JPS58225304A - Optical type mechanical quantity measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the three-dimensional mechanical quantity by causing an interference between a speckle pattern formed with a mobile diffusion surface and a reference light from a fixed reflection surface. CONSTITUTION:Light from a light source 1 irradiates a target 4 passing through a first polarized beam splitter 21. The light reflected from the target 4 enters a light receiver 7 reflected with the first PBS21. The light which enters the first PBS21 from the light source 1 and passes through first and second PBSs 21 and 22 reflected with a mirror 6 enters a light receiver 7 as reference light. A speckle pattern is formed on the light receiver 7 in such a manner as to be overlapped by a Michelson interference fringe. The three-dimensional mechanical quantity is measured from the movement of the speckle pattern and the movement of the interference fringe.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical mechanical quantity measuring device that uses optical interference to determine mechanical quantities such as displacement amount, displacement speed, and vibration frequency.

The purpose of the present invention is to realize a device of this type with a simple structure that can measure various mechanical quantities in the S dimension with high precision and high resolution without contacting the object to be measured. An interference pattern is superimposed on a speckle pattern by interfering with a diffuser surface and a fixed reflection surface, and one-dimensional mechanical quantity measurement is performed from the movement of the speckle pattern and the movement of the interference pattern.

FIG. 1 is a configuration explanatory diagram showing an example of a device according to the present invention. In the figure, reference numeral 1 denotes a light source, for example, a HeNe laser light source is used, from which coherent light is emitted. it
, 12 is a lens, which constitutes a beam expander BX that expands the light emitted from the light source 1 and converts it into parallel light. 2
1 is the first polarizing beam splitter (hereinafter abbreviated as PB3)
Then, the light beam from the light source 1 entering through the beam expander BX is split into two directions. 22 is the PBS of #IE2, which is installed rotated by 45 degrees with respect to the 1'' PBS, and has the role of causing the two types of light incident there to interfere to create stripes. 31. 32 is a lens with a focal length of f□ and f2, respectively; 30 is an aperture plate installed between lenses 31 and 32 at a distance of f from lens 31 and f2 from lens 32; A through hole with a diameter d is provided.

Reference numeral 4 denotes a target having a diffusing surface 40, which is installed at a distance from the lens 32 by a distance of 1<1 (preferably approximately O~2f2);
A three-dimensional measured mechanical quantity in the z-direction is given.

51 is installed between the lens 32 and the target 4.
The 4th plate and 6 are mirrors, which are installed at a slight angle Δθ with respect to the optical axis C4 of the light source 10.
A light beam from the light source 1 divided by 21 enters. 5
2 is installed between the first PB321 and ζku 6.
4 and 7 are light receivers that receive the light emitted from the second PBS 22.

FIG. 2 is a plan view showing an example of the structure of the light receiving surface of this light receiver 7. As shown in FIG. Here, for example, an image sensor 71 such as a COD configured by arranging a large number of light receiving elements in a 7-ray pattern.
．． 72 are arranged such that the arrangement directions of the light receiving elements are orthogonal to each other.

FIG. 3 is a configuration diagram showing an electrical circuit in the apparatus shown in FIG. 1. In this figure, 70 is, for example, C
The clock oscillator is composed of a CD and drives each of the optical receivers 71 and 72, and applies a clock signal of, for example, a frequency fo to each optical receiver. 81.82 inputs the output frequency signals fx, fy from each photoreceiver 71.72, and a reference frequency signal fR□ and a stone electric sensor 11, and 83 inputs the frequency signal fx from the photoreceiver 71. ,
The electric mixer 91.92.93 that mixes this and the reference frequency signal fR□ is a four-bass filter that passes a specific frequency signal in the corresponding t#Sukamono output signal, and 41.42.43 is a Counters 6 count the frequency signals from each of the low-pass filters 91, 92, and 93, and 6 is a manually operated arithmetic circuit that counts the frequency signals from each counter 41, 42, and 43. Four setsa are used. Reference numeral 60 denotes a display device, for example, a CRT, which displays the calculation results of the calculation circuit 6.

The operation of the device configured as described above is as follows. The light with a large wavelength emitted from the light source 1 is sent to the beam expander B.
The light is expanded by X, becomes parallel light, and enters the first PBS 21. Of the light incident here, the light component (P wave) whose vibration direction is parallel to the incident plane passes through the lens 31, the aperture plate 30. The parallel light is irradiated onto the diffusing surface 40 of the target 4 through the lens 32 and the λ/4 plate 5 and the metal plate 1. The parallel light irradiated onto the diffusing surface 40 of the target 4 undergoes random phase modulation due to the unevenness of this diffusing surface and is reflected, and this reflected light is reflected again by the λ14 plate 51. Lens 32.
Returns through the aperture plate 30° lens 31 and returns to the first PBS.
21.

Here, 3 lenses, 30 aperture plates. The lens 32 functions as a low-pass filter that lowers the spatial frequency of light passing through it, and is not necessarily necessary.

The light re-entering the first PBS passes through the λ14 plate 51 twice, so the 906 polarization plane rotates and becomes 8 waves.]
, is reflected by this PBS 21 and is incident on the second PBS 22... Of the light that has entered the first PBS 21 from the light source 1, eight wave components are reflected here and are transmitted to the λ14 plate 5.
2, is reflected by the mirror 6, passes through the λ14 plate 52 again, and enters the first PBS 21 again. This light becomes a P wave, passes through this PH1021, and becomes a second P wave.
The light enters the BS 22 as a reference light. 2nd PBS 2
2 is placed rotated by 45 degrees with respect to the first PBS 21, and here, the reflected light from the target 4 whose polarization planes differ from each other by 90', and the reflected light from the light source 1 by ζ2 4. Of the incoming reference light, 456 components are transmitted as shown in Fig. 4, and an interference pattern is created on the light receiver 7. good.

FIG. 5 is a diagram showing an example of a pattern obtained on the light receiver 7, in which Michael interference fringes are superimposed on a speckle pattern 8P. In this pattern, when the target 4 is displaced in the X(y OF) direction, the speckle pattern 8P is
) direction. Further, when the target 4 is displaced in the dew direction, the Michelson interference pattern MP is displaced in the X direction, and at this time, the speckle pattern sp does not move.

In this case, if the distance between the lenses 31 and 32 is f1+f2 and the target 4 is irradiated with a plane wave, a so-called pure movement state can be achieved.In this state, the light receiving surface of the light receiver 7 The average speckle diameter of the resulting speckle pattern is given by (f×λ)l(π×d). t
In addition, the average pitch of the interference pattern is given by λ/sinΔ0, and it is desirable to select so that 5 to 10 stripes are included in one speckle pattern.

Therefore, the distance t between the lens 32 and the target 4
Also, the distance from the lens 31 to the light receiver 7 is unrelated to the state of line movement, the diameter of speckles, and the pitch of the image.

Each of the light receivers 71.72 of the light receiver 7 is driven by a clock signal of frequency fc applied to one end of the clock oscillator 70.
Frequency signals fx and fy whose fundamental frequency is /N (where N is the number of bits of the photoreceiver 71.72) are output.

FIG. 6 is an explanatory diagram showing the frequency/number spectrum of the frequency signal fx obtained from each received light @71. The envelope line of the peak has a peak due to interference fringes at the frequency of fR2 (!R2) fR The peak Pm is the moving speed! The frequency is shifted by fmx proportional to ldX/dt. Moreover, if the target 4 moves in the dew direction, the peak of the envelope line moves.

1""fgKk""C, 1lPf8"・°'1-1"・
), 72 also output frequency signal and frequency f
Mixing with R1, that is, performing hetero-four dyne detection,
Each output is passed through a low-pass filter 91, 92 and a counter 41.
42, a signal corresponding to the frequency shift Δfmx e (blue my ) accompanying the displacement of the target 4 in the x (y) direction is obtained, for example, with a peak Pm corresponding to the m-th harmonic. The arithmetic circuit 6 inputs these signals and performs a predetermined calculation, for example, an integral calculation, thereby being able to know the displacements 1x and y of the target 4 in the x and y directions. Similarly, the gokina 83 mixes the frequency signal output from the light receiver 71 and the frequency fR□, and passes the signal through the low-pass filter 93. By passing through the counter 43, a signal corresponding to the shift Δfz of the envelope peak is obtained. The calculation circuit 6 inputs this signal and performs a predetermined calculation to determine the displacement amount 2 of the target 4 in the rich direction. In addition, Δfmx, Δfmy
, Δfz change polarity to positive or negative depending on the moving direction of the target 4, so that the moving direction can be determined at the same time.

The device configured in this way can simultaneously measure three-dimensional displacement using a beam from one light source, and the overall configuration can be simplified. Furthermore, since the signals obtained from each light receiver are frequency signals, calculation processing is easy and various mechanical quantities can be measured with high resolution.

In the above embodiment, the mirror 6 may have other configurations, such as a prism or a Keeb corner with an apex angle of t'12+Δθ12, as long as the incident light and the reflected light are inclined by Δθ. In addition, 9, here, the light receivers 71, 72,
Although it is assumed that an image sensor such as a COD is used, a pattern detector such as a combination of a spatial filter may also be used. Furthermore, if there is sufficient optical power, an optical system using a half-gin-23 as shown in Fig. 7 may be used.
Although the case of measuring the amount of displacement in the *3'e'' direction has been described, it is also possible to measure various three-dimensional mechanical quantities such as the displacement speed of the target 4, the number of vibrations (9 rotations), or the change in shape.

As explained above, according to the device according to the present invention, mechanical quantities such as three-dimensional displacement of a target can be measured with high resolution without contacting the target to which the mechanical quantity to be measured is given. .

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an example of a device according to the present invention, FIG. 2 is a configuration explanatory diagram of a light receiver used in the device shown in FIG. 1, and FIG. 3 is a configuration block diagram showing an electrical circuit. , Fig. 4 is an explanatory diagram of the wavefront of the light irradiated to the optical receiver, Fig. 5 is an explanatory diagram showing an example of the pattern created on the light receiving surface of the optical receiver, and Fig. 6 is an explanatory diagram of the signal obtained from the optical receiver. FIG. 7 is an explanatory diagram showing a frequency spectrum, and FIG. 7 is an explanatory diagram showing main parts of another optical system of the present invention. 1... Light source, 21, 22... Polarizing beam splitter, 31° 32... Lens, 30... Diaphragm plate, 4...
...Target, 40...Diffusion surface, 51.52...
λ/2 plate, 6... Mi2-17... Light receiver. Figure 2

Claims (2)

[Claims] (1) Coherent light from a light source is irradiated onto the diffusing surface of the target to which the mechanical quantity to be measured is given, and on a reflecting means that reflects the incident light so that the incident light and the outgoing light form a predetermined angle. , irradiating the light receiving means with the diffused light from the diffusing surface and the reflected light from the reflecting means, detecting the movement of the pattern created by the diffused light, and detecting the movement of the pattern formed by the diffused light,
Measuring the mechanical quantity in the dimensional direction, detecting the movement of the pattern where the diffused light and the reflected light interfere with each other.
An optical mechanical quantity measuring device that measures mechanical quantities in the axial direction perpendicular to the dimensional axis. (2) A quantity measuring device that uses an image sensor as a means for detecting pattern movement, performs heterodyne detection on the frequency signal from the image sensor, and performs predetermined calculations using the obtained frequency signal.