an image sensor, for example, CCD type 40
A one-dimensional line sensor with 96 pits receives optical information from the second optical element group 63. 65 is a video signal generation circuit that photoelectrically converts optical information received by the image sensor 64 to obtain an analog voltage. Reference numeral 36 denotes an A/D conversion circuit that performs analog-to-digital conversion, and converts the aforementioned analog voltage into digital data with a resolution of about 10 bits. A memory circuit 37 stores the output of the A/D conversion circuit 36.

The video signal stored in this memory circuit 67 is processed to calculate a snack. In order to facilitate the subsequent explanation, a model diagram of the work to be measured in the fourth time is shown, an example of a waveform diagram of the video signal is shown in Fig. 5, and the processing to be performed according to Figs. 4 and 5 is shown. State whether it is necessary.

Figure 4 (1) is a model diagram showing the cross section of a watch with hands,
1 is the clock drive unit, 402 is the dial, 403 is the hour hand, 40
4 is a minute hand, and 405 is a second hand.

The thickness of a typical watch's hands is approximately 150 μm for the hour and minute hands, and 120 μm for the second hand.The gap between the dial 402 and the hour hand 403 is A, the gap between the hour hand 406 and minute hand 404 is B1, the gap between the minute hand 404 and second hand 405 is C. When the above A,
B and C need to be set to approximately 100 to 300 μm.

It is absolutely necessary that the needles do not rub against each other as they rotate, and it is automatically measured whether the gaps A, B, and C are within appropriate ranges.

FIG. 4(2) shows the irradiation of a light beam onto the watch body when using an optical system to be described later, and 406 is an elliptical beam that spreads almost one-dimensionally.

An elliptical beam has a higher energy density than a circularly spread beam, and optical information with a good S/N ratio can be obtained.

FIG. 5(1) is a waveform diagram of an example of a video signal obtained when the watch body shown in FIG. 4 is irradiated with an elliptical light beam. 501 is a dark area caused by the driving body 401 and dial 402 of the clock in FIG.
02.504.506 is a bright area due to the gaps A, B, and C mentioned above. FIG. 5(2) is the bright part 504 of FIG. 5(1).
FIG. 2 is a waveform diagram showing a video signal when a portion thereof is enlarged.

The video signal that is actually obtained is a signal that contains some noise components, and when the threshold cold level 508 is determined and binarized, especially if there is noise as shown at the cross point 509 at the threshold cold voltage, Figure 5 (
As shown in 3), if the image is binarized as it is, the processing when calculating the dimensions later becomes very complicated, so it is necessary to use a processing method that is not affected by noise.

Returning to FIG. 1 again, the video signal processing method will be explained.

68 samples the video signal held in the memory circuit 67 every integer n bits (n≧2) and binarizes it, and stores the bits where the brightness (1, 0) of the binarized data changes. This is the first binarization processing unit that calculates the number).

The above-mentioned integer n is determined by the size of the workpiece 32, the magnification of the optical system, the number of bits of the image sensor, etc., but is preferably about several tens of bits. FIG. 6 shows a waveform diagram when correcting the binarization of a video signal. Figure 6 (1) shows an enlarged view of the video signal, and Figure 6 (2) shows the n
It shows binary data when sampled bit by bit.

In FIG. 6(1), the black circles indicate the sampled bit numbers mentioned above. If there is noise as shown in the video signal 601, and that location is a sampled bit, the data when binarized becomes 0, resulting in an error, as shown in 602 in FIG. 6(2). Also, if the bit position of noise 601 is not the timing to be sampled, 2
Valued data is not affected in any way.

Furthermore, even if there is fine noise at the threshold level position as shown in FIG. 5(2), the binarized data is not affected at all.

In this way, performing binarization processing while sampling every n bits not only increases (shortens) the processing time, but also makes it less susceptible to noise (than the method of sampling every 1 bit). It has the effect of

Now, let's talk about the noise in the video signal.
Although it is convenient to use a laser beam as a light source to create the very long and narrow elliptical beam shown in Figure (2) noise occurs due to fluctuations in light intensity distribution, vibrations of the workpiece to be measured, etc.

62 in FIG. 1 is a noise correction processing section which changes the content of the data of the video signal held in the memory circuit 37 based on the data from the first binarization processing section 38. At this point, it is necessary to determine whether or not it should be treated as noise.

Depending on the shape of the workpiece 32 to be measured, etc., only the binarization process (
If this is known, it may be determined that it is clearly noise as shown in FIG. 6(2). Therefore, the data after binarization is shown in FIG. 6(3)K.

As described above, noise-corrected binarized data is obtained over the entire area, but this binarized data is rough data, and exact changes in binarization at the threshold level are obtained. A certain change point that does not include the information must be calculated again.

FIG. 1 40 shows the second binarization processing unit, and the changes in the brightness and darkness of the binarization in terms of the threshold luck level are based on the calculation results of the first binarization processing unit 38 and the noise correction processing unit 39 described above. This is to accurately calculate the rising and falling bit numbers of the signal, and samples each bit.

Sampling point 6 shown in Figure 6 (1) in Figure 6 (4)
6 shows an enlarged view of the video signal between 06 and 604. This is a case where noise is present just at the threshold level. FIG. 6(5) shows the binarization data when the video signal of FIG. 6(4) is sampled bit by bit. When there is so-called numerical chattering in the binarized data, it is necessary to correct it in order to simplify the processing when calculating dimensions. Now, when finding the bit number at the rising edge of a change in binarization, if there are multiple rising changes in that section, such as 605.606.607, calculate the average point of each change and use it as the rising change point. Bye. Alternatively, the change point can be determined by weighting the magnitude of the change, and furthermore, the change point can be determined by interpolating into finer steps than the actual bit number.

Through the binarization processing described above, binarized data for calculating gaps that does not include the influence of noise can be obtained.

Reference numeral 41 in FIG. 1 is a dimension calculation processing unit, which calculates actual snacking.

FIG. 7 shows a waveform diagram of an example of the binarization pattern of the clock example shown in FIG. 4(1), and the gap calculation will be explained.

In Fig. 7, X is the dark area due to the hour hand 403, Y is the dark area due to the hour hand 403.
3 and the bright part due to the gap between the minute hand 404, Z is equal to X+Y. Now, the period from the falling edge 701 of the binarized data to the next falling edge 702 is defined as a first period. That is, Z is the number of bits in the first period.

703 is the place where the rise of Fukuma Kurenai changes within the first period of Moanki, from the fall of 701 to the rise of 7?
The period up to 3 is the second period.

That is, X is the number of bits in the second period.

As explained in Fig. 3, when the threshold level is determined and binarized, the change point of the binarization changes depending on the magnitude of the threshold level. Even if you search for , you will not get an accurate value. According to experimental results, the value of z=x+y hardly depends on the value of the threshold l-ruby level, so it can be used as a reference for calculating the gap.

Although X and Y cannot be determined individually with high precision, x, y, and z, the relational expression is stored as a device constant in the dimension calculation processing unit 41, and the number of bits Z included in the first period described above and the number of bits X included in the second period are calculated. By taking the difference between the two and performing arithmetic processing using the above relational expression, the snacking Y can be accurately determined without depending on the value of the threshold level.

Note that it is preferable that the threshold level not be determined from the absolute value of the voltage of the video signal, but after normalization based on the maximum and minimum values of the voltage of the video signal.

Using the method described above, gaps in other parts can be found in the same way.

FIG. 8 is a principle diagram of an apparatus showing an embodiment of the optical system. 8
0 is a He-N e laser. 81 has a focal length of f
1 is a cylindrical lens, and 82 is a plano-convex lens with a focal length of f2. The combination of the cylindrical lens 81 and the plano-convex lens 82 is the first optical element group 31 that converts the beam shape of the light beam 800 emitted from the laser light source 80. Plano-convex lens 82. The light beam 801 emitted from the focal plane becomes an elongated, so-called elliptical beam that spreads almost one-dimensionally at its focal plane. A workpiece 32 to be measured is placed on the focal plane.

86 and 85 are plano-convex with focal lengths of f3 and f4, respectively;
84 is a spatial filter. Plano-convex lens 83
and d85 and the spatial filter 84 form the second optical element group 66.
Configure. The combination of plano-convex lenses 86 and 85 increases the magnification of bright and dark optical information contained in the light beam 801 to f4/f.
Convert with a ratio of only 3.

When a laser beam is used as a light source and the size of the work to be measured is small, the light beam 801 contains optical noise due to the influence of diffraction, so the spatial filter 84 cuts the harmonic components and converts the fundamental wave. Allows components close to that to pass through. A light beam 802 emitted from a plano-convex lens 85 is received by an image sensor such as a CCD line sensor to obtain a video signal as described above.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, the S/N ratio of brightness and darkness is high (it is less affected by disturbances such as fluctuations in the position of the workpiece to be measured), and stable video signals can be obtained. Furthermore, when performing binarization processing, it is possible to obtain
Stable binarized data can be obtained, and dimension measurement that is not influenced by the binarization threshold level value is possible. The present invention can be applied not only to gap measurement as described in the embodiments, but also to pattern recognition, etc., and is highly effective.

[Brief explanation of drawings]

Fig. 1 is a system block diagram of an embodiment of the present invention, Fig. 2 is a principle diagram showing a conventional method for measuring clearance, Fig. 3 is a waveform diagram of a method for calculating a gap according to the conventional technique, and Fig. 4 The figure is a schematic diagram of the workpiece to be measured. Figure 5 is a waveform diagram of an example of a video signal caused by clock hands. Figure 6 is a waveform diagram of an example when correcting the binarization of a video signal. Figure 7 8 is a waveform diagram illustrating the calculation of a gap from binarized data, and FIG. 8 is a principle diagram of an apparatus of an embodiment of the optical system of the present invention. 61...First optical element group, 36...Second optical element group, 38゛...First binarization processing unit, 39...
...Noise correction processing section, 40...Second binarization processing section, 41...
・Dimension calculation processing unit, 80...He-Ne laser, 84...
...Spatial filter. Figure 2 Figure 3 Figure 7c;l Figure 5

Claims (1)

[Claims] a light source, a first optical element group that converts the shape of a light beam from the light source, and a first optical element group that irradiates the workpiece to be measured with the light beam from the first optical element group and converts the obtained optical information. 2
an image sensor that receives optical information from the second optical element group, a video signal generation circuit that performs photoelectric conversion of the optical information of the image sensor, and an A/D conversion circuit for the video signal. and a memory circuit for the A/D conversion circuit output signal, and the video signal held in the memory circuit is sampled every n bits where n≧2.
a first binarization processing section that converts the data into a value and calculates a bit number of a change in brightness of the binarized data; a noise correction processing unit that changes the data content of the video signal stored in the memory; and a noise correction processing unit that samples the stored video signal bit by bit from the first binarization processing unit and the noise correction processing unit, and converts the stored video signal into binary data. a second binarization processing unit that calculates rising and falling bit numbers of the binarized data whose brightness changes; The number of bits included in the first period from the rising edge of data to the next rising edge or from the falling edge to the next falling edge, and the bits included in the second period from the falling edge to the rising edge included in the first period. 1. A gap measuring device comprising: a dimension calculation processing unit that calculates a gap from a difference between a number and a number.