JPS63115285A - Optical character reader - Google Patents

Abstract

PURPOSE:To receive the reflected light from an illuminated character or the like on an image sensor with a uniform illuminance by increasing the illuminance of a light source according as going from the center toward ends of the visual field illuminated with the light source. CONSTITUTION:Plural LEDs 9 having the same luminance are arranged on a substrate 8 as a surface light source 2 arranged in a hand-scanner 1. The number of LEDs 9 arranged at ends of the illuminated visual field is larger so that LEDs are arranged more closely toward ends of the illuminated visual feld. Since characters or the like placed at ends of the illuminated visual field are more illuminated than the center of the visual field, the reflected light from these characters or the like is stronger than that from characters or the like in the center. However, the reflected light from ends of the visual field is more attenuated than that from the center and both of them are received on an image sensor with the same illuminance. As the result, read character or the like are accurately discriminated because the reflected light from characters or the like is received on the image sensor with a uniform illuminance.

Description

[Detailed Description of the Invention] <Industrial Application> The present invention relates to an optical character reading device that optically reads objects to be read, such as characters and bar codes. This is designed so that the reflected light is received by the image sensor with uniform illuminance.

<Conventional technology> In the distribution industry such as supermarkets and department stores,
In order to quickly obtain information necessary for management such as sales management and product management, 1. Sales information collected for each individual product and various information generated at the purchasing and delivery stages are entered into a computer so that each department can effectively use this information according to its own purpose. A system that processes, processes, and transmits information, the so-called POS (Poi
nt of 5ales (point of sale) is widespread.

A hand-held optical character reader is used to input information at the POS, which is more efficient in input time than conventional manual input using a keyboard.

As shown in FIG. 4, the hand-held optical character reading device uses light 3 emitted from a plurality of light sources 2 arranged in a hand scanner 1 to read characters, symbols, etc. written on a sheet of paper 4. The reflected light 5 is received by the image sensor 6. Then, the intensity of the light received by the image sensor 6 is converted into the intensity of an electrical signal, and the electrical signal is binarized,
Characters, symbols, etc. are identified based on the binary signal. Further, a lens system 7 is arranged between the light source 2 and the image sensor 6 so that the image sensor 6 receives light from the entire field of view illuminated by the light source 2, that is, the range in which characters, etc. can be read by the hand scanner 1. . Note that 8 is a substrate on which the light source 3 is disposed.

<Problems to be Solved by the Invention> In an optical character reading device, if the characters, etc. within the field of view illuminated by the light source 2 have the same density, then the light received by the image sensor 6 with the same brightness is It is necessary to do so.

However, when comparing the edges and the center of the field of view to be illuminated,
Generally, the lens system 7 has a property that the image at the edge of the field of view is darker than the image at the center. Therefore, when the field of view for reading characters, etc. with the hand scanner 1 is uniformly illuminated with the light 3 emitted from the light source 2, when the illuminance is adjusted to the image sensor output of the center image, the images at the edges become dark and the image sensor output is in short supply. On the other hand, if the illuminance is adjusted to the image sensor output of the image at the edge, there is a risk that the image sensor output will be too large or saturated, making it impossible to accurately identify characters, etc. .

The present invention has been made to solve the above-mentioned problems, and aims to provide an optical character reading device in which light reflected from characters etc. illuminated by a light source is received on an image sensor with uniform illuminance. It is something.

Means for Solving the Problems> In order to solve the above problems, the present invention provides a system in which light irradiated from a plurality of light sources is applied to an object to be read, such as characters or symbols, and the reflected light is received by an image sensor. An optical character reading device that converts the intensity of light into an electrical signal to optically read the object to be read, comprising an illumination unit that increases the illuminance of the light source from the center to the edge of the field of view illuminated by the light source. It is characterized by

Effects> The illumination means according to the present invention allows the illuminance at the edges of the visual field to be higher than at the center.

Embodiments The present invention will now be described in detail with reference to illustrated embodiments. It should be noted that the same parts as in the prior art will be described with the same reference numerals.

As shown in this figure, a light emitting diode (hereinafter referred to as LED) 9 with the same brightness is used as a light source to irradiate light onto objects to be read, such as characters and symbols placed inside a hand scanner (not shown).
A plurality of curved lines are arranged on the substrate 8. Otsu's LED9
are arranged in large numbers at the edges of the field of view to be illuminated, so that they become denser as they go from the center of the field of view to the edges. As shown in Figure 4, a lens system and an image sensor (not shown) are arranged behind the LED 9. 8
Reference character a is a hole through which reflected light emitted from the LED 9 from an object to be read, such as characters or symbols, passes when the reflected light is received by the image sensor.

In this way, by arranging a large number of LEDs 9, which are light sources, from the center of the field of view to the edges tζ, characters, etc. located at the edges of the field of view to be illuminated are illuminated with stronger intensity than at the center of the field of view. , the reflected light is also stronger compared to the reflected light of characters, etc. located at the center. However, the optical path of the reflected light is longer at the edges than at the center of the field of view, and the image at the edges becomes darker due to passing through the lens system, so the light reflected from the edges of the field of view is smaller than the light reflected from the center. The attenuation increases, and the image sensor receives the light at the same illuminance. The light received by the image sensor is converted into a strong and weak electrical signal, which is then binarized, and characters, etc., are identified based on the binarized electrical signal.

FIG. 2 is a schematic diagram showing a second embodiment of the present invention, and FIG. 3 is an equivalent circuit diagram thereof. In this embodiment, LEDs 9m and 9m of the same brightness are placed above and below the hole 8a of the substrate 8.
9b-9c, 9d, 9e, 9f and 9g, 9h, 91, 9
j・9k・9! are arranged facing each other at equal intervals. And LEI) 9a, 9f and 9g-9j, L
ED9b/9e and 9h/9k.

LEDs 9c and 9d and 91 and 9j are connected in parallel, and resistors R and 91 are connected to LEDs 9a, 9f, 9g, and 91, respectively.
, LED9b/9e/9h/9k to resistor, LED9c
・A resistor is connected in series to 9d and 91°9j.

Here, the resistance value to the resistor Rt l ''+1' is R,<
Since it is connected to each LED 9a to 9I,
When more DC voltage is applied, (LED9a/9f-9g
・97), (LED9b・9e・9h・9k), (LE
A large current flows in the order of D9c, 9d, 91, and 9j). Therefore, the illuminance of the LED that illuminates the edge of the field of view is higher than that of the LED that illuminates the center of the field of view, and the first
Similar to the embodiment, reflected light from characters etc. is received on the image sensor at the same illuminance.

Further, in the third embodiment, the resistance values of the resistors Ri ``a p FL3 shown in FIGS. 2 and 3 of the second embodiment are made equal.Then, each L E D having the same emission wavelength
9 a ~ 91, (LED9a/9f-9g-94)
, (LED9 b -9e・9h・9k)
(This is a configuration in which LEDs with higher brightness are arranged in the order of LED9c, 9d-9i, and 9N, that is, the LEDs that illuminate the edges of the field of view rather than the center of the field of view.In this case, the LEDs that illuminate the center of the field of view also LE illuminating the edge of
In D, the illuminance can be increased, and as in the first embodiment, the reflected light from characters etc. is received on the image sensor at the same illuminance.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, by providing an illumination means that increases the illuminance of the light source from the center to the edge of the visual field illuminated by the light source, characters, etc. Since the reflected light from the image sensor is received with uniform illuminance on the image sensor, 2
It facilitates digitization and enables accurate identification of read characters, etc.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a first embodiment of the present invention, Fig. 2 is a schematic diagram showing a second and third embodiment of the invention, Fig. 3 is an equivalent circuit diagram thereof, and Fig. 4 is a schematic diagram showing a first embodiment of the present invention. FIG. 2 is a sectional view showing the main parts of the optical reading device. In the drawings, 1 is a hand scanner, 2 is a light source, 6 is an image sensor, 7 is a lens system, 9.9a to 9j are LEDs R8, R3 is a resistor.

Claims (4)

[Claims] (1) Light emitted from multiple light sources is applied to the object to be read, such as letters or symbols, and the reflected light is received by an image sensor, and the intensity of the received light is converted into an electrical signal to optically read the object to be read. An optical character reading device for reading characters, comprising: illumination means that increases the illuminance of the light source from the center to the edge of the visual field illuminated by the light source. (2) The optical character reading device according to claim 1, wherein the illumination means arranges a larger number of light sources as it goes from the center to the edge of the field of view to be illuminated. (3) The optical character reading device according to claim 1, wherein the illumination means increases the current flowing through the light source as it goes from the center to the edge of the field of view to be illuminated. (4) The optical character reading device according to claim 1, wherein the illumination means increases the brightness of the light source as it goes from the center of the field of view to the edges.