JP2013081075A - Reading apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reading apparatus capable of taking a picture of the entire image at a generally uniform brightness while preventing the light intensity reduction in a peripheral area even when being subjected to an influence of lenses on an imaging device.SOLUTION: In an image taken by a camera, the light intensity in a peripheral area is generally reduced due to an influence of lenses. In order to increase the light intensity in the peripheral area, LED elements are disposed at a position closer to the end of a glass board (original platen) to increase the illuminance in the peripheral area; and prisms 21-23 having a concave slope are provided on the incident surfaces 8b and 9b of the light guide to refract the output light in the edge area toward a central area. This makes it possible to illuminate the edge area of the glass board at a higher illuminance. By illuminating the peripheral area with a high illuminance to eliminate light intensity reduction in the peripheral area on the image plane due to the influence of the lenses, the image can be taken while illuminating the entire glass board with a generally uniform brightness.

Description

  The present invention relates to a reading device including an illumination device including a light emitting element and a light guide.

  2. Description of the Related Art Conventionally, in a reading device such as a copying machine or a scanner, an object to be read is placed on a platen made of a glass plate or the like, and an image pickup device (camera) is irradiated by illuminating the surface to be read from below the platen with a lighting device. ). As an illumination device of such a reading device, there is one that uses an LED as a light source. For example, an LED is provided at one end in a longitudinal direction of a rod-shaped light guide and a light reflecting portion that extends in the longitudinal direction of the light guide The light to be read is emitted from the LED into the light guide body in a direction perpendicular to the longitudinal direction by the light reflecting portion to irradiate the surface to be read as a linear light source (see, for example, Patent Document 1). ).

JP 2010-146868 A

  The conventional reading apparatus uses a so-called line sensor as an image reading means, and in response to this, linear light is emitted from the light guide, and the reading object is placed in the longitudinal direction of the linear light source ( The portion irradiated with the linear light source is imaged by moving in a direction (sub-scanning direction) orthogonal to the main scanning direction. On the other hand, there is a reading apparatus in which the entire surface of the document table is imaged at once by a camera or the like as an imaging apparatus.

  Such a reading apparatus that captures an image of the entire surface of the document table at one time is effective for use as an OCR for authenticating a passport or a license. In an image taken by a camera as an imaging device, the amount of light gathers in the central portion of the imaging surface due to the influence of the imaging lens provided on the front side of the imaging surface, and the light amount in the peripheral portion decreases, thereby making the peripheral portion clear. There is a problem that video cannot be obtained.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is that the amount of light in the peripheral portion does not decrease even under the influence of the lens in the imaging device. It is an object of the present invention to provide a reading apparatus that can shoot the entire surface of an image with substantially uniform brightness.

  The reading device according to the present invention is disposed in a transparent reading object placing unit on which a reading object is placed, and obliquely upward to illuminate the reading object placed on the reading object placing unit. A reading device comprising: an illuminating device; and an imaging device that images the reading object illuminated by the illuminating device, wherein the illuminating device emits light from the light emitting element and reads the light from the light emitting element. A rod-shaped light guide for guiding it toward the mounting unit, and the light guide has a direction of emitting light from the light emitting element toward the end of the reading target mounting unit. The optical path refracting unit is configured to be refracted on the center side of the mounting unit.

  According to the present invention, when the light emitting element is arranged near the end of the reading object placing portion, the light traveling from the light emitting element toward the end near the end of the reading object placing portion is refracted toward the central portion. Since the optical path refracting portion is provided in the light guide, the portion near the end of the reading object placing portion can be irradiated with higher illuminance. As a result, the peripheral portion is irradiated with high illuminance in response to a decrease in the amount of light in the peripheral portion of the image screen due to the influence of the lens, so that the entire surface of the reading object placing portion is imaged to have substantially uniform brightness. be able to.

1 is an overall perspective view of a reading apparatus to which the present invention is applied. Side view showing the main part inside the reader (A) is a principal part perspective view of an upper light guide, (b) is a principal part perspective view of a lower light guide. Front view of illumination board showing the arrangement of LED elements Explanatory drawing corresponding to FIG. 2 showing the optical path of the emitted light (A) is sectional drawing which shows the external shape of the output surface of an upper light guide, (b) is sectional drawing which shows the external shape of the output surface of a lower light guide Characteristic diagram showing the light distribution of white LED elements and infrared LED elements in a graph Explanatory drawing which shows the state which shifted the position of the infrared LED element Explanatory drawing which shows distribution of irradiation range by infrared LED element Explanatory drawing which shows the state which shifted the position of the ultraviolet LED element Explanatory diagram showing the illuminance distribution in the image due to the effect of the camera lens (A) is explanatory drawing which shows the optical path refractive part provided in the upper side light guide, (b) is explanatory drawing which shows the optical path refractive part provided in the lower side light guide. Explanatory drawing which shows distribution of the range which raised the illumination intensity by a white LED element

  According to a first aspect of the present invention, there is provided a transparent reading object placing unit on which a reading object is placed, and the reading object placed on the reading object placing unit. A reading apparatus comprising: an illuminating device that illuminates obliquely upward; and an imaging device that images the reading object illuminated by the illuminating device, wherein the illuminating device includes a light emitting element and the light emitting element. And a rod-shaped light guide for guiding the light from the light-emitting element toward the reading object mounting portion, and the light guide travels from the light emitting element toward the end of the reading object mounting portion. The optical path refracting section is configured to refract the light emitting direction toward the center of the reading object placing section.

  According to this, when the light emitting element is arranged near the end of the reading object placing portion, the light path refraction that refracts light from the light emitting element toward the portion near the end of the reading object placing portion toward the center side. Since the portion is provided on the light guide, it is possible to irradiate the portion closer to the end of the reading object placing portion with higher illuminance. As a result, the peripheral portion is irradiated with high illuminance in response to a decrease in the amount of light in the peripheral portion of the image screen due to the influence of the lens, so that the entire surface of the reading object placing portion is imaged to have substantially uniform brightness. be able to.

  According to a second aspect of the present invention, in the first aspect of the invention, the optical path refracting portion is formed by a slope that is concave or convex on the incident surface of the light guide.

  According to this, since the light incident on the light path refracting part can be refracted by the light path refracting part provided on the incident surface of the light guide, the light can be directed in any direction by simply changing the form of the light path refracting part. Can be refracted.

  Further, in a third aspect based on the first aspect or the second aspect, at least two rows of the light guide and the light emitting element are provided at positions that are in a perspective relationship with respect to the reading object placement unit, A refractive index of the optical path refracting portion provided in the light guide in a row close to the reading object placement portion is configured to be larger than that in a far row.

  According to this, since the refractive index of the optical path refracting part provided on the light guide near the reading object mounting part is increased, the emitted light can be spread widely with a large refractive index. Since it is close to the portion, it is possible to prevent the irradiation range of the light emitted from the light guide from becoming narrow.

  In a fourth aspect based on the first to third aspects, the light guide diffuses light directed from the light emitting element toward the central portion of the reading object placing portion toward the central portion. The second optical path refracting unit is included.

  According to this, when the imaging device is disposed corresponding to the central portion in the longitudinal direction of the light guide, the light traveling toward the central portion side of the reading object placing portion is dispersed to the central portion side. In addition, it is possible to prevent the light from being biased near the imaging device and to prevent a decrease in illuminance in the portion directly above the imaging device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall perspective view showing an example of a reading apparatus according to the present invention. The reading device 1 has a substantially rectangular parallelepiped housing 2 having a hollow inside and is used on a desk or the like. In the following description, the vertical direction is assumed to be in a state where the reader 1 is placed on a desk.

  FIG. 2 is a side view showing a main part of the reading apparatus according to the present invention. As shown in FIG. 2, a glass plate 3 as a reading object placing portion is provided on the upper surface of the housing 2 over substantially the entire surface. For example, a passport 4 as an object to be read is placed on the upper surface of the glass plate 3 with the read surface 4 a facing the glass plate 3.

  Inside the housing 2, a main substrate 5 is disposed in the vicinity of the bottom surface of the housing 2 below the glass plate 3. The main board 5 is provided with a control circuit, a drive circuit, and the like (not shown) of the reading device 1. An illuminating substrate 6 is disposed at an upper position on one end side of the main substrate 5 and is inclined upward so as to face the back surface of the glass plate 3. The support structure for fixing the substrates 5 and 6 to the housing 2 may be a known screwing structure and is not shown.

  As shown in FIG. 4, the LED board 7 in which a plurality of LED elements as light emitting elements are arranged is arranged in the upper and lower rows on the illumination board 6, and as shown in FIG. 3, each LED row 7 is arranged. Each of the rod-shaped light guides (upper light guide 8 and lower light guide 9. These are collectively referred to as “light guides 8 and 9” hereinafter so as to cover the emission surfaces of the respective LED elements. And the lighting device is configured in this manner. Between the illumination board 6 and the light guides 8 and 9, resin spacers 16 each having an opening corresponding to each LED element of the LED array 7 arranged on the illumination board 6 are arranged. ing. The wall surface of the opening provided in the spacer 16 has a tapered shape spreading in the light emitting direction of the LED element, and the light emitted from the LED element is reflected by this wall surface and efficiently guided into the light guides 8 and 9. It is burned.

  FIG. 3A is a perspective view of a main part of the upper light guide 8, and FIG. 3B is a perspective view of a main part of the lower light guide 9. As shown in FIG. 3A, the upper light guide 8 has a shape in which the left and right sides thereof are line-symmetrical at the central portion in the longitudinal direction. 3 (b) showing the front view of the lower light guide 9 as well, which is screwed to the illumination board 6 with the spacers 16 sandwiched between the mounting holes 8a provided at the locations. The illumination board 6 has a shape that is line symmetric as shown in FIG. 5 and has spacers 16 sandwiched between the mounting holes 9a provided at three locations in the longitudinal center and both ends. (Each screw is not shown). In this way, the light guides 8 and 9 are each configured as a single body. However, the LED array 7 is disposed at a position corresponding to the central portion in the longitudinal direction of each light guide 8 and 9 on the illumination board 6. In addition, since the portion does not have an optical function, the light guides 8 and 9 may be divided at the central portion in the longitudinal direction. In this way, electrical components can be arranged on the illumination board 6 corresponding to the divided portion, so that the mounting efficiency of the illumination board 6 is improved.

  As shown in FIG. 1 and FIG. 2, an image of the surface to be read 4 a of the passport 4 placed on the upper surface of the glass plate 3 is imaged at the center in the longitudinal direction of the upper light guide 8 and on the upper side thereof. A camera 13 as an imaging device is provided, and a reflecting mirror 14 for bending the optical path of the image of the read surface 4 a toward the camera 13 is provided at a position facing the camera 13. The reason for bending the optical path in this manner is effective for making the reading device 1 compact.

  FIG. 4 is a front view of an illumination board showing the arrangement of LED elements according to the present invention. FIG. 4 shows the arrangement of the LED elements of each LED row 7 arranged on the illumination board 6. In the portion corresponding to the upper light guide 8, two ultraviolet LED elements UV 1 and UV 2 for ultraviolet rays, infrared rays are provided from the center to the right side along the upper reference line L 1 in the longitudinal direction of the upper light guide 8. Infrared LED element IR1, white LED element WL1 for visible light, two ultraviolet LED elements UV3 and UV4, infrared LED element IR2, and white LED element WL2 are arranged in this order. Moreover, each LED element of the LED row 7 of the left side part from the center part of the figure of the upper side light guide 8 is arrange | positioned left-right symmetrically with respect to the said right side.

  Similarly, in the portion corresponding to the lower light guide 9, four ultraviolet LED elements UV 5. UV6 / UV7 / UV8, infrared LED element IR3, white LED element WL3, ultraviolet LED element UV9, and white LED element WL4 are arranged in this order. Further, the LED elements of the LED row 7 in the left part from the center of the lower light guide 9 in the figure are also arranged symmetrically with respect to the right side.

  First, when irradiating with white light suitable for visual confirmation by an operator on a monitor or obtaining an image of a surface to be read like an image scanner, the glass plate 3 is formed by white LED elements WL1 and WL3 on the center side. It is desirable to illuminate the entire (original surface) as uniformly as possible. In this case, unevenness can be reduced if the light emitted from the white LED elements WL1 and WL3 is sufficiently diffused by the light guides 8 and 9.

  FIG. 5 is an explanatory view corresponding to FIG. 2 showing the optical path of the outgoing light, FIG. 6A is a cross-sectional view showing the outer shape of the outgoing face of the upper light guide 8 in the present invention, and FIG. 3 is a cross-sectional view showing an outer shape of an emission surface of the light body 9. FIG. Hereinafter, the path of light emitted from each of the light guides 8 and 9, particularly the stray light generation process, will be described with reference to FIG. 5, and the configuration for preventing stray light generation will be described with reference to FIG. 6. As described above, when diffusing light for the purpose of uniform illumination, the diffusion range can be simply increased by adjusting the curved surfaces of the exit surfaces 8d and 9d of the light guides 8 and 9, If the diffusion becomes excessive, that is, if the outgoing direction of the outgoing light from the outgoing faces 8d and 9d is excessively widened, as shown by the broken line arrow Lm1 and the two-dot chain line arrow Lm2 in FIG. Part of the emitted light travels toward the reflecting mirror 14, and light that is reflected by the reflecting mirror 14 and then travels toward the glass plate 3 is generated. Such light Lm1 and Lm2 may be reflected by the lower surface 3a of the glass plate 3 and reflected by the reflecting mirror 14 to be directed to the camera 13 in some cases.

  The stray light due to the reflection may be avoided by adjusting the positional relationship among the light guides 8 and 9, the camera 13, and the reflecting mirror 14. When the irradiation is to be performed as uniformly as possible, the design of the positional relationship is complicated.

  On the other hand, in this invention, it respond | corresponds with the shape of the output surface 8d * 9d of the light guides 8 * 9. As shown in FIG. 6A, the outline forming the exit surface 8d in the cross section viewed from the longitudinal direction of the upper light guide 8 is formed by an arc having a radius Ra in the range A on the reflecting mirror 14 side. In the range B on the glass plate 3 side, an arc having a radius Rb is formed. The radius Ra is smaller than the radius Rb and is asymmetric with respect to the optical axis CL of the white LED element WL1. Similarly, the outer shape forming the exit surface 9d in the cross section viewed from the longitudinal direction of the lower light guide 9 is an arc having a radius Rc in the range C on the reflecting mirror 14 side, as shown in FIG. 6B. In the range D on the glass plate 3 side, an arc having a radius Rd is formed. The radius Rc is smaller than the radius Rd and is asymmetric with respect to the optical axis CL of the white LED element WL3.

  Thereby, the emission directions of the light Lw1 and Lw2 (solid arrows in FIG. 5) that are closest to the reflecting mirror 14 of the emitted light emitted from the ranges A and C of the emission surfaces 8d and 9d of the light guides 8 and 9 Can be tilted and emitted so as to return to the light Lm1 and Lm2 by angles θ1 and θ2, respectively, inside the light guides 8 and 9. The sizes of the angles θ1 and θ2 can be arbitrarily changed according to the sizes of the radii Ra and Rc, and the emission directions of the lights Lw1 and Lw2 can be further away from the reflecting mirror 14 by making the diameters smaller. . In this way, it is possible to eliminate the light that enters the camera 13 due to the reflection as described above, and it is possible to prevent the image of the camera 13 from being overexposed.

  Then, the radius Ra / Rc is set so as to secure the emission angle to be the light Lw1 / Lw2, and the ranges A / C and the radii Rb / Rd and the radii Rb / Rd and the glass plate 3 have uniform illuminance. Each range B and D is set. In this way, by combining arc surfaces having different curvatures, the light (Lm1 and Lm2) that directly hits the reflecting mirror 14 after being emitted from the exit surfaces 8d and 9d of the light guides 8 and 9 is eliminated. 3 can ensure a uniform illuminance distribution.

  In the above embodiment, the exit surface 8d (9d) is formed with two different radii Ra · Rb (Rc · Rd). However, the exit surface 8d (9d) is a combination of three or more different radii, that is, a non-single arc surface. The surface 8d (9d) may be formed. In any case, it is preferable to form a curved surface that smoothly changes from one radius to the other at the boundary between different radii.

  In each of the exit surfaces 8d and 9d, for example, when the respective average radii are obtained from the weighted average of the radii Ra and Rb (Rc and Rd) using the ratio A: B (C: D) of each range, The average radius of the exit surface 9d of the lower light guide 9 is made smaller than the average radius of the exit surface 8d of the upper light guide 8. Since the lower light guide 9 is farther than the glass plate 3 than the upper light guide 8, the irradiation range from the lower light guide 9 is further expanded in the case of the same radius, as described above. By reducing the average radius of the exit surface 9d of the lower light guide 9, the irradiation range can be narrowed, and even if there is a difference in perspective with respect to the glass plate 3 between the light guides 8 and 9, the illuminance It is possible to prevent non-uniform illuminance distribution due to the spread of the range.

  In the present embodiment, as shown in FIG. 4 above, among the plurality of LED elements constituting each LED row 7, a shift is made in a direction orthogonal to the reference lines L 1 and L 2 on the surface of the illumination substrate 6. Some are arranged. Here, the reference line L1 is orthogonal to the optical axis CL of the white LED element WL1, and the reference line L2 is orthogonal to the optical axis CL of the white LED element WL2. Although FIG. 4 shows an embodiment, a specific arrangement will be described below. The extending direction of the reference line L1 (L2) as the arrangement direction of the LED elements WL, IR, and UV is the X direction, and the reference line L1 (L2) is viewed from the arrangement direction of the LED elements WL, IR, and UV. A direction perpendicular to the surface and along the surface of the illumination substrate 6 is defined as a Y direction.

  First, a shift (−d shown in FIG. 4) on the lower side in the Y direction (the direction away from the glass plate 3) with respect to the reference line L1 of each LED element corresponding to the upper light guide 8 will be described. Note that d is an arbitrary shift amount. The white LED element W on the center side is positioned on the reference line L1, and the infrared LED element IR1 as the second light emitting element provided next to the white LED element WL1 is on the lower side (-d in FIG. 4). The outer infrared LED element IR2 is positioned on the line. The four ultraviolet LED elements UV1 to UV4 are shifted in different sizes on the lower side.

  In the deviation in the Y direction in FIG. 4 with respect to the reference line L2 of each LED element corresponding to the lower light guide 9, the white LED element WL3 on the center side is positioned on the line, and the adjacent infrared LED element IR3 is also Located on the line. The five ultraviolet LED elements UV5 to UV9 are shifted in different sizes on the lower side.

  The LED elements are arranged in this way even when white light, infrared light, and ultraviolet light having different light distribution characteristics are used by using the same light guides 8 and 9 (emission surfaces 8d and 9d). This is to enable the glass plate 3 to be irradiated with a substantially uniform illuminance distribution, and each shift amount is set to an appropriate value so as to obtain a substantially uniform illuminance distribution.

  The outermost white LED elements WL2 and WL4 are arranged in correspondence with the protrusions 11 and 12 provided at both ends in the longitudinal direction of the light guides 8 and 9, as shown in FIG. ing. The protrusions 11 and 12 are provided with rear surface portions 11a and 12a on the outer side in the longitudinal direction of the light guides 8 and 9, and the second emission surfaces 11b and 12b in a rearward inclined state on the inner side in the longitudinal direction of the light guides 8 and 9. Is provided. Light emitted from the white LED elements WL2 and WL4 enters the protrusions 11 and 12, and is further reflected by the inner surfaces of the back surface portions 11a and 12a, and is directed from the second light emitting surfaces 11b and 12b to the central portion side of the light guides 8 and 9. The light is emitted obliquely toward. Thereby, it can respond to authenticity determination, such as a passport to which OVI (Optically Variable Ink) which changes color according to the difference in irradiation angle is given.

  The arrangement of the LED elements other than the white LED elements WL2 and WL4 will be described. First, the white LED elements WL1 and WL3 are arranged so that the illuminance distribution of white light on the glass plate 3 is substantially uniform.

  The light guides 8 and 9 have a kamaboko-shaped cross section extending along the reference lines L1 and L2, and the illuminance distribution is uniformized with respect to the bending direction (Y direction) of the exit surfaces 8a and 9a as described above. Although it can be easily realized by a combination of arc surfaces having a plurality of radii, the illuminance distribution in the extending direction of the reference lines L1 and L2 cannot be adjusted by the curvature of the exit surfaces 8d and 9d. Therefore, according to the difference in the spread of the emitted light depending on the distance of the light guides 8 and 9 with respect to the glass plate 3, in the present embodiment, the white LED element WL1 corresponding to the upper light guide 8 as shown in FIG. Is arranged closer to the center of the glass plate 3, and the white LED element WL3 corresponding to the lower light guide 9 is arranged outside the white LED element WL1.

  FIG. 7 is a characteristic diagram showing the light distribution of the white LED element and the infrared LED element of the present invention in a graph. Hereinafter, the infrared LED elements IR1 to IR3 will be described. The light distribution characteristic of the infrared LED element IR is narrower than the light distribution characteristic (two-dot chain line) of the white LED element WL as shown by the solid line in FIG. 7, and the wavelength of the infrared light is visible light (white light). Therefore, infrared light is less likely to be refracted at the medium boundary than white light. Therefore, when the same lens (prism) is used, infrared light can be irradiated only in a narrow range with respect to white light. In addition, as an irradiation range, both the curved direction and the linear direction (longitudinal direction of the light guides 8 and 9) of the output surfaces 8d and 9d of the light guides 8 and 9 are targets.

  As described above, the exit surfaces 8d and 9d of the light guides 8 and 9 are formed in a shape that prioritizes the uniform illumination distribution by the white LED elements WL, and each of the light guides 8 and 9 is used. The arrangement of the infrared LED elements IR1 to IR3 will be described below.

  In the upper light guide 8, the infrared LED element IR is arranged next to the white LED element WL so as to be basically at the same position as the white LED element WL. Thereby, the center side of the glass plate 3 is irradiated by the infrared LED element IR1 inside the light guide 8 in the longitudinal direction, and the side edge side of the glass plate 3 is irradiated by the infrared LED element IR2 outside the longitudinal direction of the light guide 8. Irradiate.

  As described above, the outer infrared LED element IR2 of the upper light guide 8 is disposed on the reference line L1, but the inner infrared LED element IR1 is located below the reference line L1. A fixed amount is shifted.

  FIG. 8 is an explanatory diagram showing a state in which the position of the infrared LED element is shifted. As described above, the emission direction of the emitted light from the upper light guide 8 by the infrared LED elements IR1 and IR2 arranged in a shifted manner is shown in FIG. In FIG. 8, the solid line indicates the inner infrared LED element IR1 shifted downward from the reference line L1 (that is, the side where the radius of the emission surface 8d is small), and the two-dot chain line indicates the outer side located on the reference line L1. The infrared LED element IR2 is shown, and each outgoing light is indicated by an arrow. As shown in the figure, the upper side of the emitted light from both infrared LED elements IR1 and IR2 is emitted in substantially the same direction, but the lower side of each emitted light is the infrared LED element IR2 arranged on the reference line L1. Is spread out downward and emitted.

  In the upper range (radius Rb) of the exit surface 8d, the radius is larger than the lower range (Rb> Ra) and faces the glass plate 3 as described above. The change in the emission direction at 8d is not so great. The two infrared LED elements IR1 and IR2 are in a relative translational relationship with respect to the incident surface 8b, and the optical axes of the emitted lights from the infrared LED elements IR1 and IR2 are parallel to each other.

  FIG. 9 is an explanatory diagram showing the distribution of the irradiation range by the infrared LED element. Hereinafter, the irradiation ranges S1 and S2 on the glass plate 3 by the infrared LED elements IR1 and IR2 will be described with reference to FIG. In addition, an irradiation range is demonstrated using the vertical and horizontal direction in the figure of the glass plate 3. FIG.

  The irradiation range S2 by the infrared LED element IR2 arranged on the reference line L1 is elongated as shown in FIG. On the other hand, since the irradiation range S1 by the infrared LED element IR1 arranged to be shifted downward from the reference line L1 is narrowed to the upper side as described above, the light guide 8 of the glass plate 3 as shown in the figure. It becomes the range shortened in the vertical direction. The infrared LED element IR1 is arranged near the center of the light guide 8 in the longitudinal direction, and the irradiation range S1 is the central portion in the horizontal direction of the glass plate 3, so that the infrared LED element IR1 alone is the glass plate 3. Illuminance decreases for the vicinity of the side edge in the horizontal direction.

  In order to compensate for this, the vicinity of the side edge of the glass plate 3 is irradiated by the outer infrared LED element IR2. The outer infrared LED element IR2 is arranged on the reference line L1, and the emission light emitted from the emission surface 8d spreads downward as shown in FIG. 8, so that the irradiation range is as shown in FIG. Thus, the vicinity of the side edge of the glass plate 3 can be irradiated over the entire length in the vertical direction.

  On the other hand, since the infrared LED element IR1 arranged corresponding to the upper light guide 8 irradiates the front side (near the upper light guide 8) of the glass plate 3, the rear side (upper guide) of the glass plate 3 is irradiated. The illuminance on the side far from the light body 8 is reduced. Therefore, the rear side of the glass plate 3 is irradiated by the infrared LED element IR3 arranged corresponding to the lower light guide 9 as shown in S3 of FIG.

  In addition, in the boundary which shows each irradiation range S1-S3 of FIG. 9, although it is illustrated so that the whole surface of the glass plate 3 may not be irradiated and partitioned, it only shows the general range of each irradiation range S1-S3, The illuminance does not drop sharply outside the boundary, and the necessary illuminance is obtained even at the outer part of the boundary. In particular, in the portion between the irradiation ranges S1 and S3, sufficient illuminance is obtained because the portions where the illuminances are reduced overlap. In this way, as shown in FIG. 9, the entire surface of the glass plate 3 could be irradiated with sufficient illuminance and substantially uniformly by the irradiation ranges S1 to S3 by the infrared LED elements IR1 to IR3.

  Next, the arrangement | positioning point of the ultraviolet LED element UV is demonstrated. Since the wavelength of the ultraviolet light is shorter than that of the white light, the ultraviolet light is more easily refracted than the white light, and when the same lens (prism) is used, the ultraviolet light is slightly condensed with respect to the white light. However, the light distribution characteristic of the UV LED element UV, which is generally easily available, is considerably wider than the light distribution characteristic of the white LED element WL, and the emission range of the ultraviolet light emitted from the emission surfaces 8d and 9d of the light guides 8 and 9 is large. Since UV light is wider than white light, UV light is diffused more than white light in both the curved direction of the exit surfaces 8d and 9d and the linear direction (longitudinal direction of the light guides 8 and 9). The

  FIG. 10 is an explanatory diagram showing a state in which the position of the ultraviolet LED element is shifted. Thereafter, using FIG. 10, similarly to the infrared LED element IR, the emission surfaces 8d and 9d of the light guides 8 and 9 are formed in a shape that prioritizes the uniform illumination distribution by the white LED elements WL, The arrangement of the ultraviolet LED elements UV1 to UV9 when the light guides 8 and 9 are used will be described below.

  In the upper light guide 8, when the ultraviolet LED element UV is disposed on the reference line L 1, the light distribution characteristics of the ultraviolet light as described above, from the emission surface 8 d as shown by the two-dot chain line in FIG. The emitted light is greatly spread and emitted, resulting in a problem that the illuminance decreases. Further, if there is light that is greatly refracted toward the lower side of the light guide 8 due to the wide light distribution of the ultraviolet LED element UV and the refractive index of the ultraviolet light, the reflecting mirror 14 is caused by the light. May be directly irradiated. Even in the case of ultraviolet light, if there is light directly illuminating the reflecting mirror 14, the reflected light may become stray light and enter the camera 13.

  On the other hand, in the case of the ultraviolet LED element UV1 shifted by a predetermined amount with respect to the reference line L1, as shown by the solid line in FIG. 10, the emitted light from the exit surface 8d is on the reference line L1. Compared with the case of being arranged in the upper side, the upper side is substantially the same direction, but the lower side is directed upward. Thereby, since the irradiation range with respect to the glass plate 3 by the ultraviolet LED element UV1 is narrowed, the illuminance can be prevented from being lowered, and since the emission direction of the emitted light on the lower side of the light guide 8 is directed upward, the reflecting mirror 14 is directly irradiated. Can be prevented.

  Therefore, the ultraviolet LED elements UV1 to UV4 arranged corresponding to the light guide 8 are arranged so as to be shifted downward with respect to the reference line L1 (that is, the side where the radius of the emission surface 8d is small) as described above. ing. Further, the adjacent ultraviolet LED elements UV1 and UV2 are arranged so as to be shifted relative to the reference line L1 in the Y direction. This is because when the adjacent objects are the same in the Y direction, the irradiation position in the Y direction is the same. Therefore, when there is uneven illuminance in each Y direction, it is emphasized and unevenness is prevented from occurring. Because. Similarly, the adjacent ultraviolet LED elements UV3 and UV4 are also relatively displaced in the Y direction. The amount of deviation is as large as possible within a range where the irradiation range does not change greatly. In this way, mutual interference due to the light distribution between adjacent ones can be reduced as much as possible.

  Similarly, in the lower light guide 9, the ultraviolet LED elements UV <b> 5 to UV <b> 9 are respectively shifted downward with respect to the reference line L <b> 2 and are also shifted in the Y direction between adjacent ones. Has been. In addition, although each ultraviolet LED element UV1-UV9 is arrange | positioned more than another LED element, it is because the output of the generally easily available ultraviolet LED element is relatively low.

  Further, the reading device 1 of the present embodiment functions as an OCR (Optical Character Reader). OCR in reading a passport or a license may be used for authenticity determination. In that case, it is desirable to make the illuminance distribution on the entire surface of the glass plate 3 as uniform as possible in order to read it as accurately as possible. Note that white light is used for illumination when reading as OCR.

  FIG. 11 is an explanatory diagram showing an illuminance distribution in an image due to the influence of a camera lens. As shown in FIG. 11, generally, an image captured by the camera 13 has a problem that the peripheral light amount on the screen decreases due to the influence of so-called vignetting and the cosine fourth power law. A sufficient amount of light can be obtained in the circle of the broken line in FIG. 11, for example, which is the central portion Sc collected by the lens of the camera 13 with the object of the imaging range as the entire surface of the glass plate 3, but the periphery outside the range Sc The amount of light decreases in the portion Ss. In order to obtain a uniform light amount on the entire surface of the screen (glass plate 3), it is conceivable to increase the light amount of the peripheral portion Ss by, for example, 10 to 20% from the light amount of the central portion Sc.

  FIG. 12A is an explanatory view showing a prism provided on the upper light guide, and FIG. 12B is an explanatory view showing a prism provided on the lower light guide. Hereinafter, a configuration for adjusting the illuminance distribution on the document surface will be described with reference to FIGS. The adjustment of the illuminance distribution includes two configurations: a configuration corresponding to the above-described decrease in the amount of peripheral light, and a configuration that prevents a decrease in illuminance at the central portion of the document surface due to the structure of the reading apparatus according to the present invention. In the following description, it is assumed that the camera 13 is positioned on the right side of the drawings in FIGS. First, the portion facing the white LED element WL1 on the incident surface 8b of the upper light guide 8 is constituted by an inclined surface formed to be concave with respect to the incident surface 8b, as shown in FIG. 12 (a). The first prism 21 serving as the optical path refracting section and the second prism 22 serving as the second optical path refracting section configured by a plurality of similarly inclined slopes are provided. In the present embodiment, since the light emitting element is not disposed at a position corresponding to the central portion in the longitudinal direction of the light guides 8 and 9 (see FIGS. 1 and 4), the document surface facing the central portion in the longitudinal direction is Although it is disadvantageous in terms of illuminance, the first prism 21 is formed of a slope that is recessed on the side edge side of the glass plate (original surface) 3 with respect to the white LED element WL1, and the above-described white LED element WL1 The light Lw3 emitted toward the side edge is refracted toward the center. Thereby, the light which leaks to the outer side of the glass plate 3 can be condensed on the peripheral part inner side part of the glass plate 3, and the illumination intensity of the part can be raised.

  On the other hand, the second prism 22 is composed of a plurality of small slopes recessed continuously on the center side of the glass plate 3 with respect to the first prism 21, and each slope is provided with pitches p1 to p4. It is formed in a sawtooth shape. The second prism 22 disperses and refracts the light Lw4 emitted from the white LED element WL1 toward the central portion. Since the upper light guide 8 is close to the glass plate 3 and has a short light traveling distance, the light does not sufficiently strike the center of the glass plate 3 when the second prism 22 is not provided, and the illuminance directly above the camera 13 is high. Extremely low. In contrast, the second prism 22 having a larger inclination angle θ2 with respect to the incident surface 8b than the first prism 21 is refracted toward the center of the glass plate 3 to prevent a decrease in illuminance at the center of the glass plate 3. Can do. The reason why the second prism is provided at a narrower pitch than that of the first prism is a measure for imparting a relatively large tilt angle θ2 to the second prism while the size of the light guide is limited.

  Next, as shown in FIG. 12B, a slope formed to be concave with respect to the incident surface 9b in the portion facing the white LED element WL2 of the incident surface 9b of the lower light guide 9. A third prism 23 is provided as an optical path refracting section constituted by The third prism 23 is provided in the same manner as the first prism 21, and concentrates the light Lw5 leaking outside the glass plate 3 on the inner peripheral portion of the glass plate 3 to increase the illuminance of that portion. Can do.

  On the other hand, the lower light guide 9 is a plane on which the incident surface 9b is formed on the center side of the glass plate 3 opposite to the third prism 23. This is because, since the lower light guide 9 is far from the glass plate 3, the white LED element WL <b> 2 is directed toward the center of the glass plate 3 even if it is flat without providing an optical path refracting portion like the second prism 22. This is because the light Lw6 emitted in this way can reach the center of the glass plate 3.

  In the present embodiment, the prism formed of the inclined surface inclined with respect to the incident surfaces 8b and 9b is formed by recessing the incident surfaces 8b and 9b, but may be formed by projecting.

  FIG. 13 is an explanatory diagram showing the distribution of the range in which the illuminance by the white LED elements is increased, and shows the illuminance distribution by the respective white LED elements WL1 and WL2 due to the provision of the respective prisms 21-23. The strong illuminance range S4 by the left and right white LED elements WL1 of the upper light guide 8 is substantially the upper half in the figure on the upper light guide 8 side of the glass plate 3, as shown in FIG. Usually, the light beam that illuminates the portion directly above the camera 13 is a light beam that can avoid the camera 13, resulting in a significant decrease in illuminance. However, as described above, the second prism 22 irradiates the light directly distributed over the range of the portion directly above the camera 13, but the intensity of illumination is suppressed. The position of the white LED element WL1 in the X direction and the shapes of the first and second prisms 21 and 22 are set so as to obtain such an illuminance distribution. As the shape of the prism (optical path refracting portion), the inclination angle θ of the inclined surface with respect to the incident surface 8b, the length L of the inclined surface, the pitches p1 to p4 when a plurality of inclined portions are continuously provided, etc. (FIG. 12A) However, the inclination angle θ corresponds to θ1 and θ2 in FIG.

  The strong illuminance range S5 by the left and right white LED elements WL3 of the lower light guide 9 is a substantially lower half in the figure on the side farther from the lower light guide 9 of the glass plate 3, as shown in FIG. Across the entire surface. Since this portion corresponds to the peripheral portion Ss in FIG. 11, the illuminance should be increased over the entire region. Therefore, the same applies to the portion closer to the center of the glass plate 3 as in the range S4 in FIG. The position of the white LED element WL3 in the X direction and the shape of the third prism 23 (the inclination angle θ and the length L of the inclined surface in the same manner as described above) are set so as to irradiate to the extent.

  In this way, a desired illuminance distribution on the glass plate 3 can be realized with a simple structure in which the first to third prisms 21 to 23 are provided on the incident surfaces 8b and 9b of the light guides 8 and 9, respectively. it can. In particular, since it is possible to cope with the difference in perspective with respect to the glass plate 3 by changing the shape of each prism 21 to 23, the versatility is high.

  In the illustrated example, the lower light guide 9 is not provided with a plurality of short sloped prisms (second prisms 22) on the center side of the glass plate 3, but the specification of the reading device and the glass plate 3 are not included. Depending on the distance, the second prism 22 may be provided with an optical path refracting unit composed of a plurality of inclined surfaces with different lengths and pitches of the individual inclined surfaces.

  Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to such embodiments so that those skilled in the art can easily understand, and departs from the spirit of the present invention. It is possible to change appropriately within the range not to be. In addition, all the components shown in the above embodiment are not necessarily essential, and can be appropriately selected without departing from the gist of the present invention.

  For example, in the description of the embodiment, the optical path refracting portion is constituted by a slope that is inclined with respect to a plane orthogonal to the incident optical axis, but is called a prism, but the optical path refracting portion has a function of bending the optical path. Any optical device may be used, and the present invention is not limited to a sloped shape that is concave or convex with respect to the incident surfaces 8b and 9b. In the above embodiment, the light guides 8 and 9 arranged in two rows have been described. However, the light guides 8 and 9 may be arranged in three rows or more, or in a single row when the application is limited. There may be.

  The reading apparatus according to the present invention can capture an image of the entire surface with a substantially uniform light amount even when the light amount in the peripheral portion of the image of the image pickup device is reduced due to the influence of the lens, and is useful as a copying machine, a scanner, or the like.

1 Reading Device 3 Glass Plate (Reading Object Placement Unit)
6 Illumination board 7 LED row 8 Upper light guide 8b Incident surface 9 Lower light guide 9b Incident surface 13 Camera (imaging device)
14 reflecting mirror 21 first prism 22 second prism 23 third prism WL1, WL3 white LED element (light emitting element)

Claims (4)

A transparent reading object placement unit on which the reading object is placed;
An illuminating device disposed obliquely upward to illuminate the reading object placed on the reading object placing unit;
A reading device comprising: an imaging device that images the reading object illuminated by the illumination device;
The illumination device includes a light emitting element, and a rod-shaped light guide for guiding light from the light emitting element toward the reading object mounting portion,
The light guide includes an optical path refracting unit that refracts an emission direction of light from the light emitting element toward an end side of the reading object mounting unit toward a central part of the reading object mounting unit. The reading device.   The reading apparatus according to claim 1, wherein the optical path refracting unit is formed by an inclined surface that is concave or convex on an incident surface of the light guide. The light guides and the light emitting elements are provided in at least two rows at positions that are in perspective relation to the reading object placement unit,
The refractive index of the optical path refracting unit provided in the light guide in a row close to the reading object placement unit is larger than that in a far row. Reader.   2. The light guide includes a second optical path refracting unit that diffuses light from the light emitting element toward a central part of the reading object placing part to the central part. 4. The reading device according to any one of 3.

Images