JPS6154570A - Bar code reader using light source diffusing filter - Google Patents

Abstract

PURPOSE:To secure the even luminous intensity of the transmitted light by setting a diffusing filter at the front of a light source of a bar code reader containing an array of LEDs. CONSTITUTION:Each LED of a light source has high luminance and high directivity. The distribution of luminous intensity of the LED has a wave form as shown by BF. This waveform distribution emerges also on the surface of a bar code label 2 if no diffusing filter 5 is provided. The light is diffused but the luminance has no reduction with use of the filter 5. Then an even distribution is secured for luminous intensity as shown by AF.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a barcode reader.

(Prior Art) Recently, in order to process large amounts of product data at each stage of product production, storage, distribution, sales, etc. by computer, product identification numbers have been displayed using barcodes on product containers, packaging, etc. Became.

Barcodes are generally combinations of wide lines (or bars) and narrow bars that encode numbers, letters, or other information.

Barcodes are displayed by printing on containers, packaging, etc., or by affixing barcode labels.

The barcode is optically read by a manual or automatic barcode reader, converted into an electrical signal, and input into a computer for processing.

There are various types of barcode readers, but the basic principle of most of them is optical reading. That is, barcodes are irradiated with light and their widths are identified based on the amount of light reflected from each bar. To implement this, there are two methods: scanning a narrow beam spot in a direction perpendicular to the bar and sequentially reading the reflected light from each bar with one light receiving element, and setting up multiple light receiving elements and associating them with the bar. It can be roughly divided into two methods: a method in which the surface of the barcode is uniformly irradiated and the reflected light from each bar is simultaneously read by a corresponding light receiving element.

In the barcode reader according to the latter method, the irradiation light source is mounted just inside the opening at the tip of the barcode reader at a certain angle with the reflection optical axis.

Recently, there has been a growing demand for improved reading performance of barcode readers, and linear light sources are now being used in which multiple high-intensity, highly directional LEDs are arranged at regular intervals in a straight line in the same direction as the barcode bars. There is. In such a light source, each LED has high directivity, so the overlapping range of each irradiation beam is narrow.

Therefore, the illuminance distribution on the surface of the barcode label to be irradiated is bright on the irradiation optical axis of each LED and dark between adjacent irradiation optical axes, resulting in a wavy distribution. In order to eliminate such unevenness in illuminance and achieve a uniform illuminance distribution, there are examples in which a wide directional LED is used or a cylindrical lens or the like is placed in front of the LED. However, in the case of a wide-directivity LED, a higher brightness is required, which increases power consumption. Also, what is the structure of how to arrange cylindrical lenses etc.? ! It's complicated and expensive.

[Problem to be solved]

An object of the present invention is to provide a barcode reader using a light source diffusion filter that is simple in structure and highly cost-effective.

[Means for solving problems]

A barcode reader using a light source diffusion filter according to the present invention is covered with a light-blocking cover, has an opening at one end of the cover, and is made up of a plurality of high-density, high-directivity LEDs arranged inside the opening. A light source illuminates the barcode facing the aperture, the reflected light from the barcode passes through an optical system and is simultaneously received by a light receiver with multiple light receiving elements arranged, and the electrical signals from this light receiver are processed. A barcode reader that identifies barcodes is constructed by providing a highly transparent scattering filter parallel to the front surface of the light source between the light source and the aperture.

[Effect]

A highly transparent scattering filter placed between the light source and the aperture diffuses the narrow beam of light emitted from each LED without reducing the total luminous flux (passes through the scattering filter. The illuminance of the surface of the barcode illuminated by the light is equalized.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 does not show an embodiment of a barcode reader using a light source diffusion filter according to the present invention.

In the figure, reference numeral 1 indicates a reading head of a barcode reader, which is a part that is held and used by an operator. 2 indicates a barcode label.

The reading head 1 is covered with a light-shielding cover 3 except for the opening 3- at the tip facing the barcode label 2.

The cover 3 is preferably made by molding upper and lower cases each having a U-shaped cross section using a plastic plate or the like, inserting the internal components of the reading head 1, and then gluing the upper and lower cases together.

Further, in FIG. 1(B), the cover 3 at the tip expands in the direction in which the bars of the bar code are arranged to widen the opening 3-. Since there are various sizes of barcode labels, this is designed to accommodate all of them. Since such a tip shape is not directly related to the gist of the present invention, details will be omitted.

A light source 4 for irradiating a barcode label, a scattering filter 5, an optical system 6, a light receiver 7, and a signal processing section 8 are installed inside the light-shielding cover 3. The output of the signal processing section 8 is connected to a computer (not shown) by a connection line 9 through a through hole 3'' provided at the center of the rear part of the cover 3.

Light [4 is multiple LEDs @ii! It is arranged on I. The number of LEDs is determined by taking into account the volume of the tip, the brightness of each LED, the directivity, etc.

As shown in FIG. 1A, the light source 4 is mounted so as to prevent reflected light from scattering by providing a certain angle (θ) between the irradiation optical axis F1 and the light receiving axis F3.

A scattering filter 5 is installed between the light source 4 and the aperture 3. The scattering filter 5 is made by processing the surface of a highly translucent plate such as glass, and the incident light from one surface is not reflected but undergoes complex refraction before being emitted from the other surface. Although the light is diffused by passing through the scattering filter 5, the luminous intensity does not decrease. Therefore, the scattering filter has a light source diffusion-like ability. The scattering filter 5 connects the light source 4 and the aperture 3-
and at a position away from the reflection optical axis F3, so that its surface is perpendicular to the irradiation optical axis F1 and parallel to the front surface of the LED array.

FIG. 2 shows changes in the irradiated light due to the arrangement of the light source 4 and scattering filter 5 as described above. In the figure, each LED of the light source has high brightness and high directivity (indicated by Fl). Therefore, the illuminance distribution due to these lights exhibits a wavy shape as shown by BF. This wavy distribution would be the same on the surface of the barcode label 2 if the scattering filter 5 were not present.

AF indicates the illuminance distribution after passing through the scattering filter 5.

In this way, the distribution is even.

By providing the scattering filter 5 as described above, the illuminance on the surface of the barcode label 2 becomes uniform. That trM
There is no unevenness in the reflected light from each bar of the M'-barcode. The reflected light F3 is transmitted through an optical system 6 consisting of a combination of lenses.
, and becomes a parallel light beam F4, which is converged on the photoreceiver 7.

The light receiver 7 has a necessary number of light receiving elements arranged in a straight line, corresponding to the number of bars of the bar code. The electric @ signal charged and converted by each light receiving element is sent to the signal processing section 8.

The signal processing section 8 processes and digitizes each of these signals, and then sends them to the computer via the connection 1j19.

〔effect〕

By placing a scattering filter in front of the light source of a barcode reader in which LEDs are arranged, the illuminance of the transmitted light is equalized.

As a result, barcode reading errors due to uneven illuminance, which are likely to occur when using highly directional LEO, can be prevented and reliability is improved.

In addition, only a small number of high-brightness LEDs can be used, which helps in downsizing and reducing power consumption.

[Brief explanation of drawings]

FIGS. 1A and 1B are cross-sectional views of embodiments of the present invention,
FIG. 2 is an explanatory diagram of illuminance distribution. 2... Barcode label, 3... Cover, 3'... Opening, 4... Light source, 5... Scattering filter, light source Diffusion filter, 7.
...Receiver.

Claims (1)

[Claims] 1. Covered with a light-shielding cover, an opening is provided at one end of the cover, and a light source consisting of a plurality of high-intensity, highly directional LEDs arranged diagonally inside the opening illuminates the barcode facing the opening. , in a barcode reader that identifies the barcode by guiding reflected light from the barcode from the opening to a light receiver consisting of a plurality of light receiving elements provided in the cover and processing electrical signals from the light receiver; A barcode reader using a light source diffusion filter, characterized in that a highly transparent scattering filter is interposed between the light source and the aperture in parallel with the front surface of the light source.