JPH0821849A - Measuring method for high-temperature body by laser doppler system - Google Patents

Abstract

PURPOSE:To reduce the deterioration of the measurement accuracy due to the effect of the radiation light emitted from a high-temperature body and resolve impossible measurement in measuring the moving speed and length of the high-temperature body. CONSTITUTION:Laser beams (a) are radiated to a high-temperature body from two directions, scattered beams (b) emitted from the high-temperature body and having the intensity proportional to the brightness of interference fringes generated by the interference with both laser beams (a) are received by a light sensor 2, a Doppler signal (d) is outputted, and the speed and length of a measured object are measured based on the Doppler signal (d). The beam shape of the laser beams (a) radiated to the high temperature body is narrowed, and its energy density is increased. A receiving lens 3 having a long focal distance is arranged in front of the light sensor 2 to narrow the measuring visual field, and the received quantity of the radiation light by the light sensor 2 is reduced. A wavelength filter passing the wavelength band of the laser beams (a) is arranged in front of the light sensor 2 so that no light other than the wavelength band of the laser beams (a) is fed to the light sensor 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring method used for measuring the speed, length and the like of a hot body (for example, an iron plate being manufactured) by a laser Doppler method.

[0002]

2. Description of the Related Art The inventor of the present invention has previously developed the measurement of the speed and length of a high heat element by the laser Doppler method. The measurement principle is as shown in FIG. 4, in which laser light a from a laser light source 5 such as a He—Ne laser is converted into parallel light through a collimator lens 6, and the parallel light is deflected by a deflecting beam splitter 7 for preventing return light. It is put into a beam splitter 9 through a λ / 4 plate 8 and is divided into two beams. One of the laser beams a is directly reflected, and the other laser beam a is reflected by a mirror 10, so that both laser beams a are crossed at a cross angle φ. When irradiated to 1, high heat element 1
The scattered light b from the photosensor 2 is received by the photosensor (photoelectric converter: for example, photodiode: PD) 2 through the light receiving lens 3 and heterodyne detected, and the Doppler signal d is output from the photosensor 2. Is.

The Doppler frequency fd of this Doppler signal d
Is represented by the following equation. fd = 1 / T = 1 / (d / v · cos Δθ) = v · cos Δθ / d = v · cos Δθ / {λ / (2sinφ / 2)} = 2v / λ · sinφ / 2 · cos Δθ fd: Doppler frequency v: traveling speed of the high-heat body 1 λ: laser wavelength (632.8 nm) φ: beam crossing angle Δθ: deviation angle from the normal of the beam and the right angle of the high-heat body 1 As described above, the Doppler frequency fd Is proportional to the traveling speed v of the high-heat body 1, so that the traveling speed v can be obtained according to the measurement principle, and the length of the high-heat body 1 can be measured by integrating the traveling speed v with time. it can.

When the high heat element 1 is irradiated with the laser beam a as shown in FIG. 4, scattered particles b are generated by the fine particles of the high heat element 1. In this case, by irradiating the laser light a from two directions, the interference of the two laser light a causes the interference of the laser light a as shown in FIG.
Interference fringes are generated as shown in (a), and the scattered light b has an intensity proportional to the brightness of the interference fringes. If this scattered light is received by the optical sensor 2, the output of the optical sensor 2 becomes a signal having a waveform as shown in FIG. This is the Doppler signal d, and its level is proportional to the contrast difference of the interference fringes, as is clear from the relationship between FIGS. 6 (a) and (b), and (c) and (d).

[0005]

The conventional method of measuring the speed, length, etc. by the laser Doppler method has the following problems when measuring the high heat element 1. ． As the temperature of the high heat element 1 rises, the emitted light from the high heat element 1 increases. For this reason, the difference in brightness between the interference fringes of the laser light a is reduced, the level of the Doppler signal is reduced, and if it is significant, measurement becomes impossible. Further, even when measurement is possible, if the level of the Doppler signal is lowered, the S / N ratio is deteriorated and the measurement accuracy is lowered. By the way, the relationship between the temperature of the high heat element 1 and the level of the Doppler signal is as shown in Table 1.
When the temperature is 1100 ℃, it is -20dB than when it is 25 ℃.
m, that is, 1/10.

[0006]

[Table 1]

[0007]. The high-heat body 1 is generally soft due to high heat, the bending of the tip end, the rising of the blade, and the like become large, and the measurement distance between the high-heat body 1 and the Doppler sensor easily changes. This fluctuation also lowers the Doppler signal level. This decrease in level, together with the decrease in level due to the temperature, makes measurement more difficult.

[0008] An avalanche photodiode (APD) is usually used for the optical sensor 2 of FIG. This AP
D has an AGC function of increasing the sensitivity when the incident light is weak and decreasing the sensitivity when the incident light is strong. Therefore, when the temperature of the heating element 1 rises and the amount of emitted light increases, the difference in brightness between the interference fringes of the laser light a decreases and the level of the Doppler signal decreases. Moreover, at this time, the emitted light is emitted by the optical sensor 2.
Since the total amount of light incident on the optical sensor 2 increases, the sensitivity decreases due to the AGC function of the optical sensor 2. For this reason, the accuracy of measurement decreases more and more, and if it is significant, the measurement becomes impossible.

An object of the present invention is to reduce the deterioration of the measurement accuracy due to the effect of the radiated light generated from the high heat element when measuring the moving speed, length, etc. of the high heat element by the laser Doppler method, and the measurement becomes impossible. To solve that.

[0010]

A method for measuring a high heat element by a laser Doppler method according to claim 1 of the present invention is to irradiate the high heat element 1 with laser light a from two directions as shown in FIG. Scattered light b emitted from the heating element 1 and having an intensity proportional to the brightness of the interference fringes generated by the interference of the two laser lights a.
Is received by the optical sensor 2 and output as a Doppler signal d, and the speed, length, etc. of the DUT 1 are measured based on the Doppler signal d. 2B and 2C show the cross-sectional area of the beam shape of the laser light a with which the high-temperature body 1 is irradiated.
This is a method of narrowing it as shown in.

According to the second aspect of the present invention, the method for measuring a high-heat body by the laser Doppler method, as shown in FIG. 1, emits light from the high-heat body 1 by irradiating the high-heat body 1 with laser light a from two directions. The scattered light b having an intensity proportional to the contrast of the interference fringes generated by the interference of the two laser lights a is received by the optical sensor 2 and is output as the Doppler signal d, and the velocity of the DUT 1 is measured based on the Doppler signal d. In the method of measuring the high-heat body 1 by the laser Doppler method for measuring the length, etc., by using a light receiving lens 3 arranged in front of the optical sensor 2 having a long focal length,
This is a method in which the measurement visual field is narrowed as in (a), (b) and (c).

According to the third aspect of the present invention, in the method for measuring a high heat element by the laser Doppler method, as shown in FIG. 1, when the high heat element 1 is irradiated with laser light a from two directions, the high heat element 1 emits light. The scattered light b having an intensity proportional to the contrast of the interference fringes generated by the interference of the two laser lights a is received by the optical sensor 2 and is output as the Doppler signal d, and the velocity of the DUT 1 is measured based on the Doppler signal d. In the method of measuring the heat-generating body 1 by the laser Doppler method in which the length and the like are measured, a wavelength filter 4 that passes the wavelength band of the laser light a is arranged in front of the optical sensor 2 as shown in FIG. 3C. In this way, light other than the wavelength band of the laser light a is prevented from entering the optical sensor 2.

[0013]

According to the first aspect of the present invention, in the method for measuring a high heat element by the laser Doppler method according to the first aspect of the present invention, the area of the beam shape of the laser beam a (FIG. 2a) with which the high heat element 1 is irradiated is shown in FIG.
Since the width is narrowed as in (b) and (c), the energy density of the laser light a emitted from the laser light source 2 becomes higher as the area becomes smaller, and the difference in brightness between the interference fringes becomes larger, which is proportional to that. As a result, the output of the Doppler signal d also becomes large, the C / N at the time of measurement is improved, and the measurement accuracy is improved.

[0014]

According to the second aspect of the present invention, in the method for measuring a high-heat body by the laser Doppler method according to the second aspect of the present invention, the light receiving lens 4 arranged in front of the optical sensor 2 as shown in FIG. Since the measurement field of view is narrowed by using a long one, the scattered light b (light necessary for measurement) generated from the measurement field of view of the high heat element 1 is received by the optical sensor 2, but is radiated from the outside of the measurement field of view. The emitted light (light not necessary for measurement) is removed. Therefore, the sensitivity of the optical sensor 2 does not decrease due to the emitted light that is not necessary for measurement, and the decrease in measurement accuracy is suppressed.

[0015]

According to the third aspect of the present invention, in the method for measuring a high heat element by the laser Doppler method according to the third aspect of the present invention, as shown in FIG. 3 (c), a wavelength filter which passes the wavelength band of the laser light a in front of the optical sensor 2 is provided. Since 4 is arranged, almost no light other than the wavelength band of the laser light a is incident on the optical sensor 2, and the reduction in the contrast difference of the interference fringes due to the influence of the radiated light which is not necessary for measurement is reduced. In addition, the amount of light received by the optical sensor 2 is reduced by the amount of radiated light that is not required for measurement being cut by the wavelength filter 4, and the sensitivity is less reduced due to the AGC function of the optical sensor 2.

[0016]

[Embodiment 1] A first embodiment of the method for measuring a high heat element by the laser Doppler method of the present invention will be described with reference to FIG.
1 has basically the same configuration as that of FIG. 4, except that in FIG. 1, a first cylindrical lens (cylindrical lens) 12 is arranged between a collimating lens 6 and a deflecting beam splitter 7, and λ Between the quarter plate 8 and the beam splitter 9
That is, the tachylindical lens (cylindrical lens) 13 is arranged.

The cylindrical lenses 12 and 13 have the same shape, and as shown in FIG.
The laser light a parallel to the plane 17 of 2, 13 has an area d,
When the incident light has a size of e, f, and g, the lenses 12, 13
An elongated image of h, i, j, and k is formed (converted into an elongated area) on the front side of the curved surface 18 side.

For example, when the beam shape (cross-sectional shape) of the laser light a generated from the laser light source 5 is circular as shown in FIG. 2A and its diameter is 8 mm, its area is about 5 mm.
It is 0 mm ² . This laser light a is passed through the cylindrical lenses 12 and 13 to have a width of 8 m as shown in FIG.
If it is made into an elongated shape with m and a vertical width of 2 mm, the area will be about 16
In mm ² , the energy density is about ⅓ of that in FIG. 2A, and the energy density of the laser beam a is tripled. Further, as shown in FIG. 2 (c), if the width is 8 mm and the vertical width is 1 mm, the beam shape has an area of about 8 mm ^2, which is about 1/6 of that of FIG. 2 (a).
Area, that is, the energy density of the laser beam a is about 6 times.

In FIG. 1, the first and second cylindrical lenses 12 and 13 are arranged such that the plane 17 thereof is the incident side of the laser light a and the curved surface 18 is the emission side of the laser light a. , The laser light a incident from the plane 17 is curved surface 18.
The cross-sectional area of the laser light a emitted from the laser is reduced.

In FIG. 1, when a laser light source 5 such as a semiconductor laser is driven by a laser diode drive circuit 11, laser light a is output, and this laser light a is converted into parallel light through a collimator lens 6, which is converted into parallel light. By passing through the first cylindrical lens 12, it is converted into an elongated area as shown in FIG. 1 (b), which passes through the deflecting beam splitter 7 and the λ / 4 plate 8 and further into the second system. By passing through the lindcal lens 13, it is converted into an elongated area again as shown in FIG. It is incident on the beam splitter 4 and is split into two beams. One of the laser beams a is beamed.
The high heat element 1 is directly irradiated from the beam splitter 4, and the other laser beam a is reflected by the mirror 10 and is applied to the high heat element 1 at the crossing angle φ.

At this time, the intensity of the scattered light b generated by the fine particles of the heating element 1 changes in proportion to the difference in brightness between the interference fringes (FIG. 1b) caused by the interference of the laser light a from two directions. The scattered light is collected through the light receiving lens 3, received by the optical sensor 2, the Doppler signal is output from the optical sensor 2, amplified by the amplifier 20, and output to the measurement unit. The Doppler signal d is output in the measurement unit. Based on this, the traveling speed v of the high heat element 1 is obtained. Further, the traveling distance (length) of the high-heat body 1 can be obtained based on the traveling speed v.

The radiant light emitted from the high heat element 1 is the high heat element 1.
The higher the temperature is, the stronger the temperature becomes. Therefore, the difference in brightness between the interference fringes is reduced under the influence of the temperature, and the level of the Doppler signal is reduced accordingly. However, in the embodiment of FIG. , The beam shape of the laser beam 2 is narrowed by the second cylindrical lenses 12 and 13, so that the laser beam a is narrowed as compared with the case where the laser beam a in FIG. 2A is used as it is. The energy density of No. 2 is increased, the contrast difference of the interference fringes becomes clear, and the level reduction of the Doppler signal is suppressed.

In FIG. 1A, the two cylindrical lenses 12 and 13 are used to narrow the beam shape of the laser beam 2 in two steps. However, only one of the cylindrical lenses is used. The number of the cylindrical lenses 12 and 13 may be one if the area can be reduced to a desired area.

In the embodiment shown in FIG. 1, the AC component contained in the Doppler signal d output from the optical sensor 2 is cut by the capacitor C to obtain the monitor signal e. The monitor signal e is amplified by the monitor amplifier 21 and displayed on a display such as a level meter or an indicator of the monitor section. From the display, it is possible to detect the inclination θ of the high heat body 1 with respect to the normal line of the bisector of the two laser beams a using one laser light source 5 as a light source, and the positional deviation of the high heat body 1 with respect to the laser light source 2. .

[0025]

[Embodiment 2] A second embodiment of the present invention is shown in FIGS.
It is shown in (c). This embodiment is the same as the case of FIG. 1 in the basic measurement method, but is different from that of the optical sensor 2 as shown in FIG. 3B in order to suppress the influence of the radiated light from the high heat body 1. The light receiving lens 3 arranged in front has a long focal length. If a light-receiving lens 3 having a short focal length, for example, F ₂ shown in FIG. 3A is used, the field of view of the measurement point entering the optical sensor 2 becomes wide, as clearly shown in FIG. If a long focal length, for example, F ₁ shown in FIG. 3A is used, the field of view of the measurement point entering the optical sensor 2 becomes narrow as clearly shown in FIG. 3B. Therefore, in the second embodiment in which the one having a long focal length is used, the scattered light b generated from the measurement visual field of the high heat element 1 is generated.
(The light necessary for measurement) is received by the optical sensor 2,
Emission light (light not necessary for measurement) emitted from the outside of the measurement field of view is removed. Therefore, the sensitivity of the optical sensor 2 does not decrease due to the emitted light that is not necessary for measurement, and the decrease in measurement accuracy is suppressed.

[0026]

[Embodiment 3] A third embodiment of the present invention is shown in FIG. This embodiment is the same as the case of FIG. 1 in the basic measurement method, except that the wavelength band of the laser light a is set in front of the optical sensor 2 in order to suppress the influence of the radiated light from the high heat body 1. The narrow band wavelength filter 4 is arranged to allow the light to pass but remove the other bands. As a result, the high heat element 1
The radiated light emitted from is removed by the same wavelength filter 4 and does not enter the optical sensor 2, and almost no light other than the laser light a enters the optical sensor 2. For this reason, the reduction of the contrast difference of the interference fringes due to the influence of the radiated light not required for the measurement is reduced, and the amount of light received by the optical sensor 2 is reduced by the amount of the radiated light not required for the measurement being cut by the wavelength filter 4. Therefore, the decrease in sensitivity due to the AGC function of the optical sensor 2 is reduced.

[0027]

According to the first aspect of the present invention, in the method for measuring a high-heat body by the laser Doppler method, the beam shape of the laser beam a with which the high-heat body 1 is irradiated is changed so that the energy density thereof becomes high, so that the interference occurs. The difference between light and dark stripes becomes clear, the output of the Doppler signal d becomes large, the C / N at the time of measurement is improved, the measurement accuracy is improved, and the inability to measure is eliminated.

[0028]

According to the second aspect of the present invention, in the method for measuring a high heat element by the laser Doppler method, since the light receiving lens 4 arranged in front of the optical sensor 2 has a long focal length, the emitted light The decrease in the difference in brightness of the interference fringes due to the influence is reduced, the C / N at the time of measurement is improved, the measurement accuracy is improved,
The decrease in sensitivity due to the AGC function of the optical sensor 2 is reduced,
Unmeasurable is also eliminated.

[0029]

According to the third aspect of the present invention, in the method for measuring a high heat element by the laser Doppler method, the wavelength filter 4 that passes the wavelength band of the laser light a is arranged in front of the optical sensor 2, so that the influence of the radiation light is exerted. The decrease in the contrast difference of the interference fringes due to is reduced, the C / N at the time of measurement is improved, the measurement accuracy is improved,
The decrease in sensitivity due to the AGC function of the optical sensor 2 is reduced,
Unmeasurable is also eliminated.

[Brief description of drawings]

FIG. 1A is an explanatory view showing an embodiment of a method for measuring a length of a high heat element by a laser Doppler method of the present invention, and FIG. 1B is an explanatory view of a cylindrical lens in FIG. 1A.
FIG. 1C is an explanatory diagram of interference fringes in the measuring method of FIG.

2A to 2C are explanatory views in the case of narrowing the beam shape of laser light.

3A is an explanatory view showing a relationship between a focal length of a light receiving lens and a measurement visual field, FIG. 3B is an explanatory view showing a relationship between a measurement visual field when the focal length of the light receiving lens is long, and FIG. FIG. 3 is an explanatory view showing the relationship with the measurement visual field when the focal length of the light receiving lens is short and a filter is provided.

4A is an explanatory view showing an example of a method for measuring the length of a high heat body by a laser Doppler method previously developed by the applicant of the present application, and FIG. 4B is an explanatory view of interference fringes in FIG.

5A and 5B are explanatory diagrams showing the relationship between the contrast difference of interference fringes and the Doppler signal.

6A to 6D are explanatory diagrams showing the relationship between the contrast difference of interference fringes and the level of a Doppler signal.

[Explanation of symbols]

 1 high heat body 2 optical sensor 3 light receiving lens 4 filter a laser light b scattered light d Doppler signal

Claims (3)

[Claims] 1. Laser light (a) is applied to a high heat element (1) from two directions.
The scattered light (b), which is emitted from the high heat element (1) by irradiating the laser beam and has an intensity proportional to the brightness of the interference fringes generated by the interference of the two laser beams (a), is received by the optical sensor (2) and the Doppler A high heat body (1) by a laser Doppler system, which outputs as a signal (d) and measures the speed, length, etc. of the high heat body (1) based on this Doppler signal (d).
In the measuring method of 1., the cross-sectional area of the beam shape of the laser beam (a) with which the high heat element (1) is irradiated is narrowed, and the method for measuring the high heat element by the laser Doppler method. 2. A laser beam (a) is applied to a heating element (1) from two directions.
The scattered light (b), which is emitted from the high heat element (1) by irradiating the laser beam and has an intensity proportional to the contrast of the interference fringes generated by the interference of the two laser beams (a), is received by the optical sensor (2) and the Doppler A high heat body (1) by a laser Doppler system, which outputs as a signal (d) and measures the speed, length, etc. of the high heat body (1) based on this Doppler signal (d).
In the above measuring method, a high-heat body by a laser Doppler system characterized in that a light receiving lens (3) arranged in front of the optical sensor (2) has a long focal length to narrow the measurement field of view. Measuring method. 3. A laser beam (a) is applied to the heating element (1) from two directions.
The scattered light (b), which is emitted from the high heat element (1) by irradiating the laser beam and has an intensity proportional to the brightness of the interference fringes generated by the interference of the two laser beams (a), is received by the optical sensor (2) and the Doppler A high heat body (1) by a laser Doppler system, which outputs as a signal (d) and measures the speed, length, etc. of the high heat body (1) based on this Doppler signal (d).
In the measuring method of 1., by disposing a wavelength filter (4) that passes the wavelength band of the laser light (a) in front of the optical sensor (2), light other than the wavelength band of the laser light (a) is provided to the optical sensor (2). Is a laser doppler method for measuring high heat elements, which is characterized in that it is not incident.