JPS6215404A - Non-contact system diameter measuring instrument - Google Patents

Abstract

PURPOSE:To easily measure a diameter and with a high accuracy even in case of a moving object, by projecting an image of a circular object moving at a constant speed, to a photodetector, calculating two kinds of diameters, based on a specified peak of its output, and thereafter, averaging them. CONSTITUTION:A circular image 4 of a moving circular object to be measured 3 is projected onto a photodetector array 1. This array 1 connected alternately 2n pieces of detectors, inputs its each output to a differential amplifier circuit 5 and obtains a signal having 2n pieces of peaks. In this state, first of all, by an arithmetic means 7, an approximate diameter is calculated, based on the first peak of the output signal. Also, by an arithmetic means 8, a diameter D1 is calculated from a peak amplitude of the output signal of the time when the circular image 4 has been held completely on the array 1. Also, by an arithmetic means 9, a diameter D2 is calculated, based on the appearance time of the same peak. Thereafter, by an arithmetic means 10, the diameter D1 and D2 are averaged and corrected by a moving speed value, by which a diameter is calculated.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to a method for determining the diameter of a moving circular object that moves at a substantially constant speed and has a shape that forms a circular image on a photodetector, such as a sphere or a disk. It is for non-contact measurement, and includes a spatial filter with a differential configuration consisting of an optical system, a photodetector array, and a differential amplifier circuit, and a non-contact diameter measuring device such as an arithmetic unit. It is related to.

(Prior Art) Various methods have been devised in the past as means for measuring the dimensions of an object in a non-contact manner. In principle, there are many methods in which dimensions are obtained by capturing images of a stationary object using multiple detectors, and methods in which the object is moved at a constant speed and the time it takes to pass a certain point is measured.

The former method of obtaining dimensions by capturing images of a stationary object with a large number of detectors has the following problems. The resolution of a measurement is essentially the maximum measuring range of the detector, since it is based on the fact that the number of photodetectors onto which the image of the object to be measured is projected is proportional to the dimensions of the object. ÷
The number of detectors depends on the number of detectors. Therefore, in order to achieve high precision, many detectors and associated complex force signal processing circuits are required. Also, when the object moves, Either use a fully parallel processing circuit that processes the output signals of all photodetectors simultaneously, or scan the output signals of individual detectors at a speed that allows the object to move at a negligible speed. Therefore, this method has difficulty in high-precision measurement and is considered unsuitable for measuring the dimensions of moving objects.

In the case of a method in which the object to be measured is moved at a constant speed and the time taken to pass a certain point is measured, there are error factors as described below. That is, in order to obtain high accuracy, it is necessary to eliminate errors in capturing the front and rear ends of the object to be measured, and it is necessary to use a very narrowly focused light beam or a very narrow slit. In addition, fluctuations in the moving speed and direction of the object to be measured directly cause errors in the measured values, so it is necessary to use a device that moves the object to be measured accurately at a constant speed and in a fixed direction, or to change the moving speed and direction of the object to be measured. There is no choice but to use a means of measuring with high precision.

In this way, even with this method, in order to obtain high accuracy, auxiliary means must be added and a complicated configuration must be adopted.

(Problems to be Solved by the Invention) An object of the present invention is to provide a simple structure for moving objects that are difficult to measure with conventional non-contact dimension measuring devices as described above. An object of the present invention is to provide a non-contact type diameter measuring device that is not easily affected by fluctuations in the moving speed of an object and can perform highly accurate measurements.

(Summary of the Invention) In order to achieve this object, the present invention uses an optical system to generate a circular image of an object to be measured, which is a moving circular object having a shape such as a sphere or a disk and moving at a substantially constant speed. A waveform projected onto a spatial filter having a differential configuration consisting of a rectangular photodetector array and a differential amplifier circuit, and having a characteristic peak that depends on the diameter of the measured object of the output signal of the spatial filter. By using a configuration in which the data is processed by a subsequent arithmetic unit, and by using a method to obtain the diameter of the measured object through simple calculations for waveform processing, high-precision measurement can be achieved with a simple configuration. ing.

(Structure of the Invention) Next, the present invention will be specifically described with reference to embodiments shown in the drawings. FIG. 1 shows the configuration of an embodiment of the present invention. In the figure, reference numeral 1 denotes a rectangular photodetector array of 2n pieces of the same size arranged at equal intervals. Each photodetector outputs an electrical signal proportional to the area of the portion illuminated with light and the light intensity. Although various materials and structures are conceivable for the photodetector, a configuration using a photodiode using a pn junction (17 and 81) will be described as an example. Using photolithography technology, it is easy to fabricate an array of St photodiodes of the same size on the same substrate, and can be produced at low cost with high dimensional accuracy.

A circular image (4) of a circular object to be measured (3) is projected onto the photodetector array using the optical system 2 in the figure. In the figure, the configuration is based on a lens system, but a system in which an image of a circular object to be measured is projected onto a photodetector array using a parallel light beam may also be used.

summing all the odd-numbered outputs of the photodetector array;
All even-numbered outputs are summed and these two are input to the differential amplifier circuit (5). When a photodiode is used as a photodetector, its output current is proportional to the amount of received light, so the differential amplifier circuit is of a current amplification type. The optical system, photodetector array, and differential amplifier configured in this manner form a spatial filter with a differential configuration.

The output of the differential amplifier is connected to the arithmetic unit w(6). The arithmetic unit processes the waveform of the output signal of the differential amplifier circuit, which has a characteristic peak that depends on the diameter of the object to be measured, by signal processing as described in the operating principle described later, and has the function of obtaining the diameter of the object to be measured. A microconbeater equipped with an A/D converter is constructed of a digital or analog electric circuit that performs substantially the same processing as the microconbeater.

(Principle of operation) The present invention is capable of outputting a circular image of an object to be measured, which is a moving circular object having a shape such as a sphere or a disk and moving at a substantially constant speed, onto a spatial filter with a differential configuration. Focusing on the fact that the signal waveform has a characteristic peak that depends on the diameter of the object to be measured, the diameter of the object to be measured is obtained by performing simple calculations on the waveform of the output signal. Below, the characteristics of the waveform of the output signal of the spatial filter having a differential configuration and the signal processing method of the present invention will be explained.

Image f of a circular object moving at a constant speed V as shown in Figure 1
When (x, y) is projected by a lens or a parallel beam onto a spatial filter constituted by a photodetector array represented by a spatial weighting function h (x, y), the instantaneous value of the output coefficient g(t) is given by the following equation.

g(t)=g(xo,yo)−Kfdxfdyf(x,
y) h(x-xo+y-yo) fi) Here, Xo
-■t+c1. y, 2C6+ c,,c,, : constant=proportional coefficient whereas, f(x,y)? : As a black circular image on a white background, and h (x, y) as a weight function of a configuration in which 2n photodetector arrays of the same size are alternately connected in a differential type, the following (2) ( When expressed as in equation 3) and performing integration, equation (1) and equation (4) are obtained.

Here, D=diameter of image of object to be measured, P: pitch of photodetector array, w: width of photodetector, L: length of photodetector, n logarithm of slit, k
= 0.1, 2. −・,n−1゜Here, a, ,b,
:X coordinate 1g of the left and right ends of the first photodetector that crosses the object
o2 Output value when there is no target.

Normalized amplitude G(t) = (g(t) - g1)
)/KP and the normalized time T=t-V/P, the results of which were simulated by a computer are shown in FIG. The diameter of the image of the object to be measured is taken as a parameter, and D=0. ]XP
24 waveforms were produced from D=2.4×P. Time t is the time O when the center of the object reaches the front end of the slit. This waveform shows that although the position of the zero point remains unchanged, the rise 9 of the waveform, the phase of the peak (displacement in the time direction), and the amplitude change depending on the size of the object.

Focusing on the characteristics of the waveform peaks, the absolute value of the amplitude of the first peak increases monotonically according to the diameter of the object to be measured, and has an anisotropic shape from the second and subsequent peaks. . Furthermore, when the center of the image of the object to be measured passes through 2n photodetectors, 2n large peaks are formed, and small peaks sometimes exist between the large peaks. In the following, peak means a large peak. The peaks that appear when both the front and rear ends of the moving circular image are projected onto the photodetector array have the same regular waveform. By focusing on these characteristics, information on the diameter of the object to be measured can be obtained from the waveform.

As time information, from the rise of the output waveform, the first . Second. FIG. 3 shows the relationship between the time to the center of the third peak and the normalized diameter D/P. At the kth peak, there is a linear relationship with D≦kP−W, 2PT=(D + W
+P(k-1)), and when kP-W<D, 2PT 岑P(1(-1)).

As the amplitude characteristics, the first. Second. The amplitude of the third peak is taken and the relationship with D/P is shown in FIG. Amplitude G of the first peak
The absolute value of (tz) does not have a linear relationship with the diameter of the object to be measured, but it increases monotonically, so the diameter of the object to be measured can be calculated from the measurement of G(tz). . As the calculation means, there may be a method in which the relationship between G(tz) and D is stored in advance in the memory of the calculation device as 1 to 1, and the table is referred to as necessary. On the other hand, for the kth peak, D=lP−W(+=1.2
．． ..., k), the sign of the differential coefficient is reversed. Also, as the number increases by 1, the output increases. If i corresponding to the observed force D is obtained, it becomes a monotone function if 1 is determined, so it can be measured in a similar manner.

Based on the above considerations, the flow for obtaining the diameter of the object to be measured is shown below.

(1) Obtain the approximate value D0.

■Detect the first peak of the signal waveform that exceeds a preset threshold, and determine the time t from the first rise time to the first peak.

and measure the vibration @c(tz).

(2) From G(tl), obtain the approximate diameter D0 of the object. By using the relationship of peak 1 in FIG. 4 and by means such as table reference.

■Decide which peak to measure 1. (It will be referred to as the k-th one.) The method for determining k is preferably selected so that, for example, P is the photodetector pitch and W is the photodetector width so that (k-1)P-WEDo≦kP-W. By selecting in this manner, it is possible to select a peak having a regular waveform that appears when both the front and rear ends of the moving circular image are projected onto the photodetector array. , and for the sake of simplicity, a specific k value. It may be selected without depending on k, or a method of selecting a plurality of k and averaging the obtained measured values may be used.

■Approximate speed value V. get.

To get vo, for example. and tl y p, it is best to calculate using the following formula.

2・tz ・Vo=Do+W (Do<P
-W case) 2・tz・Vo=P+ε(Do-P+W)
/P (in the case of P-W≦Do) ε is a constant. Also, for simplification, an approximate value of the velocity estimated in advance may be used, or it may be measured by another means.

The means for carrying out the above (2) is as shown in Figure 1. This is calculation 7.

(2) Measurement using amplitude information ■Do and V. Using the equation below, that is, the relationship shown in Figure 3,
Estimate the time tk of the c-th peak.

2-tk-Vo=Do+W+P(k-1) (2) Check around the estimated time to detect the second peak, and measure its time tk and amplitude G(tk). The detection means may be such that all waveforms are stored in advance in a memory or the like, or a peak is searched for using a microcomputer, or the peak may be detected in real time near the estimated time. Since the estimated time is obtained, there is no chance of losing sight of the peak in question.

■ Obtain the diameter of the circular image of the object to be measured using the relationship shown in Figure 3 from G(tz) by referring to a table or other means, and further calculate the diameter D1 of the object from the known magnification of the optical system. get.

The means for performing this is the D1 operation 8 in FIG.

(3) Measurement using time information ■ Obtain the speed V from the tk and tl obtained by the above measurements using the following formula.

2・tk・V=D2+W+ P・(k−1,) ■tk and ■. (or ■) Use the formula below to estimate the time tz of the zero crossing point before or after the l(th peak.

2-t·V=2=tk-v±0.5-P■ Check around the estimated time to detect the zero cross point and measure tz.

It is used to correct the error in time measurement (or the value of velocity V) by comparing with the estimated value.

The means for performing this is the D2 operation 8 in FIG.

(4) Obtain diameter measurements.

(2) The measured value is the average of Dl obtained in (2) and D2 obtained in (3).

Furthermore, it has a function that allows switching, rather than discarding D2 and choosing Dl in situations where there are large fluctuations in time measurement or speed, and discarding Dl and choosing D2 in situations where there is a large error due to non-uniformity of the optical system. Also good.

The means for performing this is the D operation 10 in FIG.

(Effects of the Invention) Since the present invention has the above-described configuration, the present invention has a simple structure, is less susceptible to fluctuations in the moving speed of the object to be measured, and can perform highly accurate measurements. Since the measurement is performed without making the object stand still, the measurement can be carried out quickly, especially in applications where a large number of objects to be measured are to be measured in succession.

Furthermore, the combination of the photodetector array and the arithmetic unit has a configuration suitable for integration, and can be manufactured at low cost through mass production.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the waveform of the output signal of the differential amplifier circuit, and Fig. 3 is a diagram showing the normalized peak time and the normalized diameter of the object to be measured. FIG. 4 is a diagram showing the relationship between the normalized peak amplitude and the normalized diameter of the object to be measured. 1 is a photodetector array, 2 is an optical system, 3 is a circular object to be measured,
4 is a circular image, 5 is a differential amplifier circuit, 6 is an arithmetic unit, 7 is a means for calculating the approximate diameter of the circular image, 8 is a means for calculating the diameter of the circular object to be measured, 9 is a means for calculating the diameter of the circular object; Means for calculating the diameter of the circular object to be measured; 10 indicates means for calculating the true diameter of the circular object to be measured. Patent applicant: Anritsu Electric Co., Ltd. Agent: Patent attorney: Ryotabe Koike

Claims (1)

[Claims] A photodetector array (1) consisting of 2n rectangular photodetectors of the same size arranged at equal intervals; and a circular object to be measured (3) that moves at a substantially constant speed. Image (4
) on the photodetector array; and an optical system (2) that receives the sum of the outputs of the odd-numbered photodetectors and the sum of the outputs of the even-numbered photodetectors of the photodetector array. , a differential amplifier circuit (5) that outputs a signal having 2n peaks when the circular image passes through the photodetector array; (1) from the first rise time of the waveform of the output signal from the differential amplifier circuit exceeding a preset arbitrary threshold; Time t_ to the first peak of the waveform of the output signal
1 and the amplitude G(t_1) of the first peak, and
means (7) for calculating an approximate diameter D_0 of the circular image corresponding to the peak amplitude G(t_1); (2) both front and rear ends of the moving circular image are projected onto the photodetector array; means (8) for calculating the diameter D_1 of the circular object from the k-th (1≦k≦2n) peak amplitude G(t_k) that appears when the state is; (3) a moving circular image; From the k-th (1≦k≦2n) peak appearance time t_k that appears when both front and rear ends of the circle are projected onto the photodetector array and the zero-crossing point appearance time t_z before or after that peak, means (9) for calculating the moving speed V of the shaped image, and calculating the diameter D_2 of the circular object from the moving speed V, the peak appearance time t_k, and the zero cross point appearance time t_z; (4) the calculation; means (10) for calculating the true diameter D of the object to be measured by averaging the diameters D and D of the object to be measured and correcting the speed error using the calculated moving speed V; Non-contact diameter measuring device.