JPH0316614B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thick-walled liquid in which at least a portion of the body is under the influence of the pressure to be measured, and a light entrance surface and a light exit surface are isolated from the pressure space to be measured. This invention relates to a new pressure sensor using a lens.

Conventionally, pressure sensors have been known based on various principles, such as those that utilize the expansion and contraction of bellows and those that utilize a resistance wire strain meter, but the present invention is based on a completely new principle.

A first object of the invention is to provide a pressure sensor that is compact, robust and non-explosive.

A second object of the present invention is to provide a pressure sensor that can be remotely monitored using light.

The structure and operation of the present invention will be explained below with reference to the illustrated embodiments.

In the embodiment shown in FIG. 1, A is a thick liquid lens, B is a lens holder, O ₁ is a light projection surface of a light projector,
O ₂ is the light-receiving surface of the photoreceiver.

The thick liquid lens A is formed of a lens outer shell 1 made of an elastically deformable transparent plastic material and a transparent liquid 2 sealed inside the lens outer shell, and further includes lens protection and light shielding as necessary. A belt member 3 that also serves as a belt is attached to the body to protect it,
Block out external light.

The lens holder B includes a wall portion 11, a lens holder 12, and a projector mounting portion 13 for shielding the light incident surface and light output surface (spherical surface) of the lens from the pressure space to be measured and for shielding external light. , the lens holder 12 is provided with a window 15 so that the measured pressure P in the external space of the lens holder B can affect the body of the liquid lens A. There is.

A liquid lens A is held in the lens holding portion 12 via an expandable rubber seal 16 so as to maintain airtightness inside and outside the case.

An optical fiber 21 as a light emitter is held in the light emitter holding part 13 by an elastic plug 22, a nut 23, and a rubber bush 24, and an optical fiber 25 as a light receiver is held in the light receiver holding part 14 by an elastic plug 26. , a nut 27, and a rubber bush 28.

The material for the lens outer shell 1 is, for example, polysilohexyl methacrylate (with a refractive index of 15°C).
1.507), polystyrene (refractive index 1.592 at 15°C), polymethyl methacrylate (refractive index 1.491 at 20°C)
Plastics such as are suitable.

The liquid to be filled in the lens outer shell 1 is as follows:
For example, glycerin (refractive index 1.473 at 20°C), carbon tetrachloride (refractive index 1.461 at 20°C), seda oil (refractive index 1.516 at 20°C), paraffin oil (refractive index 1.48 at 20°C),
Benzene (refractive index 1.501 at 20°C) is suitable.

FIG. 2 is a diagram for explaining the principle of operation of the present invention. In Figure 2a, the radius of curvature r of both convex surfaces of the lens is 2.8 mm, the thickness d is 4.6 mm, the refractive index n of the lens material is 1.45, and the refractive index _n0 of each space on the light emitting side and the light receiving side is 1.0. Then, the focal length f becomes 4.2 mm. Note that the focal length is the distance between the first focal point _F1 and the first principal surface.
H ₁ , and each distance between the second principal surface H ₂ and the second focal point F ₂ . Incident ray L ₁ parallel to optical axis F ₁ , F ₂
reaches the second focal point _F2 via the optical path shown by the solid line, but according to the calculation, as shown by the dotted line, it travels straight to the second principal surface _H2 , is refracted at the second principal surface _H2 , and reaches the second focal point F2. _F2
It is safe to assume that the country is headed for The first and second principal surfaces are virtual surfaces that serve as a reference for focal length measurement in this way.

FIG. 2b shows an optical system in an embodiment of the present invention, and the end surface O ₁ of the optical fiber 21 serving as the projector is
The end surface O ₂ of the optical fiber 25 serving as the light receiver is located on the optical axis at a distance 2f from the first principal surface H ₁ and a distance 2f from the second principal surface H ₂ . When the emitter and receiver are arranged in this way, the light transmitted through the optical fiber 21 and projected from the surface O ₁ is focused on the surface O 2, and the other end of the optical fiber 25 (not shown) is condensed onto the surface O ₂ . ) can detect the maximum output light. Points O ₁ and O ₂ having such a relationship are called mutually conjugate positions.

When the pressure to be measured (pressure applied to the lens barrel) is at the standard value, the state shown in Figure 2 b is obtained.
When the distance l of O ₁ O ₂ is adjusted and the pressure to be measured increases, the liquid lens A deforms as shown in FIG. 2c. That is, the thickness is d'(d'>d), the radius of curvature is r'(r'<r), and the focal length is
f′ (f′<f), and the first and second principal surfaces H′ ₁ , H′ ₂
Points O′ ₁ and O′ ₂ of 2f′ move inward from O ₁ and O ₂ , respectively. The conjugate point of O ₁ also moves from O ₂ to O″ ₂ , and the light projected from O ₁ passes through the optical path shown by the solid line.
After forming an image on the optical fiber ₂₅ , it is slightly diffused and a part of it enters the light receiving surface _O2 .
The output light from the other end (not shown) is much weaker than in the case of FIG. 2b. That is, since the output light from the other end of the optical fiber 25 changes as a function of the pressure to be measured P, the pressure to be measured can be determined by measuring the intensity of the output light.

As can be seen from the dimensions of the liquid lens exemplified above, the pressure sensor according to the present invention can be formed into an extremely small size and has a simple and robust structure, so that its application range is extremely wide.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of one embodiment of the present invention, and FIGS. 2 a to 2 c are drawings showing the operating principle of the present invention. Explanation of main symbols: A: Liquid lens, B: Case, 21: Emitter (optical fiber), 25: Light receiver (optical fiber).

Claims (1)

[Scope of Claims] 1. A thick liquid lens composed of a lens outer shell made of an elastically deformable transparent plastic material and a transparent liquid filled and sealed inside the lens outer shell; A body of the thick liquid lens. a lens holder that holds the thick liquid lens in such a way that at least a portion of the lens is placed under the influence of the pressure to be measured, and the light entrance surface and the light exit surface are isolated from the pressure space to be measured; the thick liquid lens; a projector disposed within the lens holder so as to project light toward a light incident surface of the lens holder; and a position of the projector within the lens holder when the measured pressure is a predetermined value. a light receiver disposed at a conjugate position to receive the light emitted from the liquid lens; and the pressure to be measured is determined by measuring the light intensity of the light emitted from the liquid lens received by the light receiver. A pressure sensor that meets your needs. 2. The pressure sensor according to claim 1, wherein the light projector and the light receiver are each an end of an optical fiber.