JPH09203741A - Aberration speedometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable velocity components in a direction orthogonal to the direction of the visual line of measuring personnel to be measured by calculating an aberration from the intervals between interference fringes detected from a light beam illuminating a subject for measurement and that reflected from it. SOLUTION: When a moving object 10 moving in the direction of a velocity vector 12 comes to a position orthogonal to the direction of the visual line of measuring personnel (direction of application of illuminating light 18), illuminating light 18 is applied to a half mirror 14 from a laser beam 13. Part of the light is transmitted 14 to illuminate a CCD 15, while the rest is reflected 14 and illuminates and is reflected by a corner cube 11. This reflected light 19 illuminates and transmits through the mirror 14 and illuminates and is reflected by a mirror 16. It is further reflected 14 to illuminate the CCD 15. If there is relative speed between the moving object 10 and the measuring personnel 17, the illuminating light 18 and the reflected light 19 do not become parallel but cause an aberration, producing interference fringes on the surface of the CCD 15. The aberration is calculated from the intervals between the interference fringes and the wavelength of the illuminating light 18, and the relative speed is calculated on the basis of the aberration. Thus velocity components in the direction orthogonal to the visual line of the measuring personnel can be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical differential velocity meter that measures the speed of a moving body by using laser light.

[0002]

2. Description of the Related Art Conventionally, as a speedometer for measuring the speed of a moving body in a non-contact manner, a laser
There is a Doppler velocimeter (for example, "Applied optics-Introduction to optical measurement-" by Toyohiko Yatagai, published by Maruzen kk, 1988.
Issuing year etc.). This Laser Doppler Speedometer
The velocity is measured by heterodyne detection of the Doppler shift of the scattered light generated by the movement of the moving body.

A conventional laser Doppler velocimeter will be described with reference to the drawings. FIG. 3 is an explanatory diagram showing a conventional laser Doppler velocimeter. In the figure, (1) shows the configuration of a laser Doppler velocimeter by the reference light method, (2) the two-incidence light method (differential method), and (3) the one-incidence light method.
1a and 1b are half mirrors that transmit a part of incident light and reflect the rest, 2 is a mirror, 3 is a photodetector, 4 is a beam splitter, 5 and 5a and 5b are lenses, and 6, 7 and 8 are slits. , Vector v is the velocity vector of the moving body, vector k
s, ks ₁ and ks ₂ are wavenumber vectors of incident light, and vectors ko, ko ₁ and ko ₂ are wavenumber vectors of scattered light.

The operation of the conventional example having the above configuration will be described for each method. (1) Reference Light Method The incident light having the wave number vector ks is bisected by the half mirror 1a, the reflected light is applied to the mirror 2 as the reference light, and then reflected by the half mirror 1b to be incident on the photodetector 3.
Further, the transmitted light is applied to the moving body that moves at the velocity vector v, and the scattered light having the wave number vector ko is incident on the photodetector 3 through the half mirror 1b. The two laser beams incident on these photodetectors 3 overlap each other to generate interference fringes. Therefore, the velocity of the moving body can be obtained by measuring the interval of the interference fringes.

(2) Two-incidence light method (differential method) The incident light is wavenumber vector ks by the beam splitter 4.
_It is divided into two beams of ₁ and ks ₂ and then radiated to a moving body having a velocity vector v via a lens 5a. The scattered light from the moving body enters the photodetector 3 through the slit 6, the lens 5b, and the slit 7. The incident scattered light causes interference fringes as in (1), and the velocity of the moving body can be obtained by measuring this interval.

(3) One-incidence light method Incident light of wave number vector ks is applied to a moving body of velocity vector v, and scattered light of wave number vectors ko ₁ and ko ₂ is transmitted through slit 8, lens 5 and slit 7. It is incident on the detector 3. The incident scattered light produces interference fringes as in the case of (1), and the velocity of the moving body can be obtained by setting this interval.

As described above, in any of (1), (2), and (3), the velocity of the moving body can be obtained by measuring the interval of the interference fringes generated in the optical measuring instrument 3. However, since all of them utilize the Doppler effect of light, it is only possible to stop the relative speed between the measurer and the moving body in the direction of the line of sight of the measurer. That is, it is impossible to measure the velocity component orthogonal to the direction of the line of sight of the measurer.

[0008]

As described above, the conventional speedometer utilizing the Doppler effect of light has a problem that it cannot measure the velocity component orthogonal to the line of sight of the measurer. The present invention is intended to solve such a problem, and an object thereof is to provide a speedometer capable of measuring a speed component orthogonal to the line-of-sight direction of a measurer.

[0009]

In order to achieve such an object, the optical differential velocity meter according to the present invention irradiates an object to be measured with irradiation light, and the irradiation light and the object to be measured of the irradiation light are used. Interference fringe detection means for detecting the interval of the interference fringes generated by superimposing the reflected light of the above, and the optical line difference is obtained from the interval of the interference fringes, and the velocity of the DUT in the direction orthogonal to the irradiation light is calculated. And speed calculation means. With such a configuration, the present invention can measure the optical path difference generated between the irradiation light applied to the moving body and the reflected light, and from this optical path difference, it is orthogonal to the line of sight of the measurer. The velocity component of the moving body can be measured.

[0010]

Next, details of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing one embodiment of the present invention. In the figure, 10 is a moving body which is an object to be measured, 11 is a corner cube which is provided on the moving body 10 and reflects light, 12 is a velocity vector of the moving body 10, 13 is a laser light source, and 14 is an incident light. A half mirror for transmitting the remainder and reflecting the rest, 15 is a CCD (Charge Cou
pled Device), 16 is a mirror, 17 is a laser light source 13
Interference fringe detection means composed of a half mirror 14, a CCD 15, and a mirror 16, 18 irradiation light, 19 reflected light, 20 interference fringes, ε is the optical path difference between the irradiation light 18 and reflected light 19, θ Is the angle of incidence of the irradiation light 18 on the CCD 15, and ΔL is the interval of the interference fringes.

The operation of the present invention having the above configuration will be described in detail. The moving body 10 is moving together with the velocity vector 12 from the lower side to the upper side in the figure. When the moving body 10 comes to a position orthogonal to the line-of-sight direction (irradiation direction of the irradiation light 18) of the measurer, the irradiation light 18 is irradiated from the laser light source 13 to the half mirror 14. A part of the irradiation light 18 passes through the half mirror 14 and is irradiated to the CCD 15, and the remaining laser light is reflected by the half mirror 14 and irradiated to the corner cube 11 provided on the moving body 10. The irradiation light 18 is reflected by the corner cube 11 and is applied to the half mirror 14 as reflected light 19. The reflected light 19 is transmitted through the half mirror 14, is reflected by the mirror 16, is reflected by the half mirror 14, is further reflected by the half mirror 14, and is irradiated by the CCD 15.

At this time, if the relative speed between the moving body 10 and the interference fringe detection means (measurer) 17 is v, the irradiation light 18 and the reflected light 19 to the corner cube 11 are not parallel, and The optical error ε is generated as shown in. ε = v / c (ε << 1) (1) Here, c is the speed of light, and the relative speed v is the speed in the direction orthogonal to the irradiation light 18.

Next, a method of detecting the optical path difference ε will be described with reference to FIG. FIG. 2 is an explanatory diagram showing interference fringes generated in the CCD 15 of FIG. When there is a relative velocity v between the moving body 10 and the interference fringe detection means (measuring person) 17, an optical path difference ε is generated between the irradiation light 18 and the reflected light 19, and the CCD 15
Interference fringes 20 occur on the surface. The distance between the interference fringes 20 is Δ
Let L be the wavelength λ of the irradiation light 18, the optical path difference ε, and the irradiation light 1
From the incident angle θ of 8 on the CCD 15, ΔL = λ / (sin ε + sin θ) holds.

Here, if θ = 0 and ε << 1, then ΔL
= Λ / ε, and ε = λ / (ΔL) (2). From the above, ΔL detected by the CCD 15 and the wavelength λ of the irradiation light 18 are substituted into the equation (2) to obtain ε, and this ε is substituted into the equation (1) to obtain the relative velocity v. . Note that the above calculation is performed by a speed calculating means (not shown).

[0015]

As described above, according to the present invention, the optical path difference generated between the irradiation light to the object to be measured and its reflected light is calculated, and the speed of the object to be measured is calculated from the optical path difference. Therefore, the velocity component of the measured object in the direction orthogonal to the line of sight of the measurer can be measured. Further, by measuring the interval of the interference fringes between the irradiation light and the reflected light, highly accurate speed measurement can be performed.

[Brief description of drawings]

FIG. 1 is a sectional view and an explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing interference fringes generated in the CCD of FIG.

FIG. 3 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

1a, 1b, 14 ... Half mirror, 2, 16 ... Mirror,
3 ... Photodetector, 4 ... Beam splitter, 5, 5a, 5b
... Lens, 6, 7, 8 ... Slit, 10 ... Moving body, 11
… Corner cubes, 12… Moving direction of moving body 10, 13
... laser light source, 15 ... CCD, 17 ... interference fringe detection means,
18 ... Irradiation light, 19 ... Reflected light, 20 ... Interference fringes, ε ... Optical path difference, θ ... Optical misalignment between the irradiation light 18 and the reflected light 19, ΔL ... Interval of interference fringes.

Claims (4)

[Claims] 1. Interference fringe detection means for irradiating an object to be measured with irradiation light, and detecting an interval of interference fringes generated by superposing the irradiation light and the reflected light from the object to be measured of the irradiation light, An optical path difference velocimeter, comprising: a speed calculating unit that calculates an optical path difference from an interval of interference fringes and calculates a speed of an object to be measured in a direction orthogonal to the irradiation light. 2. The interference fringe detection means according to claim 1, wherein the laser light source for irradiating the laser light of a predetermined wavelength and a part of the laser light are transmitted and the remaining laser light is reflected to the object to be measured. The half mirror that irradiates, the mirror that reflects the laser light that is reflected by the DUT and then passes through the half mirror, and the laser light that is reflected by the mirror and then reflected by the half mirror and the laser light that passes through the half mirror. An optical path difference speedometer characterized by comprising a light receiving element for receiving light. 3. The velocity calculation means according to claim 1, wherein the velocity calculation means divides the wavelength of the irradiation light by the interval of the interference fringes generated in the light receiving element to obtain the optical error, and multiplies the optical error by the optical error. An optical cross-velocity velocimeter, characterized in that the velocity of an object to be measured is obtained thereby. 4. The optical path difference speedometer according to claim 2, wherein the light receiving element is a CCD.