Speed measurement device and speed measurement method

Abstract

A velocity measurement device is provided with: a beam splitter (20) that splits reflected light from a moving object to be measured (10) into first light and second light; an object-side telecentric lens or both-side telecentric lens (4) that receives reflected light; a comparison unit (301) that compares the amplitude of a first signal, which is a signal obtained by spatially filtering first light at a first distance (L) from the optical splitter (20), and the amplitude of a second signal, which is a signal obtained by spatially filtering second light at a second distance (L + D) from the optical splitter (20); and a movement speed calculation unit (302) that calculates the movement speed of the object to be measured (10) on the basis of a signal having a large amplitude between the first signal and the second signal.

Description

Technical Field

[0001] The invention relates to a speed measuring device and a speed measuring method. Background Art

[0002] A method for measuring the moving speed of an object in a non-contact manner is proposed. Patent document 1 states that: two spatial filters are arranged at positions with different optical path lengths from the object, so that the reflected light from the object is imaged on both sides of the two spatial filters, and the moving speed of the object is calculated using the frequencies of both signals filtered by the two spatial filters.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 53-138381 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In conventional non-contact speed measuring devices, when the distance between an object and the speed measuring device changes, the position of the image formed by the reflected light from the object deviates from the spatial filter, so that the speed of the object cannot be accurately measured. Therefore, one of the objects of the present invention is to provide a speed measuring device and a speed measuring method that can accurately measure the speed of an object even if the distance between the object and the speed measuring device changes.

[0008] Solutions for solving problems

[0009] The speed measuring device of the scheme of the present invention comprises: a spectrometer, which divides the reflected light from the moving measuring object into a first light and a second light; an object-side telecentric lens or a double-side telecentric lens, which receives the reflected light; a comparison unit, which compares the amplitude of a first signal with the amplitude of a second signal, wherein the first signal is a signal obtained by spatially filtering the first light at a first distance from the spectrometer, and the second signal is a signal obtained by spatially filtering the second light at a second distance from the spectrometer; and a moving speed calculation unit, which calculates the moving speed of the measuring object based on the signal with a larger amplitude between the first signal and the second signal.

[0010] The velocity measurement device may further include: a first spatial filter for spatially filtering the first light at a first distance from the spectrometer; and a second spatial filter for spatially filtering the second light at a second distance from the spectrometer.

[0011] In the velocity measurement device, the first spatial filter and the second spatial filter may each include a photodetector, and the photodetectors may be arranged in a stripe shape at a predetermined pitch.

[0012] In the velocity measurement device, the first spatial filter and the second spatial filter may each include a grating having light shielding portions arranged in stripes at a predetermined pitch, and a photodetector receiving light having passed through the grating.

[0013] Alternatively, the speed measuring device may further include: a first imaging element for imaging the first light at a first distance from the spectrometer; a second imaging element for imaging the second light at a second distance from the spectrometer; and an image processing unit for performing spatial filtering on the images respectively captured by the first imaging element and the second imaging element.

[0014] In the velocity measurement device described above, the object-side telecentric lens or the both-side telecentric lenses may be arranged before the beam splitter in the traveling direction of the reflected light.

[0015] In the velocity measurement device described above, the object-side telecentric lens or the both-side telecentric lenses may be arranged after the beam splitter in the traveling direction of the reflected light.

[0016] The velocity measurement device may further include a light source for irradiating light toward the object to be measured.

[0017] The speed measurement method of the scheme of the present invention includes: dividing the reflected light from the moving measurement object into a first light and a second light through a spectrometer; receiving the reflected light through an object-side telecentric lens or a two-side telecentric lens; comparing the amplitude of a first signal with the amplitude of a second signal, wherein the first signal is a signal obtained by spatially filtering the first light at a first distance from the spectrometer, and the second signal is a signal obtained by spatially filtering the second light at a second distance from the spectrometer; and calculating the moving speed of the measurement object based on the signal with a larger amplitude between the first signal and the second signal.

[0018] In the velocity measurement method, the first signal obtained by spatially filtering the first light and the second signal obtained by spatially filtering the second light may be obtained by photodetectors respectively arranged in stripes at a predetermined pitch.

[0019] Alternatively, in the above-mentioned speed measurement method, a first signal obtained by spatially filtering the first light and a second signal obtained by spatially filtering the second light are obtained respectively through a grating and a photodetector, wherein the grating has a shading portion arranged in a stripe shape at a prescribed interval, and the photodetector receives light passing through the grating.

[0020] Alternatively, the speed measurement method further includes: photographing the first light at a first distance from the spectrometer; photographing the second light at a second distance from the spectrometer; and spatially filtering the images photographed by the first photographing element and the second photographing element.

[0021] In the above velocity measurement method, the object-side telecentric lens or the double-side telecentric lenses may be arranged before the beam splitter in the traveling direction of the reflected light.

[0022] In the above velocity measurement method, the object-side telecentric lens or the double-side telecentric lenses may be arranged after the beam splitter in the traveling direction of the reflected light.

[0023] The velocity measurement method may further include irradiating light to the object to be measured.

[0024] Effects of the Invention

[0025] According to the present invention, it is possible to provide a speed measuring device and a speed measuring method which can accurately measure the speed of an object even if the distance between the object and the speed measuring device varies. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram showing a speed measuring device according to an embodiment.

[0027] Figure 2 Schematic diagram showing a photodetector according to an embodiment.

[0028] Figure 3 It is a schematic graph showing the temporal change of the intensity of the signal according to the embodiment.

[0029] Figure 4 : is a schematic graph showing the frequency spectrum of the signal according to the embodiment.

[0030] Figure 5 It is a schematic diagram showing a speed measuring device according to an embodiment.

[0031] Figure 6 Schematic diagram showing a photodetector according to an embodiment.

[0032] Figure 7 : is a schematic graph showing the temporal variation of the intensity of two signals according to the embodiment.

[0033] Figure 8 : is a schematic graph showing the time variation of the difference between two intensities of a signal according to an embodiment.

[0034] Fig. 9 It is a schematic diagram showing a speed measuring device according to an embodiment.

[0035] Fig.10 It is a schematic diagram showing a speed measuring device according to an embodiment. DETAILED DESCRIPTION

[0036] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the accompanying drawings, the same or similar parts are represented by the same or similar reference numerals. However, the accompanying drawings are schematic. Therefore, specific dimensions and the like should be judged in accordance with the following description. In addition, the accompanying drawings also include parts with different dimensional relationships and ratios.

[0037] like Figure 1 As shown, the speed measuring device of the embodiment includes: a spectrometer 20 for dividing the reflected light from the moving measuring object 10 into a first light and a second light; an object-side telecentric lens or a double-side telecentric lens 4 for receiving the reflected light; a comparison unit 301 for comparing the amplitude of a first signal obtained by spatially filtering the first light at a first distance L from the spectrometer 20 and the amplitude of a second signal, wherein the first signal is a signal obtained by spatially filtering the first light at a first distance L+D from the spectrometer 20, and the second signal is a signal obtained by spatially filtering the second light at a second distance L+D from the spectrometer 20; and a moving speed calculation unit 302 for calculating the moving speed of the measuring object 10 based on the signal with a larger amplitude of the first signal and the second signal. The comparison unit 301 and the moving speed calculation unit 302 are included in a central processing unit (CPU: Central Processing Unit) 300, for example.

[0038] The object 10 to be measured moves in parallel. The object 10 to be measured moves relative to the speed measuring device. For example, the speed measuring device may be stationary and the object 10 to be measured may move, or the object 10 to be measured may be stationary and the object 10 to be measured may move. In the case where the speed measuring device is stationary and the object 10 to be measured moves, examples of the object 10 to be measured include films and nonwoven fabrics, but are not particularly limited. In the case where the object 10 to be measured is stationary and the speed measuring device moves, examples of the object 10 to be measured include road surfaces, but are not particularly limited.

[0039] The speed measuring device of the embodiment may also include a light source 30 that irradiates light to the measuring object 10. As the light source 30, a laser and a light-emitting diode (LED) can be used, but there is no particular limitation. The intensity of the light is, for example, constant. The speed measuring device of the embodiment may also include an irradiation lens 31 that makes the light emitted by the light source 30 become parallel light. The light source 30 irradiates light, thereby generating reflected light from the measuring object 10. However, in the case where reflected light is generated from the measuring object 10 by sunlight or surrounding illumination light even if the light source 30 does not irradiate light, the light source 30 may not be provided.

[0040] The double-sided telecentric lens 4 includes: a first lens 40 for focusing reflected light; and a second lens 41 for making the reflected light focused by the first lens 40 into parallel light. The principal rays on the object side of the first lens 40 are parallel. Therefore, even if the distance between the first lens 40 and the measuring object 10 changes, the imaging magnification is constant. The first lens 40 is arranged so that its optical axis is substantially perpendicular to the measuring object 10. The second lens 41 is arranged so that its optical axis is substantially perpendicular to the measuring object 10. For example, the optical axis of the first lens 40 coincides with the optical axis of the second lens 41. The aperture 61 may be arranged between the first lens 40 and the second lens 41. The first lens 40, the second lens 41 and the aperture 61 may also be arranged in the lens barrel 71. The double-sided telecentric lens 4 is arranged, for example, between the measuring object 10 and the spectrometer 20. It should be noted that an object-side telecentric lens may be used instead of the double-sided telecentric lens 4.

[0041] The spectrometer 20 divides the reflected light into a first light and a second light. There is no difference between the first light and the second light in that they are reflected lights from the measured object 10. The speed measuring device of the embodiment may also include: a first spatial filter 50 for spatially filtering the first light at a first distance L from the spectrometer 20; and a second spatial filter 51 for spatially filtering the second light at a second distance L+D from the spectrometer 20. The first distance L is different from the second distance L+D. The starting point of the first distance and the second distance is, for example, the intersection of the optical axis of the telecentric lens 4 on both sides and the spectrometer 20.

[0042] Since the first distance L is different from the second distance L+D, when the image of the measurement object 10 is formed on the first spatial filter 50, the image of the measurement object 10 is blurred at the second spatial filter 51. In addition, when the image of the measurement object 10 is formed on the second spatial filter 51, the image of the measurement object 10 is blurred at the first spatial filter 50.

[0043] like Figure 2As shown, the first spatial filter 50 and the second spatial filter 51 may each include a photodetector 52, and the photodetector 52 is arranged in a stripe shape at a predetermined pitch P. The pitch P of the first spatial filter 50 is the same as the pitch P of the second spatial filter 51. Figure 1 The photodetector of the first spatial filter 50 shown converts the first light after spatial filtering into a first signal as an electrical signal. The photodetector constituting the second spatial filter 51 converts the second light after spatial filtering into a second signal as an electrical signal. The first signal and the second signal are amplified by the amplifiers, respectively, and sent to the comparison unit 301.

[0044] like Figure 3 As shown in FIG. 1 , the first signal and the second signal each include an AC component having a frequency proportional to the speed of the measurement object 10 and the pitch P of the first spatial filter 50 and the second spatial filter 51. Here, when the image of the measurement object 10 is clearly formed on the first spatial filter 50 and the image of the measurement object 10 is blurred on the second spatial filter 51, the amplitude of the first signal is as follows: Figure 3 As shown in (A), the amplitude of the second signal is relatively large. Figure 3 When the image of the measurement object 10 is clearly formed on the second spatial filter 51 and the image of the measurement object 10 is blurred on the first spatial filter 50, the amplitude of the first signal is as follows: Figure 3 As shown in (B), the amplitude of the second signal is relatively small. Figure 3 As shown in (A), it is relatively large.

[0045] When the first signal and the second signal are accumulated for a predetermined time and subjected to Fast Fourier Transform (FFT) processing, the following is obtained: Figure 4 The spectrum (amplitude spectrum) shown in FIG. 1 is a spectrum in which positive frequencies that give amplitude peaks except for those near zero are the frequencies of the signal. Here, when the image of the measurement object 10 is clearly imaged on the first spatial filter 50 and the image of the measurement object 10 is blurred on the second spatial filter 51, the peak amplitude in the spectrum of the first signal is as follows: Figure 4 As shown in (A), the peak amplitude in the spectrum of the second signal is relatively large. Figure 4 When the image of the measurement object 10 is clearly formed on the second spatial filter 51 and the image of the measurement object 10 is blurred on the first spatial filter 50, the peak amplitude in the spectrum of the first signal is as shown in (B). Figure 4 As shown in (B), the peak amplitude in the spectrum of the second signal is relatively small. Figure 4As shown in (A), the S / N ratio (signal-to-noise ratio) of the spectrum assigned to the large amplitude peak is higher than the S / N ratio of the spectrum assigned to the small amplitude peak. When determining the frequency of the signal, the reliability of the spectrum assigned to the large amplitude peak is higher than the reliability of the spectrum assigned to the small amplitude peak. It should be noted that the spectrum can also be a power spectrum.

[0046] therefore, Figure 1 The comparison unit 301 shown compares the amplitude of the first signal with the amplitude of the second signal, and selects the signal with the larger amplitude. Alternatively, the comparison unit 301 may also compare the spectrum of the first signal with the spectrum of the second signal, and select the signal with the larger peak amplitude. In addition, in the spectrum, the narrower the half-width of the peak, the larger the peak amplitude, so the comparison unit 301 may also compare the spectrum of the first signal with the spectrum of the second signal, and select the signal with the smaller half-width of the peak. At least one of the comparison unit 301 and the moving speed calculation unit 302 calculates the frequency F of the selected signal. Moreover, the moving speed calculation unit 302 calculates the moving speed V of the measured object 10 using, for example, the following formula (1).

[0047] V=FP / M(1)

[0048] Here, P is the pitch of the first spatial filter 50 and the pitch of the second spatial filter 51. M is the magnification achieved by the two-sided telecentric lens 4. It should be noted that in the calculation of the moving speed V, the period of the signal can also be used instead of the frequency F of the signal.

[0049] In the case where the second lens 41 is present, the magnification M of formula (1) is the same regardless of whether the first signal or the second signal is used. However, in the case where the second lens 41 is not present, the magnification of the first lens 40 is different depending on the position of the first spatial filter 50 and the position of the second spatial filter 51. Therefore, in the case where the second lens 41 is not present and the first signal is used, the magnification at the position of the first spatial filter 50 is used, and in the case where the second lens 41 is not present and the second signal is used, the magnification at the position of the second spatial filter 51 is used.

[0050] When the distance between the speed measuring device and the object to be measured is constant, the moving speed of the object to be measured can be stably measured by imaging the object to be measured on one spatial filter. However, it is possible that the distance between the speed measuring device and the object to be measured cannot be kept constant due to the shaking of either the speed measuring device or the object to be measured. In the case of only one spatial filter, when the image of the object to be measured on one spatial filter is blurred, the moving speed of the object to be measured may not be calculated. In contrast, the speed measuring device of the embodiment is provided with a first spatial filter 50 and a second spatial filter 51 having different optical path lengths from the object to be measured 10. In order to calculate the moving speed, the speed measuring device selects a signal with a large amplitude in the first signal and the second signal after spatial filtering to calculate the moving speed of the object to be measured. Therefore, even if the distance between the speed measuring device and the object to be measured 10 changes in a shortened or lengthened manner, the moving speed of the object to be measured 10 can be accurately calculated. It should be noted that the speed measuring device of the embodiment may also be provided with more than three spatial filters, and the speed measuring device selects a signal with the largest amplitude in the more than three signals after spatial filtering to calculate the moving speed of the object to be measured.

[0051] exist Figure 1 , an example is shown in which the telecentric lens is arranged before the beam splitter 20 in the traveling direction of the reflected light, but the telecentric lens may also be arranged after the beam splitter 20. For example, Figure 5 As shown, the speed measuring device of the embodiment may also include: a double telecentric lens 4A for receiving the first light; and a double telecentric lens 4B for receiving the second light. The double telecentric lens 4A and the double telecentric lens 4B are arranged so that the intersection of their respective optical axes is located at the beam splitter 20.

[0052] The two-side telecentric lens 4A includes: a first lens 40A for focusing the first light; and a second lens 41A for making the first light focused by the first lens 40A parallel light. For example, the optical axis of the first lens 40A coincides with the optical axis of the second lens 41A. An aperture 61A may be arranged between the first lens 40A and the second lens 41A. The first lens 40A, the second lens 41A and the aperture 61A may also be arranged in the lens barrel 71A.

[0053] The two-side telecentric lens 4B includes: a first lens 40B for focusing the second light; and a second lens 41B for making the second light focused by the first lens 40B parallel light. For example, the optical axis of the first lens 40B coincides with the optical axis of the second lens 41B. An aperture 61B may be arranged between the first lens 40B and the second lens 41B. The first lens 40B, the second lens 41B and the aperture 61B may also be arranged in the lens barrel 71B.

[0054] It should be noted that an object-side telecentric lens may be used instead of the two-side telecentric lenses 4A and 4B.

[0055] When the telecentric lens is disposed after the beam splitter 20 in the traveling direction of the reflected light, the comparison unit 301 and the moving speed calculation unit 302 are the same as described above.

[0056] like Figure 6 As shown, Figure 1 and Figure 5 The first spatial filter 50 and the second spatial filter 51 shown may also respectively include: first photodetectors 53 arranged in stripes at a predetermined pitch P; and second photodetectors 54 arranged in stripes at a predetermined pitch P. The second photodetectors 54 are arranged in the gaps between the first photodetectors 53, and the stripe portions of the first photodetectors 53 and the stripe portions of the second photodetectors 54 are arranged alternately.

[0057] The first photodetector 53 and the second photodetector 54 are connected to a differential amplifier 303. Figure 7 As shown in FIG. 1 , the phase of the signal after photoelectric conversion by the first photodetector 53 is inverted relative to the phase of the signal after photoelectric conversion by the second photodetector 54. The differential amplifier 303 obtains the difference between the signal after photoelectric conversion by the first photodetector 53 and the signal after photoelectric conversion by the second photodetector 54. Figure 8 The differential signal shown in FIG. 1 is a differential signal in which the offset component is removed. The differential amplifier of the first spatial filter 50 amplifies the differential signal and sends the amplified differential signal as the first signal to the comparison unit 301. The differential amplifier of the second spatial filter 51 amplifies the differential signal and sends the amplified differential signal as the second signal to the comparison unit 301. By removing the offset component, the amplification factor of the signal can be increased.

[0058] like Fig. 9 As shown in FIG. 1 , the first spatial filter 50 may include: a grating 150 having a light shielding portion arranged in a stripe shape at a predetermined pitch P; a lens 151 for focusing the light that has passed through the grating 150; and a photodetector 152 for receiving the light that has passed through the grating 150 and has been focused by the lens 151. The photodetector 152 sends the first signal to the comparison unit 301. In addition, the second spatial filter 51 may include: a grating 250 having a light shielding portion arranged in a stripe shape at a predetermined pitch P; a lens 251 for focusing the light that has passed through the grating 250; and a photodetector 252 for receiving the light that has passed through the grating 250 and has been focused by the lens 251. The photodetector 252 sends the second signal to the comparison unit 301. In this case, the photodetectors 152 and 252 may not be in a stripe shape.

[0059] like Fig.10As shown, the speed measuring device of the embodiment may also include: a first imaging element 255 that captures the first light at a first distance L from the spectrometer 20; a second imaging element 256 that captures the second light at a second distance L+D from the spectrometer 20; and an image processing unit 304 that performs spatial filtering on the images captured by the first imaging element and the second imaging element. The image processing unit 304 performs processing equivalent to the spatial filtering of the first light at the first distance L from the spectrometer 20 on the image captured by the first imaging element 255, and generates a first signal. In addition, the image processing unit 304 performs processing equivalent to the spatial filtering of the second light at the second distance L+D from the spectrometer 20 on the image captured by the second imaging element 256, and generates a second signal.

[0060] As described above, the present invention is described through the embodiments, but it should not be understood that the description and drawings forming part of the present disclosure are contents that limit the present invention. For those skilled in the art, various alternative embodiments, examples and application techniques should become apparent based on the present disclosure. For example, the spatial filter may also include a grating and a planar photodetector that is in close contact or proximity to the grating. It should be understood that the present invention includes various embodiments not described herein, etc.

[0061] Description of Reference Numerals

[0062] 4: Telecentric lens on both sides; 4A: Telecentric lens on both sides; 4B: Telecentric lens on both sides; 10: Measurement object; 20: Spectrometer; 30: Light source; 31: Illumination lens; 40: First lens; 40A: First lens; 40B: First lens; 41: Second lens; 41A: Second lens; 41B: Second lens; 50: Spatial filter; 51: Spatial filter; 52: Photodetector; 53: Photodetector; 54: Photodetector; 71: Lens barrel; 71A: Lens barrel; 71B: Lens barrel; 150: Grating; 151: Lens; 152: Photodetector; 250: Grating; 251: Lens; 252: Photodetector; 255: Image sensor; 256: Image sensor; 301: Comparison unit; 302: Moving speed calculation unit; 303: Differential amplifier; 304: Image processing unit.

Claims

1. A speed measuring device, comprising: A spectrometer that splits reflected light from a moving measurement object into a first light and a second light; The object side telecentric lens or the two side telecentric lenses receive the reflected light; a comparing unit, which compares an amplitude of a first signal and an amplitude of a second signal, wherein the first signal is a signal obtained by spatially filtering the first light at a first distance from the spectrometer, and the second signal is a signal obtained by spatially filtering the second light at a second distance from the spectrometer; as well as The moving speed calculation unit calculates the moving speed of the measurement object based on the signal with a larger amplitude among the first signal and the second signal.

2. The speed measuring device according to claim 1, further comprising: a first spatial filter, configured to perform spatial filtering on the first light at the first distance from the beam splitter; and The second spatial filter is used to perform spatial filtering on the second light at the second distance from the beam splitter.

3. The speed measuring device according to claim 2, wherein: The first spatial filter and the second spatial filter each include a photodetector, and the photodetectors are arranged in a stripe shape at a predetermined pitch.

4. The speed measuring device according to claim 2, wherein: The first spatial filter and the second spatial filter each include: a grating having light shielding portions arranged in stripes at a predetermined pitch; and a photodetector receiving light having passed through the grating.

5. The speed measuring device according to claim 1, further comprising: a first photographing element, for photographing the first light at the first distance from the beam splitter; a second photographing element, for photographing the second light at the second distance from the beam splitter; as well as The image processing unit performs spatial filtering on the images captured by the first imaging element and the second imaging element respectively.

6. The speed measuring device according to claim 1, wherein: The object-side telecentric lens or the both-side telecentric lenses are arranged before the beam splitter in the traveling direction of the reflected light.

7. The speed measuring device according to claim 1, wherein: The object-side telecentric lens or the both-side telecentric lenses are arranged after the beam splitter in the traveling direction of the reflected light.

8. The speed measuring device according to claim 1, wherein: A light source is further provided for irradiating light toward the measurement object.

9. A method for measuring speed, comprising: Splitting reflected light from the moving measurement object into first light and second light by a spectrometer; receiving the reflected light through the object-side telecentric lens or the telecentric lenses on both sides; comparing an amplitude of a first signal and an amplitude of a second signal, wherein the first signal is a signal obtained by spatially filtering the first light at a first distance from the beam splitter, and the second signal is a signal obtained by spatially filtering the second light at a second distance from the beam splitter; as well as The moving speed of the measurement object is calculated based on the signal having a larger amplitude among the first signal and the second signal.

Images