JPH04349585A - Optical reader - Google Patents

Abstract

PURPOSE:To obtain the optical reader which can be manufactured at a low cost and can be assembled easily, and also, on enlarge read depth of a recording medium. CONSTITUTION:This optical reader is provided with an LED array 2 consisting of LEDs 2a-2f arranged along the lengthwise direction of a bar-code 8 and a light guiding body 9 for projecting light emitted from this LED array 2 to the bar-code 8 and reads information recorded in the bar-code 8. In the peripheral part of an optical path of light projected from this light guiding body 9, reflecting bodies 15, 16 for reflecting a part of a projected light to the end part in the lengthwise direction of the bar-code 8 are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical reading device such as a barcode scanner that illuminates a recording medium on which information is optically recorded and receives reflected light to read information recorded on the recording medium. .

0002

2. Description of the Related Art In general, an optical reading device includes an LED array consisting of a plurality of LEDs arranged in the length direction of a recording medium such as a bar code, and a guide that projects light emitted from the LED array onto the recording medium. It includes a light body, a lens that collects reflected light reflected by the recording medium, and a detection body that detects an image of the recording medium formed by the lens. In such an optical reading device, when the light reflected by the recording medium is focused by a lens and formed into an image on the detection object, the received light illuminance at the periphery is lower than the received light illuminance at the center, so the detection In some cases, the amount of light received by the recording medium becomes uneven, making it difficult to read the longitudinal ends of the recording medium.

[0003] Therefore, in the past, for example,
As described in Japanese Patent Application Laid-Open No. 59-24383, etc., a larger drive current is supplied to the LEDs located at the ends of the LED array than to the LEDs located at the center. An optical reading device has been proposed. In this conventional optical reading device, the emitted light intensity at the ends of the LED array is higher than that at the center, and then, as described above, when the lens forms an image on the detection object, the received light illuminance at the periphery is lower than that at the center. Since the light illuminance is lower than the light illuminance, the amount of light received by the detection object is made uniform over the entire area, and even the longitudinal ends of the recording medium can be reliably read. Note that there is also a device that makes the luminance of light emitted at the end of the LED array relatively high by arranging the LEDs relatively densely at the end of the LED array.

FIG. 4 is a diagram illustrating this type of conventional optical reading device. FIG. 4 shows an LED array and a light guide, and the distance from the LED array 2 is in the Y-axis direction, and the distance Y is The received light illuminance distribution in the X direction on the recording medium surface at each position is shown. The conventional optical reading device shown in FIG. 4 includes an LED array 2 consisting of, for example, six LEDs 2a to 2f arranged in sequence on a printed circuit board 1, and a semi-cylindrical light guide 3. In the LED array 2, the LEDs 2a, 2b, 2e, and 2f at the ends are arranged more densely than the LEDs 2c and 2d at the center. In such an optical reading device, since the emission illuminance at the ends of the LED array 2 is higher than the emission illuminance at the center, the LED
When a recording medium is located relatively close to the array 2, for example at a distance y1, the received light illuminance at both ends of the recording medium is higher than that at the center, and as shown by the solid line 4 in FIG. It shows a peak-shaped illuminance distribution curve.

[0005] Furthermore, as described in, for example, JP-A-59-27377 and JP-A-2-138681, the illuminance of light emitted at the ends is set higher than that at the center as described above. It has an LED array and a light guide that converges or diverges the light emitted from the LED array in the length direction of the recording medium, and compares the received light illuminance at the edge of the recording medium with the received light illuminance at the center. Optical reading devices have been proposed that have an increased height. Even with this conventional optical reader,
Since the amount of light received at the detection body is equal to that at the center at the edges, and the amount of light received at the detection body is made uniform over the entire area, it is possible to reliably read the edges of the recording medium in the length direction.

FIG. 5 is a diagram illustrating this type of conventional optical reading device. FIG. 5 also shows an LED array and a light guide, and the distance from the LED array 2 is in the Y-axis direction, and the distance Y is The received light illuminance distribution in the X direction on the recording medium surface at each position is shown. The conventional optical reading device shown in FIG. 5 has an LED array 2, and instead of the semi-cylindrical light guide 3 described above, it is provided with another light guide 5 made of a Fresnel lens or the like. Even in such an optical reading device, the luminous intensity at the ends of the LED array 2 is higher than that at the center, and the light guide 5 directs the light emitted from the LED array 2 in the longitudinal direction of the recording medium. Since it converges or diverges, LED array 2
When there is an information medium at a relatively close position, for example, at a distance y3 from The distribution curve is shown. The same is true when the information medium is located at a relatively far position, for example, at a distance y4, and the received light illuminance on the information medium is higher at both ends than at the center, as shown by the solid line 6a in FIG. shows a bimodal illuminance distribution curve.

[0007]

[Problems to be Solved by the Invention] However, in the conventional optical reading device described above, in the former case where the luminous intensity at the ends of the LED array 2 is higher than that at the center, the LED
The illuminance distribution at a distance y2 further away from the array 2 has a mountain-shaped shape in which the received illuminance is high at the center of the recording medium and becomes lower toward the edges, as shown by the solid line 4a in FIG. It shows. In this way, as the recording medium moves away from the LED array 2, the received light illuminance at the edge of the recording medium tends to decrease significantly, making it particularly difficult to read the edge of the recording medium, which limits the reading depth of the recording medium. There was a problem with being exposed.

In the latter case, where the luminous intensity at the end of the LED array 2 is made relatively high and the light is converged or diverged by the light guide 5, a Fresnel lens or the like having a complicated shape is used as the light guide 5. Since this is necessary, the manufacturing cost increases, and the relative positional relationship between the light guide 5 and each of the LEDs 2a to 2f must be set accurately. The problem was that it was difficult to place the Note that the light guide 5 and each LED 2a
If the relative positional relationship between the light guide 5 and the LEDs 2a to 2f is not set accurately, the error in the relative positional relationship will significantly affect the light because the distance between the light guide 5 and the LEDs 2a to 2f is small. The light cannot be converged or diverged at a desired position, and it is difficult to set the received light illuminance at the edges of the recording medium to be higher than the received light illuminance at the center.

The present invention has been made in view of the actual situation in the prior art, and its purpose is to provide an optical reader that is inexpensive to manufacture, can be easily assembled, and can increase the reading depth of recording media. The goal is to provide equipment.

0010

[Means for Solving the Problems] In order to achieve this object, the present invention provides an LED array consisting of a plurality of LEDs arranged along the length of a recording medium on which information is optically recorded; In an optical reading device that includes a light guide that projects light emitted from an LED array onto the recording medium and reads information recorded on the recording medium, the periphery of the optical path of the light projected from the light guide. The recording medium is provided with a reflector that reflects a portion of the projected light toward the longitudinal end of the recording medium.

[0011]

[Operation] As described above, the present invention provides a reflector at the periphery of the optical path of the light projected from the light guide, and uses this reflector to direct a part of the projected light to the end of the recording medium in the longitudinal direction. Since the light is reflected towards the edges of the recording medium, the received light illuminance at the edges of the recording medium is higher than the received light illuminance at the center.
The lengthwise end of the recording medium can be reliably read, and the reading depth of the recording medium can be increased. Further, since a Fresnel lens or the like having a complicated shape is not required as the light guide, a cylindrical lens, for example, can be used, so the manufacturing cost is low. Further, the reflector is provided at a relatively distant position from the LED, and the reflector and the LED
Since there is little need to accurately set the relative positional relationship with D, assembly is easy.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the optical reading device of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of essential parts showing an embodiment of the optical reading device of the present invention, FIG. 2 is an explanatory view showing the end portions of a reflector and an LED array provided in the optical reading device of FIG. 1, and FIG. 3 is FIG. FIG. 3 is a diagram showing the illuminance distribution of the optical reading device. In addition, in FIGS. 1 to 3, parts equivalent to those shown in FIGS. 4 and 5 described above are given the same reference numerals. That is, 1 is a printed circuit board, 2 is an LED array, and 2a to 2f are LEDs. In addition, in FIG. 3 as well as in FIGS. 4 and 5, the LE
In addition to showing the D array and light guide, LED array 2
The received light illuminance distribution in the X direction on the recording medium surface at the position of the distance Y is shown, with the separation distance from the recording medium being taken as the Y-axis direction.

The optical reading device of this embodiment shown in FIG. 1 includes a case 7 bent at a predetermined angle. It has opposing open ends 7a. Case 7
Inside, there is an LED array 2, a light guide 9 consisting of a semi-cylindrical lens or the like that projects the light emitted from the LED array 2 onto the barcode 8 via the open end 7a, and the barcode. 8, the optical path of the light incident from the aperture end 7a is refracted by a predetermined angle to create a reading optical path 10.
a lens 12 that collects the light reflected by the reflective mirror 11 to form an image of the barcode 8, and a detection body such as a line sensor 13 that detects the image of the barcode 8. and a reading circuit 14 that reads information recorded on the barcode 8 by processing the detection signal emitted from the line sensor 13. A pair of reflectors 15 and 16 are provided at the periphery of the optical path of the light projected from the light guide 9 to reflect a portion of the projected light toward the longitudinal ends of the barcode 8. ing. These reflectors 15 and 16 are connected to the case 7, respectively.
The opening end 7a is made of aluminum foil or the like that is attached to the inside of the
are placed near both sides of the As shown in FIG. 2, the reflective surface 16a of one of the reflectors 16 is formed from a part of a paraboloid whose focal point is the approximate light emission center P of the LEDs 2e and 2f located at the end of the LED array 2. There is. The reflective surface of the other reflector 15 is also formed in the same manner.

In this embodiment, although not shown, when the drive circuit is activated in response to the operation of a push button, etc., each LED is activated.
2a to 2f are emitted with a constant current for a predetermined period, and this light is projected from the light guide 9 to the barcode 8 via the open end 7a. Accordingly, when the light reflected by the barcode 8 enters from the opening end 7a, this light is refracted by a predetermined angle by the reflection mirror 11 and guided to the reading optical path 10, and after being condensed by the lens 12, The formed image of the barcode 8 is detected by the line sensor 13. Next, the detection signal emitted from this line sensor 13 is sent to a reading circuit 14.
The information recorded in the barcode 8 is read by processing the barcode 8. And the LEDs 2a and 2b at the end
, 2e, 2f are arranged relatively densely, so LE
The emission illuminance at the ends of the D array 2 is higher than that at the center, and a part of the light projected from the light guide 9 is reflected by the reflectors 15 and 16 at the longitudinal ends of the barcode 8. The distance y from the LED array 2
The received light illuminance at positions 3 and y4 is higher at both ends than at the center, and exhibits bimodal illuminance distribution curves as shown by solid lines 17 and 18 in FIG. 3, respectively. In this illuminance distribution, when the barcode 8 is located at a separation distance y3, the barcode 8 can be detected by the line sensor 13 in the readable range W3, and the barcode 8 can be detected by the line sensor 13 at a short distance x0 from the edge of this range W3. The illuminance is set so that the position closer to the center has the maximum illuminance. The same applies to the readable range W4 at the separation distance y4. Incidentally, the illuminance distribution of the conventional optical reading device explained based on FIG. 5 mentioned above is shown by the broken line 19 in FIG.

In the embodiment configured as described above, the open end 7
Reflectors 15 and 16 are provided near a, and the reflectors 15,
16 allows illumination from near the ends of the barcode 8, so even if the distance between the barcode 8 and the LED array 2 is large, the illuminance received at the ends of the barcode 8 is equal to the illuminance received at the center. It can be made comparatively higher. For example, even if the barcode 8 is located at a distance y4, the received light illuminance at the end of the readable range W4 is higher than that at the center, as shown by the solid line 18 in FIG. Since the amount of light received by the sensor 13 is made uniform over the entire area, the longitudinal ends of the barcode 8 can be reliably read by the line sensor 13, and the depth of reading of the recording medium can be increased. Furthermore, since the light guide 9 is made of a cylindrical lens or the like, and there is no need for a Fresnel lens or the like having a complicated shape, the manufacturing cost is low. Reflectors 15 and 16 are provided at positions relatively apart from the LEDs 2a to 2f.
Since there is little need to accurately set the relative positional relationship between LED 6 and LEDs 2a to 2f, assembly is easy. Furthermore, since a part of the projected light is reflected by the reflectors 15 and 16 at the peripheral part of the optical path of the light projected from the light guide 9, the illuminance distribution at the separation distance y3 decreases rapidly outside the readable range W3. Therefore, unnecessary illumination can be reduced compared to a conventional optical reading device in which the received light illuminance is distributed as shown by the broken line 19. In this embodiment, a light guide made of a cylindrical lens or the like is exemplified, but a Fresnel lens may be used as the light guide if necessary.

[0016]

Since the present invention is constructed as described above, the manufacturing cost is low, assembly is easy, and the reading depth of the recording medium can be increased.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts of an embodiment of an optical reading device of the present invention.

FIG. 2 is an explanatory diagram showing an end portion of a reflector and an LED array included in the optical reading device of FIG. 1;

FIG. 3 is a diagram showing the illuminance distribution of the optical reading device of FIG. 1;

FIG. 4 is a diagram illustrating an example of a conventional optical reading device.

FIG. 5 is a diagram illustrating another example of a conventional optical reading device.

[Explanation of symbols]

2 LED array 2a-2f LED 7 Case 8 Barcode (recording medium) 9 Light guide 15, 16 Reflector P Approximate emission center

Claims (1)

[Claims] Claim 1: An LE consisting of a plurality of LEDs arranged along the length of a recording medium on which information is optically recorded.
In an optical reading device that includes a D array and a light guide that projects light emitted from the LED array onto the recording medium, and reads information recorded on the recording medium, the light emitted from the light guide An optical reading device characterized in that a reflector is provided at the periphery of the optical path of the light to reflect a part of the projected light toward the longitudinal end of the recording medium.