JPS6249586A - Optical reader - Google Patents

Abstract

PURPOSE:To prevent dust, etc. from adhering to photodetecting optical parts by a simple constitution, by providing a transparent plate in a case which only a reflected light passes through. CONSTITUTION:An irradiated light by an LED 2 is reflected by an object 3 of a bar-code, etc., and the reflected light transmits through a transparent plate 1 provided on a case for making only a reflected only pass through, and for cutting off a surrounding light, photodetected by an image sensor 6 through photodetecting parts such as a reflecting mirror 4 and a lens 5, etc., and read of the bar-code, etc. is executed. By this simple cut-off constitution, a contamination caused by an adhesion of dust, etc. to the photodetecting parts is prevented, and read can be executed stably extending over a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention illuminates a character or code with a plurality of light emitting elements, and the reflected light is received by an image sensor via a light-receiving optical component to detect the character or code. The invention relates to optical reading devices such as barcode readers and OCR.

2. Description of the Related Art Conventional optical reading devices such as barcode leagues and OCR systems have a configuration as shown in FIG. 2a.

That is, in FIG. 2a, 2 is L as a light emitting element.
ED, 3 is an object illuminated by LED 2. The light reflected from the object 3 is imaged on an image sensor 6 via a reflecting mirror 4 and a lens 5. 7 is a signal processing circuit that amplifies the output signal photoelectrically converted by the image sensor 6, and 8 is a decoder that inputs the output signal of the signal processing circuit 7 via the cable 10 and decodes it. Note that 9 is a case.

Another conventional example has been proposed in which a transparent plate 1 is provided at the opening side end of the case 9, as shown in FIG.

Problems to be Solved by the Invention In the configuration shown in FIG. 2a, the light receiving optical components (reflector 4,
Dirt and dust often adhered to the lens 5). As a result, the amount of light received by the image sensor 6 was reduced, characters or codes could not be seen in parts, and the reading performance was degraded. Additionally, there was a problem in that it was often necessary to disassemble and clean the device in order to remove these deposits.

In addition, in the configuration shown in Figure 2, the light emitted from the LED 2 is reflected once when it is reflected by the object 3 such as a character or code, and once before it is reflected and reaches the light-receiving optical component.
Since the light passes through the transparent plate 1 twice, the amount of light received by the image sensor e is significantly reduced. Therefore, in order to increase the amount of light from the LED 2, it is necessary to increase the current flowing through the LED 2, resulting in an increase in power consumption and a problem that the life of the LED 2 is shortened.

The present invention has been made in view of this point, and an object of the present invention is to provide an optical reading device that has a simple configuration and isolates the light-receiving optical component from the external environment.

Means for Solving the Problems The present invention solves the above problems by using a plurality of LEDs.
In an optical reading device that illuminates a character or code with a light receiving optical component, the reflected light is received by an image sensor via a light receiving optical component, and the character or code is detected, the light receiving optical component is isolated from the external environment. A transparent plate is placed at a position through which only the reflected light passes.

Operation: Due to the simple configuration described above, dust and dirt do not adhere to the light-receiving optical components.

Embodiment FIG. 1 shows an embodiment of the present invention, which is a barcode league in which the light-receiving optical components, image sensor, etc. are housed in one case.

Note that the same components as in the conventional example will be described with the same numbers.

In FIG. 1, 1 is a transparent plate and 2 is an LED. L.E.
The light emitted from D2 illuminates the barcode (object) 3, and the reflected light reaches the reflection mirror 4 via the transparent plate 1. 5 is a lens for forming an image on the image sensor 6. 9 is a case for storing these. The electrical signal obtained by photoelectric conversion by the image sensor 6 is amplified by the signal processing circuit 7, reaches the decoder 8 through the cable 1o, and is decoded.

In the case of this embodiment, the transparent plate 1 is a 2ffil++ thick acrylic plate with a transmittance of 93%, and the LED 2 is a 20mA-
50x1 for 20mcd red I, ED, reflector 4
A 2tran mirror was used. Lens 5 has a focal length of 3
0mm%F number 4 convex lens, image sensor 6 is 204
An 8-pit C0D one-dimensional image sensor was used, with a field of view of 7ofi and an optical path length of 145mm.
Although it seems appropriate to place it at a position of mm, in this example it was placed at a position of 20 mm. This is because if this position is too close to the opening, the transparent plate 1 will be easily scratched, and if it is too far away, dust will easily collect and cleaning will be difficult.

FIG. 3 shows a signal waveform when looking at a white paper with a reflectance of 90 cm under an illuminance of 602x.

A is a case without a transparent plate, and b is a case with a transparent plate reel.

The waveform b has a 20% lower intensity than the waveform a.

This will reduce reading performance, so the signal processing circuit 7
Increase the signal amplification factor within 20%. The signal waveform at this time is shown in FIG. 4, which is almost the same as in the case without the transparent plate in FIG. 3a. In addition, a reading test was conducted on 100 actual barcode samples under this condition, and the results were good.

When used for a long period of time, dust and dirt may adhere to the surface of the transparent plate (acrylic plate) 1, which may cause the signal waveform to become smaller and the reading performance to deteriorate. In order to prevent this, the transparent plate 1 was treated with antistatic treatment.

The above reading device was placed in a sealed container with 10 years of dust (sand dust and cotton dust), and the air inside was stirred with a fan, but even after 100 hours, antistatic treatment was applied. No lumps adhere to the transparent plate,
The signal waveform was the same as that shown in FIG. 4, and the reading performance was very good, unchanged from the initial state.

Effects of the Invention As described above, according to the present invention, it is possible to isolate the light-receiving optical component from the external environment with an extremely simple configuration, so that dust, dirt, etc. can be prevented from adhering to the light-receiving optical component. This ensures good reading performance over a long period of time. In addition, there is no need to disassemble and clean to remove these garbage, so it is extremely useful from a practical point of view.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical reading device showing an embodiment of the present invention, FIG. 2 is a sectional view of a conventional optical reading device, and FIG. 3 is a main signal waveform in this embodiment and the conventional example. 4 are signal waveform diagrams when the amplification factor of the signal processing circuit is increased in this embodiment. 1... Transparent plate, 2... LED, 3...
...Object, 4...Reflector, 6...
・Lens, 6... Image sensor, 7...
...Signal processing circuit, 8...Decoder, 9...
···Case. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
--Spring board 2--- LED 3---L image 4-Anti-M 5-M-lens 6-11 Image assembly 9-11 Goose Figure 2 (Re Figure 3) 1 Figure 4 J!Open

Claims (1)

[Claims] In an optical reader that illuminates characters or codes with a plurality of light emitting elements, and receives the reflected light on an image sensor via a light-receiving optical component to detect the characters or codes, the light-receiving optical component is isolated from the external environment. An optical reading device in which a transparent plate for blocking is placed at a position within the case through which only the reflected light passes.