JPH04220587A - Method for detecting inclination and position deviation of object to be measured in measurement of traveling speed and length of object to be measured in laser doppler system - Google Patents

Abstract

PURPOSE:To enable inclination and position deviation to be corrected by adjusting direction and position of a laser beam based on a detection signal of inclination and position deviation of an object to be measured for laser light source when setting the object to be measured. CONSTITUTION:A laser light source 2 emits a laser beam to an object to be measured 1 and a sensor 3 receives a scattering light b from the object to be measured 1. The sensor 3 uses a four-division detector 5 and receives the scattering light b by a detector 5 through a cylindrical lens 4. An output level of each pair is obtained with two opposing light-receiving portions 6 and 7 and 8 and 9 as pairs out of a doppler signal d which is output from four light- receiving portions 6-9 of the detector 5 and an inclination of the object to be measured 1 for the light source 2 or a position deviation of the object to be measured 1 for the light source 2 is detected from the output level.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to the laser Doppler method when measuring the moving speed, length, etc. of an object to be measured.
The inclination of the object to be measured with respect to the normal line of the bisector of two beams with the laser light source as the light source, and the positional deviation of the object to be measured with respect to the laser light source are detected, and the This corrects the inclination of the object and the positional deviation of the object to be measured, so that errors in measuring speed, length, etc. due to the inclination or positional deviation do not occur.

0002

2. Description of the Related Art Measuring the moving speed and length of an object to be measured using a laser Doppler method was first developed by the inventor of the present invention. The measurement principle is as shown in Figure 1.
Laser light a from a laser light source 2 such as a laser is split into two by a beam splitter 11, and one of the laser lights a and the laser light a reflected by a mirror 12 are separated at an intersection angle. When the object to be measured (for example, a traveling body such as a rope) 1 is irradiated with φ, the scattered light b from the object to be measured 1 is transmitted to the sensor (
The light is received by a photoelectric converter (photoelectric converter) 3 and subjected to heterodyne detection, and the Doppler signal d is output from the sensor 3.

Doppler frequency fD of this Doppler signal d
is expressed by the following formula. fD =2v/λ sinφ/2・cos ΔθfD
: Doppler frequency v: Traveling speed of the object to be measured λ: Laser wavelength (632.8 nm) φ: Beam crossing angle Δθ: Angle of deviation from the right angle between the beam normal and the object to be measured As shown in the above equation Since the Doppler frequency fD is proportional to the moving speed v of the object d, according to the measurement principle, the same moving speed v
Of course, the length of the object to be measured 1 can be measured by integrating the moving speed v over time.

0004

[Problems to be Solved by the Invention] In the method of measuring moving speed, length, etc. using the laser Doppler method, the measurement target is When the direction of object 1 is tilted by θ as shown in Figure 8, cos θ
There is a problem in that this speed error becomes an error in the measurement length (integral value of speed).

Furthermore, when the position of the object to be measured 1 becomes farther from the laser light source 2 by Δl than the predetermined position (shifts in position) as shown in FIG. As a result, the output level of the Doppler signal d decreases. Also,
Conversely, when the position of the object to be measured 1 approaches the laser light source 2 by .DELTA.l from the predetermined position, the amount of scattered light b from the object to be measured 1 increases and the output level of the Doppler signal d increases.

In this case, there is no particular problem as the output level of the Doppler signal d increases, but when the output level of the Doppler signal d decreases, the processing section that processes the Doppler signal d has trouble distinguishing the Doppler signal d from noise. If it is not possible to do so, or if the output level is extremely low, the Doppler signal d may not be input to the processing section. For this reason, there was a problem in that the Doppler signal d was missing at that portion, and the length of the object to be measured 1 was measured to be shorter than the actual length, resulting in a measurement error.

[0007]

OBJECTS OF THE INVENTION The purpose of the present invention is to solve measurement errors in moving speed, length, etc. caused by inclination and positional deviation of the object to be measured with respect to the laser light source. When setting the laser light source to face the object to be measured, the inclination of the object to be measured and the positional deviation of the laser light source with respect to the laser light source are detected, and the laser is activated based on the detection signal. By adjusting the direction and position of the light source, the above-mentioned inclination and positional deviation can be corrected.

[0008]

[Means for Solving the Problems] Prior to the development of the present invention, the inventor of the present invention determined the relationship between the inclination of the object to be measured with respect to the laser light source and the output light level, and the distance from the laser light source to the object to be measured. The relationship between this and the output light level was studied intensively.

As a result, when the object to be measured 1 is tilted by θ/2 with respect to the laser light source 2 as shown in FIG. 9, the beam intersection angle of the beam 1 becomes φ/4, and the laser beam a It has been found that when it is specularly reflected and input to the sensor 3, the output level of the Doppler signal d increases as shown in FIG.

[0010] Furthermore, the positional deviation of the object to be measured 1 is 0 (distance 1).
Figure 1 shows the output level of Doppler signal d when
1, when the position of the object to be measured 1 is closer to the laser light source 2 by Δl as shown in Fig. 10 (-Δl), the output level of the Doppler signal d is high as shown in Fig. 11. It has also been found that when the distance is Δl (+Δl) as shown in FIG. 10, the output level of the Doppler signal d becomes low as shown in the figure.

The present invention was developed based on the above findings. In the present invention, as shown in FIG. In a method for measuring the moving speed, length, etc. of an object to be measured using a laser Doppler method, which outputs a Doppler signal d and measures the moving speed, length, etc. of the object to be measured 1 based on the Doppler signal d. As shown in FIGS. 2 to 4, a four-division detector 5 is used as the sensor 3, and the scattered light b is received by the four-division detector 5 through the cylindrical lens 4. Four light receiving sections 6, 7, 8, 9
Among the Doppler signals d output from the Doppler signal d, the output level of each pair is determined by pairing the two opposing light receiving sections 6 and 7 and 8 and 9, and from the output level, the inclination of the object to be measured 1 with respect to the laser light source 2 is determined. , or a positional shift of the object to be measured 1 with respect to the laser light source 2.

0012

In the present invention, the scattered light b passing through the cylindrical lens 4 shown in FIG. 2 is received by the four-part detector 5. In this case, if the object to be measured 1 is not tilted, the shape of the scattered light b received by the four-part detector 5 will be a perfect circle as shown in FIG. 9, the light is evenly received.

When the object to be measured 1 is tilted downward to the right, the shape of the scattered light b received by the four-part detector 5 is a perfect circle as shown in FIG. 6,
Out of 7, 8, and 9, the amount of light received by the light receiving section 4 is the largest.

When the object to be measured 1 is tilted upward to the right, the shape of the scattered light b received by the four-part detector 5 is a perfect circle as shown in FIG. 6,
Among 7, 8, and 9, the amount of light received by the light receiving section 3 is the largest.

In any of the above cases, the four-division detector 5 outputs the Doppler signal d according to the amount of received light, so the output level of the Doppler signal d of each pair is determined by setting the light receiving sections 6 and 7 and 8 and 9 as a pair. By detecting this, it is possible to detect whether the object to be measured 1 is tilted, whether it is tilted upward to the right or downward to the right.

When the object to be measured 1 is not displaced, the shape of the scattered light b received by the four-part detector 5 is as shown in FIG.
It becomes a perfect circle as shown, and has four light receiving parts 6, 7, 8,
9, the light is evenly received.

When the object to be measured 1 approaches the laser light source 2, the position of the object to be measured 1 is in front of the focal length of the cylindrical lens 4, so that the scattered light b received by the quadrant detector 5 The shape of is based on the characteristics of the cylindrical lens 4 as shown in Figure 4.
It becomes a horizontally oblong ellipse that slopes upward to the left as shown in a, and among the four light receiving sections 6, 7, 8, and 9, the amount of light received by the light receiving section 4 is the largest.

When the object to be measured 1 is separated from the laser light source 2, the position of the object to be measured is beyond the focal length of the cylindrical lens 4, so that the light is received by the quadrant detector 5. Due to the characteristics of the cylindrical lens 4, the shape of the scattered light b is an oblong ellipse that slopes upward to the right as shown in Fig. 4, c.
Of the four light receiving sections 6, 7, 8, and 9, the amount of light received by the light receiving section 3 is the largest.

Therefore, by detecting the output level of the Doppler signal d of each pair of light receiving sections 6 and 7 and 8 and 9, it is possible to check whether the object to be measured 1 is displaced from the laser light source 2. It is possible to detect whether the object is approaching or moving away.

If the monitor signal detected as described above is displayed digitally or analogously, the laser light source 2 can be directly connected to the object 1 before measuring the speed, length, etc. of the object 1. When setting the laser light source 2 so as to face it, the direction and position of the laser light source 2 can be adjusted while looking at it so that the output level matches the reference value.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the principle of a method for measuring the length of an object to be measured using the laser Doppler method. In this length measurement method, a laser beam a outputted from a laser light source 2 such as a semiconductor laser is irradiated onto the object 1 to be measured through a beam splitter 11, and the beam is split by the beam splitter 11. The laser beam a reflected by the mirror 12 is irradiated onto the object to be measured 1 at an intersection angle φ.

Scattered light b from the object to be measured 1 is received by the sensor 3 through the condenser lens 10 and the cylindrical lens 4 as shown in FIGS. 2 and 5. In the present invention, a four-division detector 5 is used as the sensor 3, and the Doppler signals d output from the light receiving sections 6, 7, 8, and 9 are synthesized by the differential amplifier 15 and input to the measuring section, and the Doppler signal d is d is processed in the measuring section to determine the moving speed v of the object to be measured 1, and the length of the object to be measured 1 is determined based on this moving speed v. In this case, the output signal of the differential amplifier 15 will be as shown in FIG. 6, for example.

At the same time, the Doppler signals d output from the four light receiving sections 6, 7, 8, and 9 of the quadrant detector 5 are shown in FIG.
The output level of each pair is detected by the differential amplifiers 16 and 17 shown in FIG. The inclination and positional deviation of the object to be measured 1 are detected based on the output level of each pair outputted from the device 17. In this case, the signal for detecting the inclination of the object to be measured 1 is as shown in FIG.

[0024]

According to the present invention, the inclination and positional deviation of the object to be measured 1 with respect to the laser light source 2 can be easily detected. Moreover, the positional deviation of the object to be measured 1 can be corrected by using the cylindrical lens 4.
Since it is detected as a deviation from the focal length of the object to be measured 1
Even if the surface is uneven and the scattering state is not constant, positional deviation can be detected accurately. In addition, if the detected tilt or positional deviation is displayed in analog or digital form,
While watching this, adjust the direction and position of the laser light source 2,
The inclination and positional deviation of the object to be measured 1 can be easily corrected prior to measurement.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of a method for measuring the length of an object using a laser Doppler method.

FIG. 2 is an explanatory diagram showing an embodiment of the detection method of the present invention.

FIG. 3 is an explanatory diagram of scattered light from a four-part detector when the object to be measured is tilted in the present invention.

FIG. 4 is an explanatory diagram of scattered light from a four-part detector when the object to be measured is shifted by one position in the present invention.

FIG. 5 is an explanatory diagram of a detection signal extraction method in the present invention.

FIG. 6 is an explanatory diagram of detection signals in FIG. 5;

FIG. 7 is an explanatory diagram of a tilt detection signal in FIG. 5;

FIG. 8 is an explanatory diagram showing the relationship between the incident angle of the beam and scattered light when the object to be measured is tilted.

FIG. 9 is an explanatory diagram showing the relationship between the inclination angle of the object to be measured and the output level.

FIG. 10 is an explanatory diagram showing the deviation in distance from the object to be measured to the laser light source.

FIG. 11 is an explanatory diagram showing the relationship between the distance difference from the object to be measured to the laser light source and the output level.

[Explanation of symbols]

1 Object to be measured 2 Laser light source 3 Sensor 4 Cylindrical lens 5 Quadrant detector 6-9 Light receiving part a Laser light b Scattered light d Doppler signal

Claims (1)

[Claims] Claim 1: A laser beam a is emitted from a laser light source 2 to an object to be measured 1.
The sensor 3 receives the scattered light b from the object to be measured 1 and outputs the Doppler signal d.
In a method for measuring the moving speed, length, etc. of a measured object 1 based on the laser Doppler method, a four-part detector 5 is used as the sensor 3. The scattered light b is received by the quadrant detector 5 through the cylindrical lens 4, and among the Doppler signals d output from the four light receiving sections 6, 7, 8, and 9 of the quadrant detector 5, the The two light receiving sections 6 and 7 and 8 and 9 are taken as a pair, and the output level of each pair is determined.
Movement of the object to be measured using the laser Doppler method, which is characterized by detecting the inclination of the object to be measured 1 with respect to the laser light source 2 or the positional deviation of the object to be measured 1 with respect to the laser light source 2 from the output level thereof. Method for detecting inclination and positional deviation of objects to be measured in speed, length measurements, etc.