JP7807982B2 - Optical non-contact speedometer calibration system and optical non-contact speedometer calibration method - Google Patents

Description

The present invention relates to a calibration system for an optical non-contact speedometer and a calibration method for an optical non-contact speedometer.

Non-contact speedometers can measure the speed of an object without contact, and are used, for example, to measure the conveying speed of sheets such as film or nonwoven fabric. In order to maintain the accuracy of non-contact speedometers, methods for calibrating them have been proposed.

JP 8-304452 A describes a method of calibrating a non-contact speedometer by placing a measurement target of known length, using a moving device to move a non-contact speedometer parallel to the measurement target at a given speed, measuring the relative speed of the measurement target with respect to the measurement target, calculating the measurement length of the measurement target from the speed measured by the non-contact speedometer, and comparing the measured length with the known length of the measurement target.

JP 9-113526 A describes a method of calibrating a non-contact speedometer by placing an endless belt of a known length between a pair of pulleys, calculating the reference speed of the endless belt from the rotation speed and known length of the endless belt, measuring the speed of the endless belt with a non-contact speedometer, and comparing the speed measured by the non-contact speedometer with the reference speed.

JP 2017-173216 A describes a method of calibrating a non-contact velocimeter by detecting scattered light from a moving surface plate using a non-contact velocimeter to calculate the period of the beat signal, and then dividing the moving distance of the surface plate by the period of the beat signal to calculate the spacing between the interference fringes formed in the measurement area by the non-contact velocimeter.

Japanese Patent Application Publication No. 8-304452 Japanese Patent Application Publication No. 9-113526 Japanese Patent Application Laid-Open No. 2017-173216

Conventional methods for calibrating non-contact speedometers use a reference measurement object of known length, but during calibration, it may be necessary to measure or set an accurate measurement time when calculating length from speed. Therefore, one of the objects of the present invention is to provide a calibration system and a calibration method for an optical non-contact speedometer that do not require a reference measurement object of known length.

A calibration system for an optical non-contact speedometer according to one aspect of the present invention includes a pipe that is transparent to the inspection light emitted by the optical non-contact speedometer to be calibrated, a fluid supply device that supplies fluid to the pipe, a flow velocity sensor provided in the pipe that measures the speed of the fluid flowing through the pipe as a reference speed, and a calibration signal generation unit that generates a calibration signal for calibrating the measured speed of the optical non-contact speedometer based on the measured speed of the fluid measured by the optical non-contact speedometer and the reference speed.

The above-mentioned optical non-contact speedometer calibration system may further include a holder for holding the optical non-contact speedometer.

In the above-mentioned optical non-contact speed meter calibration system, the holding unit may hold the optical non-contact speed meter so that the test light is irradiated at a position facing the flow velocity sensor.

In the above-mentioned optical non-contact speed meter calibration system, the fluid supply device may supply fluid to the pipe at a plurality of different supply speeds.

The above-mentioned optical non-contact speed meter calibration system may further include a temperature control device that controls the temperature of the piping.

The above-mentioned optical non-contact speedometer calibration system may further include a calibration signal transmission unit for transmitting a calibration signal to the optical non-contact speedometer.

In the above-mentioned optical non-contact speed meter calibration system, the calibration signal may be configured to bring the measured speed closer to the reference speed.

In the above-mentioned optical non-contact speed meter calibration system, the piping and fluid supply device may be configured so that the fluid flow in the piping is laminar.

A method for calibrating an optical non-contact velocimeter according to one aspect of the present invention includes supplying a fluid to a pipe that is transparent to the test light emitted by the optical non-contact velocimeter to be calibrated; measuring the velocity of the fluid flowing through the pipe as a measurement velocity using the optical non-contact velocimeter; measuring the velocity of the fluid flowing through the pipe as a reference velocity using a flow velocity sensor provided in the pipe; and generating a calibration signal for calibrating the measurement velocity based on the measurement velocity and the reference velocity.

The above-mentioned method for calibrating an optical non-contact velocimeter may further include positioning the optical non-contact velocimeter so that the test light is irradiated at a position opposite the flow velocity sensor.

In the above-mentioned method for calibrating an optical non-contact velocity meter, fluid may be supplied to the pipe at multiple different supply speeds.

The above-mentioned method for calibrating an optical non-contact velocity meter may further include controlling the temperature of the pipe.

The above-mentioned method for calibrating an optical non-contact speedometer may further include transmitting a calibration signal to the non-contact speedometer.

In the above-mentioned method for calibrating an optical non-contact speed meter, the calibration signal may be configured to bring the measured speed closer to the reference speed.

In the above-mentioned method for calibrating an optical non-contact velocimeter, the fluid may be flowed through the pipe so that the flow of the fluid in the pipe is laminar.

The present invention provides a calibration system and a calibration method for an optical non-contact speed meter that do not require a reference measurement object of known length.

FIG. 1 is a schematic diagram showing a calibration system for an optical non-contact speed meter according to an embodiment. FIG. 2 is a schematic perspective view of the flow velocity sensor according to the embodiment. FIG. 3 is a schematic cross-sectional view of the flow velocity sensor according to the embodiment. FIG. 4 is a schematic diagram showing an optical non-contact speed meter according to an embodiment. FIG. 5 is a schematic diagram showing an optical non-contact speed meter according to an embodiment. FIG. 6 is a schematic diagram showing an optical non-contact speed meter according to an embodiment. FIG. 7 is a schematic graph showing the relationship between the reference speed and the measured speed according to the embodiment. FIG. 8 is a schematic graph showing the relationship between the reference speed and the measured speed according to the embodiment. FIG. 9 is a flowchart of a method for calibrating an optical non-contact speed meter according to an embodiment. FIG. 10 is a schematic diagram showing a calibration system for an optical non-contact speed meter according to an embodiment. FIG. 11 is a schematic diagram showing a calibration system for an optical non-contact speed meter according to an embodiment.

Embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings, identical or similar parts are represented by identical or similar reference numerals. However, the drawings are schematic. Therefore, specific dimensions, etc. should be determined in reference to the following description. Naturally, there are also parts in which the dimensional relationships and ratios differ between the drawings.

As shown in FIG. 1, the calibration system for an optical non-contact speed meter according to the embodiment includes a pipe 20 that is transparent to the inspection light emitted by the optical non-contact speed meter 10 to be calibrated, a fluid supply device 30 that supplies fluid to the pipe 20, a flow velocity sensor 40 provided in the pipe 20 that measures the velocity of the fluid flowing through the pipe 20 as a reference velocity, and a calibration signal generation unit 301 that generates a calibration signal for calibrating the measured velocity of the optical non-contact speed meter 10 based on the measured velocity of the fluid measured by the optical non-contact speed meter 10 and the reference velocity.

The fluid may be a liquid or a gas. For example, the fluid has at least one of the following properties: scattering the inspection light, reflecting the inspection light, diffracting the inspection light, and modulating the transmission characteristics of the inspection light. The fluid may contain at least one of a substance that scatters the inspection light, reflects the inspection light, diffracts the inspection light, and absorbs the inspection light. The property of the substance that scatters the inspection light, reflects the inspection light, diffracts the inspection light, or absorbs the inspection light may be selected depending on the wavelength of the inspection light. The object may be composed of particles. Examples of liquids include, but are not limited to, water, salt water, and oil.

The fluid supply device 30 includes, for example, a container 31 that stores a fluid, a flow path 32 that connects the container 31 to the pipe 20, and a flow control device 33 provided in the flow path 32. The fluid in the container 31 can be sent unidirectionally to the pipe 20 via the flow path 32 using gravity. Alternatively, the fluid in the container 31 can be sent to the pipe 20 via the flow path 32 using a fluid machine such as a pump. Still alternatively, the fluid in the container 31 can be sent to the pipe 20 via the flow path 32 by pressure applied to the container 31. The flow control device 33 controls the flow rate of the fluid supplied to the pipe 20. A valve or a flow controller can be used as the flow control device 33. The fluid flow rate may be set based on the diameter of the pipe 20. The fluid supply device 30 may supply the fluid to the pipe 20 at a plurality of different supply speeds. The fluid supply device 30 may further include a damper that absorbs pressure fluctuations.

At least the portion of the pipe 20 that is irradiated with the inspection light emitted by the optical non-contact speed meter 10 must be transparent to the inspection light. The pipe 20 is preferably configured to prevent turbulence in the fluid. At least one of the pipe 20 and the fluid supply device 30 is preferably configured to ensure laminar fluid flow in the pipe 20. The pipe 20 is, for example, a straight pipe having a predetermined length. The flow velocity sensor 40 is, for example, provided on the side of the pipe 20. The flow velocity sensor 40 abuts, for example, the outer surface of the pipe 20. It is preferable that there are no irregularities near the inner surface of the pipe 20 where the flow velocity sensor 40 is provided. The flow velocity sensor 40 is not particularly limited as long as it can measure the speed of the fluid flowing through the pipe 20. Examples of flow velocity sensors 40 include thermal flow velocity sensors, ultrasonic flow velocity sensors, and electromagnetic flow velocity sensors. The type of flow velocity sensor 40 may be selected depending on the type of fluid. It is preferable that the flow velocity sensor 40 is a different type of speed meter from the optical non-contact speed meter 10. For example, the flow velocity sensor 40 is a non-optical flow velocity sensor.

An example of a thermal flow sensor is a microflow sensor. As shown in Figures 2 and 3, the microflow sensor includes a substrate 41 having a cavity 46, an insulating film 45 arranged on the substrate 41 to cover the cavity 46, a heater 42 provided on the insulating film 45, an upstream temperature-measuring resistor 43 provided upstream of the heater 42, and a downstream temperature-measuring resistor 44 provided downstream of the heater 42.

The portion of the insulating film 45 that covers the cavity 46 forms an insulating diaphragm. The heater 42 is positioned at the center of the insulating film 45 that covers the cavity 46, and heats the fluid flowing through the pipe 20. The upstream resistance temperature element 43 is used to detect the temperature of the fluid upstream of the heater 42, and the downstream resistance temperature element 44 is used to detect the temperature of the fluid downstream of the heater 42.

When the fluid in the pipe 20 is stationary, the heat applied by the heater 42 diffuses symmetrically in the upstream and downstream directions. Therefore, the temperatures of the upstream and downstream temperature measuring elements 43 and 44 are equal, and the electrical resistances of the upstream and downstream temperature measuring elements 43 and 44 are equal. In contrast, when the fluid in the pipe 20 is flowing from upstream to downstream, the heat generated by the heater 42 is carried downstream. Therefore, the temperature of the downstream temperature measuring element 44 is higher than the temperature of the upstream temperature measuring element 43. As a result, a difference occurs between the electrical resistance of the upstream temperature measuring element 43 and the electrical resistance of the downstream temperature measuring element 44. The difference in the electrical resistance of the downstream temperature measuring element 44 and the upstream temperature measuring element 43 is correlated with the speed and flow rate of the fluid in the pipe 20. Therefore, the velocity and flow rate of the fluid flowing through the pipe 20 can be calculated from the difference between the electrical resistance of the downstream temperature measuring resistor 44 and the electrical resistance of the upstream temperature measuring resistor 43.

If the flow velocity sensor 40 shown in FIG. 1 is an ultrasonic flow velocity sensor, the ultrasonic flow velocity sensor has, for example, an ultrasonic oscillator that abuts against the side of the pipe 20, and measures the flow velocity of the fluid using changes in ultrasonic frequency due to the movement of the fluid. If the flow velocity sensor 40 is an electromagnetic flow velocity sensor, the electromagnetic flow velocity sensor measures the flow velocity of the fluid using changes in electromagnetic induction due to the movement of the fluid.

The optical non-contact velocimeter 10 irradiates the fluid in the pipe 20 with inspection light and calculates the velocity of the fluid based at least on the light reflected from the fluid.

The optical non-contact speedometer 10 may be a laser Doppler speedometer. When the optical non-contact speedometer 10 is a laser Doppler speedometer, the optical non-contact speedometer 10 includes a light source 201 that emits laser light, as shown in FIG. 4. The laser light passes through a collimating lens 202 and is split into two beams by a half mirror 203. One of the split laser beams is reflected by a mirror 204, and the two laser beams enter the pipe 20 at an incident angle θ and interfere with each other. The scattered light or reflected light generated within the pipe 20 is collected by a collecting lens 205 and received by a light-receiving element 206.

The relationship between the frequency F of the Doppler signal obtained from the light receiving element 206, the velocity V of the fluid, the wavelength λ of the laser light, and the incident angle θ of the laser light is given by the following equation (1).
F=(2V/λ)sinθ (1)
The wavelength λ of the laser light and the incident angle θ of the laser light can be obtained in advance. The frequency F of the Doppler signal can be obtained by performing a Fourier transform on the time change of the light received by the light receiving element 206. Therefore, by obtaining the frequency F of the Doppler signal, the optical non-contact velocimeter 10 calculates the velocity V of the fluid.

The optical non-contact velocimeter 10 may be a self-coupling velocimeter. When the optical non-contact velocimeter 10 is a self-coupling velocimeter, it includes a light source 211 that emits laser light, as shown in FIG. 5 . The laser light is incident on the pipe 20. Scattered or reflected light generated within the pipe 20 travels along the same optical path as the irradiated light, but in the reverse direction. The returning light that re-enters the optical resonator within the light source 211 interferes with the laser light generated in the optical resonator. This interference means that a self-coupling effect occurs within the optical resonator. The interference waveform generated by the self-coupling is detected by the light-receiving element 212. Based on the period of the interference waveform, the optical non-contact velocimeter 10 calculates the velocity of the fluid.

The optical non-contact speedometer 10 may be a spatial filter speedometer. When the optical non-contact speedometer 10 is a spatial filter speedometer, the optical non-contact speedometer 10 includes a light source 221 that emits light, as shown in FIG. 6. The light source 221 may be a laser light source or an LED. The fluid in the pipe 20 is irradiated with concentrated light from an oblique direction so as to provide dark-field illumination for the light-receiving optical system of the optical non-contact speedometer 10. The scattered or reflected light generated in the pipe 20 is concentrated by a focusing lens 222, and an image of the fluid is formed on a grating 223 having a periodic transmittance distribution.

If the magnification of the light-receiving optical system is M and the velocity of the fluid is V, the image on the grating 223 moves at a velocity MV. Light transmitted through the grating 223 is received by the light-receiving element 224. The period F of the signal of the transmitted light received by the light-receiving element 224 is given by the following equation (2), where p is the spacing between the gratings 223.
F=MV/p (2)
The magnification M of the light receiving optical system and the spacing p of the grating 223 can be obtained in advance, so by measuring the frequency F, the optical non-contact velocimeter 10 calculates the velocity V of the fluid.

The response speed of at least one of the optical non-contact speed meter 10 and the flow velocity sensor 40 shown in Figure 1 may be adjusted so that the response speed of the optical non-contact speed meter 10 and the flow velocity sensor 40 match.

The calibration system for an optical non-contact speed meter according to the embodiment may further include a holder 50 that holds the optical non-contact speed meter 10. The holder 50 holds the optical non-contact speed meter 10 so that the test light is irradiated at a position facing the flow velocity sensor 40, for example.

The calibration signal generation unit 301 generates a calibration signal to bring the measured speed closer to the reference speed. The optical non-contact speed meter 10 transmits the measured speed to the calibration signal generation unit 301 via a wired or wireless connection. The flow velocity sensor 40 transmits the reference speed to the calibration signal generation unit 301 via a wired or wireless connection. The calibration signal generation unit 301 receives the measured speed from the optical non-contact speed meter 10 and receives the reference speed from the flow velocity sensor 40.

The calibration signal generation unit 301 compares the measured speed with the reference speed. For example, as shown in FIG. 7, if the measured speed and the reference speed are the same, the calibration signal generation unit 301 does not generate a calibration signal. As shown in FIG. 8(a), if the measured speed is faster than the reference speed, the calibration signal generation unit 301 generates a calibration signal that calibrates the measured speed so that the measured speed is equal to the reference speed. As shown in FIG. 8(b), if the measured speed is slower than the reference speed, the calibration signal generation unit 301 generates a calibration signal that calibrates the measured speed so that the measured speed is equal to the reference speed.

The calibration signal is not particularly limited as long as it can calibrate the speed measured by the optical non-contact speed meter 10 shown in FIG. 1. For example, the calibration signal may include a coefficient or formula by which the measured speed calculated by the optical non-contact speed meter 10 is multiplied. The formula may be a linear expression or a polynomial expression. Alternatively, the calibration signal may be a signal that calibrates the sensitivity of the optical system or the strength and frequency of the electrical signal of the electrical circuit used by the optical non-contact speed meter 10 to calculate the measured speed.

The calibration system for a non-contact speedometer according to the embodiment further includes a calibration signal transmission unit 302 for transmitting the calibration signal generated by the calibration signal generation unit 301 to the optical non-contact speedometer 10. The optical non-contact speedometer 10 is configured to receive the calibration signal and calculate a calibrated measured speed based on the calibration signal.

The calibration system for a non-contact speed meter according to the embodiment may further include a control unit 303 for controlling at least one of the fluid supply device 30, the optical non-contact speed meter 10, and the flow velocity sensor 40 via a wired or wireless connection. The control unit 303 controls at least one of the flow rate and flow velocity of the fluid supplied by the fluid supply device 30 to the piping 20. The control unit 303 controls the start and stop of speed measurement by the optical non-contact speed meter 10. The control unit 303 controls the start and stop of speed measurement by the flow velocity sensor 40.

The calibration signal generation unit 301, calibration signal transmission unit 302, and control unit 303 are included in, for example, a central processing unit (CPU) 300.

Next, with reference to Figure 9, we will explain the calibration method for the optical non-contact speed meter according to this embodiment.

In step S101, in response to a command from the control unit 303, the optical non-contact velocimeter 10 begins measuring the velocity of the fluid when no fluid is flowing in the pipe 20, and the measured velocity measured by the optical non-contact velocimeter 10 is reset to zero. In step S102, in response to a command from the control unit 303, in response to a command from the flow velocity sensor 40 when no fluid is flowing in the pipe 20, the flow velocity sensor 40 begins measuring the velocity of the fluid, and the reference velocity measured by the flow velocity sensor 40 is reset to zero.

In step S103, the control unit 303 instructs the fluid supply device 30 to supply fluid to the pipe 20 at a predetermined flow rate. After a predetermined time has passed during which the flow rate of the fluid in the pipe 20 has stabilized, in step S104, the control unit 303 instructs the optical non-contact velocimeter 10 to measure the velocity of the fluid and transmit the measured velocity to the calibration signal generation unit 301. In step S105, the control unit 303 instructs the flow velocity sensor 40 to measure the velocity of the fluid and transmit a reference velocity to the calibration signal generation unit 301. Steps S103 and S104 may be performed in parallel.

In step S106, the control unit 303 instructs the fluid supply device 30 and flow velocity sensor 40 to end measuring the fluid velocity. In step S107, the calibration signal generation unit 301 generates a calibration signal based on the received reference velocity and measured velocity. In step S108, the calibration signal transmission unit 302 transmits the calibration signal generated by the calibration signal generation unit 301 to the optical non-contact velocity meter 10. The optical non-contact velocity meter 10 is configured to receive the calibration signal and thereafter calculate the calibrated measured velocity.

Steps S103 to S106 may be performed at multiple different fluid supply speeds. In this case, the calibration signal generation unit 301 generates a calibration signal so that the measured speed is equal to the reference speed at each of the multiple different fluid supply speeds.

Although the present invention has been described above using embodiments, the descriptions and drawings that form part of this disclosure should not be understood as limiting this invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

For example, as shown in FIG. 10, the calibration system for an optical non-contact speedometer according to an embodiment may further include a time information providing device 400 that provides timestamps to the measured speed and the reference speed. The time information providing device 400 communicates with the optical non-contact speedometer 10 and the flow velocity sensor 40 via wired or wireless communication, and transmits time information to the optical non-contact speedometer 10 and the flow velocity sensor 40. The time information providing device 400 may be connected to an access point of the CPU 300 for wireless connection with the optical non-contact speedometer 10 and the flow velocity sensor 40.

When transmitting a measured speed, the optical non-contact speed meter 10 assigns a timestamp to the measured speed based on time information. When transmitting a reference speed, the flow velocity sensor 40 assigns a timestamp to the reference speed based on time information. The calibration signal generator 301 compares the measured speed and reference speed transmitted at the same time based on the timestamp. This makes it possible to generate a highly accurate calibration signal.

Furthermore, for example, as shown in FIG. 11 , the calibration system for an optical non-contact speed meter according to the embodiment may further include a temperature control device 21 that controls the temperature of the pipe 20. When the fluid flow velocity is low, convection may occur in the fluid due to a temperature gradient within the pipe 20. The temperature control device 21 controls the temperature of the pipe 20 so that the temperature of the pipe 20 remains constant.

As such, it should be understood that the present invention encompasses various embodiments not described herein.

10: Optical non-contact speedometer, 20: Piping, 21: Temperature control device, 30: Fluid supply device, 31: Container, 32: Flow path, 33: Flow control device, 40: Flow rate sensor, 41: Substrate, 42: Heater, 43: Upstream temperature-sensing resistor, 44: Downstream temperature-sensing resistor, 45: Insulating film, 46: Cavity, 50: Holding unit, 201: Light source, 202: Collimating lens, 203: Half mirror, 204: Mirror, 205: Condenser lens, 206: Light-receiving element, 211: Light source, 212: Light-receiving element, 221: Light source, 222: Condenser lens, 223: Grating, 224: Light-receiving element, 301: Calibration signal generation unit, 302: Calibration signal transmission unit, 303: Control unit, 400: Time information providing device

Claims (7)

A pipe that is transparent to the inspection light emitted by the optical non-contact speedometer to be calibrated;
a fluid supply device for supplying a fluid to the piping;
a flow velocity sensor provided in the pipe that measures the velocity of the fluid flowing through the pipe as a reference velocity;
a calibration signal generating unit configured to generate a calibration signal for calibrating the measured velocity of the optical non-contact velocimeter based on the measured velocity of the fluid measured by the optical non-contact velocimeter and the reference velocity;
a holder for holding the optical non-contact speed meter;
Equipped with
the holding unit holds the optical non-contact velocimeter so that the inspection light is irradiated at a position facing the flow velocity sensor.
Optical non-contact speedometer calibration system. The optical non-contact velocimeter calibration system of claim 1, wherein the fluid supply device supplies the fluid to the piping at a plurality of different supply rates. The optical non-contact speed meter calibration system of claim 1, further comprising a temperature control device that controls the temperature of the piping. The optical non-contact speedometer calibration system of claim 1, further comprising a calibration signal transmission unit for transmitting the calibration signal to the optical non-contact speedometer. The optical non-contact speed meter calibration system of claim 1, wherein the calibration signal is configured to bring the measured speed closer to the reference speed. The optical non-contact velocimeter calibration system of claim 1, wherein the piping and the fluid supply device are configured so that the flow of the fluid in the piping is laminar. supplying a fluid to a pipe that is transparent to an inspection light emitted by an optical non-contact speed meter to be calibrated;
measuring a velocity of the fluid flowing through the pipe as a measurement velocity using the optical non-contact velocimeter;
measuring a velocity of a fluid flowing through the pipe as a reference velocity with a flow velocity sensor provided in the pipe;
generating a calibration signal for calibrating the measured velocity based on the measured velocity and the reference velocity;
Including ,
The optical non-contact velocimeter is disposed so that the inspection light is irradiated at a position facing the flow velocity sensor.
How to calibrate an optical non-contact speedometer.