JPH0678946B2 - Color detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a color detection device having a detection head using an optical fiber.

“Prior Art” A conventional color detection device using an optical fiber uses a light-projecting optical fiber bundle and a light-receiving optical fiber bundle that have the same optical characteristics. The strict consideration is not given to the placement of the fiber bundle at the detection head.

That is, in FIG. 2, the aperture angle of the optical fiber 10 is set to 2
Let α be the detection distance, and let the length of the cross section when the optical fibers are bundled be R. The cross section length S of the detection area of the surface 6 to be detected is S = 2ltan α + R (1) .

Therefore, when using a commonly used optical fiber, i.e., one with an opening angle of 50 degrees or more, the detection area tends to be large.To detect a minute area, the detection distance should be extremely short, or Alternatively, it is necessary to reduce the number of light-projecting fiber bundles or to add an optical system such as a lens to the detection head.

FIG. 3 shows a specific example of the prior art in which the light projecting optical fiber bundle 3 and the light receiving optical fiber bundle 4 are adjacent to each other to form the detection head 1. In this structure, the illumination spot 7 and the light receiving area 8 on the surface 6 to be detected are displaced.
In other words, it is inaccurate when checking what is being detected with the naked eye, and the detection area tends to be larger than the detection head.

"Object" The object of the present invention is to make the detecting distance extremely short, to change the number of optical fibers for projecting light, to add an optical system such as a lens to the detecting head in view of the above-mentioned conventional defects. It is an object of the present invention to accurately detect color information of a minute area without any special device and without degrading the detection characteristics.

[Summary of the Invention] In order to achieve the object, the present invention uses optical fibers having a small opening angle in a light-projecting optical fiber bundle, which are collectively arranged in the central portion of a detection head. An optical fiber bundle with a large opening angle is used for the bundle, and this is arranged around the projection optical fiber bundle of the detection head. With this configuration, the reference light guided by the projection optical fiber bundle is the surface to be detected. A minute and uniform illuminating spot is generated on the optical axis, and the reflected light containing color information is efficiently incident on the light receiving optical fiber. Further, since the illumination spot remains the detection area as it is, it is possible to easily confirm which part is detected by the detection head.

[Examples] Examples of the present invention will be described below with reference to the drawings.

That is, in FIG. 1, the detection head 1 is composed of a tubular body 2, a light projecting optical fiber bundle 3 and a light receiving optical fiber bundle 4 housed in the tubular body. The light-projecting fiber bundle 3 guides the reference light from the light source (not shown) to the surface 6 to be detected of the object 5 and irradiates it, and in this embodiment, the optical aperture angle thereof is set. But
Light fiber bundle 3 for projecting light below 30 degrees
Is arranged at the center of the tubular body 2. Further, the light receiving optical fiber bundle 4 receives the reflected light including the color information of the detected surface 6 obtained by the reference light, and in this embodiment, the optical aperture angle thereof is set to 50 degrees or more. Further, the light receiving optical fiber bundle 4 is arranged in the cylindrical body 2 around the light projecting optical fiber bundle 3 concentrically with the light projecting optical fiber bundle.

[Operation] In the above configuration, the reference light guided by the light projecting fiber bundle 3 is applied to the surface to be detected 6 according to the formula (1), and becomes the illumination spot 7. Next, the reflected light containing color information from the surface to be detected 6 is reflected from the illumination spot 7 as diffuse reflected light and enters the light receiving optical fiber bundle 4. At this time, the light receiving optical fiber bundle follows the formula (1), and because of the concentric circle structure of the detection head 1, it has the light receiving region of the detection region 8, so that the diffuse reflection light from the illumination spot 7 is received, but other than the illumination spot 7. The light from the area is also received. However, the light quantity of useful color information from the illumination spot 7 is sufficiently larger than the other light quantity, that is, S /
Since the N ratio is sufficiently large, it is considered equivalent to detecting only the illumination spot 7.

For comparison with the prior art, in FIG. 1, there are shown an optical fiber bundle having an opening angle of 68 degrees and an optical fiber fiber having an opening angle of 24 degrees for the projection optical fiber bundle 3. Comparing using the formula (1) under the condition that the detection distance is 5 mm and the diameter of the light projecting fiber bundle 3 is 2 mm, the illumination spot 7 is
The former has a diameter of 8.7 mm and the latter has a diameter of 4.1 mm, and it is understood that the detection head 1 in the present invention is excellent.

"Effect" In the present invention, as described above, the light receiving optical fiber bundle is concentrically arranged around the light projecting optical fiber bundle, and the light projecting optical fiber bundle is optically small at the end face of the detection head. Since the optical fiber bundle for receiving light is formed by the optical fiber having the opening angle and the optical fiber bundle for receiving light is formed by the optical fiber having the optically large opening angle, it is possible to detect the color information of the minute area which cannot be obtained by the conventional technology. The present invention can be realized without deterioration of detection characteristics or special measures, and has an effect of easily confirming which part is detected by the detection head.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of a color detecting device according to the present invention, FIG. 2 is a side sectional view showing a concept of a detection area and a detection distance in an optical fiber, and FIG. 3 is a conventional photodetecting device. It is a sectional side view. DESCRIPTION OF SYMBOLS 1 ... Detection head, 2 ... Cylindrical body, 3 ... Projection optical fiber bundle, 4 ... Receiving optical fiber bundle, 5 ... Object, 6 ... Detected surface, 7 ... Illumination spot, 8 ... Detection area, 10 ... Light Fiber.

Claims (2)

[Claims] 1. A light projecting optical fiber bundle that guides a reference light from a light source to a detection surface and irradiates the detection surface, and receives reflected light including color information of the detection surface obtained by the reference light. And a light receiving optical fiber bundle that leads to the light receiving element constitutes a detection head, the light emitting optical fiber bundle is arranged in the center of the detection head, and the light receiving optical fiber bundle is the light emitting optical fiber bundle. And is concentrically arranged around it, and at the end face of the detection head, the light projecting optical fiber bundle is formed by an optical fiber having an opening angle which is optically smaller than that of the light receiving optical fiber bundle. A color characterized in that the light receiving optical fiber bundle is formed by an optical fiber having an opening angle that is optically larger than that of the light projecting optical fiber bundle. Detection device. 2. An optical opening angle of the light projecting optical fiber bundle is set to 30 degrees or less and an optical opening angle of the light receiving optical fiber bundle is set to 50 degrees or more on the end face of the detection head. The color detection device according to claim 1, wherein: