JP2013089288A - Lighting device and reading device with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device capable of improving the efficiency of using light emitted from a light source, suppressing occurrence of stray light, and moreover reliably preventing blown-out highlight caused by the spray light made incident into an imaging device.SOLUTION: The lighting device is provided with a spacer 52 interposed between a substrate 12 for holding a light source 11 and a light guide 13. This spacer includes an opening 53 through which light emitted from the light source is made incident into an incident face 15 of the light guide, and this opening is made in a tapered shape with its inner diameter becoming larger from a substrate side to a light guide side. Specifically, the spacer is formed of a material having optical transparency.

Description

  The present invention relates to an illumination device that illuminates a reading surface of a document and a reading device including the same.

  In a reading apparatus that reads an image of a document, the reading surface of the document is illuminated by an illumination device, and the reflected light is received by an image sensor to output an image signal. Conventionally, an illumination device provided in the reading device is generally one using a fluorescent tube, but in recent years, one using an LED element as a light source is becoming widespread from the viewpoint of energy saving.

  In such an illumination device using an LED element as a light source, since the LED element serves as a point light source, it is necessary to devise a uniform illuminance distribution on the reading surface of the document. A technique for using a light body to function as a line light source is known (see Patent Document 1). With this technique, a uniform illuminance distribution can be obtained with a small number of LED elements. In addition, a technique in which a plurality of LED elements are arranged in one direction is known (see Patent Document 2). Here, a lens-shaped resin cap having a light condensing effect is provided on the LED element, and the light intensity shortage at the end portion is eliminated to obtain a uniform illuminance distribution.

  In addition, a technique is known in which a plurality of different types of LED elements, that is, LED elements that emit white light, infrared light, and ultraviolet light, respectively, are provided and used properly according to the application (see Patent Document 3). ). In this case, the white LED element is turned on in a normal application for visual confirmation by an operator using a monitor, and red is used for character recognition of a manuscript whose character is described on a background image using a passport or the like. When the outer LED element is turned on and an image drawn with a fluorescent ink for preventing counterfeiting is acquired with a passport or the like, the ultraviolet LED element is turned on.

JP 2010-146868 A JP 2004-177851 A JP 2010-2000187 A

  Now, in the reading device, it is inevitable that the light emitted from the illumination device is reflected by a mirror or a document table that bends the optical path of the reflected light on the reading surface of the document, but becomes stray light. When entering the imaging device, a portion where the luminance is partially increased appears in the read image. In particular, when the amount of stray light incident on the camera increases, the output of the image sensor reaches a saturation level, so-called whiteout occurs, and tone information disappears at the part where this whiteout occurred, which improves image processing. It is difficult to do so, and a configuration that can prevent overexposure is desired.

  Here, as disclosed in Patent Document 3, when a large number of LED elements are arranged on a single substrate, man-hours can be reduced and manufacturing costs can be reduced. Since the illumination device is simply arranged close to the document table, the illuminance distribution on the reading surface becomes non-uniform, and the light emitted from the LED element is emitted in multiple directions. There arises a problem that the utilization efficiency of light emitted from the LED element is lowered and stray light is generated.

  In contrast, a configuration in which a light guide is provided as disclosed in Patent Document 1 and a structure in which a resin cap as disclosed in Patent Document 2 is provided in a configuration in which the LED elements are arranged on a substrate. When applied, the illuminance distribution on the reading surface can be improved, but it does not surely prevent the light emitted from the illumination device from being emitted in multiple directions. The problem of occurrence cannot be solved sufficiently.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to improve the utilization efficiency of light emitted from the light source and to suppress the generation of stray light. Furthermore, another object of the present invention is to provide an illuminating device configured to reliably prevent whiteout that occurs when stray light enters an imaging device, and a reading device including the illuminating device.

  The illumination device of the present invention includes a light source, a substrate that holds the light source, a light guide that guides light emitted from the light source in a predetermined direction, and an intermediate support interposed between the light guide and the substrate. The intermediate support has an opening through which the light emitted from the light source is incident on the incident surface of the light guide, and the opening is formed from the substrate side. It is set as the structure formed in the taper shape where an internal diameter becomes large gradually toward the said light guide body side.

  Further, the reading device of the present invention is an imaging device that images the illumination device, a transparent document table on which a document is placed, and a reading surface of the document illuminated by the illumination device via the document table. It is set as the structure provided with these.

  According to the present invention, since the opening of the intermediate support has a tapered shape, the light emitted from the light source can be condensed, thereby improving the utilization efficiency of the light emitted from the light source and suppressing the generation of stray light. be able to. The intermediate support serves as both a member for condensing light and a member for supporting the light guide on the substrate, and the light guide is stable with respect to the substrate without interfering with the light source on the substrate. Can be supported.

1 is an overall perspective view showing a reading device 1 according to a first embodiment. Side view showing a main part of the reading device 1 Sectional view of the lighting device 5 Front view of illumination board 12 The front view which shows the state which attached the spacer 14 to the illumination board 12 The front view which shows the state which attached the spacer 14 and the light guide 13 to the illumination board 12 The perspective view which looked at the spacer 14 from the front side (light guide 13 side) Schematic sectional view showing the progress of light in the spacer 14 according to the first embodiment The side view which shows the condition of the stray light in the reader 1 which concerns on 1st Embodiment. Schematic sectional view showing the progress of light in the spacer according to the second embodiment Characteristic chart showing transmittance according to wavelength by resin The side view which shows the condition of the stray light in the reader which concerns on 2nd Embodiment

  A first invention made to solve the above problems includes a light source, a substrate that holds the light source, a light guide that guides light emitted from the light source in a predetermined direction, the light guide, and the light guide. An intermediate support interposed between the substrates, and the intermediate support has an opening through which light emitted from the light source enters the incident surface of the light guide. The opening is configured to have a tapered shape in which the inner diameter gradually increases from the substrate side toward the light guide side.

  According to this, since the opening of the intermediate support has a tapered shape, the light emitted from the light source can be condensed, thereby improving the utilization efficiency of the light emitted from the light source and suppressing the generation of stray light. it can. The intermediate support serves as both a member for condensing light and a member for supporting the light guide on the substrate, and the light guide is stable with respect to the substrate without interfering with the light source on the substrate. Can be supported.

  According to a second aspect of the present invention, the intermediate support is formed of a light transmissive material.

  According to this, the ratio of the light which permeate | transmits in the internal peripheral surface of an opening part can be increased, and the ratio of the light diffusely reflected by the internal peripheral surface of an opening part can be reduced significantly. The stray light that enters the imaging device and causes whiteout is mainly caused by scattered light due to diffuse reflection. Therefore, it is possible to prevent whiteout due to stray light by reducing the ratio of diffusely reflected light. it can.

  According to a third aspect of the present invention, the intermediate support is formed of a material having a light transmittance of 80% or more.

  According to this, the ratio of the light diffusely reflected on the inner peripheral surface of the opening can be sufficiently reduced, and whiteout due to stray light can be reliably prevented.

  In this case, since the light transmittance varies depending on the wavelength, a material having a transmittance of 80% or more at the wavelength of the light emitted from the light source to be used may be selected. For example, in the case of only a light source that emits white light, a material having a white light transmittance of 80% or more may be selected. In particular, when there are a plurality of types of light sources including a light source that emits ultraviolet light, the material may be selected based on the transmittance of the ultraviolet light at which the light transmittance is lowest.

  According to a fourth aspect of the present invention, the intermediate support is formed of any one of a methacrylic resin, a polycarbonate resin, and a cycloolefin resin.

  According to this, even in the case of ultraviolet light that has the lowest light transmittance, the light transmittance is 80% or more, so even with a configuration equipped with a light source that emits ultraviolet light, whiteout due to stray light is reliably prevented. be able to.

  According to a fifth aspect of the invention, the light guide is formed in a bar shape that is long in one direction, a plurality of the light sources are arranged on the substrate side by side in the longitudinal direction of the light guide, and the intermediate support is The light guide is provided so as to extend over substantially the entire length, and the opening is provided for each of the plurality of light sources.

  According to this, the light collection efficiency can be increased for each of the plurality of light sources. And compared with the structure which provides the member which raises condensing efficiency for every some light source, a number of parts can be reduced and manufacturing cost can be reduced.

  According to a sixth aspect of the present invention, the illumination device, a transparent document table on which a document is placed, and an imaging device that images the reading surface of the document illuminated by the illumination device via the document table, It is set as the structure provided with.

  According to this, since the document can be read simply by placing the document on the document table, it is possible to improve the convenience for the user, and in particular, a document (such as a passport) formed by binding a plurality of sheets together ( This is suitable for reading a (form).

  According to a seventh aspect of the present invention, the apparatus further includes a mirror that reflects reflected light from the reading surface of the document and guides the reflected light to the imaging device.

  According to this, it is possible to reduce the size of the reading apparatus by bending the optical path of the reflected light on the reading surface of the document with the mirror. On the other hand, the mirror causes stray light that causes whiteout, that is, light emitted from the light guide outside the normal angle range is reflected by the mirror and the document table, and becomes stray light. However, it is possible to reduce light emitted outside the normal angular range by increasing the light collection efficiency by the tapered opening of the intermediate support. Therefore, generation of stray light incident on the image pickup apparatus can be suppressed and whiteout can be prevented.

  Further, according to an eighth aspect of the present invention, the imaging device and the illumination device are configured such that light transmitted through the intermediate support formed of a light-transmitting material and radiated to the outside from the side surface of the imaging device. The configuration is arranged so as not to enter the corner.

  According to this, it is possible to avoid that light leaking from the side surface of the intermediate support directly enters the imaging device, thereby preventing whiteout from occurring due to light leaking from the side surface of the intermediate support. Can do. For this reason, it is not necessary to provide a means for preventing the light transmitted through the intermediate support from leaking from the side surface, and the manufacturing cost can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is an overall perspective view showing a reading device 1 according to the first embodiment. The reading device 1 includes a housing 2, a document table 4 on which a document 3 such as a passport is placed, an illumination device 5 that illuminates a reading surface 3a of the document 3 placed on the document table 4, and an illumination device. For controlling a camera (imaging device) 6 that images the reading surface 3 a of the original 3 illuminated by 5, a mirror 7 that guides reflected light from the reading surface 3 a of the original 3 to the camera 6, and the illumination device 5 and the camera 6. And a main board 8 on which such components are mounted.

  FIG. 2 is a side view showing a main part of the reading device 1. The lighting device 5 and the camera 6 are disposed in the vicinity of one side wall of the housing 2, and the camera 6 is disposed above the lighting device 5. The document table 4 is made of a transparent glass plate and is provided on the upper surface of the housing 2. A mirror 7 is disposed below the document table 4. The mirror 7 is provided in a state where the reflecting surface 7a is inclined toward the camera 6 side. The camera 6 is provided in a state inclined downward so as to face the mirror 7. The illumination device 5 is provided so as to be inclined upward so as to face the document table 4.

  In the reading apparatus 1 configured as described above, the light emitted from the illumination device 5 enters the document table 4 to illuminate the reading surface 3 a of the document 3 placed on the document table 4, thereby reading the document 3. The reflected light from the surface 3 a is reflected by the mirror 7 and enters the camera 6. In this way, the optical path of the reflected light on the reading surface 3a of the document 3 is bent by the mirror 7, so that the size of the reading device 1 can be reduced.

  FIG. 3 is a cross-sectional view of the lighting device 5. FIG. 4 is a front view of the illumination board 12. FIG. 5 is a front view showing a state in which the spacer 14 is attached to the illumination board 12. FIG. 6 is a front view showing a state in which the spacer 14 and the light guide 13 are attached to the illumination board 12. FIG. 7 is a perspective view of the spacer 14 as viewed from the front side (light guide 13 side).

  As shown in FIG. 3, the illumination device 5 includes an LED element (light source) 11, an illumination substrate 12 that holds the LED element 11, and a light guide 13 that guides light emitted from the LED element 11 in a predetermined direction. And a spacer (intermediate support) 14 interposed between the light guide 13 and the illumination board 12.

  As shown in FIGS. 4 to 6, the light guide 13 is formed in a bar shape long in one direction, and two light guides 13 are arranged in parallel in the vertical direction so that the longitudinal direction is substantially horizontal. As shown in FIG. 2, the two light guides 13 share the illumination area on the document table 4, and the upper light guide 13 near the document table 4 handles the illumination area near the illumination device 5. The lower light guide 13 far from the document table 4 is in charge of the illumination area far from the illumination device 5. The light guide 13 is made of a resin material having optical transparency such as acrylic resin (PMMA).

  Further, as shown in FIG. 3, the light guide 13 has an incident surface 15 on the side facing the LED element 11, and an output surface 16 on the side opposite to the incident surface 15. The incident surface 15 is formed in a planar shape orthogonal to the optical axis of the LED element 11. Although not shown here, a prism is formed on the incident surface 15, whereby the light amount distribution in the longitudinal direction of the light guide 13 can be optimized.

  On the other hand, the emission surface 16 is formed such that a cross section cut along a plane orthogonal to the longitudinal direction of the light guide 13 forms an arc shape. As a result, as shown in FIG. 2, the light emitted from the emission surface 16 can be limited to a predetermined angle range, and in particular, the light emitted from the light guide 13 can be prevented from entering the mirror 7. As will be described in detail later, when the light emitted from the light guide 13 is incident on the mirror 7, the light becomes stray light and is reflected by the mirror 7 and the document table 4 to be incident on the camera 6, thereby forming a read image. Causes whiteout.

  As shown in FIG. 4, a plurality of LED elements 11 are arranged on the illumination board 12 along the longitudinal direction of the light guide 13 so as to cover the LED elements 11 constituting the upper LED element array. The upper light guide 13 is disposed, and the lower light guide 13 is disposed so as to cover the LED elements 11 constituting the lower LED element array.

  In particular, in the present embodiment, the LED element 11 is provided with three types of light sources: a white LED element 11wl that emits white light, an infrared LED element 11ir that emits infrared light, and an ultraviolet LED element 11uv that emits ultraviolet light. ing. For example, an infrared LED element 11ir having a peak wavelength of 850 nm is used, and an ultraviolet LED element 11uv having, for example, a peak wavelength of 365 nm is used. Here, the white LED element 11wl, the infrared LED element 11ir, and the ultraviolet LED element 11uv are collectively referred to as the LED element 11 as appropriate.

  These LED elements 11 are selectively used according to the application, and the white LED element 11wl is turned on in a normal application for visual confirmation by an operator using a monitor. In the case of performing character recognition of a document in which characters are described on a background image using a passport or the like, the infrared LED element 11ir is turned on. Thereby, it is difficult to capture the background image, and the accuracy of character recognition can be improved. When acquiring an image drawn with fluorescent ink for preventing counterfeiting with a passport or the like, the ultraviolet LED element 11uv is turned on.

  The LED element 11 has a longitudinal direction of the light guide 13 so that an optimal light amount distribution can be obtained in consideration of the light distribution characteristics of the LED element 11 and the difference in refractive index between white light, infrared light and ultraviolet light. The positions are shifted in a direction orthogonal to the direction. The LED elements 11 are arranged symmetrically about the center line. Further, the LED element 11 is not disposed at a position corresponding to the central portion of the light guide 13 in the longitudinal direction, and the central portion of the light guide 13 does not have an optical function.

  As shown in FIG. 3, the spacer 14 supports the light guide 13 on the illumination board 12 with a predetermined space between the illumination board 12 and has a substantially flat plate shape (see FIG. 7). The light guide 13 is provided so as to extend over substantially the entire length (see FIG. 5). The spacer 14 is made of a resin material such as polycarbonate resin and is colored white.

  The spacer 14 is provided with an opening 21 through which the light emitted from the LED element 11 enters the incident surface of the light guide 13 so as to penetrate the spacer 14 in the thickness direction. The opening 21 is formed to have a tapered shape in which the inner diameter gradually increases from the illumination substrate 12 side toward the light guide 13 side. In particular, in the present embodiment, the opening 21 has a substantially truncated cone shape (conical shape) centering on the center line in the thickness direction of the spacer 14, that is, the optical axis direction of the LED element 11, and the plurality of LED elements 11. (See Fig. 5). Thereby, the light emitted from the LED element 11 can be collected in a predetermined angle range and incident on the light guide 13. In addition, the inner peripheral surface of the opening 21 is mirror-finished so that diffuse reflection on the inner peripheral surface of the opening 21 is suppressed.

  The LED element 11 is a chip-shaped surface-mount type, and is soldered onto the illumination board 12 on which a wiring pattern is formed, and is provided in a state of protruding from the main surface of the illumination board 12. In particular, in the white LED element 11wl and the infrared LED element 11ir, the hemispherical lens portion protrudes greatly from the main surface of the illumination board 12. For this reason, by providing the spacer 14 between the illumination board 12 and the light guide 13, the LED element 11 mounted on the illumination board 12 illuminates the light guide 13 without interfering with the light guide 13. The substrate 12 can be stably supported.

  The surface of the spacer 14 on the side of the illumination board 12 is recessed in the vicinity of the LED element 11, and the spacer 14 contacts the illumination board 12 at a portion other than the vicinity of the LED element 11. Further, in the white LED element 11wl and the infrared LED element 11ir, the lens portion is accommodated in the opening 21.

  As shown in FIG. 3, the illumination board 12 and the spacer 14 are fastened to each other by a screw 31. The screws 31 are inserted into the mounting holes 32 of the illumination board 12 and the mounting holes 33 provided at both ends in the longitudinal direction of the spacer 14 as shown in FIG. Further, as shown in FIG. 3, the spacer 14 is positioned on the illumination board 12 by fitting the projection 34 protruding to the illumination board 12 side of the spacer 14 into the mounting hole 35 of the illumination board 12. Thereby, the spacer 14 is connected with the illumination board | substrate 12 by a total of 4 points | pieces of 2 points | pieces at the edge part of a longitudinal direction.

  On the other hand, the spacer 14 and the light guide 13 are fastened to each other by a screw 36. As shown in FIG. 5, the screws 36 are provided at the mounting holes 37 provided at both ends in the longitudinal direction of the spacer 14 and at both ends in the longitudinal direction of the light guide 13 as shown in FIG. 6. Are inserted into the mounting holes 38 formed. Further, the spacer 14 and the light guide 13 are fastened to each other by a screw 39 at the center in the longitudinal direction. The screw 39 is inserted into the mounting hole 40 provided in the light guide 13 and the mounting hole 41 provided in the spacer 14 as shown in FIG. Thereby, the light guide 13 is connected with the spacer 14 at three points, that is, both ends and the center in the longitudinal direction.

  FIG. 8 is a cross-sectional view showing the progress of light in the spacer 14 according to the first embodiment. FIG. 9 is a side view illustrating a situation of stray light in the reading device 1 according to the first embodiment.

  As shown in FIG. 8, most of the light emitted from the LED element 11 is directly incident on the incident surface 15 of the light guide 13 and is emitted from the emitting surface 16 within a normal angle range. A part of the light emitted from the LED element 11 is incident on the inner peripheral surface of the opening 21, but since the inner peripheral surface of the opening 21 is mirror-finished, The incident light is specularly reflected. At this time, the opening 21 has a tapered shape, and thus the specularly reflected light is emitted from the emission surface 16 within a normal angle range as indicated by an arrow A.

  Thus, since the opening part 21 of the spacer 14 makes a taper shape, the light which LED element 11 emits can be condensed, and the utilization efficiency of the light which LED element 11 emits by this can be improved.

  In addition, diffuse reflection occurs along with specular reflection on the inner peripheral surface of the opening 21, and scattered light due to this diffuse reflection is generated, but this scattered light deviates from the normal angular range as indicated by arrows B and C. The light is emitted from the light guide 13 in the same direction. As shown in FIG. 9, the light deviating from the normal angle range is incident on the mirror 7, where it is reflected and becomes stray light. The stray light is reflected by the document table 4 and then reflected again by the mirror 7 and enters the camera 6.

  When stray light is incident on the camera 6 in this manner, a portion where the luminance is partially increased appears in the read image. In particular, when the amount of stray light incident on the camera 6 increases, so-called whiteout occurs in which the output of the image sensor reaches a saturation level. Since the gradation information disappears in the portion where the whiteout occurs, it is difficult to improve the image processing. The second embodiment described below solves the problem of whiteout due to such stray light.

  Note that whiteout usually indicates a case where the brightness (brightness) of a pixel becomes an upper limit when illuminated with white light, but the same state occurs with infrared light and ultraviolet light. When the original is read with each of the infrared LED element 11ir and the ultraviolet LED element 11uv turned on, the output of the image sensor reaches a saturation level, and the brightness of the pixel ( A state in which (brightness) is at the upper limit is also referred to as overexposure.

(Second Embodiment)
FIG. 10 is a cross-sectional view showing the progress of light in the spacer 52 according to the second embodiment. The points not particularly mentioned below are the same as in the first embodiment.

  In the illumination device 51 according to the second embodiment, the spacer (intermediate support) 52 is formed of a light-transmitting material. As a material for forming the spacer 52, it is preferable to use a resin having a light transmittance of 80% or more. Specifically, an acrylic resin, particularly a methacrylic resin (PMMA), a polycarbonate resin, and a cycloolefin-based resin are used. Is preferred. The material of the spacer 52 will be described in detail later.

  Like the opening 21 of the first embodiment, the inner peripheral surface of the opening 53 is mirror-finished so that diffuse reflection on the inner peripheral surface of the opening 53 is suppressed. For this reason, when the light emitted from the LED element 11 is incident on the inner peripheral surface of the opening 53, specular reflection mainly occurs. At this time, the opening 53 has a tapered shape. As shown, the light is emitted from the light guide 13 within a normal angle range.

  Further, since the spacer 52 is formed of a light-transmitting resin material and has a refractive index larger than that of air, the total reflection does not occur on the inner peripheral surface of the opening 53 and the light enters the inner peripheral surface of the opening 53. A part of the light is reflected, and the remaining part is transmitted from the inner peripheral surface of the opening 53 and proceeds to the inside of the spacer 52 as indicated by arrows B and C. Further, although diffuse reflection also occurs on the inner peripheral surface of the opening 21, as shown by an arrow D, a part of the scattered light due to the diffuse reflection is transmitted from the inner peripheral surface of the opening 53 and proceeds to the inside of the spacer 52. .

  Here, as described above, the scattered light due to the diffuse reflection on the inner peripheral surface of the opening 53 is the main cause of stray light incident on the camera 6 (see FIGS. 8 and 9). Increasing the proportion of light (transmission component) transmitted from the inner peripheral surface and proceeding to the inside of the spacer 52 and decreasing the proportion of light diffusely reflected on the inner peripheral surface of the opening 53 (reflection component) makes it incident on the camera 6. Stray light can be suppressed.

  On the other hand, the reflection does not depend on the incident angle but depends on the transmittance of the substance. That is, the ratio between the transmissive component and the reflective component is determined by the transmittance of the material forming the spacer 52. Therefore, when a material having a high transmittance is used for the spacer 52, the ratio of the transmission component can be increased and the ratio of the reflection component can be suppressed to a low level, thereby suppressing the stray light incident on the camera 6. Reflection can be divided into two types: specular reflection and diffuse reflection. By improving (smoothing) the surface properties of the inner peripheral surface of the opening 53, the ratio of specular reflection is increased, and the ratio of diffuse reflection is increased. As described above, it is possible to suppress scattered light due to diffuse reflection, which is the main cause of stray light.

  Note that most of the light that is specularly reflected by the inner peripheral surface of the opening 53 is emitted from the light guide 13 in a normal angle range, but the light due to the specular reflection travels in a direction outside the normal angle range and stray light. It may be the cause of. However, the proportion of light that becomes stray light due to specular reflection is originally low, and it becomes stray light due to the complex repetition of specular reflection, so the light is greatly attenuated during the specular reflection, so stray light due to specular reflection is a problem. It will not be.

  Next, a resin material for forming the spacer 52 will be described.

  FIG. 11 is a characteristic diagram showing the transmittance according to the wavelength for each resin. Here, the transmittance of methacrylic resin (PMMA), cycloolefin resin, polycarbonate resin, nylon resin, and ABS resin is shown. Each resin is transparent and does not contain a colorant or an ultraviolet absorber.

  The light transmittance varies depending on the wavelength. In this embodiment, the white LED element 11wl, the infrared LED element 11ir, and the ultraviolet LED element 11uv are used as the light source, but the transmittance is in the ultraviolet light region among the white light, infrared light, and ultraviolet light. The lowest. On the other hand, as described above, in order to suppress scattered light due to diffuse reflection that causes stray light, it is necessary to increase the light transmittance. Therefore, the transmittance condition required for the material of the spacer 52 is ultraviolet light. It becomes the most severe. That is, if the transmittance condition can be satisfied with ultraviolet light, sufficient transmittance can be obtained with white light and infrared light.

  Therefore, when selecting the material of the spacer 52, the material is selected based on the transmittance of ultraviolet light. Some ultraviolet LED elements have various peak wavelengths. Here, the transmittance condition is determined by ultraviolet light having a wavelength of 365 nm. The transmittance of ultraviolet light with a wavelength of 365 nm is about 85% for methacrylic resin, about 90% for cycloolefin resin, about 80% for polycarbonate resin, about 70% for nylon resin, and about 55% for ABS resin. ing.

  Here, the spacer 52 was formed of several types of resins, and an experiment was conducted to examine the occurrence of whiteout. Based on the occurrence of whiteout in this experiment, the conditions for the transmittance required for the spacer 52 were examined. .

  In the experiment, for each spacer 52 formed of methacrylic resin, nylon resin and ABS resin, the occurrence of whiteout in ultraviolet light having a wavelength of 365 nm was examined. Specifically, a tracing paper sandwiched between clear files was placed on the document table, captured by a camera to obtain a read image, and pixels that caused whiteout in the read image were examined.

  As a result of this experiment, in the methacrylic resin having a transmittance of about 85%, no pixel causing whiteout in the read image was detected. On the other hand, in the case of nylon resin with a transmittance of about 70% and ABS resin with a transmittance of about 55%, pixels that are whiteout in the read image were detected.

  From this experimental result, if the transmittance of ultraviolet light with a wavelength of 365 nm is about 85% or more, whiteout can be completely prevented. In consideration of the occurrence of whiteout, if the transmittance is 80% or more, a practically sufficient effect can be obtained for suppressing the occurrence of whiteout.

  When a resin material for forming the spacer 52 is selected based on the transmittance condition, a resin satisfying 80% or more of the transmittance of ultraviolet light having a wavelength of 365 nm is a methacrylic resin, a polycarbonate resin, or a cycloolefin resin. In addition, when the spacer 52 is formed of these resins, generation of whiteout can be suppressed by any of white light, infrared light, and ultraviolet light.

  Here, the resin material for forming the spacer 52 is selected on the basis of the ultraviolet light having the strictest transmittance conditions. However, this is a case where a light source that emits ultraviolet light is provided, and a light source that emits ultraviolet light. For example, when only a light source that emits white light is selected, a resin material that forms the spacer 52 is selected based on white light, that is, a material that has a transmittance of 80% or more with white light is selected. That's fine.

  In this way, by using a material having a light transmittance of 80% or more for the spacer 52, whiteout caused by stray light can be eliminated, thereby improving accuracy of software processing such as character recognition. it can. In addition, stray light cannot be completely eliminated, and a portion with high luminance may appear in the read image. However, the amount of stray light is suppressed to such an extent that the output of the image sensor of the camera 6 does not reach a saturation level. In this case, gradation information is not lost even in a high-luminance part in the read image, and can be improved by image processing.

  In addition, when an acrylic resin is used as the material of the spacer 52, the acrylic resin is excellent in workability, and therefore the polishing accuracy can be increased in the mirror finishing process of the inner peripheral surface of the opening 53. Therefore, the opening 53 The ratio of diffuse reflection on the inner peripheral surface of the light source can be reduced, thereby increasing the light collection rate and improving the light utilization efficiency.

  FIG. 12 is a side view illustrating a situation of stray light in the reading apparatus according to the second embodiment. As shown in FIG. 10, the light that passes through the inside of the spacer 52 without being reflected by the inner peripheral surface of the opening 53 finally passes outside from the side surface of the spacer 52, as shown in FIG. 12. It may cause stray light.

  However, since the camera 6 is disposed toward the mirror 7 and the light emitted from the side surface of the spacer 52 does not enter the angle of view α of the camera 6, it does not enter the camera 6 directly. Further, since the mirror 7 is located on the light emitting side of the illumination device 51, the light emitted from the side surface of the spacer 52 does not enter the mirror 7, and is reflected by the mirror 7 and the document table 4 to be reflected by the camera. 6 does not enter.

  Further, the light that passes through the spacer 52 and exits to the outside is not used for the purpose of illuminating the document. As a result, the light is wasted, resulting in a decrease in light use efficiency. It does not surpass the merit of reducing overexposure.

  In addition, in this embodiment, as shown in FIG. 4, it has three types of light sources (white LED element 11wl, infrared LED element 11ir, ultraviolet LED element 11uv) which each emit white light, infrared light, and ultraviolet light. Although the present invention is configured, the present invention is not limited to this, and any one or two of the above three types of light sources, or a configuration having other types of light sources is also possible. In this case, the material of the spacer 52 may be selected based on the light having the lowest transmittance among the light emitted from the plurality of types of light sources.

  In the present embodiment, as shown in FIG. 2, the optical path of the reflected light on the reading surface 3 a of the document 3 is bent by the mirror 7, thereby reducing the size of the reading device 1. It is also possible to adopt a configuration without providing the above. However, as described above, stray light incident on the camera 6 is often generated when the light emitted from the light guide 13 is reflected by the mirror 7 in a direction out of the normal angle range. The configuration according to the second embodiment that solves the problem of overexposure due to is particularly effective when the mirror 7 is provided.

  In the present embodiment, the entire intermediate support (spacer 52) is formed of a light-transmitting material. However, in the present invention, light incident on the inner peripheral surface of the opening is the intermediate support. In order to achieve such a state, at least a portion extending from the inner peripheral surface of the opening to a predetermined range is required to transmit light. A structure formed of a material having properties may be used.

  In the present invention, the wavelength of the light source (white LED element 11wl, infrared LED element 11ir, ultraviolet LED element 11uv) is not particularly limited, but in particular, ultraviolet light degrades the resin material forming the spacer. It is preferable to adopt a wavelength that does not cause deterioration of the resin material. For example, ultraviolet light having a wavelength of 315 nm causes remarkable deterioration of the acrylic resin. It is preferable to use one that emits 365 nm ultraviolet light.

  The illumination device according to the present invention and the reading device provided with the illumination device can improve the utilization efficiency of light emitted from the light source, suppress the generation of stray light, and further, white light generated when the stray light enters the imaging device. This has the effect of reliably preventing jumps, and is useful as an illuminating device that illuminates the reading surface of a document and a reading device including the same.

DESCRIPTION OF SYMBOLS 1 Reading apparatus 3 Original, 3a Reading surface 4 Original stand 5 Illuminating device 6 Camera 7 Mirror, 7a Reflecting surface 11 LED element (light source)
11wl white LED element 11ir infrared LED element 11uv ultraviolet LED element 12 illumination substrate 13 light guide 14 spacer (intermediate support)
15 entrance surface 16 exit surface 21 opening 51 illumination device 52 spacer (intermediate support)
53 opening

Claims (8)

A light source;
A substrate for holding the light source;
A light guide that guides light emitted from the light source in a predetermined direction;
An intermediate support interposed between the light guide and the substrate,
The intermediate support has an opening through which the light emitted from the light source enters the incident surface of the light guide, and the opening extends from the substrate side toward the light guide. An illuminating device characterized in that it is formed into a tapered shape with an gradually increasing inner diameter.   The lighting device according to claim 1, wherein the intermediate support is made of a light-transmitting material.   The lighting device according to claim 2, wherein the intermediate support is made of a material having a light transmittance of 80% or more.   The lighting device according to claim 3, wherein the intermediate support is formed of any one of a methacrylic resin, a polycarbonate resin, and a cycloolefin resin. The light guide is formed in a bar shape long in one direction,
A plurality of the light sources are arranged on the substrate side by side in the longitudinal direction of the light guide,
The said intermediate support body is provided so that it may extend over the substantially full length of the said light guide, and the said opening part was opened for every said some light source. 4. The lighting device according to any one of 4. The lighting device according to any one of claims 1 to 5,
A transparent platen on which the document is placed;
A reading apparatus comprising: an imaging device that images a reading surface of the original illuminated by the illumination device via the document table.   The reading apparatus according to claim 6, further comprising a mirror that reflects reflected light from the reading surface of the document and guides the reflected light to the imaging apparatus.   The imaging device and the illumination device are arranged so that light transmitted through the intermediate support made of a light-transmitting material and radiated to the outside from the side surface does not enter the angle of view of the imaging device. The reading device according to claim 6 or 7, wherein the reading device is configured.

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