JPS63111403A - Displacement measuring instrument - Google Patents

Abstract

PURPOSE:To measure an extremely close interval with high accuracy by finding the displacement of an object body by utilizing a leak of light in a reflecting surface. CONSTITUTION:Luminous flux L1 from a laser light source 1 is incident on an optical component 2 at an angle thetai1 of incidence and projected at an angle thetai2 of projection to become luminous flux L4, which travels to a photoelectric sensor 3 and is converted photoelectrically. The output of the sensor 3 is inputted to a processor 4 in the form of a voltage or current. At this time, a little light leaks to an external field from the border between the optical component 2 and the medium as the external field. Namely, when the objective body 5 comes close to the bottom surfaces S of the optical component 2 up to wavelength order, luminous flux L2 is reflected at a point B while the leaking light is absorbed by the objective body 5 to become pieces of luminous flux L3 and L4, so that the luminous flux traveling the sensor 3 is reduced. This is found from the output of the photoelectric sensor 3 and the output is measured, so that the interval (x) is calculated by the processor 4 and displayed on a display device 6.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a non-contact displacement measuring device, and in particular, the present invention relates to a non-contact displacement measuring device, and in particular, the present invention relates to a non-contact displacement measuring device, and in particular, to a non-contact displacement measuring device, which measures the displacement of a target object by utilizing the seepage of light from a reflective surface. This invention relates to a displacement measuring device that measures displacement with high precision.

(Prior art) Conventionally, as a non-contact measurement method using light, as shown in Fig. 6, a He-Ne laser beam (B) is applied to a target object (A).
The spot of light hitting the target object (A) is captured using a lens system (C), for example, by PAD (Po5ition8).
In the case of an optical t1 element (D) (C element, for example, 10XIQ*m of light hits the element surface, a voltage proportional to u(x, y) is output. There is a method in which the image is formed on a surface (possible) and the variation in the distance ma+ between the senna (E) and the object (A) is calculated from this output voltage.

Such a displacement meter is commercially available.

On the other hand, as another method, as shown in Fig. 7, the target object (
Arrange the F) and sensor (G) surfaces as shown in the figure, and attach the senna (
G)? Reflected light from Ili! By using the interference between
There are ways to get it out. Although there are not many commercially available devices using this method, it is an extremely common measurement method.

However, in the former method using PSD, the resolution of the displacement a is generally on the order of several μm to several tens of μm, which is on the order of several hundred times the wavelength of light. Also, the working pressure% (
w'ork distance) is several myt to several tens
Order is required. In the latter interference method, the resolution of the displacement d is on the order of a fraction of the wavelength of light. For example, if the optical path in the figure is J, then from the well-known interference condition 2L=nλl ''=1+2131 λ: W of light
For J that satisfies the length, bright stripes can be detected. Also,
For J that satisfies , dark stripes can be detected. Therefore, in the displacement detection method using interference using this, the first thing that can be detected is a dark stripe at 1 = λ/4 (when m = 1), and the working distance (work distance) λ
Generally, λ is approximately /4 or more and 1 resolution/(1 to 32) (when interpolation is used).

(Problems to be Solved by the Invention) The present invention was made in consideration of the fact that the above-mentioned conventional displacement measurement method has a long working distance and a limit to the measurement fW degree. Displacement that measures the distance to the target object or the displacement of the object with extremely high resolution (several tenths to several σ of the wavelength λ) at a working distance close to (specifically, within wavelength λ) The purpose is to provide a measuring device.

[Structure of the invention]

(Means and actions for solving the problem) A light source that emits light, an incident surface that enters the light, and a method that totally reflects the light that has entered the interior through the incident surface and interrogates the object to be measured. an optical means having a total reflection surface provided on the surface, and a photoelectric conversion means for receiving light from the total reflection surface and photoelectrically converting the light from the total reflection surface. Displacement is measured based on the functional relationship with the amount.

(Example) Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of the displacement measuring device of this embodiment. This device consists of a laser light source (II) that emits He-Ne laser light, and an optical component (II) that passes through and reflects the laser beam.
) and a photodiode that measures the sight of the laser beam,
A photoelectric sensor (3) such as a phototransistor, a processing device (4) mainly composed of a microcomputer that inputs the output ('4 voltage or current) of the photoelectric sensor (3) and performs the processing described below, and this processing device ( The display device (6) displays the distance X between the optical component (2) and the target object (5) or the displacement 11dx of the target object (5), which is the processing result in step 4). Here, the target object (5) is an object through which light passes, such as a glass plate.

Next, the operation of the displacement measuring device having the above configuration will be described.

First, a light beam L1 emitted from a laser light source (1) enters a point A on the left side of an optical component (2) as shown in FIG. 1, for example, at an incident angle θ11. The transmitted light then enters the optical component at a refraction angle of θ1°. Now, if the refractive index of the optical component (2) is nap and the refractive index of the medium outside the optical component (2) is nout, then from the well-known law of refraction or 5nell's law, θ1. / order θtl ””nop / nout ==
It becomes nQp out. In general, if the outside medium is all air, napout ) 1. The light flux disease that advances inside the optical component (2) is caused by the bottom surface S of the optical component (2).
is incident on point B at an incident angle θ. In this invention, the incident angle θ is set to satisfy θ, >θ−. However, θr is the critical angle -02":: nout -op =
nout /nop (An angle that satisfies l.

This is a state of so-called total reflection, and shows that all the elements of the light flux are reflected at angle θ2 to become a light flux L3, which heads toward the right side of the optical component. At point C on the right side of optical component (2), similarly to what happened at left side point A, according to the law of refraction, period θ12 / 5uII9t, =: nop-out
The light beam exits the optical component at an angle θi, which has the relationship: This luminous flux L4 is directed to the photoelectric sensor (3) mentioned above and is photoelectrically converted. The output obtained from the sensor (3) is input to the processing device (4) in the form of voltage or current.

In conventional macroscopic optics, it is generally considered that the light totally reflected by the bottom surface S of the optical component (2) does not exist outside the optical component. However, when viewed microscopically, it is recognized that light leaks slightly into the outside world at the boundary between the optical component (2) and the outside medium. Therefore, the bottom surface S of the optical component (2) is shown enlarged as shown in FIG. The refractive index nop − of this optical component (2) with respect to the external medium
When out = n, the virtual transmitted light and luminous flux are
Considering this, and according to the law of refraction, -θim/-θim=n without losing the killing effect. Therefore, if we set -θ-1θIm/n from now on, the luminous flux L! The phase term of is . That is, it can be seen that although the oscillating part is attenuated at the finger distance Z from the boundary, it still emits a wave m (luminous flux).

It is said that the substantial penetration depth of the luminous flux is M=2/21t, that is, approximately the wavelength.

Therefore, let's consider having a second object absorb this oozing light. In other words, when the target object (5) is brought close to the bottom 4s of the optical component (2), the distance X from the target object (5) becomes greater than the distance of the wavelength order (0.3 to 0.6 μm). , the luminous flux is totally reflected at point B,
Luminous flux L3. Become L4 and head towards Photoden Center (3).

However, when the target object (5) approaches the bottom surface S of the optical component (2) up to (BLfk order), the light flux L2 becomes It flows inside the object (5), and as a result, it is reflected at point B, resulting in a luminous flux of 8.L, which reduces the luminous flux heading towards the sensor (3).This is reflected by the output of the photoelectric sensor (3). What we captured in Figure 3 shows that the 5gi degree of the luminous flux L4 decreases rapidly as the object (5) approaches.Therefore, we measured the output of the photoelectric sensor (3) and calculated this value (change fl
) to the interval X (or its change 1tdx) t, calculated by a processing device (4) using a microcomputer,
Display on the display device ffl+6). Processing device (4)
When calculating the interval X, the interval χ is 0 as shown in Figure 3.
．． The relationship between the photoelectric sensor (3) output and X is approximated by a straight line in the range of 15/jm to 0.45/jm (range a, b), and the interval xft is determined from the output.

As described above, the displacement measuring device of this embodiment is capable of measuring a very close distance (within the wave length) to the target object (5) at an extremely high f# degree (λ/10 to λ/1000). can. Further, the area of the plane required for measurement may be 2'' in diameter, and a non-contact displacement meter with an extremely small tip can be constructed. Furthermore, it has the advantage that distance measurement can be performed by simply forming a light beam.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways as described below.

■ Figure 1 shows an example using a He-Ne laser beam as a light source, but other light sources may include laser beams such as argon, semiconductor laser beams, general halogen lamps, infrared lamps, ultraviolet lamps, etc. Part (2) - Any light source can be used as long as it generates a beam of light that is transmitted through t and totally reflected at its bottom surface S.

(2) Although we have shown an example of using a photoelectric conversion element such as a photodiode as the light receiving system, a photodiode can be used as long as it is an element that can convert the amount of light into electricity.

Elements such as a phototransistor, a photomultiplier, or a photomultiplier tube can be considered. In addition, as a special example, it may also be used for images, such as a CCD element or an image pickup tube. However, in a converter (sensor) that targets such images, it is safe to process the image and extract the estimated amount of light hitting the imaging surface.

■ In Figure 1, an isosceles prism as shown in the figure is considered as the optical component (2), and the light beam is of the type in which the light is refracted at the left and right sides. However, the role of this optical component (2) is only to have the function of total reflection of the luminous flux at its bottom surface S, and as long as this condition is met, various types of optical component shapes are possible.

Optical component (2) in FIG. 4 is an example of this. In FIG. 1, since the light flux enters the optical component (2) from the left and right sides, the component device is relatively large. However, this is improved in Fig. 4. That is, the light source (1).

The photoelectric sensor (31) is installed above the prism, and the light beam vertically incident from the top surface of the prism (2) is totally reflected on the left and right sides and the bottom surface, creating an optical path as shown in the figure.Optical component (2) (
The phenomenon that occurs at the bottom surface of the prism is the same as described above.

■In the present invention, as shown in Fig. 1, the light totally reflected by the bottom surface S of the optical component (2) is received by the light sensor (3), and when the target object (5) approaches, the light beam Lt is Escape to the object side,
As a result, a method is adopted in which a decrease in the amount of light directed toward the sensor (3) is detected as the luminous flux, L,.

On the other hand, in Fig. 5, the principle is the same, but the light flux that has entered the approaching target object (5) is detected by the photoelectric sensor (3).
), and the amount of light that can be detected by this sensor (3) increases as the target object (5) approaches the bottom surface S of the optical component (2). . Although the structure of the hypochondrium treatment after the photoelectric sensor (3) is not shown in the figure, it is the same 6N as in FIG. 1.

Similar X Similar.

〔Effect of the invention〕

The present invention has the following special effects.

(c) As a conventional method for measuring minute intervals, a method using optical interference is generally used, as described above.

This method has a working distance of several wavelengths and a measurement resolution of λ~
'/1000 order.

In contrast, the present invention can measure very close distances (within the wave length) to the target object with very high precision (''/i.

~”/1000).

(b) In the conventional measurement method using interference of light, it is necessary for the opposing surfaces of the optical component and the target object to cause interference, and therefore, generally, a plane large enough to observe interference fringes is required.

However, according to the present invention, ordinary He-
A Ne laser light source (beam diameter 11 mm) can be used, the required plane at point B is about 2 mm, and a non-contact displacement meter with an extremely small tip can be constructed.

(c) Conventional optical interference methods have a wide measurement range of several wavelengths, but they do not require the generation and analysis of the entire image to analyze fringes, or the need for such complicated processing. , complex processing circuits were required for stripe analysis, such as counting the number of stripes that moved. but,
According to the present invention, distances can be measured very easily with high resolution and accuracy by simply detecting the amount of light.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a displacement measuring device according to an embodiment of the present invention, Figs. 2 and 3 are explanatory diagrams of the measurement principle of Fig. 1, and Figs. 4 and 5 are illustrations of other embodiments of the present invention. FIGS. 6 and 7, which show an example displacement measuring device, are explanatory diagrams of the prior art. (1) Dual source. (2) Dualistic components (optical means). (3) Binary electric sensor (photoelectric conversion means). (4): Processing device 4 & (calculating means). (5) Two target objects (objects to be measured). Agent Patent Attorney Nori Ken Yudo Takehana Kikuo\ku\'' wSZ Figure 3 Figure 154 Figure J' Figure 5 Iris 2 Figure 6 -F Figure 7

Claims (3)

[Claims] (1) An optical system having a light source that emits light, an entrance surface that receives the light, and a total reflection surface that totally reflects the light that has entered the interior through the entrance surface and is provided facing the object to be measured. photoelectric conversion means for outputting an electrical signal indicating a change in the total reflection light totally reflected by the total reflection surface according to the displacement of the object to be measured; and calculating means for calculating the distance or displacement based on the fact that the distance between the object to be measured and the electrical signal has a functional relationship. (2) The displacement measuring device according to claim 1, wherein the photoelectric conversion means receives and photoelectrically converts the totally reflected light totally reflected by the total reflection surface. (3) Claims characterized in that the photoelectric conversion means receives and photoelectrically converts the light that leaks to the object to be measured without being totally reflected on the total reflection surface and passes through the object to be measured. 1. Displacement measuring device according to item 1.