JPH0236358A - Space filter speed sensor - Google Patents

Abstract

PURPOSE:To accurately measure the speed of a body to be measured by providing a space filter with gratings at different intervals, and selecting the speed corresponding signal of the body to be measured from the output signal of the space filter according to the grating intervals and size. CONSTITUTION:On a substrate 1, a 1st space filter part 7 is provided by arranging electrodes 3 and 5 in a lattice shape and a 2nd space filter part 13 is formed of electrodes 9 and 11 similarly; and a transparent electrode 15 are provided on the filter parts 7 and 13. The output signals of the electrode 3 and 5 are supplied to a differential amplifier 25 through input terminals 17 and 19 to remove DC components and the resultant signals are supplied to a spectral analyzer 27 to find the peak frequency, which is supplied to a computer 33. Further, the output signals from the electrodes 9 and 11 are also supplied to an amplifier 29 through terminals 21 and 23 to remove DC components and the signals are supplied to the computer 33 through an analyzer 31. Further, the computer 33 detects the speed of the body to be measured according to the output signals of the filter parts 7 and 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention 1 (Field of Industrial Application) The present invention relates to a spatial filter speed sensor that detects the moving speed of an object to be measured using a spatial filter.

(Prior art) A speed sensor using a spatial filter can measure the moving speed of an object without contact by receiving light from the object, so it is useful for measuring the speed of vehicles, etc. It is used for.

FIG. 5 is a diagram showing the basic configuration of a spatial filter speed sensor. The spatial filter speed sensor focuses light with an irregular brightness distribution from an object 41 moving at a speed V onto a spatial filter 45 through an objective lens 43, and photoelectrically converts this light into an electrical signal. The moving speed of the object to be measured 41 is detected from the frequency of this output signal. If the object to be measured 41 moves at a speed V and the magnification of the optical system consisting of the objective lens 43 is m, then the elephant on the spatial filter 45 moves at a speed m
Move with y.

The spatial filter 45 has a one-dimensional narrow band pass characteristic in the traveling direction, and extracts a specific spatial frequency component from the irregular brightness and darkness distribution of the object to be measured 41 .

The spatial filter 45 outputs a signal with a frequency f that is proportional to the speed 2 of the object 41 to be measured. Here, if the lattice spacing of the spatial filter 45 is p, then the velocity ■ can be determined by the following equation.

v=f-p/m (1) As can be seen from this equation, by measuring the frequency "," the velocity (2) of the object to be measured 41 can be detected.

The measurement method described above is based on the assumption that the object to be measured 41 has an irregular brightness/darkness distribution and there is no square component, but in reality, the object to be measured 41 has an irregular brightness/darkness distribution. It also has a regular pattern, and may have certain spatial frequency components stronger than other frequency components. For example, such cases include rocks and patterned carpets.

Now, in a spatial filter velocity sensor that has an optical system with a magnification of 1, a pattern with an interval of about 5 times the lattice interval of the spatial filter, that is, about 115 spatial frequency components of the spatial frequency selected by the spatial filter is transferred to other frequencies. Fig. 6 shows the power spectrum distribution of the output signal of the spatial filter when the moving speed of the object is measured by the spatial filter speed sensor, considering the object to be measured has a force stronger than the component. It can be seen from the figure that there are two types of strong frequency components, f2, in the output signal of the spatial filter. The frequency f1 corresponds to the spatial frequency due to the regular pattern of the object to be measured, and is given by the following equation.

f + = m - V / 5p - (2) Also, the frequency r2 is due to the irregular brightness distribution due to the movement of the object to be measured, and corresponds to the moving speed of the object to be measured, and is determined by the above-mentioned formula (1). .

(Problems to be Solved by the Invention) As described above, when measuring the speed of an object having a regular pattern, etc. using a spatial filter ladder speed sensor, a signal having two types of frequency components is output from the spatial filter. There is a problem in that it is not possible to identify which signal corresponds to the moving speed of the object to be measured, and the speed of the object to be measured cannot be detected correctly.

The present invention has been made in view of the above, and its purpose is to provide a space in which the speed of an object to be measured can be accurately detected without being affected by the regular pattern of the object. An object of the present invention is to provide a filter speed sensor.

[Structure of the invention] (Means for solving one problem) In order to achieve the above object, the spatial filter velocity sensor V of the present invention receives light from a measured object with a spatial filter, and detects light from the spatial filter. A spatial filter speed sensor that detects the speed of an object to be measured from the frequency of an output signal, wherein the spatial filter includes a plurality of gratings provided at different intervals, and the spatial filter is configured based on the size of the plurality of grating intervals. The gist of the present invention is to have a selection means for selecting a signal corresponding to the speed of the object to be measured from the output signals of the object.

(Function) In the spatial filter speed sensor of the present invention, the spatial filter is provided with a plurality of gratings whose spacing is determined, and the velocity of the object to be measured is determined from the output signal of the spatial filter based on the width of the spacing between the plurality of gratings. The corresponding signal is selected.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a perspective view showing the configuration of a spatial filter used in a spatial filter velocity sensor according to an embodiment of the present invention. The spatial filter shown in the figure has a first spatial filter section 7 formed by interlocking a first electrode 3 and a second electrode 5 formed in a comb shape so as to form a lattice on a substrate 1. and a second spatial filter section 13 formed by interlocking a third electrode 9 and a fourth electrode i11, which are similarly formed in a comb shape so as to form a lattice on the substrate 1.
and a transparent electrode 15 provided so as to overlap these spatial filter sections 7.13.

The size of the grid spacing of the first spatial filter section 7 formed by interlocking the comb-like sections of the first and second electrodes 3.5 is I)+, and the size of the grid spacing of the third and fourth electrodes 3.5 is I) Electrode 9.
The size of the interval between the grids of the second spatial filter section 13 formed by interlocking the 11 comb-like sections is p2.

The spatial filter configured as described above is the sixth filter described above.
As shown in the figure, each of the electrodes 3.5.9.11 is illuminated by light from the object to be measured through the objective lens.
Photoelectric conversion occurs between the transparent electrode 15 and the transparent electrode 15, and a current flows. In this case, when the image of the object to be measured formed on the spatial filter moves with the movement of the object to be measured, a frequency peak proportional to the moving speed of the object will be generated according to equation (1) described above. A signal is extracted from the spatial filter. It is.

Figure 2 shows each electrode 3.5°9.1 of the spatial filter in Figure 1.
1 is a sized block diagram showing the configuration of a signal processing circuit that processes an output signal from 1. FIG. In the figure, output signals from the first and second electrodes 3 and 5 of the first spatial filter section 7 are input to the differential amplifier 2 via input terminals 17 and 19, respectively.
5 to remove the direct current component, and then supplied to a spectrum analyzer 27 where the input frequency is analyzed to determine the peak frequency, and this data is supplied to the computer 33. Further, the output signals from the third and fourth electrodes 9° 11 of the second spatial filter section 13 are similarly supplied to both input terminals of the differential amplifier 29 via the input terminals 21 and 23, respectively, and are converted into direct current. The components are removed and then fed to a spectrum analyzer 31 for input frequency analysis to determine peak frequencies, and this data is fed to a computer 33.

The computer 33 detects the speed of the object to be measured based on the output signals from the first spatial filter section 7 and the second spatial filter section 13 as described above, and its operation will be explained next. Before doing so, the principle will be explained using FIG.

When the object to be measured moves at a speed v r, in addition to an irregular brightness distribution corresponding to the moving speed of the object to be measured, an irregular brightness distribution corresponding to the moving speed of the object to be measured is obtained on the spatial filter. Assuming that a regular pattern is generated in the moving direction of the object at a speed V, the spectral distribution of the output signals of the first spatial filter section 7 and the second spatial filter section 13 at this time is as shown in Fig. 3. , <b> appear as shown in 1.

In FIG. 3(a), which shows the spectral distribution of the output signal from the first spatial filter section 7, the spectrum indicated by reference numeral 51 is generated by a regular pattern of the object to be measured, and this frequency is When the magnification of the optical system is expressed as m, it becomes l1lv/q, which is determined by the pattern spacing q, which is unrelated to the lattice spacing of the spatial filter, and the spread of the frequency distribution is small, resulting in a rough spectrum.Symbol 53 The spectrum indicated by is a frequency spectrum corresponding to the moving speed of the object to be measured, has a frequency mv/pH determined by the lattice spacing p1 of the first spatial filter section 7, and has a wider frequency distribution than the spectrum 51. has.

Similarly, in the spectral distribution of the output signal from the second spatial filter section 13 shown in FIG.
The frequency is mv/q, which is determined by the pattern interval Q'C. The spectrum indicated by reference numeral 57 is a frequency spectrum corresponding to the moving speed of the object to be measured, and is a spectrum of a frequency corresponding to the moving speed of the object to be measured.
It has a frequency mV/p2 determined by a grid spacing p2 of 3.

From the relationship shown in FIG.
It can be seen that the spectra 51.55 measured in , respectively, have the same frequency mV/Q even though the respective lattice spacings of the first spatial filter section 7 and the second spatial filter section 13 are different.

On the other hand, the normal spectrum 53.57 corresponding to the moving speed of the object to be measured has a frequency of IIV/+1 according to the respective lattice spacings D+ and +12 of the first spatial filter section 7 and the second spatial filter section 13. +, n+v/p2, and if these frequencies are fA and tB, the ratio of these frequencies f A /f s is the ratio of the lattice spacing + 12/
pl (that is, to f/f port = p2/F
l+). Therefore, if a frequency is selected in which the frequency ratio of each output signal obtained from the first spatial filter section 7 and the second spatial filter section 13 is equal to the ratio of the grid spacing, the moving speed of the object to be measured can be determined from this frequency. It can be detected.

Next, the operation will be explained with reference to the flow charts and explanatory diagrams shown in FIGS. 4(a) and 4(b).

First, the above relationship r8/f B =D is determined by the ratio of the grid spacing among the combinations of the plurality of frequency components of the output signals of the spatial filter section 7 and the second spatial filter section 13 of the ITI.
2 /D + is established, and in order to find the moving speed of the object to be measured from the frequencies fA and fB at that time,
First spatial filter section 7 and second spatial filter section 1
The peak values detected by spectrum analysis of the output signal of 3 in the spectrum analyzer 27.31 of the circuit shown in FIG.
For example, A1. A2. A3. Lined up with...
Further, the filter from the second spatial filter section 13 is, for example, B1.
．． B2. B3. ... (step 110.12
0). Note that the size of the spectrum having a peak becomes large when the spectrum is selected depending on the lattice spacing or when the spectrum has a regular pattern.

Arrange them in descending order of power and then compare them.

The combination of this comparison is shown in FIG. 4(b), for example.

Comparisons are made in order of power as indicated by ■, ■, ... until the relationship fA/rB=I)z/i)+ is established (steps 130, 140>. In this case, fA
When the combination =fB occurs, this frequency component can be determined to be a frequency component of a regular pattern, so this combination is excluded.

When the relationship fA/fB=p2/p1 holds true as a result of the above comparison, the moving speed of the object to be measured (■) can be determined by substituting that frequency into equation (1).
Step 150).

Furthermore, by using the algorithm mentioned above,
Power line noise in the frequency spectrum 50 or 60
Noise 100 or 120 Hz due to Hz or flickering lights
Even when a speed signal appears, information having a speed signal can be appropriately selected.

[Effects of the Invention] As explained above, according to the present invention, a spatial filter is provided with a plurality of gratings having different spacings, and the object to be measured is selected from among the output signals of the spatial filter based on the ratio of the spacings of the plurality of gratings. Since the signal corresponding to the speed of the object to be measured is selected, even if the object to be measured has a regular pattern, unnecessary signals due to the regular pattern, etc. are removed and the signal corresponding to the speed of the object to be measured is selected. By selecting only the corresponding signal, the speed of the object to be measured can be accurately detected using this signal.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of a spatial filter used in a spatial filter speed sensor according to an embodiment of the present invention, and FIG. 2 is a circuit block diagram of a spatial filter speed sensor using the spatial filter of FIG. 1. , Fig. 3 is a diagram showing the power spectrum detected by the spatial filter of Fig. 1, and Fig. 4 is a diagram showing the power spectrum detected by the spatial filter of Fig. 1.
Figures (a) and (b) are a flowchart showing the operation of the spatial filter velocity sensor in Figure 2 and an explanatory diagram thereof, respectively;
Fig. 5 is a diagram showing the configuration of a general spatial filter, and Fig. 6 is a diagram showing the frequency spectrum of an output signal when the velocity of a measured object having a regular pattern is measured using a conventional spatial filter. . 1... Substrate 3... First electrode 5... Second electrode 7... First spatial filter section 9
...Third electrode 11...Fourth electrode 13...Second spatial filter section 15...Transparent electrode 25.29...Differential amplifier 27
．． 31...Spectrum analyzer 33...Computer Figure 1 Figure 2

Claims (1)

[Claims] A spatial filter speed sensor that receives light from an object to be measured with a spatial filter and detects the speed of the object from the frequency of an output signal from the spatial filter, the spatial filter having a plurality of spatial filters provided at different intervals. A spatial filter velocity sensor comprising: a grid; and selection means for selecting a signal corresponding to the velocity of the object from the output signal of the spatial filter based on the size of the plurality of grid intervals.