JPH0128431Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an omnidirectional optical sensor using optical fiber.

Conventionally, photomultipliers, photodiodes, and other photoelectric conversion elements have been used as light intensity detectors.
Since the photoelectric conversion characteristics are dependent on the angle of incidence of light, in order to accurately measure the brightness of a certain point in three-dimensional space, the dependence of the photoelectric conversion characteristics of the element on the angle of incidence must be investigated and corrected. There is a need. However, this method is time-consuming and has the disadvantage that accurate measurement values cannot be obtained. These problems can be solved by using a small omnidirectional optical sensor, but
Conventionally, optical sensors with such characteristics have not been available.

The inventors of the present invention have been intensively considering the development of an omnidirectional optical sensor that can accurately and easily measure the amount of light no matter which direction the light enters in three-dimensional space. The book discovered that by creating a structure in which transparent spheres with a diameter larger than the fiber diameter and a light-diffusing layer on the surface were bonded together, it was possible to design an omnidirectional optical sensor that solved all of the conventional problems at once. Completed the idea.

An example of the structure of the omnidirectional optical sensor according to the present invention is shown in the drawing. In the figure, 1 is a transparent sphere, 2 is a translucent light-diffusing layer covering the sphere, and 3 is an optical fiber, one end of which is joined to the sphere, and the other end faces the light-receiving surface of the photodiode 4. Well, holder 5
Fixed by

If we consider a case in which a single ray of light enters a semitransparent light diffusion layer placed in three-dimensional space from a certain direction, this incident ray is diffused by the light diffusion layer and converted into light that travels in various directions. . Some of the light is reflected from the original space, and some of it becomes light that travels inside the sphere at various angles. When the light traveling inside this sphere hits the light diffusion layer on the opposite side, it is diffused in the same way as before, generating light that travels at various angles. As in the previous figure, some of the light travels outside the sphere and some of it travels inside the sphere. By repeating this, the amount of light inside the bulb will decrease, but
It can be changed into light containing various angular components. Therefore, light with various angular components exists within the sphere, regardless of the direction of incidence of the incident light beam. When an optical fiber is bonded to such a sphere, an amount of light proportional to the amount of light inside the sphere can be transmitted to the photodiode. In other words, it does not depend on the angle of incidence of the incident light,
It becomes possible to illuminate the photodiode with an amount of light proportional to the amount of incident light, allowing it to be used as an omnidirectional optical sensor.

As the optical fiber 3, that is, the optical fiber, both glass and plastic can be used, but plastic is preferable because it has a large diameter and is easy to process. Glass-based optical fibers with a core-sheath structure include those with a multicomponent glass core and a plastic sheath, those with a quartz glass core and a plastic sheath, cores,
A sheath made of quartz glass, etc. is used. On the other hand, plastic optical fibers that use polymethyl methacrylate resin for the core and fluorine-containing resin for the sheath, or those that use polystyrene for the core and polymethyl methacrylate resin for the sheath, are used. Among these, plastic optical fibers using polymethyl methacrylate as a core are preferred because they have relatively good optical transmission performance and are easy to process.

The transparent sphere 1 used in the present invention can be made of either glass or plastic. These transparent spheres have a larger diameter than the optical fibers to be joined. As the diameter of the optical fiber becomes larger, the area of the joint surface with the optical fiber 3 decreases relatively compared to the surface area of the entire sphere 1, so the area of light that can be caught becomes wider and the measurement accuracy also improves. The mechanical strength of the surface is reduced. Therefore, the diameter of the sphere 1 is preferably about 2 to 100 times the diameter of the optical fiber 3.

The light diffusing layer 2 used in the present invention is preferably one in which white pigment is dispersed in a paint so that light rays incident from any angle pass through the diffusing layer and become uniform when they enter the sphere 1. As the white pigment, magnesium carbonate, magnesium oxide, alumina, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, zinc oxide, etc. can be used.

The coating material for dispersing these pigments is preferably one that is commercially available and highly transparent. The transparent sphere 1 and the optical fiber 3 are bonded using melt adhesion or an adhesive. When using an adhesive, it is preferable to select an adhesive that has high adhesive strength, high transparency, and has a refractive index relatively close to that of the core of the optical fiber 3.

The omnidirectional optical sensor created in this way can accurately capture the amount of light incident from any direction in three-dimensional space, so it is expected to have a wide range of uses as a light antenna.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view showing an example of the omnidirectional optical sensor of the present invention. The symbols used in the drawings are 1...transparent sphere, 2...light diffusion layer, 3...optical fiber, 4...photodiode, 5...holder.

Claims (1)

[Scope of utility model registration request] An omnidirectional optical sensor made by bonding to one end of an optical fiber a transparent sphere having a diameter larger than the diameter of the fiber and having a light diffusing layer on its surface.