JPH10221252A - Light reflectance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light reflectance measuring device at a low cost having a small-sized sensing part by embodying it in an optical system of simple structure. SOLUTION: A transparent material is used to form a holder 30 which supports an optical fiber 10 leading the reflected light to a light receiving element 20. The joint part of the optical fiber 10 with the holder 30 near the measuring surface 100a is made also transparent, and the holder 30 is arranged so that the light illuminating from the outside passes the inside of the optical fiber 10 and illuminates the opposing measuring surface 100a of the cross-section 10a of optical fiber 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light reflectance measuring apparatus for measuring the reflected light of an object by illuminating the surface of the object and detecting the intensity of the reflected light from a light emitting element (40) as a light source. The present invention relates to the structure of the detection unit up to the light receiving element (20).

[0002]

2. Description of the Related Art A light reflectance measuring apparatus of the type in which a cross section (10a ') of a conventional optical fiber (10') is brought into direct contact with a measuring surface (100a) to measure the light reflectance of the measuring surface (100a). Is configured as shown in FIG.

[0003] The optical fiber (10 ') used is usually as thin as 1 millimeter or less in outer diameter in order to narrow the measurement range. To support it from the surroundings. However, since the holder (30 ') is opaque, a cross section (10a') of the optical fiber (10 ') is formed.
Is pressed against the measurement surface (100a).
There is no light for illuminating a) and no reflected light can be obtained. Therefore,
A light emitting element (40 ') such as an LED is attached behind the optical fiber (10') as a light source, and a light beam (L5) emitted from the light emitting element (40 ') travels straight through the half mirror (70) to form one end of the optical fiber (10'). The cross section (10b ') is inserted, the cross section (10a') at the other end is taken out, and the measurement surface (100
a) was illuminated. Then, the measurement surface (10
The light reflected at 0a) travels in the optical fiber (10 ') in the opposite direction, but on the reflection surface (70) of the half mirror (70).
The light element (2) reflected at a) and turned in the direction of R5
0 ′), and the light receiving element (20 ′) has a surface (100).
The structure was such that only the light reflected in a) entered.

[0004]

In the detection section of the conventional light reflectance measuring device, the light to be illuminated and the reflected light pass through the same optical fiber (10 ') as described above. A half mirror (70) or a part having an equivalent function is required to separate the light from the light emitting element (4), though not shown in FIG.
0 ′), half mirror (70), optical fiber (1
0 ′), a structure that holds the light receiving element (20 ′) in a fixed relationship is required, and these components are high-precision ones or require adjustment, so that they are expensive devices and, in addition, are compact. There were problems such as difficulty in conversion.

An object of the present invention is to solve these conventional problems and to provide an inexpensive and small-sized detection unit of a light reflectance measuring device.

[0006]

In order to achieve the above object, in the light reflectance measuring apparatus of the present invention, the material of the holder (30) supporting the optical fiber (10) is made transparent and the holder (30) is made of a transparent material. Light emitting element (4
0).

[0007]

The light reflectance measuring apparatus having the above-described configuration is similar to the conventional method in that the cross section (10) of the optical fiber (10) is used.
It is possible to illuminate the measuring surface (100a) facing a).

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described with reference to FIG.
First, a holder made of transparent material such as acrylic (3
0) is attached to a case (60) made of an opaque material, and the surface of the holder (30) other than the end surface (30a) at the tip of the portion that comes out of the case (60) is provided with: It is covered with a light-shielding film (31) made of an opaque material by coating or the like so as to block external light.

The center of the holder (30) is placed on the holder (30) such that the end face (30a) of the tip of the holder (30) and the cross section (10a) of the optical fiber (10) are substantially flush with each other. To optical fiber (10)
Are fixed by a transparent adhesive or press-fitting.

A sleeve (50) made of a light-impermeable material is fixed to the other end of the optical fiber (10) on the side of the cross section (10b) by an adhesive.
Furthermore, so as not to separate from each other and to prevent light from entering,
Phototransistor of sleeve (50) and light receiving element (20) is a cover of heat shrink tube made of opaque material (51)
It is fixed by. The base (20b), the sleeve (50), and the cover (51), to which the terminals (20c) of the circuit connection portion of the light receiving element (20) are attached, are made of an opaque material that does not allow light to pass through. Therefore, the optical fiber (1) is connected to the light receiving portion (20a) of the optical element (20).
Only light that has passed through 0) can enter.

Then, inside the case (60), the tip (40a) of the light emitting element (40) serving as a light source, from which the LED emits light, approaches the holder (30) and is close to the holder (30). It is arranged.

Here, considering the nature of light entering and exiting the optical fiber (10), first, as shown in FIGS. 3 and 4, the optical fiber (10) has a core material (10c) having a large refractive index and a core material (10c) having a small refractive index. They are made of a material coating (10d), which is made of a colorless and transparent material such as glass or plastic in order to reduce transmission loss and extend transmission distance.

The cross section (1) of the optical fiber (10)
0a) is incident on the optical fiber (1) as shown in FIG.
In the case of a light ray (L3A) having a small angle (A) with respect to the center line (CL) of (0), the inside of the core material (10c) is covered (10).
The light beam (L3B) having a large angle (B) with respect to the center line (CL) of the optical fiber (10) can travel through the section (10b) while repeating total internal reflection at the boundary portion with d). In the case of (1), the inside of the core material (10c) is covered (1
0d), and penetrates the boundary (10d).
b) cannot be reached.

FIG. 4 shows a case where light is going to cross the optical fiber (10) from the outer diameter of the optical fiber (10).
And a small angle (a) with the outer diameter of the coating (10d).
In the case of (1), since the light is totally reflected on the surface of the coating (10d) like the light beam (L4a), the light cannot enter the optical fiber (10). Further, in the case of a large angle (b) with the outer diameter, at a distance (H) somewhat away from the cross section (10a), the light can enter the inside of the optical fiber (10) like a light beam (L4bh), but go out again. And cannot reach the section (10a).

However, when the position where the light beam enters the outer diameter portion of the coating (10d) at a large angle (b) is a distance (h) very close to the cross section (10a), the light beam (L4bh) in FIG. Can pass through the section (10a).

Therefore, in the present invention using the optical fiber (10) having the above-mentioned properties, light emitted from the light emitting element (40) enters the inside of the holder (30) from the outer surface (30b) of the holder (30). However, when the entered light hits the boundary between the outer part of the holder (30) and the light-shielding film (31) or the boundary between the outer part and the air layer inside the holder (30), the light is totally reflected by the angle, but the holder (30) Has a complicated shape, the light is reflected at various angles in all directions, and the light passes through the entire inside of the holder (30). Since the space between the holder (30) and the optical fiber (10) is fixed by a transparent adhesive or press-fitting and light can pass therethrough, a part of the light in the light (FIG. L
2) As shown in the cross section (10) of the outer diameter portion of the optical fiber (10).
From the vicinity of a), it enters the core material (10c) inside the optical fiber (10) obliquely at a large angle (b) and passes through the cross section (10a) of the optical fiber (10) to measure the object (100). The point (P) on the surface (100a) is reached.

The light reaching the point (P) is irregularly reflected if the surface of the measurement surface (100a) has irregularities. Therefore, the reflected light is, for example, R2a, R2b, R2c, R2 in FIG.
The light is reflected in various directions such as 2d and R2e.
In this, some rays (R2a, R2e) pass through the optical fiber (10) and return to the holder (30) like the rays (L3B) in FIG. 3, but the rays (R2b, R2) in FIG.
c, R2d) exits the cross section (10b) and enters the light receiving element (20) while totally reflecting inside the optical fiber (10) like the light ray (L3A) in FIG.

From the light receiving element (20), an electrical output corresponding to the amount of reflection from the incoming measurement surface (100a) is obtained, and the reflectance is obtained by comparing this output with a reference output. Become like

[0019]

Since the present invention is configured as described above, it has the following effects.

Light for illuminating the measurement surface (100a) mainly passes through the inside of the holder (30), and also illuminates the measurement surface (100a).
The light reflected by the optical fiber (10) passes through the optical fiber (10), and the paths through which the light travels are independent of each other. Alternatively, components having equivalent functions are not required, and an inexpensive device can be provided.

The light that illuminates the measurement surface (100a) is part of the light that passes through the entire inside of the holder (30) vertically and horizontally, and has an outer diameter near the cross section (10a) at the tip of the optical fiber (10). Leaks from the optical fiber (10) into the optical fiber (10).
The same result can be obtained as long as the cross section (10a) of the optical fiber (a) and the optical fiber (10) is substantially the same plane, and the other light emitting element (40), optical fiber (10), light receiving element (20), holder ( Since there is no part requiring high precision in the positional relationship of 30), high-precision parts and adjustment work are not required, and an inexpensive apparatus can be provided.

Further, the light receiving element (20) is also mounted on the holder (3).
Since the device can be arranged inside the device (0), the entire device can be downsized.

In this embodiment, a light-shielding film (31) for blocking light from entering the holder (30) from outside is provided on a part of the outer peripheral portion of the holder (30). The measuring device is a cross section (10a) of the optical fiber (10).
Is used to measure the reflectance only in a narrow range of the measurement surface (100a) opposed thereto, so that the measurement surface (100a) exits from the other end surface (30a) of the holder (30).
Is for illuminating the outside of the measurement range.
Therefore, a thin light-shielding film may be provided on the end face (30a) so as not to affect the amount of light emitted from the cross section (10a) of the optical fiber (10). When the amount does not affect the measurement, or when the light of the wavelength used for the measurement does not exist around the use environment, the same effect can be obtained without providing the light shielding film (31). It is clear.

[Brief description of the drawings]

FIG. 1 is an overall view of a detection unit of a light reflectance measuring device according to the present invention.

FIG. 2 is a detailed view of the vicinity of a measurement surface of a detection unit of the light reflectance measurement device according to the present invention.

FIG. 3 is an explanatory diagram of light entering from a cross section of an end of an optical fiber.

FIG. 4 is an explanatory diagram of light crossing the optical fiber from an outer diameter portion of the optical fiber.

FIG. 5 is a diagram of a detection unit of a light reflectance measuring device according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Optical fiber 20 Light receiving element 30 Holder 40 Light emitting element 50 Sleeve 51 Cover 60 Case 100 Measurement object 100a Measurement surface

Claims (1)

[Claims] 1. A method in which a cross section (10a) of an optical fiber (10) is brought into direct contact with a measurement surface (100a) to receive reflected light, and at least measurement of a holder (30) supporting the optical fiber (10) is performed. Face (100
The portion close to a) is made of a transparent material, and the joint near the measuring surface (100a) of the optical fiber (10) and the holder (30) is also transparent so that the light illuminating the holder (30) from the outside can emit the optical fiber ( A light reflectivity measuring apparatus having a structure capable of illuminating an opposing measuring surface (100a) of a cross section (10a) of an optical fiber (10) through the inside of 10).