JP2005077982A - Optical reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the occurrence of nonuniform illuminance despite the use of a plurality of LEDs. <P>SOLUTION: The optical reading apparatus emits a light from a lighting device 11 to a subject and condenses reflected light from the subject onto a light-receiving element via a lens. In the optical reading apparatus, the lighting device 11 includes the LEDs 3 arranged at predetermined intervals; a cylindrical lens 8 by which diverging outgoing light from the LEDs 3 is converged into parallel light; diverging member 9 which restrains nonuniform illuminance of the LEDs 3; and a prism sheet 10 disposed in between the LEDs 3 and the cylindrical lens 8 and is in contact with the cylindrical lens 8 which separates the light of the LEDs 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical reading apparatus that captures an image by irradiating a subject such as a card, a check, or a passbook with light. More specifically, the present invention relates to an improvement of an illumination device for an optical reader.

  2. Description of the Related Art An optical reader that irradiates a subject with light and collects reflected light on a light receiving element to capture an image is used (for example, see Patent Document 1). As an illuminating device 100 used in this type of optical reading device, for example, as shown in FIG. 8, a plurality of LEDs 101 arranged at a predetermined interval, an LED substrate 102 on which these LEDs 101 are arranged, and this LED substrate 102 , A cylindrical lens 104 that converges the diffused irradiation light emitted from the LED 101 into parallel light, and a diffusion member 105 that suppresses uneven illuminance of the LED 101. By arranging a plurality of LEDs 101 in a straight line, the illumination device 100 can be used as a line light source.

  Then, diffused light is emitted from the LED 101, passes through the cylindrical lens 104, converges to parallel light, and is irradiated onto the subject. The light beam applied to the subject is reflected on the upper surface of the medium. This reflected light enters a light receiving element such as a CCD and is converted into an electric signal.

JP-A-6-318734

  However, since the illumination device 100 irradiates the subject with light rays from the LED 101 that is a plurality of point light sources only through the cylindrical lens 104 and the diffusing member 105, the linear light is likely to be uneven. That is, a certain part of the LED 101 becomes bright and becomes dark between the LEDs 101, and a bright part and a dark part may appear in order in the longitudinal direction of the linear light. When unevenness of light rays occurs in the illumination device 100, unevenness also appears in the captured image of the subject.

  Accordingly, an object of the present invention is to provide an optical reader that can suppress the occurrence of uneven illuminance while using a plurality of LEDs.

  In order to achieve such an object, the invention described in claim 1 is an optical reader that irradiates a subject with irradiation light from an illuminating device and collects reflected light from the subject on a light receiving element via a lens. The illuminating device includes a plurality of LEDs arranged at a predetermined interval, a cylindrical lens that converges emitted light diffused from the LEDs into parallel light, a diffusion member that suppresses uneven illuminance of the plurality of LEDs, and a plurality of LEDs. And a prism sheet for splitting the emitted light between the cylindrical lens and the cylindrical lens.

  Therefore, since the diffused light emitted from the LED is dispersed by the prism sheet, the light is uniformly diffused between a part of the LED and a part between the LEDs. Since the diffused light beam is incident on the cylindrical lens, it is possible to suppress illuminance unevenness of the light beam that illuminates the subject.

  According to a second aspect of the present invention, in the optical reader according to the first aspect, the prism sheet is positioned in contact with the cylindrical lens. Therefore, the prism sheet positioning operation can be simplified. In addition, it is possible to increase the accuracy of positioning of the prism sheet and reliably suppress unevenness in the illuminance of the light beam.

  As described above, according to the optical reading device of the first aspect, since the diffused light emitted from the LED is dispersed by the prism sheet, the light is homogeneous in a portion where the LED is located and a portion between the LEDs. Is diffused. Since the diffused light beam is incident on the cylindrical lens, it is possible to suppress illuminance unevenness of the light beam that illuminates the subject. Therefore, it is possible to achieve high-quality capture by suppressing the occurrence of image unevenness in the captured subject.

  According to the optical reader of the second aspect, since the prism sheet is positioned in contact with the cylindrical lens, the prism sheet positioning operation can be simplified. In addition, it is possible to increase the accuracy of positioning of the prism sheet and reliably suppress unevenness in the illuminance of the light beam.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

  1 to 6 show an example of an embodiment of the optical reading device 1 of the present invention. As shown in FIG. 3, the optical reading device 1 irradiates the subject 4 with the irradiation light from the illumination device 11 and condenses the reflected light from the subject 4 on the light receiving element 6 through the lens 5. is there. As shown in FIG. 1, the illumination device 11 includes a plurality of LEDs 3 arranged at a predetermined interval, a cylindrical lens 8 that converges emitted light diffused from the LEDs 3 into parallel light, and uneven illuminance of the plurality of LEDs 3. And a prism sheet 10 that splits the emitted light between the plurality of LEDs 3 and the cylindrical lens 8.

  The lighting device 11 includes an LED substrate 7 on which a plurality of LEDs 3 are arranged, and a case 2 that fixes the LED substrate 7. A white LED 3 capable of obtaining high luminance is used as the light source. However, since the LED 3 is generally expensive, it is preferable that the number of points is as small as possible within a range in which a necessary and sufficient amount of light can be obtained to reduce the cost. In the present embodiment, a plurality of, for example, eight LEDs 3 are arranged on the LED substrate 7 in a line at equal intervals.

  As shown in FIGS. 4 and 5, the prism sheet 10 has a Fresnel lens shape having a large number of grooves orthogonal to the arrangement direction of the LEDs 3. In the present embodiment, the incident surface 10a of the prism sheet 10 is a flat surface, and a groove is formed on the exit surface 10b. Each vertex 10c and valley bottom 10d of the emission surface 10b form 90 degrees, and each inclined surface 10e forms 45 degrees with respect to the arrangement direction of the LEDs 3.

  According to this prism sheet 10, as shown in FIG. 4, the number of apparent LEDs 3 (indicated by a two-dot chain line in the figure) is made twice the number of actual LEDs 3 (indicated by a solid line in the figure). Therefore, the pitch of the light and darkness of the emitted linear light can be reduced to half A / 2 from the pitch A of the actual LED 3. Thereby, generation | occurrence | production of the nonuniformity of linear light can be suppressed. Further, since the prism sheet 10 has a constant shape in the direction orthogonal to the direction in which the LEDs 3 are arranged, no spectral or condensing is performed.

  The prism sheet 10 is positioned in contact with the cylindrical lens 8. The distance between the LED 3 and the prism sheet 10 is set to such a length that the light emitted from one LED 3 is split into two as shown in FIG. The cylindrical lens 8 includes separate members for the LED side portion 24 and the subject side portion 25. The LED side portion 24 and the subject side portion 25 are combined to form a cylindrical lens 8 having a substantially circular cross section.

  The prism sheet 10 is provided between the portions 24 and 25 of the cylindrical lens 8. For this reason, the LED 3 is fixed to the case 2 via the LED substrate 7 and the prism sheet 10 is fixed to the case 2 via the cylindrical lens 8, so that the LED 3 and the prism sheet 10 are positioned easily and accurately. be able to.

  Further, the optical reading device 1 of the present embodiment includes a glass plate 12 that transmits the light emitted from the LED 3 and a reflecting mirror 13 that changes the direction of the reflected light reflected by the upper surface 4a of the subject 4 to a direction in which the lens 5 is located. And a lens 5 for condensing the reflected light reflected by the reflecting mirror 13 and a light receiving element 6 for converting a light beam from the lens 5 into an electric signal. The subject 4 capable of capturing an image is, for example, a card, a check, a bankbook, or the like. As the light receiving element 6, a line type light receiving element is used.

  The glass plate 12 is fixed to the medium guide portion 2a outside the case 2 formed to protrude toward the medium path so as to be positioned between the LED 3 and the subject 4. The reflecting mirror 13 is affixed to the upper part 16 a of the bracket 16 fixed with screws 15 in the case 2. The upper portion 16a of the bracket 16 is bent at an appropriate angle toward the lens 5 so as to direct the reflected light from the medium upper surface 4a toward the lens 5. The illumination device 11 is fixed to the case 2 by a holder 17. The holder 17 is fixed to the inside of the case 2 of the optical reader 1 with a screw 14. A stop 23 for reducing the amount of reflected light is provided in front of the lens 5.

  The control device of the optical reader 1 controls an image signal from the light receiving element 6, and includes an amplifier 18, an A / D (analog / digital) converter 19, a shading processing circuit 20, and a halftone processing circuit. 21 and a white reference memory 22. The shading processing circuit 20 determines the image signal from the A / D converter 19 based on the white reference level in the white reference memory 22, and shades a portion having a higher reflectance than white that exceeds the white reference level as white. Make corrections. The halftone processing circuit 21 performs pseudo halftone processing (binarization processing) and moire removal. The white reference memory 22 stores a white reference level corresponding to shading by the LED 3.

  The operation of the optical reading apparatus 1 of the present embodiment configured as described above will be described below.

  When the subject 4 passes through the medium path and is conveyed to the vicinity of the medium guide portion 2a, a sensor (not shown) detects the subject 4. Upon receiving this detection signal, the LED 3 emits light.

  The irradiation light from the LED 3 is incident on the LED side portion 24 of the cylindrical lens 8 as shown in FIG. 1, and is split by the prism sheet 10 as shown in FIG. The split light beam is incident on the subject side 25 of the cylindrical lens 8 and converges into parallel light. The parallel light is diffused by the diffusing member 9 provided at the lower end of the illuminating device 11 and is emitted from the illuminating device 11 as linear light in which uneven irradiation is suppressed.

  The linear light passes through the glass plate 12 and is reflected by the medium upper surface 4a. The reflected light is reflected by the reflecting mirror 13 and then enters the light receiving element 6 along the optical axis of the lens 5 to be converted into an electric signal. The image signal converted by the light receiving element 6 is amplified by the amplifier 18, A / D converted by the A / D converter 19, and shading corrected by the shading processing circuit 20. The image signal from the shading processing circuit 20 is subjected to pseudo halftone processing (binarization processing) and moire removal by the halftone processing circuit 21. As a result, images such as ink characters and bar codes formed on the medium upper surface 4a are read and taken in as data.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, although a white LED is used as the LED 3 in the present embodiment, the present invention is not limited to this, and another color LED may be used.

  In the above-described embodiment, the LED side portion 24 and the subject side portion 25 constituting the cylindrical lens 8 are separated, but the present invention is not limited to this, and they may be integrated. In this case, for example, as shown in FIG. 7, a groove 26 is formed in the central portion of one cylindrical lens 8, and the LED 3 side from the groove 26 is an LED side portion 24, and the subject 4 side is a subject side portion 25. Then, the prism sheet 10 is inserted and installed in the groove 26. Also in this case, the prism sheet 10 can be installed and positioned easily and accurately.

  Furthermore, in the above-described embodiment, the cylindrical lens 8 is formed in a substantially circular cross section, but is not limited thereto, and may be a substantially semicircular cross section. Only one of the subject side portion 25 and the LED side portion 24 adjusted so as to obtain the light condensing effect is provided, and the prism sheet 10 is placed on the plane. Also in this case, the prism sheet 10 can be installed and positioned easily and accurately.

  In each of the embodiments described above, the prism sheet 10 is positioned in contact with the cylindrical lens 8, but is not limited thereto, and may be positioned in contact with the case 2, for example.

  In the above-described embodiment, the prism sheet 10 has a Fresnel lens shape. However, the prism sheet 10 is not limited to a lens that physically causes light refraction in this way, and the apparent appearance of the LED 3 depends on the properties of the material itself. The pitch may be reduced. For example, by using a member made of two materials having different refractive indexes (for example, polycarbonate and a glass component blended therewith), the internal diffusibility can be increased and the light / dark pitch can be narrowed.

It is a figure which shows the illuminating device of the optical reader of this invention, (A) is a front view, (B) is a right view and an exploded view of a cylindrical lens. It is a top view of the optical reader of this embodiment. FIG. 3 is a sectional view taken along line III-III of the optical reading device shown in FIG. 2. It is a front view which shows LED and a prism sheet. It is a perspective view which shows a part of prism sheet. It is a block diagram which shows the structure of a control apparatus. It is a side view which shows other embodiment of a cylindrical lens. It is a figure which shows the illuminating device of the conventional optical reader, (A) is a front view, (B) is a right view.

Explanation of symbols

1 Optical reader 3 LED
4 Irradiation Light 5 Lens 6 Light Receiving Element 8 Cylindrical Lens 9 Diffusion Member 10 Prism Sheet 11 Illumination Device

Claims (2)

In an optical reader that irradiates a subject with irradiation light from an illumination device and collects reflected light from the subject on a light receiving element via a lens, the illumination device includes a plurality of LEDs arranged at predetermined intervals. A cylindrical lens that converges the emitted light diffused from the LEDs into parallel light, a diffusion member that suppresses illuminance unevenness of the plurality of LEDs, and the emitted light between the plurality of LEDs and the cylindrical lens. An optical reading device comprising a prism sheet for spectral separation. The optical reader according to claim 1, wherein the prism sheet is positioned in contact with the cylindrical lens.

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