JPS6349777Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an optical reading device for reading barcodes, for example, and particularly relates to an optical reading device incorporating a light guide such as an optical fiber.

[Background of the idea]

FIG. 1 is a diagram showing a conventional optical reading device. A light emitting element 2 and a light receiving element 3 are installed side by side in a predetermined position of the case 1, one end surface of the first optical fiber 4 is connected to the light emitting element 2, and one end surface of the second optical fiber 5 is connected to the light receiving element 3. The end faces face each other. The other end surfaces of the first optical fiber 4 and the second optical fiber 5 are combined into one,
It faces one end surface of a third optical fiber 6 having a larger diameter than the optical fibers 4 and 5.

A lens 7 is provided in the reading port provided in the case 1.
is attached, and the other end surface of the third optical fiber 6 is opposed to it. Although not shown, the light emitting element 2 and the light receiving element 3 are connected to a signal processing circuit.

Lens 7 of the optical reading device configured in this way
When the light emitting element 2 approaches the barcode 9 printed on the paper 8, the light emitted from the light emitting element 2 passes through the first optical fiber 4 and the third optical fiber 6 and reaches the lens 7. The light focused by the lens 7 forms a spot on the barcode 9. The reflected light passes through the lens 7, the third optical fiber 6, and the second optical fiber again.
The light reaches the light receiving element 3 via the optical fiber 5. Since the intensity of this reflected light changes depending on the reflectance of the barcode 9, the output of the light receiving element 3 corresponds to the barcode pattern, and the barcode pattern can be read by changing this output.

By the way, in the conventional reading device, since the end surface of the third optical fiber 6 facing the lens 7 is polished perpendicularly to the optical axis of the optical fiber, the light emitted from the light emitting element 2 is transmitted to the barcode 9. Unnecessary reflection occurs at the end face of the fiber before the light reaches 200 nm, resulting in low contrast (output voltage of the light-receiving element 3) and a problem in reliability.

[Purpose of invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above and provide a highly reliable optical reading device.

[Summary of the idea]

In order to achieve the above object, the present invention is characterized in that the end surface of the third light guide such as the third optical fiber facing the lens has a spherical shape that projects outward. It is.

[Example of idea]

Next, an embodiment of the present invention will be described with reference to FIG. This figure differs from the conventional example shown in FIG. 1 in that the end surface of the third optical fiber 6 facing the lens 7 is spherical so as to protrude outward.

If the end of the third optical fiber 6 is machined to have a spherical surface in this way, when light propagating through the third optical fiber 6 at an angle θ to the peripheral surface 10 is reflected by the end surface as shown in FIG. 3, the angle β between the reflected light and the core of the third optical fiber 6 is expressed as follows: β=θ−2α+
The angle is 180 (deg).

If this angle β is larger than the critical angle of the third optical fiber 6, this reflected light cannot propagate through the third optical fiber 6. If we integrate the reflected light propagating again for all the light propagating in the third optical fiber 6 in this way, it is clear that the end is in the vertical state (α = 90deg) as in the present invention. It is better to process it into a spherical surface.

[Effect of idea]

FIG. 4 is a diagram comparing the contrast (output voltage of the light receiving element 3) when the distance between the lens 7 and the barcode 9 is changed between the reading device of the present invention and the conventional one. Note that A in the figure is the reading device of the present invention, which uses a third optical fiber 6 with a diameter of 1.6 mm.
A spherical surface with a radius of curvature of 0.8 mm was applied to the end.
On the other hand, B is a conventional reader with a similar diameter.
This is a characteristic curve using a third optical fiber 6 whose end is 1.6 mm and whose end is processed to be flat.

As is clear from this figure, since the device of the present invention does not have unnecessary reflections at the end face of the light guide unlike the conventional one, it is possible to provide a reliable optical reading device with high contrast and high S/N. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional reading device, Fig. 2 is a schematic diagram of a reading device according to an embodiment of the present invention, Fig. 3 is a diagram explaining the principle of the present invention, and Fig. 4 is a contrast characteristic diagram. . 2... Light emitting element, 3... Light receiving element, 4... First
Optical fiber, 5... Second optical fiber, 6...
Third optical fiber, 7...lens.

Claims (1)

[Scope of utility model registration request] a light emitting element; a first light guide whose one end face faces the light emitting element; a light receiving element; a second light guide whose one end face faces the light receiving element; In an optical reader comprising: a third light guide that faces the other end face of the first light guide and the second light guide, the other end face of which faces the lens; and a lens that faces the read information. . An optical reading device, wherein an end surface of the third light guide facing the lens has a spherical shape that projects outward.