JPS62285002A - Optical displacement sensor - Google Patents

Abstract

PURPOSE:To enable highly accurate measurement of an amount of displacement economically, by obtaining the amount of displacement using two detecting signals. CONSTITUTION:A sensor is composed of cylindrical glass bolts 6a, 6b provided with light-receiving surfaces exposed to the bottom of a light guide holder 3 and light-receiving elements 7a, 7b arranged on the upper ends of them. These bolts 6a, 5b guide beams of light irradiated from the bottom surfaces of them to the elements 7a, 7b. By these arrangements, a displacement of a specimen relative to the reference point P causes increase or decrease of quantity of scattered light in accordance with this displacement. This is amplified 13 and converted by a detecting circuit 14 to a displacement quantity signal for issuance as an output. This signal represents a displacement value obtained based upon a quantity of the scattered light. Consequently, 12 the displacement quantity signal issued out of the circuit 14 is obtained based upon two quantities of the scattered light, high accuracy can be available. Further, highly accurate displacement amount signal unaffected by the change of the quantity of scattered light can be produced.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical displacement sensor that optically detects the displacement of an object to be measured in a non-contact manner.

[Conventional technology]

BACKGROUND ART Conventionally, methods have been proposed that detect displacement from scattered light of light irradiated onto an object to be measured (hereinafter referred to as the object). For example, Utility Model Application No. 61-30878 proposes a device that combines one light-emitting element and two light-receiving elements, detects the amount of light reflected from an object as the amount of light received by the two light-receiving elements, and outputs a detection signal. ing. Furthermore, as shown in FIG. 8, there is a device in which light from a light emitting diode 81 is irradiated onto an object through a lens 82, and the scattered reflected light is imaged as a spot on an optical position detection element 84 by a light receiving lens 83. This detects the displacement of the object by utilizing the fact that the spot position moves with the displacement of the object.

[Problem that the invention seeks to solve]

However, although the former method, which uses the amount of reflected light, can construct an inexpensive system, it has the problem that highly accurate measurement is difficult because the amount of reflected light changes depending on the surface condition of the object. Furthermore, since the latter method directly measures the position of the spot of reflected light, it requires a relatively expensive optical position detection element or a signal processing circuit, resulting in a problem that the system as a whole tends to be expensive.

The present invention was made in view of the above problems, and is inexpensive.
Moreover, it is an object of the present invention to provide an optical displacement sensor that can measure displacement with high accuracy.

[Means for solving problems]

In order to achieve the above object, the present invention includes a light emitting means for irradiating light toward an object to be measured, and a first and second detection hole formed to transmit scattered light from the object to be measured. receiving the scattered light transmitted through the mask member and the first detection hole of the mask member, and outputting a first detection signal according to the amount of the scattered light; and the object to be measured is located far from the light emitting means. a first light receiving means provided at a position where the amount of scattered light increases according to the amount of displacement when the mask member is displaced; a second light receiving means that outputs a second detection signal and is provided at a position where the amount of scattered light decreases in accordance with the amount of displacement when the object to be measured is displaced away from the light emitting means; The present invention is characterized by comprising a detection circuit which receives a second detection signal and calculates the amount of displacement of the object to be measured based on the first and second detection signals.

[Action/effect of the invention]

According to the above configuration of the present invention, when the target object is displaced away from the light emitting means, the first light receiving means outputs the first detection signal corresponding to the amount of scattered light that increases according to the amount of displacement,
The second light receiving means outputs a second detection signal corresponding to the amount of scattered light that decreases in accordance with the amount of displacement thereof. Therefore, the detection circuit has the first. It is possible to measure the displacement of the object with high accuracy based on the second detection signal, that is, the two detection signals. In addition, the above-mentioned No. 1. Since the second light receiving means can be one that simply outputs a detection signal corresponding to the amount of scattered light, the present invention does not require relatively expensive optical position detection that directly measures the spot position as in the past. An inexpensive sensor can be provided.

〔Example〕

A first embodiment of the present invention will be described below based on the drawings.

1 is a side cross-sectional view of the first embodiment, FIG. 2 is a view in the direction of the arrow in FIG. 1, FIG. 3 is a schematic configuration diagram showing the arrangement of optical elements of the first embodiment, Figure 5 is a principle diagram used to explain the action.
FIG. 6 is a characteristic diagram showing the output characteristics.

In FIGS. 1 and 2, reference numeral 1 denotes a mask plate serving as a mask member, and the mask plate 1 has a circular first detection hole 1a, a second detection hole 1b, and a light irradiation hole IC each having a diameter of several fins. ing. Here, the first detection hole 1a and the second camphor hole 1b have the same diameter, and are set to a smaller diameter than the light irradiation hole 1c. The mask plate 1 is fixed coaxially to the cylindrical portion 2a of the tip base 2, and the tip base 2 is integrally fixed to the light guide holder 3 with four screws 11.

A lens holder 4 is fixed to the upper end of the light guide holder 3, and a sensor cover 5 that covers the upper part of the holder 3.4 is fixed along its outer periphery.

The light guide holder 3 includes cylindrical glass rods 6a and 6b having light-receiving surfaces exposed at the lower end of the holder 3, and a glass rod 6a.
Light receiving elements 7a and 7b are provided coaxially and close to the upper end surface of each of the light receiving elements 6b. glass rod 5a,
Reference numeral 6b guides light incident from the lower end surface to light receiving elements 7a and 7b provided on the upper end surface side, and uses a quartz glass rod with a diameter of about 4 cranes. Moreover, the light receiving element 7a.

7b is an element that outputs an electrical detection signal according to the amount of received light;
For example, a silicon photodiode is used.

Here, the glass rod 6a and the light receiving element 7a constitute a first light receiving means, and the glass rod 6b and the light receiving element 7b constitute a second light receiving means.

The lens holder 4 includes a light emitting element 8, a convex condensing lens 9,
A lens holding ring 10 is provided coaxially. Here, the light emitted from the light emitting element 8 is transmitted through the lens 9, the central cylindrical portion 3a of the light guide holder 3, and the light irradiation hole I of the mask plate 1.
The above configuration is arranged so that the object to be measured is irradiated with the light through C. In addition, 12 is a drive circuit for the light receiving element 1O, 13 is an amplifier circuit for amplifying the detection signals of the light receiving elements 7a and 7b, and 14 is an output signal according to the displacement of the object based on the detection signals from the light receiving elements 7a and 7b. This is a detection circuit that outputs .

Next, the arrangement of the optical elements will be explained in detail based on FIGS. 3 to 5.

In FIG. 3, if the optical axis of the irradiated light from the light emitting means constituted by the light emitting element 8, lens 9, etc. is l, then the mask plate 1
The centers of the first detection hole 1a and the second detection hole 1b are symmetrical with respect to the optical axis l. Another optical axis! The upper reference point P and the center of the first detection hole 1a, the reference point P and the second detection hole 1b
Assuming that the lines obtained by connecting and extending the centers of are reference lines m and n, the glass rods 6a and 6b are arranged parallel to the reference lines m and n, respectively, and circumscribed at Q and R, respectively.

Here, the glass rod 6a is in the direction of the optical axis l with respect to the reference line m,
In other words, the glass rod 6b is arranged so as to be circumscribed on the inside, while the glass rod 6b is arranged so as to be circumscribed on the outside in a direction opposite to the optical axis l with respect to the reference line n. It is preferable that the distance between the reference point P and the external contact point Q and the distance between the reference point P and the external contact point R be equal distances, but if these distances are different, the diameters of the glass rods 6a and 6b may be changed. and the light receiving element 7a.

Adjustment may be made so that the amount of light received by the light beams 7b becomes equal.

FIG. 4 is a schematic diagram showing the above-mentioned positional relationship, and symbols 6a and 6b in the figure represent light receiving ports on the lower end surfaces of the glass rods 6a and 6b, that is, detection spot areas of the first light receiving means and the second light receiving means (
(hereinafter referred to as a detection spot). In this way, the detection spot 6a of the first light receiving means circumscribes the reference line m and is located on the optical axis β side (inside), while the detection spot 6b of the second light receiving means circumscribes the reference line l, and It is arranged so as to be located in the opposite direction (outside) to the optical axis β.

Next, the operation will be explained based on the above configuration with reference to FIGS. 4, 5, 6, etc. Now, if there is a symmetrical object having a uniform scattering surface on a plane including the reference point P in FIG. ) is reflected as uniformly scattered light. The scattered light passes through the first detection hole 1a and the second detection hole 1b of the mask plate 1,
Proceeding along the reference lines m and n, respectively, to the detection spot 6a
.

A scattered light spot is formed near 6b. The area of the scattered light spot is illustrated by a dotted circle centered on points Q and R, and the area where this scattered light spot overlaps with the detection spots 6a and 6b is determined by the amount of light received by the light receiving elements 7a and 7b. Correspondingly, this is illustrated with diagonal lines. When the object is present at the reference point P in this manner, the detection spots 6a and 6b receive scattered light of equal area, that is, the same amount of scattered light, as shown in FIG. 5(ii).

Here, below the reference point P in Fig. 4 (in the direction of the black arrow)
When the object is displaced, both of the two scattered light spots are displaced inward (in the direction of the black arrow). Then, the amount of scattered light (ρA) increases at the detection spot 6a located inside the reference line m, and the amount of scattered light (ρ8) decreases at the detection spot 6b located outside the reference line n. On the other hand, the object is the reference point P
When displaced further upward (in the direction of the white arrow), the scattered light spot is displaced in the opposite direction (in the direction of the white arrow), and the amount of scattered light at the detection spot 6a and the detection spot 6b changes in the opposite manner to that described above.

FIG. 5 shows the detection spots 5a and 5b and the displacement position of the scattered light spot due to the displacement of the object. Figure 5 (i) shows a state where the object is displaced upward and the scattered light spot is located at the outermost position, and Figure 5 (ii) shows the scattered light spot when the object is present at the reference point P. FIG. 5(iii) shows a state in which the object is displaced downward and the scattered light spot is located at the innermost position.

FIG. 6 shows the amount of displacement of the object with respect to the reference point P and the amount of scattered light ρ1 received at the detection spots 6a and 6b.
．． The relationship between ρ and ρ is shown. Note that the amount of displacement is defined as the downward displacement with respect to the reference point P as a positive value, and the amount of scattered light ρ,, ρ is the amount of scattered light when the detection spot and the scattered light spot coincide with 1.
It is set to 0.

As mentioned above, when the object is displaced with respect to the reference point P,
The light receiving elements 7a and 7b have scattered light amounts ρ, ρ, shown in FIG.
It receives light corresponding to each and outputs a detection signal.

In other words, the light receiving element 7a receives scattered light (
ρA) increases, and the amount of scattered light received by the light receiving element 7b (ρ,) decreases as the light receiving element 7b is displaced. This is amplified by the amplifier circuit 13, converted into a displacement amount signal by the detection circuit 14, and output.

The displacement signal is a displacement value ρ, −ρ1, or (ρ8−ρ)/(ρ, +
ρm). Therefore, the displacement amount signal output from the detection circuit 14 has two scattered light amounts ρ.

The accuracy is high because it is calculated based on ρ, and if the displacement signal is (ρ8-ρA)/(ρ, 10ρ8), the accuracy is independent of changes in the amount of scattered light, that is, changes in the reflectance of the object. A good displacement signal can be output.

Next, a second embodiment will be described based on FIG.

In this embodiment, instead of the light emitting element 8 of the first embodiment, a light emitting optical fiber 18 is used which guides light from an external light source to its end face, and glass rods 6a, 6b and light receiving elements 7a, 7b are used. Instead, the light-receiving optical fibers 16a, 16b
is used to guide scattered light from an object to the outside of the sensor, and the scattered light is detected by a light receiving element (not shown) provided outside. Incidentally, since the optical arrangement relationship thereof is the same as that in the first embodiment, a description thereof will be omitted.

By using an optical fiber in this manner, the receiving and light emitting elements can be arranged separately from the sensor main body, which has the advantage of allowing the main body to be made smaller.

In the embodiment described above, the first detection hole 1a and the second detection hole 1b provided in the mask 1 are provided line-symmetrically with respect to the optical axis l, but they may be provided in asymmetrical positions. however,
At this time, the arrangement of the optical element on the light receiving side is also changed in accordance with the position of the detection hole, and the arrangement is appropriately changed so as to obtain the characteristics shown in FIG.

Further, an optical lens may be used in place of the first detection hole 1a and the second detection hole 1b in the above-described embodiment.

For example, by using a convex lens with an appropriate focal length, the displacement of the scattered light spot from the object can be magnified and measured with high precision.

[Brief explanation of the drawing]

1 is a side cross-sectional view showing a first embodiment of the present invention, FIG. 2 is a view in the direction of the arrow in FIG. 1, FIG. 3 is a schematic configuration diagram showing the arrangement of the optical elements in FIG. 1, and FIG. Figure 5 is a principle diagram used to explain the action, and Figure 6 shows how the light receiving element (
Amount of scattered light received by 7a, 7b) (ρ4.ρ8)
FIG. 7 is a side sectional view showing a second embodiment of the present invention, and FIG. 8 is a schematic configuration diagram showing a conventional example. 1... Mask having a first detection hole (1a) and a second detection hole (1b), 5a, 5a... Glass rod and light receiving element constituting the first light receiving means, 6b, 7b... Second Glass rod and light receiving element constituting the light receiving means, 8... Light emitting element, 9...
··Condenser lens. Representative patent attorney Takashi Okabe O Figure 4 Figure 5 Button PA, h Figure 6 Figure 7 j Figure 8

Claims (1)

[Scope of Claims] A light emitting means for irradiating light toward an object to be measured; a mask member in which first and second detection holes are formed to transmit scattered light from the object to be measured; Upon receiving the scattered light transmitted through the first detection hole of the mask member, a first detection signal corresponding to the amount of scattered light is output, and when the object to be measured is displaced away from the light emitting means, the amount of displacement is detected. a first light receiving means provided at a position where the amount of the scattered light increases in accordance with the amount of the scattered light; a second light receiving means provided at a position where the amount of scattered light decreases in accordance with the amount of displacement when the object to be measured is displaced away from the light emitting means; and inputting the first and second detection signals. and a detection circuit that determines the displacement of the object to be measured based on the first and second detection signals.