JPH01312407A - Displacement measuring apparatus - Google Patents

Abstract

PURPOSE:To remove a temperature drift by mounting a photodetector of an imaging system on a mounting seat having a specified linear expansion coefficient to adjust the position of the photo detector for the expansion of a head case. CONSTITUTION:The surface 3 of an object to be measured is irradiated with a light beam 1a irradiated from a light source 1 by a projection lens 2. A light receiving lens 4 lets a light spot 1b by the light beam 1a from the light source 1 irradiated to the surface 3 of the object to be measured form an image on a photo detector 5. A mounting seal 11 is interposed between the photo detector 5 and a head case 9 and has a linear expansion coefficient corresponding to the linear expansion coefficient of the head case 9 and a relatively changing temperature thereby removing a drift attributed to an optical system.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a displacement measuring device, in particular, to a displacement measuring device that irradiates the surface of an object to be measured with an original beam and uses the reflected light to change the distance to the surface of the object to be measured. Displacement measuring device (related to this) that detects the displacement of the surface of the object to be measured.

[Conventional technology]

FIG. 3 shows a conventional displacement measuring device as disclosed in, for example, Japanese Patent Publication No. 59-762, in which a light beam (1a) emitted from a light source (2
) illuminates the surface of the object to be measured (3). The light receiving lens (4) receives the light source (1) irradiated onto the surface (3) of the object to be measured.
) from the original beam (jaJ) is imaged on the photodetector (5).The processing circuit (6) is an electrical signal from the photodetector (5).

IB'%: Inputs a predetermined function 4 and generates an output according to the distance.

With the above configuration, the light beam (1a) emitted by the light source (1) is directed by the projecting lens (2), becomes an appropriately sized original socket (1b), and is directed onto the surface of the object to be measured ( 6) is irradiated. The light receiving lens (4) connects the light spora (1k)) on the surface of the object to be measured (6) to the photodetector (
5) Form an image on the light receiving surface. The optical detector (5) also receives an electrical signal I according to the position of the original spot on its light receiving surface.
A, a photoelectric conversion element that generates iB, for example, PS
D (Position 5 sensitive Det.
The position P of the light spot is determined by an element called
Accordingly, t flows IA and iB are generated, and A ””iA + iB ゛...(1) or.

B P2= ... (2) IA +
Using iB, the position of the light spot (1b) at each end .rho. of the light receiving surface can be determined from the equation. It was a cabinet.

The position of the optical substrate (1b) at the center ρ of the light-receiving surface can be determined by calculation.

Since the displacement of the surface of the object to be measured (3) is converted into the movement 1 of the light spot (1b) on the light receiving surface of the photodetector (5), one of the above equations (1) to (3) can be expressed. By multiplying the result by a conversion coefficient, an output corresponding to the distance to the surface of the object to be measured (3) can be obtained.The conversion coefficient can be calculated from the installation conditions of the optical system or found experimentally using the actual device. .

Further, the processing circuit (6) executes the above calculation and outputs the result to the outside.

Note that (6a) shows the surface of the object to be measured when the surface of the object to be measured (3) is displaced by the amount of displacement, and the light beam of the imaging system shown by the broken line is the light beam of the imaging system when the surface of the object to be measured (3) is displaced as described above. shows.

[Problem to be solved by the invention]

Since the conventional displacement measuring device is configured as described above, there are problems as described below.

In FIG. 4, symbols (1) to (5) are the same parts as shown in FIG. 6.

Meanwhile, the symbol (7) is for forming an imaging point at the center of the displaced photodetector (5a) when the helad case (9) expands and becomes the head case (9a). The position of the surface of the object to be measured, (8Jl (8a)) is the photodetector (
6J, indicating the center of (5a). In addition, (2a) p
(4a) shows the light projecting lens and the light receiving lens after the head case is expanded.

The head case (9) of the sensor section of the displacement measuring device expands or contracts due to changes in the ambient temperature during use. For example, if a mechanically fixed point is not determined in the senna portion, expansion or contraction occurs isotropically as shown in FIG. When a light source (1), a light emitting and receiving lens (*f4), and a photodetector (5) are fixed to this head case (9), the optical path formed by these optical elements is also
It is equal to the expansion of the head case (9117), and is displaced in the direction of expanding and contracting equally. The head case (9a) expands to the size indicated by the broken line.
Suppose that it becomes At this time, the displaced photodetector (5a)
The position of the measured object surface (3) for the light to enter the center (8a) of the photodetector (5) before expansion (the force is
This means that the eighth light is shifted by ΔX from the reference position of the surface of the object to be measured (3) on which the light is incident. This ΔX
The deviation becomes the output error of the displacement measuring device due to the temperature change l. This situation is shown in FIG. As can be seen from FIG. 5, the temperature of the environment in which the displacement measuring device is used increases (thereby, the measurement error increases).

This invention was made in order to solve the above-mentioned problems, and an object thereof is to obtain a displacement measuring device fIILtt that can perform highly accurate measurements without being affected by 1 meter fluctuations in the usage environment. .

[Problem [Means to solve]]

In the displacement measuring device according to the present invention, the photodetector is made of a material that has an expansion coefficient M that can eliminate drift caused by an optical system that corresponds to the linear expansion coefficient of the material of the head case and the relative change temperature. The mounting is fixed inside the head case by the seat.

[For production]

In this invention, for the photodetector of the light receiving system or the mounting seat whose linear expansion coefficient is typical for the expansion of the head case,
Different positional movements are caused to eliminate the drift caused by the optical system E.

〔Example〕

Fig. 1 shows an embodiment of the present invention, mounting seat (1j)
kX is interposed between the photodetector (5) and the head case (9), and has a coefficient of linear expansion that corresponds to the coefficient of linear expansion of the head case (9) and the relative change temperature. It is made of a material that removes the drift caused by a).

In addition, the same reference numerals as in FIG. 6 indicate the same parts.

With the above configuration, the light source port, the light emitting lens (2), the light receiving lens (4), the photodetector (5), and the head case (9)
They are housed and fixed within the head case (9), and when the environmental temperature changes, they move to a position that follows, for example, expansion of the head case (9). f, +1111 of head case (9)
Let the expansion rate be α1.

Here, as shown in Fig. 5, the coefficient of linear expansion of the material of the head case (9) is J4.
A photodetector mounting seat (11) made of a material having an H expansion coefficient α2 is attached.

ItM that has the above configuration and satisfies the relationship α, 〉α2
Temperature drift can be corrected by selecting a material with an expansion coefficient α2 and setting %L and a2 so as to cancel out the temperature drift Δx1 shown in FIG. However, L
is the distance from the center of the photodetector (5) to the head case (9).

In the above embodiment, a mounting seat (11) made of a material having a specific coefficient of linear expansion different from that of the material of the head case is interposed between the photodetector and the head case, thereby improving drift. However, as another example, as shown in FIG.
'Drift modified by intervening Ik! f# may be performed. At this time, members that satisfy the relationship α3>α may be used.

〔Effect of the invention〕

As described above, according to the present invention, the photodetector of the imaging system is mounted on a mounting seat having a predetermined coefficient of linear expansion, and the position of the photodetector is adjusted with respect to the expansion of the head case. The temperature is so low! j71t- can be removed, and the measurement a degree can be improved without being affected by temperature fluctuations in the toilet environment.

Figure 2 is a sectional view of the main parts of another embodiment, Figure 6 is a perspective view of a conventional displacement measuring device, Figure 4 6 is a schematic diagram for explaining the Ple tension due to the temperature rise in the head portion shown in FIG. 6, and FIG. 5 is a temperature drift error diagram due to the temperature rise in the head portion shown in FIG. 3.

(1)...Light source, (1a)...Light beam, (tb
)...Light slot), 121...Light projection lens, (3)...
Measured object surface, (4)...Light receiving lens, (5)...Photodetector, (9)...Head case, (11), (11a
)... Mounting seat for the photodetector.

In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A light beam from a light source is irradiated onto the surface of a predetermined object to be measured,
A light spot on the surface of the object to be measured is imaged on the light-receiving surface of a photodetector through a light-receiving lens, and an electric signal generated by the photodetector due to the imaged light reception is used to detect the object to be measured. In a displacement measuring device that calculates and outputs a distance to a surface, an optical system that corresponds to the linear expansion coefficient and relative temperature change of a head case housing the light source, the light projecting lens, the light receiving lens, the photodetector, etc. A displacement measuring device comprising: a mounting seat for the photodetector made of a material having a coefficient of linear expansion capable of eliminating drift caused by the system.