JP2020060600A - Speedometer and article manufacturing method - Google Patents

Abstract

To provide a speedometer advantageous in terms of measurement precision.SOLUTION: A speedometer for measuring speed of an object by detecting light modulated by the Doppler effect by the moving object obtains first amplitude of plural frequencies of detection signals as an offset value by executing calibration, obtains second amplitude of plural frequencies of detection signals by detecting light modulated by a moving object, corrects the second amplitude based on the offset value, determines a frequency of a band of filtering of a bandpass filter based on the second corrected amplitude, and filters a detection signal by the bandpass filter having a band of filtering of the determined frequency, thus obtaining a speed measurement value.SELECTED DRAWING: Figure 16

Description

  The present invention relates to a speedometer that detects light modulated by a moving object by the Doppler effect and measures the speed of the object, and an article manufacturing method.

  Conventionally, a Doppler velocimeter (hereinafter also simply referred to as “velocimeter”) has been used as a device for measuring the velocity of a moving object. A laser Doppler velocimeter (LDV (Laser Doppler Velocimeter)) irradiates an object with a laser beam and measures the speed of the object using the Doppler effect. Here, the Doppler effect is an effect in which the frequency (wavelength) of scattered light from an object shifts in proportion to the moving speed of the object. It is generally known that the signal obtained by LDV has a low S / N ratio. As factors that affect the measurement accuracy, it is known that high-frequency noise is mixed and so-called dropout in which the Doppler signal level decreases.

  In Patent Document 1, the Doppler signal obtained by the photodetector and having the noise removed by the bandpass filter is compared with the reference level, and the level detection signal is output. Further, the periodic error is detected by binarizing the Doppler signal, and the periodic error signal is output. Then, error signal detection is performed based on the level detection signal and the periodic error signal.

Japanese Patent Laid-Open No. 08-15436

  However, the error signal detection method of Patent Document 1 is an error only when both a level error and a periodic error occur, and an error when only one of them occurs, in order to deal with a signal with a large frequency variation. There is no way. Therefore, the measurement accuracy may be deteriorated due to the mixing of noise when the dropout does not occur. It is an exemplary object of the present invention to provide a speedometer that is advantageous in terms of measurement accuracy.

  One aspect of the present invention is a speedometer for measuring the speed of the object by detecting the light modulated by the Doppler effect by a moving object, a detection unit for detecting the light, and a The obtained signal is filtered by a bandpass filter, the signal obtained by the bandpass filter is binarized, and a period over a predetermined number of pulse intervals in the signal obtained by the binarization is measured to measure the velocity. And a processing unit that obtains a first amplitude of a plurality of frequencies of the signal obtained by the detection unit as an offset value by performing calibration, and the modulation is performed by a moving object. The second amplitude of the plurality of frequencies of the signal obtained by the detection unit is obtained by detecting the reflected light, the second amplitude is corrected based on the offset value, and the second amplitude is corrected based on the corrected second amplitude. By determining the frequency of the band of the filter of the band pass filter, by filtering the signal obtained by the detection unit using the band pass filter having the band of the filter of the determined frequency, the measured value of the velocity It is a speedometer characterized by obtaining.

  The present invention can provide, for example, a speedometer advantageous in terms of measurement accuracy.

The figure which shows the structural example of the head part of a speedometer. Schematic diagram for explaining the fringe model The figure which illustrates the relationship between the velocity of an object and the Doppler frequency. Diagram showing a configuration example of a speedometer Diagram illustrating the signal processing contents The figure which illustrates the analog signal input into a process part. Diagram illustrating the flow of processing in the processing unit Diagram illustrating the signal when dropout occurs Diagram showing the signal when noise is mixed Figure showing an example of incorrect measurement The figure which illustrates the measured value before correction and the measured value after correction. Diagram illustrating the flow of signal processing The figure which shows another example of the analog signal input into a process part. The figure which shows the example of the flow of the process in S1201 (search) The figure which illustrates the flow of the process in S1601 (calibration). The figure which shows the 2nd example of the flow of the process in S1201 (search). The figure which shows the example which concerns on the signal processing content in S1201 and S1601. The figure which shows the 2nd example which concerns on the signal processing content in S1201 and S1601.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Throughout all the drawings for explaining the embodiments, as a general rule (unless otherwise noted), the same members are designated by the same reference numerals, and the repeated description thereof will be omitted.

[Embodiment 1]
FIG. 1 is a diagram showing a configuration example of a head portion of a speedometer. Here, the head unit 100 as a detection unit includes an optical system for irradiating the object (measurement target) 10 with light and receiving light from the object 10, and constitutes a head unit of a laser Doppler velocimeter. ing. A light beam 9 emitted from a light source 1 which may include a laser diode is collimated by a collimator lens 2 and enters a diffraction grating (diffraction element) 3. The light beam 9 that has entered the diffraction grating 3 is branched into ± first-order diffracted lights (the diffraction angle is θ), which are condensed by the lens 4 and are transmitted through the EO elements 5a and 5b. The two transmitted light beams are collimated by the lenses 6a and 6b, and irradiate the object 10 from irradiation directions different from each other at an angle substantially equal to the diffraction angle θ. The irradiated light flux is diffused and reflected by the surface (generally rough surface) of the object 10. The diffusely reflected light beam is condensed through the lenses 6a and 6b and the condenser lens 7, and is incident on the light receiving element 8 which may include a photodiode. A signal obtained by photoelectric conversion in the light receiving element 8 is input to a processing unit described later as an intensity-modulated analog signal having a frequency F according to the velocity V of the object 10. Here, the frequency F is called a Doppler frequency and is represented by the following equation (1).
F = 2V / P + F_EO (1)

Here, P is the grating pitch of the diffraction grating 3, and F_EO is the drive frequency of the EO elements 5a and 5b. A fringe (interference fringe) model is known as a model for explaining the operation principle of a laser Doppler velocimeter utilizing the Doppler effect. FIG. 2 is a schematic diagram for explaining the fringe model. The two light fluxes that illuminate the object 10 intersect on the surface of the object 10 to form a fringe 11 as shown in FIG. Particles 12 having a size equal to or smaller than the fringe pitch of the fringe 11 pass through the fringe 11 (bright and dark portions thereof) at a velocity V, and thus have a frequency F as shown in FIG. Diffuse light is generated. The frequency F in this case is expressed by the following equation (2).
F = V / P_i (2)

  Here, P_i represents a fringe pitch. The diffraction angle θ is derived from the relational expression sin θ = λ / P, where λ is the wavelength of the light beam 9 emitted from the light source 1. When the incident angle of the light beam on the object 10 is equal to the diffraction angle θ, the fringe pitch P_i can be expressed as P_i = λ / 2sin (θ) = P / 2. The first term on the right side of Expression (1) is derived from this relational expression and Expression (2). The low-frequency component (envelope component) of FIG. 2B reflects the intensity distribution of the light beam 9 emitted from the light source 1, and may typically reflect the Gaussian distribution. The surface of the object 10 has a random surface roughness and can be regarded as a set of particles 12 having a plurality of random characteristics. Therefore, by summing up signals having a plurality of random phases and amplitudes as shown in FIG. 2B, a signal as shown in FIG. 2C is obtained. Here, FIG. 6 is a diagram illustrating an analog signal input to the processing unit 101 described below. Since the signal in FIG. 2 (c) obtained according to the fringe model is similar to the actual signal in FIG. 6, it can be seen that the fringe model can explain the operating principle of the laser Doppler velocimeter.

Next, the second term on the right side of Expression (1) will be described. The signal of FIG. 2C has a high frequency component reflecting the velocity of the object and a low frequency component reflecting the characteristics of the surface of the object 10. Therefore, when the velocity V approaches 0, the velocity is obtained from the signal. Becomes difficult. Moreover, the direction of the speed V cannot be detected. Therefore, in FIG. 1, the EO element is configured. Here, the EO elements 5a and 5b can be electro-optical phase modulation elements configured to include, for example, an electro-optical crystal (including, for example, a LiNbO ₃ crystal). By including such an element, the speed and the direction of the speed can be obtained even when the object is in a stopped state. The EO elements 5a and 5b can change the phase of the light flux passing through them by the applied voltage. When the EO elements 5a and 5b modulate two light fluxes respectively passing therethrough so that the phases thereof change in opposite directions at a constant frequency F_EO, the fringe 11 moves by one pitch at the frequency F_EO. . For example, the apparent phase change can be made constant by changing the voltage applied to the EO elements 5a and 5b in a sawtooth shape. Thus, if the stationary particle 12 is placed while the fringe 11 is moving at the frequency F_EO, diffuse reflected light whose intensity is modulated at the frequency F_EO is generated. That is, it is equivalent to the case where the velocity is offset in a certain direction. Therefore, by configuring the laser Doppler velocimeter including the EO elements 5a and 5b in this way, it becomes possible to detect the stationary state (zero velocity) and the direction of velocity. For example, FIG. 3 shows the relationship between the velocity V and the Doppler frequency F when the diffraction grating 3 has a grating pitch P = 5 [μm] and F_EO = 200 [kHz]. Here, FIG. 3 is a diagram illustrating the relationship between the velocity of the object and the Doppler frequency. When the lower limit of the frequency of the signal that can be processed by the processing unit described later is 100 [kHz] and the upper limit is 4.2 [MHz], the measurable speed range is -250 [mm / s] to 10 [m / s]. ] Range. The values of the grating pitch P and the phase modulation frequency F_EO can be appropriately selected according to the specifications of the laser Doppler velocimeter. Although the example in which the EO element performs the phase modulation is shown here, the phase modulation may be performed by another element such as an acoustooptic element.

  FIG. 4 is a diagram showing a configuration example of a speedometer. The intensity-modulated signal having the frequency F obtained by the head unit 100 as described above is input to the processing unit 101. The analog signal input to the processing unit via the input terminal 401 is amplified by the gain amplifier 402, filtered by the bandpass filter (BPF) 403, and binarized by the comparator 404. Based on the signal obtained by the binarization, the calculation unit 405 obtains the velocity (information thereof), and the obtained velocity (information thereof) is output from the output terminal 406.

  FIG. 5 is a diagram showing an example of signal processing contents. FIG. 5 shows the case where the velocity V of the object 10 = 9500 [mm / s] and the Doppler frequency F = 4 [MHz], (a) shows an input signal, and (b) shows binarization by a comparator. The signal obtained by is shown. FIG. 5C is a diagram showing a (reference) clock signal in the processing unit 101. The reference clock (not shown) that gives the clock signal may be inside or outside the processing unit. Here, the reference clock frequency is 40 [MHz]. In this embodiment, N consecutive rising intervals of a signal obtained by binarization are timed (counted) with a reference clock. Here, one rising interval is a time interval between two rising times in two adjacent pulses. Then, the Doppler frequency F is obtained based on the time (time period D) obtained by the time measurement, and the velocity V (information thereof) of the object 10 is obtained based on the equation (1). Here, N = 4. In the case of (b) and (c) of FIG. 5, the count value of four rising intervals in the signal obtained by binarization is 40 (count). Since the frequency of the reference clock is known, the Doppler frequency F can be obtained from the count value (clock value). Further, the speed V may be obtained by calculation based on the equation (1) or may be obtained by referring to a table prepared in advance showing the relationship between the count value (clock value) and the speed. Although the frequency of the reference clock is 40 MHz here, it can be appropriately selected according to the required Doppler frequency.

  FIG. 6 is a diagram illustrating an analog signal input to the processing unit 101 as described above. FIG. 6B is an enlarged view of a part of FIG. 6A. As described above, the signal output from the head unit 100 is a signal that has a large change in amplitude that theoretically occurs in the Doppler signal. Further, noise generated in the electric circuit (for example, switching noise of the power supply, noise caused by driving the EO element) is superimposed on the current for driving the light source 1, so that the signal output from the head unit 100 is other than the Doppler signal. Low-frequency and high-frequency noise are mixed in. The state of the signal indicated by the arrow in FIG. 6B is a state in which the amplitude of the low frequency component is small. Here, in the state (portion) below the threshold for binarization by the comparator, the signal obtained by the binarization becomes zero (missing). Such a state is also called dropout. Further, in a state (part) where the high frequency noise component exceeds the threshold value, the signal obtained by binarization may include a signal different from the Doppler signal.

  FIG. 7 is a diagram exemplifying the flow of processing in the calculation unit in the processing unit. In the processing unit 101 of FIG. 4, the signal obtained by binarization by the comparator is input to the calculation unit 405. First, in step S701, the calculation unit 405 shows the time (period over a predetermined number of pulses) of N consecutive (series) rising intervals (pulse intervals) in the signal obtained by binarization in FIG. As described above, the time is counted (counted) by the reference clock. In a succeeding step S702, it is determined whether or not the change in the index related to the period (clocked value) exceeds the threshold value. Here, the index may be the period D, the Doppler frequency F corresponding to the period D, the velocity V of the object 10 corresponding to the Doppler frequency F, or another value correlated therewith. But it's okay. Here, FIG. 8 is a diagram illustrating a signal when dropout occurs. When a dropout occurs in the analog signal including the Doppler signal around time 100 μsec as shown in FIG. 8A, pulses are generated in the signal obtained by binarization as shown in FIG. 8B. Get out. Further, FIG. 9 is a diagram illustrating a signal when noise is mixed. When noise is mixed in the analog signal including the Doppler signal around time 3 μsec as shown in FIG. 9A, the pulse is split in the signal obtained by binarization as shown in FIG. 9B. .

  FIG. 10: is a figure which illustrates the measured value which is made into an error. 8A illustrates the speed (measured value) obtained when there is a dropout as shown in FIG. When the rising intervals of every N = 4 are counted, pulse dropouts caused by dropout occur, and as a result, the count value of the reference clock may be 50 counts. When the speed is obtained based on these clocked values, the graph on the right side of FIG. When the number of pulse dropouts due to dropout increases, the error in the measured value also increases. Next, FIG. 10B illustrates the speed (measured value) obtained when noise such as that shown in FIG. 9 is mixed. In this case as well, when the rising intervals of every N = 4 clocks are measured, the count value of the reference clock may become 30 as a result of pulse breakage caused by noise mixing. When the speed is obtained based on these clock values, the graph on the right side of FIG. When the number of pulse breaks due to noise mixing increases, the error in the measured value also increases.

The change in the count value continuously acquired in time series can be considered to be within a predetermined range in consideration of the change in the speed of the object 10 within a predetermined time. For example, when the velocity V of the object 10 is 9.5 [m / s] at present and changes at an acceleration of 10 [m / s ^ 2], the velocity change in the period D for every N = 4 pieces is 10 It is only [μm / s]. The ratio of this speed change to the speed is inversely proportional to the speed, but even if V = 0.1 [m / s], the speed change is about 0.17 [mm / s] and is sufficiently small. It can be said (the ratio is about 0.17%). From the above, if the change in the index exceeds L (%) of the index (obtained in advance), it can be determined that dropout or noise mixing has occurred. L is represented by the following equation (3).
L = ((N + 1) / N-1) × 100 (3)

  Therefore, the threshold value in step S702 in FIG. 7 can be obtained as the L (%) index (obtained in advance). If the change in the index is less than or equal to the threshold value (L [%] of the index), the speed (measured value) is obtained based on the measured value in step S703. On the other hand, when the change in the index exceeds the threshold value (L [%] of the index), in step S704, the speed corresponding thereto is determined to be an error, and the speed obtained in advance is used as the measured value. In subsequent step S705, the processing unit 101 outputs the speed (measured value) to another device that needs the speed information. The threshold may be an index a × L [%] (the coefficient a is a real number that satisfies 0 <a <1).

  FIG. 11 is a diagram illustrating the measured value before correction and the measured value after correction. FIG. 11 shows the measurement result of the speed when the object 10 moves at the speed V≈9.5 [m / s]. FIG. 11A shows the measurement result when the correction (steps S702 to S704) according to the present embodiment is not performed, and FIG. 11B shows the measurement result when the correction is performed. . With reference to FIG. 11, it can be seen that according to the present embodiment, a highly accurate (high reproducibility) measurement result can be obtained as in (b) of FIG.

  As described above, according to the present embodiment, it is possible to perform robust measurement not only for dropouts but also for noise contamination, and thus to provide a speedometer advantageous in terms of measurement accuracy, for example. You can

  Next, another aspect of the processing unit 101 will be described. The bandpass filter (BPF) 403 of the processing unit 101 shown in FIG. 4 is prepared to reduce noise having a frequency other than the Doppler frequency. Here, the Q value of the BPF 403 is set to about 6 although not limited thereto. Since the Doppler frequency covers a wide band, the BPF adopts a BPF having a variable resonance frequency (center frequency). The BPF can be realized by changing at least one of R, L, and C of the RLC filter, for example. FIG. 12 is a diagram illustrating a flow of signal processing. First, in step S1201, the resonance frequency of the BPF is determined by the search described below. In the next step S1202, the resonance frequency of the BPF is set. In step S1203, the analog signal input to the processing unit 101 is filtered (filtered) by the BPF and input to the comparator. Here, the level of the signal obtained by the filtering is determined. If it is an analog signal as shown in FIG. 6, signal processing can be performed by BPF filtering. However, depending on the surface condition of the object 10, the analog signal shown in FIG. 13 may be generated and dropout may occur for a long period of time. Here, FIG. 13 is a diagram illustrating another example of the analog signal input to the processing unit. It is difficult to perform accurate speed measurement with such a signal. Therefore, in step S1203, peak hold processing is performed on the amplitude of the signal obtained by filtering with the BPF, and it is determined whether the held peak is below a preset threshold value for a preset time. If that is the case (Yes), it is judged as an error and output (step S1204), and the process returns to step S1201 (search). On the other hand, when that is not the case (No), the signal obtained by the BPF filtering is binarized by the comparator 404 and further processed by the arithmetic unit 405. In step S1205, the calculation unit 405 obtains the speed of the object 10. In subsequent step S1205, processing unit 101 outputs the speed (information) from output terminal 406 to another device.

  Step S1201 (search) in FIG. 12 is a step of determining the resonance frequency of the BPF according to the Doppler frequency in the analog signal input to the signal processing unit 101. Here, FIG. 14 is a diagram illustrating an example of the flow of processing in S1201 (search). Steps S1401 and S1402 are repeated (looped) for i = 1, 2, ..., Q. In step S1401, the resonance frequency F (i) of the BPF is set. In subsequent step S1402, the amplitude value A (i) of the signal obtained by the filtering is acquired. In step S1403 after exiting the loop, i = i_max that maximizes A (i) is obtained. In subsequent step S1404, F (i_max) is determined as the resonance frequency of the BPF. Here, FIG. 17 is a diagram showing an example relating to the signal processing contents in S1201 (search) and S1601 (calibration). The calibration will be described later. In this example, the amplitude of the signal obtained by the filtering is maximum at about 700 [kHz]. Therefore, it can be considered that the Doppler frequency is about 700 [kHz]. Based on this idea, in S1201 (search), the resonance frequency of the BPF can be determined.

  However, when the S / N ratio of the Doppler signal is low, a frequency far from the Doppler frequency may be determined as the resonance frequency of the BPF in S1201 (search). FIG. 18 is a diagram showing a second example of signal processing contents in S1201 (search) and S1601 (calibration). FIG. 18A shows the amplitude value A (i) of the signal obtained by filtering when the S / N ratio of the Doppler signal is low. In this example, the Doppler frequency is about 150 [kHz], but due to the noise generated by the head unit 100, the amplitude is maximum at about 3 [MHz]. The noise component of the head unit 100 is unique to each head unit and does not depend on the Doppler frequency. Therefore, it is possible to calibrate the speedometer by acquiring this noise information in advance.

  FIG. 15 is a diagram exemplifying the flow of processing in S1601 (calibration) in FIG. S1601 (calibration) is a step of previously acquiring information on the noise component peculiar to the head unit, and is performed without installing the object 10. Steps S1501 and S1502 are repeated (looped) for i = 1, 2, ..., Q. First, in step S1501, the resonance frequency F (i) of the BPF is set. In subsequent step S1502, the amplitude value C (i) of the signal obtained by the filtering is acquired. In step S1503 after exiting the loop, C (i) is stored as an offset value (calibration value) in the memory of the processing unit 101, for example. Here, (b) of FIG. 17 and (b) of FIG. 18 are examples of the offset value C (i) acquired and stored without installing the object 10.

  FIG. 16 is a diagram showing a second example of the flow of processing in S1201 (search). The same processes as those in the process flow of FIG. 14 are designated by the same or similar reference numerals, and description thereof will be omitted. First, step S1601 (calibration) is the process described with reference to FIG. In step S1602, noise peculiar to the head unit 100 is obtained by subtracting the offset value C (i) obtained in step S1601 from the amplitude value A (i) in F (i) acquired with the object 10 installed. The amplitude value A ′ (i) in which the influence of the component is reduced is acquired. Here, (c) of FIG. 17 and (c) of FIG. 18 are examples of the amplitude value A ′ (i). By executing the process according to FIG. 16, the resonance frequency of the BPF can be more accurately determined even when the S / N ratio of the Doppler signal is low. Further, if the process of step S1201 (search) is performed again when an error is determined in step S1203 (peak determination) in the process of FIG. 12, the signal as shown in FIG. 13 changes to the signal as shown in FIG. If you do so, you can restart the measurement immediately.

  As described above, by performing the processing described with reference to FIGS. 12 to 18, it is possible to perform the robust processing of acquiring the speed in the speedometer. The setting of the resonance frequency of the bandpass filter (BPF) 403 is, for example, when the speedometer starts speed measurement (immediately before starting), or there is an error in speed measurement (a predetermined condition is satisfied and an error occurs). If it continues), it can be executed. Further, while the speed measurement is being executed, the resonance frequency can be set (changed) based on the measured speed value.

[Embodiment 2]
In the first embodiment, the calculation unit 405 (step S702) determines whether the change in the index exceeds the threshold based on the threshold based on the index obtained immediately before (in advance). However, the threshold value may be a threshold value based on the M indices (for example, the average value thereof) obtained immediately before (in advance). Further, the average value may be a weighted average value, a geometric average value, or another average value instead of a simple average value. Further, in the first embodiment, in step S704, the speed obtained in advance is assumed to be an error and the speed obtained in advance is used as the measurement value. However, instead of this, a plurality of measurement values obtained in advance (for example, , The average value thereof) may be used as the measured value. Further, the average value may be a weighted average value, a geometric average value, or another average value instead of a simple average value. For example, if it is known in advance that the velocity fluctuation of the object 10 is small, stable measurement can be performed by increasing the value of M. Further, when the magnitude of the speed fluctuation is generally known in advance, the followability (validity) of the threshold value related to the error determination can be improved by reducing the value of M based on the magnitude. it can. According to the study by the inventors, it is known that when the acceleration of the object 10 is about 1 [G], the followability is improved by setting M = 16 or less.

[Embodiment of article manufacturing method]
The speedometer according to the embodiment described above can be used in an article manufacturing method. The article manufacturing method may include a step of measuring the speed of the object using the speedometer, and a step of processing the object whose speed is measured in the step. The processing can include, for example, at least one of processing, cutting, inspection, assembly, and selection. More specifically, for example, the extrusion speed of the molded product by an extruder can be measured to control the extrusion speed of the molded product. In addition, the speed of the (long) object conveyed by the conveyance system is measured, the speed obtained by the measurement is integrated to measure the length of the object, and the target length is determined based on the measured length. The object can be cut (cut) to have. In the article manufacturing method of the present embodiment, since the speed of an object can be measured with high accuracy in a non-contact manner using a speedometer, at least one of the performance, quality, productivity, and production cost of the article can be compared with the conventional method. Is advantageous in.

  Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist thereof.

100 Detection part (head part)
101 processing unit

Claims (5)

A speedometer for detecting light modulated by the Doppler effect by a moving object to measure the speed of the object,
A detection unit for detecting the light,
The signal obtained by the detection unit is filtered by a bandpass filter, the signal obtained by the bandpass filter is binarized, and a period over a predetermined number of pulse intervals in the signal obtained by the binarization is measured. A processing unit for obtaining the measurement value of the speed,
The processing unit is
By performing the calibration, the first amplitude of a plurality of frequencies of the signal obtained by the detection unit is obtained as an offset value,
Detecting the light modulated by the moving object to obtain the second amplitudes of the plurality of frequencies of the signal obtained by the detector,
Correcting the second amplitude based on the offset value,
Determining a frequency of a band of filtering of the bandpass filter based on the corrected second amplitude,
A speedometer, characterized in that the measured value of the speed is obtained by filtering the signal obtained by the detection unit using the bandpass filter having a band of filtering of the determined frequency. An optical system for irradiating the object with two lights whose irradiation directions are different from each other and whose phases are changed in opposite directions,
The speedometer according to claim 1, wherein the two lights are reflected by the object and detected by the detection unit.   The speedometer according to claim 1, wherein the processing unit determines a resonance frequency of the bandpass filter by determining a frequency of a band of a filter of the bandpass filter.   The processing unit obtains first amplitudes of a plurality of frequencies of a signal obtained by the detection unit in a state where an object is not arranged in a detection region of the detection unit. The speedometer according to any one of the above. Measuring the speed of an object using the speedometer according to any one of claims 1 to 4,
A step of processing the object whose speed has been measured in the step,
A method for manufacturing an article, comprising:

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