JP2010197793A - Document illumination device and image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a document illumination device and image reading apparatus for achieving high illuminance illumination without enlargement. <P>SOLUTION: A first document illumination unit 4 and a second document illumination unit 7 are arranged so that LED (Light Emitting Diode) illumination light sources 2 and 5 and light guide members 3 and 6 are mirror-symmetrically in a sub-scanning direction with respect to the center line A-A' of the sub-scanning direction of a document reading region. In the first document illumination unit 4 and the second document illumination unit 7, a multi-chip LED 1 of each of LED illumination light sources 2 and 5 is arranged so that the illumination light L points downward. Then, inside the first light guide member 3 and the second light guide member 6, the illumination lights of both document illumination units 4 and 7 are reflected so as to overlap on a document reading surface 9. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a document illumination device used for a reading device that optically reads document information, and an image forming apparatus including the image reading device.

  In recent years, light emitting diodes (LEDs) have been actively developed, and the brightness of LED elements is rapidly increasing. LEDs generally have advantages such as long life, high efficiency, high G resistance, and monochromatic light emission, and are expected to be applied in many lighting fields. One of the applications is a document illumination device used for an image reading apparatus such as a digital copying machine or an image scanner. Further, the emission spectrum of the white light emitting LED element covers the visible wavelength band, and can be used for a document illumination apparatus of a color image reading apparatus.

  For this reason, a wide variety of document illumination devices using LEDs have been proposed. In order to efficiently illuminate an image reading unit with a light beam emitted from a light emitting surface of an LED element, a technique for illuminating a diffused light beam by using a light guide plate or a reflection mirror to an appropriate degree is disclosed.

  Document illuminators using LEDs as illumination light sources have been commercialized in low speed machines, but have not yet been commercialized in medium and high speed machines. In medium and high speed machines, since the reading speed is increased, it is necessary to realize an illumination device with high illuminance.

  As the illuminance increases, the lighting efficiency needs to be improved. The illumination efficiency of the conventional lamp light source is often very low at several percent. With the increase in illuminance of the LED lighting system, the illumination efficiency is expected to become an important factor.

  Moreover, it is necessary to pay attention to ensuring safety in the LED lighting device. At present, the LED light source has a safety standard according to an LD (laser diode) light source, and it is necessary to satisfy a predetermined safety standard. The safety of the device is tested by JQA (Japan Quality Assurance Organization) and ranked according to a predetermined standard. In particular, it is necessary to avoid light damage to the user's retina in a lighting device equipped with a high power LED.

  In addition, compared with conventional lighting devices mounted on medium- and high-speed machines, there is a demand for a device size that is equal to or smaller than that.

  In addition, when the apparatus is downsized, the distance from the light source to the original surface is shortened, so that the illuminance uniformity of the illumination light in the main scanning direction is deteriorated and ripples are easily generated. Therefore, it is necessary to solve this problem. .

  Hereinafter, based on the above-mentioned problems, prior art documents of lighting devices using LEDs will be examined.

  For example, Patent Documents 1 and 2 may be cited as methods for improving the illumination performance using a reflection mirror. In Patent Documents 1 and 2, the light source and the illumination system are arranged obliquely with respect to the document irradiation surface, and the strongest radiation angle (this is usually perpendicular to the light emitting surface) among the light beams emitted from the LEDs. The light flux component with a narrow divergence angle when the center is the direction) illuminates the document surface directly, and at the same time, the light flux component with a wide divergence angle is guided to the document surface by the reflection of the mirror, etc. , There is a common feature.

  Patent Document 1 illustrates a configuration using a mirror having a curved surface, and Patent Document 2 illustrates a configuration using a flat mirror.

  Patent Document 2 has an LED structure provided with a special inclusion member including a light emitting surface.

  In Patent Documents 1 and 2, the illumination system is disposed obliquely with respect to the document surface, and the thickness of the device in the direction perpendicular to the document surface is increased. Further, the light emitting surface is directed to the document surface side, and is characterized in that the optical path length from the illumination light source to the document surface is short.

  From the disclosure information of Patent Documents 1 and 2, it is not easy for a person skilled in the art to recall a configuration in which the device can be improved thinly and the illumination optical path length can be increased to reduce ripples. If the apparatus is thinned based on the configuration conditions disclosed in Patent Documents 1 and 2, the distance from the light source to the document surface is shortened, the flatness of the illuminance distribution is lost, and ripples are frequently generated. It is done.

  Moreover, it is described that LED used in patent document 2 is a special thing which requires the member containing a light emission surface. Therefore, it is considered difficult to use a general-purpose and low-cost LED in the illumination technique disclosed in Patent Document 2.

  Further, since the patent document 1 does not show a counter-irradiation function, it is considered that when this technique is used, when a document with a step is read, the step portion becomes a shadow and a dark line is easily generated.

  Japanese Patent Application Laid-Open No. H10-228667 describes a configuration in which opposed illumination is used to cope with the floating of the document. However, in Patent Document 3, a light source is also provided on the counter illumination side, and the radiation direction of the light source is arranged obliquely on the document surface side, and the normal line of the light emitting surface of the light emitting element is the same as that of the document reading surface. Since the configuration is directed toward the direction, it is easy for the user to see the light source emitting light. Patent Document 3 does not describe a problem and a solution for preventing the user from directly viewing the light emission source.

  Further, Patent Document 3 exemplifies a configuration in which the circuit board attached to the light emitting element extends obliquely downward in the cross section in the sub-scanning direction, and the lighting device has a thick height in the cross section in the sub-scanning direction. Yes.

  As described above, in the conventional technique, it is difficult to realize an illumination system that can be configured to be oppositely irradiated and that can be configured so that the height direction of the cross section in the sub-scanning direction of the illumination device is thin.

  Moreover, in an illuminating device in which an illuminating light source is provided also on the counter illuminating device side, it is desirable that the illuminated area can be efficiently illuminated without the emitted light from one illuminating device reaching the other illuminating device side.

  However, in a device provided with a light source only on one side of a conventional counter illumination device, the device is configured and arranged to guide part of the radiated light to the mirror for counter illumination. Then, the emitted light from one lighting device is guided to the other lighting device side. The conventional technique does not disclose a problem proposal and a solution for this point.

  Furthermore, in the case of a configuration in which the illumination light source is provided only on one side of the illumination device in the determined device space, the illuminance upper limit value that can be realized becomes low. In addition, the balance of the influence of the heat radiation from the light source on the lighting device is deteriorated.

  As described above, although an illuminating device using an excellent light emitting element such as an LED has been proposed so far, an illuminating device that has solved the above-described problems has not been realized.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art and to provide a document illumination device and an image reading device that can realize high illumination illumination without increasing the size.

In order to achieve the above object, an invention according to claim 1 is directed to an LED illumination light source in which a plurality of multi-chip LEDs on which a plurality of LED light emitting chips are mounted are arranged in the main scanning direction of an illuminated area, and the LED illumination light source. An original illuminating apparatus having a manuscript illumination unit provided with a light guide member for guiding radiated illumination light to an original reading surface, the manuscript illuminating unit comprising an original illuminating unit opposed to the manuscript illuminating unit. The LED illumination light source and the light guide member in each document illumination unit are arranged in mirror symmetry with respect to the center of the document reading surface in the sub-scanning direction, and the document illumination units are read from each other. It is characterized in that it is arranged mirror-symmetrically with respect to the center of the surface in the sub-scanning direction. It is possible to improve the bright illumination, ^also by mirror symmetrical arrangement of ^the original illumination unit, on the high illuminance can be achieved, since it is possible to lower the LED illuminance of the illumination light source required to meet the same illuminance, accompanied by emission Thermal effects are mitigated.

  According to a second aspect of the present invention, in the original illuminating device according to the first aspect, the light emitting surface of the LED illumination light source is disposed so as to be opposite to and obliquely downward with respect to the original reading surface, and the light emission of the LED illumination light source is achieved. The angle formed by the normal of the surface and the normal at the center of the document reading surface in the sub-scanning direction is set to 90 degrees or less. With this configuration, the illumination light is directed downward because the LED illumination light source faces downward. Since the normal light crossing angle is set to 90 degrees or less and the illumination light path is folded back by the reflection portion of the light guide member, the illumination device is not made thick. Alternatively, the optical path length from the LED illumination light source to the document reading surface can be increased, and the illumination lights of the LED illumination light sources arranged in the main scanning direction are superimposed on each other, thereby enabling illumination with less ripple in the main scanning direction. Become.

  According to a third aspect of the present invention, in the original illuminating device according to the first or second aspect, each original illuminating unit includes a light shielding member that shields illumination light from one original illuminating unit to the other original illuminating unit. With this configuration, the illumination light can be efficiently guided to the original reading surface, and the illumination efficiency can be improved.

  According to a fourth aspect of the present invention, in the original illuminating device according to the third aspect, the light guide member of each original illuminating unit uses the illumination light as three-dimensional light in the XYZ directions and in the YZ section in the sub-scanning direction of the original reading surface. , One or more reflective surfaces that reflect illumination light in a direction that includes + Y and ± X components, one or more reflective surfaces that reflect illumination light in a direction that includes −Y and ± X components, and + Z It is composed of one or more reflecting surfaces that reflect in the direction including the component and the ± X component, one or more reflecting surfaces that reflect the illumination light in the direction including the -Z component and the X component, and a light opening. With this configuration, the illumination light from the LED illumination light source is guided to the light opening by each reflecting surface without leaking to the outside of the apparatus, and the illumination efficiency can be improved.

  According to a fifth aspect of the present invention, in the original illuminating apparatus according to the fourth aspect, at least one light guide member of the original illuminating unit guides illumination light from the LED illumination light source to the original reading surface, and the other And a member having a reflecting surface having a light shielding function with respect to the original illumination unit of the apparatus. By this structure, two functions are exhibited on the reflecting surface, thereby reducing the internal space of the apparatus and the member. Cost reduction effect is achieved by reducing the number of points.

  According to a sixth aspect of the present invention, in the original illuminating device according to the fourth aspect of the present invention, a light diffusing member is provided in the light opening. With this configuration, the light source image projected on the reflecting surface cannot be directly seen. As a result, the light energy density that reaches the user's eyes is lowered by being diffused and further diffused.

  The invention according to claim 7 is characterized in that, in the document illumination device according to any one of claims 1 to 6, the incident angle of the illumination light to the document reading surface is set to 20 degrees or more. The specularly reflected light from the document reading surface is less likely to be guided to the imaging lens that constitutes the optical system of the apparatus, so that, for example, flare images are prevented from being generated due to optical interference, and an image without white spots is formed. can get.

  The invention according to claim 8 is characterized in that, in the document illumination device according to any one of claims 1 to 7, the incident angle of the illumination light to the document reading surface is set to 60 degrees or less. The depth of illumination is increased, and the original that is floating with respect to the original reading surface can be read satisfactorily.

  According to a ninth aspect of the present invention, in the image reading apparatus, the original illumination device according to any one of the first to eighth aspects is mounted, and the original placed on the original table is illuminated by the original illumination device, The document information illuminated by the document illumination device is imaged on the image sensor via the first to third reflecting mirrors and the imaging lens, and the received light signal from the image sensor is converted into an electrical signal to obtain image information. A first traveling body that reads and holds the original illumination device and the first reflecting mirror, and a second traveling body that retains the second reflecting mirror and the third reflecting mirror are 2: 1. This configuration is characterized in that the document information is read by scanning at a speed ratio of 5 mm, and this configuration is resistant to fluctuations in the received light signal on the imaging surface due to static positional deviation of the reading optical system and dynamic position fluctuations. An image reading apparatus can be realized.

  According to a tenth aspect of the present invention, in the image reading apparatus, the original illuminating device according to any one of the first to eighth aspects is mounted, and the original placed on the original table is illuminated by the original illuminating device. Document information illuminated by the document illumination device is imaged on an image sensor via at least one reflection mirror and an imaging lens, and a light reception signal from the image sensor is converted into an electrical signal to read image information. The document illumination device, the reflecting mirror, the imaging lens, and the image sensor are held by a single traveling body, and the traveling body is scanned to read document information. Since the device, reflection mirror, imaging lens, and image sensor are held by a single traveling body, the received light signal on the imaging surface is subject to static displacement of the reading optical system and dynamic position fluctuations. Tolerate fluctuations Both can be achieved signal noise is small image reading apparatus which generates in association to the scan driver reading small.

  According to the document illumination device of the present invention, it is possible to improve illumination illuminance and to reduce the size by arranging a large number of LED light emitting chips within the main scanning width, and to mirror symmetry of each document illumination unit. The arrangement can increase the illuminance and lower the illuminance of the LED illumination light source necessary for satisfying the same illuminance, so that practical effects such as reduction of the thermal influence associated with light emission are great.

  According to the image reading apparatus equipped with the document illumination device according to the present invention, the reading optical system is more resistant to fluctuations in the received light signal on the imaging surface due to static positional deviation and dynamic position fluctuations. Thus, it is possible to realize a document reading apparatus that is small and generates little signal noise accompanying the scanning scanning.

The schematic block diagram of the structural example of the LED illumination light source in embodiment of this invention The schematic block diagram of the structural example of the LED illumination light source in embodiment of this invention 1 is a schematic configuration diagram showing a main part in an embodiment of a document illumination device of the present invention. Schematic configuration diagram showing the main part in a modification of the embodiment of the document illumination device of the present invention Schematic configuration diagram showing the main part in a modification of the embodiment of the document illumination device of the present invention Schematic configuration diagram showing the main part in a modification of the embodiment of the document illumination device of the present invention Explanatory drawing which shows the state of the light beam of the illumination light in embodiment of the document illuminating device of this invention Explanatory drawing of the illumination distribution of the subscanning direction in embodiment of the original illuminating device of this invention 1 is a configuration diagram schematically illustrating an image reading apparatus according to a first embodiment of the present invention. 1 is a configuration diagram schematically illustrating an image reading apparatus according to a second embodiment of the present invention.

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

  FIG. 1 is a schematic configuration diagram of a configuration example of an LED illumination light source according to an embodiment of the present invention.

  In FIG. 1, an LED illumination light source 2 is configured by arranging a plurality of multi-chip LEDs 1 as light emitting elements so as to be separated from each other in the main scanning direction (X direction). Each multi-chip LED 1 has a configuration in which two or more LED light-emitting chips are mounted on one chip. The multi-chip LED 1 has a strong light emission power despite its size being the same as the conventional size. For this reason, illumination with high illuminance is realized with a chip arrangement density equivalent to the conventional one.

  In the configuration example shown in FIG. 1, the interval between adjacent multichip LEDs 1 in the central portion in the main scanning direction is wider than the interval between adjacent multichip LEDs 1 in the peripheral portion in the main scanning direction (X = 0). (Equally spaced apart in the ± X direction with the (center reference position) as the center). With this configuration, it is possible to form an illuminance distribution in which the illuminance at the periphery is higher than the center in the main scanning direction on the document reading surface.

  In this way, when a document image is read by the image sensor through the reduction optical lens system as will be described later, the decrease in the peripheral light amount due to the cosine fourth law of the lens is offset, and the CCD serving as the image sensor A flat illuminance distribution can be obtained on the surface.

  Further, as in the other configuration example of the LED illumination light source shown in FIG. 2, the multi-chip LEDs 1 are arranged at equal intervals in the main scanning direction (X = 0 (center reference position) as the center and at equal intervals in the ± X direction). In this case, it is applied to an illuminating device equipped with a CIS (contact image sensor) in combination with an SLA (selfoc lens array), so that the illuminance of the CIS illumination can be increased.

  FIG. 3 is a schematic configuration diagram showing a main part in the embodiment of the document illumination device of the present invention.

  As shown in FIG. 3, the document illumination unit body according to the first exemplary embodiment includes a first document illumination unit 4 including a first LED illumination light source 2 and a first light guide member 3 configured as illustrated in FIG. 1 or 2. The second LED illumination light source 5 having the same configuration as the first LED illumination light source 2 and the second original illumination unit 7 including the second light guide member 6 having the same configuration as the first light guide member 3. It is configured.

  Further, in the first document illumination unit 4 and the second document illumination unit 7, the LED illumination light sources 2 and 5 and the light guide members 3 and 6 are placed on the center line AA ′ in the sub-scanning direction of the document reading area. On the other hand, they are arranged so as to be mirror-symmetrical (left-right symmetric in the figure) in the sub-scanning direction.

  In the first document illumination unit 4 and the second document illumination unit 7, the illumination light (emitted light) L of the multichip LED 1 of each LED illumination light source 2, 5 is disposed downward. The illumination light L from the first document illumination unit 4 illuminates the document reading surface 9 of the document placed on the contact glass 8 from the lower left to the upper right in the drawing. On the other hand, the illumination light L from the second illumination unit 2 illuminates the document reading surface 9 from the lower right to the oblique upper left in the drawing. The illumination light from the first document illumination unit 4 and the second document illumination unit 7 is superimposed on the reading area 5 of the document reading surface 9.

  In the first document illumination unit 4 and the second document illumination unit 7, each LED illumination light source 2 and 5 is equipped with a multi-chip LED 1, so that the document illumination unit consisting of only a single document illumination unit. The upper limit of illuminance can be made higher than the illumination by the body.

  Further, as shown in FIG. 3, the multi-chip LED 1 is provided in an obliquely upper portion far from the original reading surface 9 in each of the original illumination units 4 and 7, and the normal line in the radial direction of the light emitting surface of the multi-chip LED 1 is provided. It is arranged diagonally downward. In this way, being obliquely downward means that the angle formed by the normal line in the radial direction of the light emitting surface of the multichip LED 1 and the normal line on the document reading surface 9 is 90 degrees or less. The fact that the light emitting surface is facing downward means that the user cannot directly see the light emitting surface through the contact glass 8, and the optical safety is increased.

  Moreover, in FIG. 3, the 1st light guide member 3 and the 2nd light guide member 6 consist of a reflective mirror, and each cross-sectional shape is lower part 3a, 6a, upper part 3b, 6b, and , Standing side portions 3c, 3d, 6c, 6d. The first LED illumination light source 2 and the second LED illumination light source 5 are provided downward at the corners of the upper side portions 3b, 6b and the standing side portions 3c, 6c on the side far from the document reading surface 9. Further, openings 3e and 6e for emitting the illumination light L in the direction of the document reading surface 9 are provided at corners of the upper side portions 3b and 6b and the standing side portions 3d and 6d on the side closer to the document reading surface 9. ing.

  By configuring the first light guide member 3 and the second light guide member 6 in this way, the illumination light L is efficiently guided to the document reading surface 9.

  In addition, the illumination light L from the LED illumination light sources 2 and 5 reaches the document reading surface 9 by obtaining the reflection effect by the multiple surfaces of the light guide members 3 and 6, so that the entire document illumination units 4 and 7 are not thickened. Long illumination path length. In addition, since the illumination light L from the LED illumination light sources 2 and 5 overlaps in the main scanning direction, the flatness of the illuminance distribution in the main scanning direction on the document reading surface 9 becomes high. Therefore, the occurrence of ripple is suppressed.

  In this embodiment, the illumination light (radiated light) L from the LED illumination light sources 2 and 5 is reflected by the lower side portions 3a and 6a of the light guide members 3 and 6, respectively, and illuminates the document reading surface 9. The illumination optical path length can be secured approximately twice the length of the document illumination units 4 and 7.

  In addition, the intersection angle between the normal line of the light emitting surface of the multichip LED 1 and the normal line of the document reading surface 9 in each LED illumination light source 2, 5 is preferably about 35 degrees, in order to ensure illumination depth characteristics. It is a suitable angle. If the crossing angle is 20 degrees or less, flare is likely to occur due to the regular reflection component of the illumination light L, and if it is 45 degrees or more, it becomes weak against the floating of the document. The illumination angle of the illumination light L on the document reading surface 9 is preferably 20 degrees to 60 degrees.

  Further, as shown in FIG. 3, the light emission images of the LED illumination light sources 2 and 5 are brightest when viewed through the lower portions 3a and 6a of the light guide members 3 and 6, respectively. It is configured not to be directly visible to the user. There may be images on the vertical side portions 3c and 6c far from the document reading surface 9 as the light emission image that can be seen by the user, but this is a reflection image of a component with low radiation intensity.

  Furthermore, as shown in FIG. 4, by providing the light diffusion sheet 10 which is a light-diffusion member in the opening parts 3e and 6e of the 1st light guide member 3 and the 2nd light guide member 6, respectively, it is a light emission image. Is diffused to increase the size, and the light energy density reaching the user's eyes can be reduced by the light diffusion effect. And safety | security can be ensured by selecting the sheet | seat material which has appropriate light-diffusion property.

  With such a configuration that does not include the light diffusing means, it is difficult to ensure safety in the LED array light source type as the power of the light source increases.

  Further, in this embodiment, since an independent counter illumination mirror is not used, it is not necessary to guide and distribute part of the emitted light from the light source to the counter illumination mirror. Illumination light can be guided to the original illumination surface 9 as much as possible to increase illumination efficiency.

  In this embodiment, as shown in FIG. 5, it is conceivable to provide a light diffusing member 11 in the outgoing light path in the vicinity of both LED illumination light sources 2 and 5.

  Moreover, in this embodiment, as shown in FIG. 6, changing the cross-sectional shape of both the light guide members 3 and 6 suitably by a specification etc. is also considered.

  In the configuration shown in FIGS. 3 to 6, the illumination light L emitted from the first LED illumination light source 2 is generated by the second side 3d of the first light guide member 3 on the side closer to the document reading surface 9 by the second side 3d. The document illumination unit body 7 is shielded from entering. Similarly, the illumination light L emitted from the second LED illumination light source 5 enters the first document illumination unit body 4 by the standing side portion 6d on the side closer to the document reading surface 9 in the second light guide member 6. Shielded so that there is no.

  Furthermore, by using the standing side portions 3d and 6d of the light guide members 3 and 6 as reflecting surfaces, the standing side portions 3d and 6d are illustrated as shown in FIG. The illumination light L is reflected by the above and returned to the light guide members 3 and 6, respectively, and the luminous flux components guided to the document illumination area 9 from the openings 3e and 6e of the light guide members 3 and 6 are increased. Yes. That is, the light use efficiency can be increased.

  The illumination efficiency in the conventional counter-illumination mirror system is about 20%, and the ratio of main illumination to counter-illumination is about 5: 5 to 7: 3, so the illumination efficiency on the main illumination side was at most 14%. The illumination efficiency of the document illumination unit bodies 4 and 7 according to the configuration of the present embodiment is 30% or more, which is at least twice as efficient as the conventional counter illumination mirror system. In addition, in the conventional illumination method using a xenon tube, the light utilization efficiency was about 3%, but according to the configuration of the present embodiment, the light utilization efficiency was actually increased 10 times.

  As shown in FIG. 7, the illumination light L is illuminated symmetrically in the sub-scanning direction (arrow Z direction), and the distribution of illumination illuminance in the sub-scanning direction is the same as that of the first document illumination unit 4 and the second. By inverting the document illumination unit 7 in the sub-scanning direction and superimposing these, an illuminance distribution having good left-right symmetry with respect to the center of the document reading area 9 is obtained as shown in FIG.

  For example, in the case where the diffusion sheet 6 is inserted by mounting an LED light source in which 19 30-lm 2-chip multi-chip LEDs are arranged on the first document illumination unit 4 and the second document illumination unit 7, FIG. As shown in FIG. 4, a high-illuminance illumination of 70,000 Lx is realized, and a reading illumination device that can be applied to a high-speed machine can be realized.

  In the configuration example shown in FIG. 6, the specific size of the entire document illumination device including the first document illumination unit 4 and the second document illumination unit 7 is approximately 7 mm in thickness and approximately 30 mm in total length in the sub-scanning direction. The length of each of the original illumination units 4 and 7 in the sub-scanning direction is approximately 11 mm, and is extremely compact.

  3 to 6, in the configuration of the first light guide member 3 and the second light guide member 6 in the present embodiment, the illumination light L includes a + Y component and a ± X component in the YZ section in the sub-scanning direction. One or more reflecting surfaces 3a reflecting in the direction, one or more reflecting surfaces 3b reflecting the illumination light L in the direction including the -Y component and the ± X component, and the illumination light L reflected in the direction including the + Z component and the ± X component One or more reflecting surfaces 3c, one or more reflecting surfaces 3d for reflecting the illumination light L in the direction including the -Z component and the ± X component, and an opening 3e.

  Moreover, since each reflective surface in the 1st light guide member 3 and the 2nd light guide member 6 can be comprised with a plane, it is easy to manufacture. However, the shape of each reflecting surface is not limited to a flat surface. For example, each reflection surface may be two or more. In the configuration example shown in FIG. 6, the lower side portions 3a and 6a are formed as reflection planes 3a1, 3a2, 6a1, and 6a2 formed of two surfaces.

  It is desirable from the viewpoint of light utilization efficiency that the reflecting surfaces of both the light guide members 3 and 6 are spatially closed so that there is no gap between the surfaces. However, there may be a step at the connection between the surfaces of the reflecting surfaces. Further, these reflective surfaces may be surfaces having a part or all of light scattering properties, but light scattering surfaces having a surface structure with little wavelength dependency are suitable.

  In addition to the above-described configuration, a configuration in which a side mirror having a reflecting surface in the cross-sectional direction in the sub-scanning direction is added is more desirable. In this case, the side mirrors are provided at both ends of the cross section in the sub-scanning direction in both document illumination units 4 and 7.

  In addition, a side mirror may be provided in the area between the two document illumination units 4 and 7. The height of the side mirror in this region is higher than the cross-sectional height in the sub-scanning direction of both document illumination units 4 and 7, that is, by extending to a position close to the document reading surface 9. The effect of increasing the amount of light in the peripheral portion in the direction can be obtained.

  As described above, in the embodiment having the above-described configuration, each of the document illumination units 4 and 7 has both a light guide shielding function to the adjacent document illumination units and a function of increasing the illumination efficiency. There is no problem in the arrangement space required for the operation.

  In addition, as the light diffusion sheet 10 of the light diffusion member provided in the openings 3e and 6e of the light guide members 3 and 6, a transmission type light diffusion sheet is applicable. Furthermore, the Gaussian diffusion type is more preferable than the Lambert diffusion type in view of the balance of illumination efficiency, illumination distribution flatness, and safety. In the Gaussian type, the Gaussian coefficient σ is desirably 2 or more from the viewpoint of safety, and is desirably 10 or less from the light utilization efficiency.

  In addition, as shown in FIG. 6, a reflecting member is not provided in a region of ± 20 degrees or less with respect to the normal line in the cross section in the sub-scanning direction from the center of the document reading surface 9 (region inside the two-dot chain line). It is configured. As a result, the bright regular reflection component on the document reading surface 9 does not enter the opening of a reading lens (not shown), and white spots can be prevented from occurring in the document image formed on the image sensor.

  Further, when the illumination angle to the document reading surface 9 is increased, the illumination depth becomes shallower. For example, the binding margin portion of the book document is floating from the contact glass 8, so that the illumination of that portion is weakened and the image becomes dim. It is well known that In this embodiment, when the illumination angle is set to 60 degrees or less, the illumination illuminance deterioration is reduced to about 20% even when the binding margin of the book original is 2 to 3 mm.

  Next, an embodiment of an image reading apparatus equipped with the document illumination device of this embodiment will be described.

  FIG. 9 is a configuration diagram showing an outline of the image reading apparatus according to the first embodiment of the present invention.

  In FIG. 9, the illumination light L reflected by the document reading surface 9 corresponding to the document D placed on the contact glass 8 serving as a document table is imaged through the reading optical system including the imaging lens 19 and the like. Receive light above. As the image sensor 20, for example, a CCD can be used. It is possible to read the image information of the document by converting the optical signal of information on the document reading surface 9 imaged on the image sensor 20 into an electrical signal.

  A first traveling body 22 that holds the first document illumination unit 4 and the second document illumination unit 7 described with reference to FIGS. 1 to 8 and the first reflection mirror 21, and second and third reflections. By scanning the second traveling body 25 holding the mirrors 23 and 24 at a speed ratio of 2: 1 and reading the document information. Reading scanning can be performed while keeping the optical path length from the document reading surface 9 to the image sensor 20, in other words, the conjugate length of the reading optical system constant.

  In the first embodiment, since the original illuminating apparatus including the first original illuminating unit 4 and the second original illuminating unit 7 is thinned, the image reading apparatus side can also be configured to be thin and compact.

  Further, as described above, the first document illumination unit 4 and the second document illumination unit 7 have a feature that the illuminance distribution in the sub-scanning direction is flat as described above. A device excellent in the stability of the received light signal on the light receiving surface of the image sensor 20 can be realized by allowing the installation error of the optical element such as the lens 19 and the dynamic fluctuation accompanying the scanning drive. Alternatively, the tolerances of these optical elements can be relaxed.

  For this reason, an image reading apparatus that can cope with a change in the light receiving signal on the light receiving surface of the image sensor 20 due to a static positional deviation of the reading optical system or a dynamic position change is realized.

  FIG. 10 is a configuration diagram showing an outline in the second embodiment of the image reading apparatus of the present invention.

  In the second embodiment, the first document illumination unit 4 and the second document illumination unit 7 described with reference to FIGS. 1 to 8, the reflection mirror 26, the imaging lens 27, and the image sensor 28 are run as one unit. The body 29 is configured to be held. Then, the document 29 is read by driving the traveling body 29 in the sub-scanning direction.

  In the second embodiment, since it is not necessary to drive the reflection mirror 26 at the time of scanning and reading, the drive mechanism and the like can be simplified, and the entire apparatus can be reduced in size and weight.

  Even if vibration or the like is generated when the traveling body 29 is driven to scan, the relative displacement between the document illumination units 4 and 7, the reading optical system (the reflection mirror 26 and the imaging lens 27), and the image sensor 28. However, since there is an advantage that the number is smaller than that in the first embodiment shown in FIG. 9, the characteristics of the optical signal received on the light receiving surface of the image sensor 28 are stabilized. The reason why such an image reading apparatus can be realized in a compact manner is that the illumination device including the first document illumination unit 4 and the second document illumination unit 7 is thin and small as described above. .

  The present invention relates to a document illuminating device used in a reading device such as a digital copying machine or an image scanner, an illuminating device for illuminating an object for reading an original image, various image reading devices including the illuminating device, and the image The present invention can be applied to an image forming apparatus provided with a reading device, and the image forming apparatus can be applied to a copying machine, a facsimile machine, a printer, or a multi-function machine combining some of them.

1 LED chip
2 LED illumination light source (first LED illumination light source)
3 1st light guide member 3a Lower side part 3a1, 3a2 Lower side reflection plane 3b Upper side part 3c, 3d Standing side part 3e Opening part 4 1st original illumination unit 5 2nd LED illumination light source 6 2nd Light guide member 6a Lower side portion 6a1, 6a2 Lower side reflection plane 6b Upper side portion 6c, 6d Vertical side portion 6e Opening portion 7 Second document illumination unit 8 Contact glass 9 Document reading surface 10 Light diffusion sheet 11 Light diffusion member DESCRIPTION OF SYMBOLS 19 Imaging lens 20 Image pick-up element 21 1st reflective mirror 22 1st traveling body 23 2nd reflective mirror 24 3rd reflective mirror 25 2nd traveling body 25
26 Reflecting mirror 27 Imaging lens 28 Imaging element 29 Traveling body

Japanese Unexamined Patent Publication No. 2006-4416 JP 2006-295810 A JP 2008-067276 A

Claims (10)

An LED illumination light source in which a plurality of multi-chip LEDs mounted with a plurality of LED light emitting chips are arranged in the main scanning direction of the illuminated area, and a light guide member for guiding illumination light emitted from the LED illumination light source to the document reading surface A document illumination device provided with a document illumination unit body comprising:
The document illumination unit body is composed of a document illumination unit opposed to each other, and the LED illumination light source and the light guide member in each document illumination unit are mirror-symmetric with respect to the center of the document reading surface in the sub-scanning direction. An original illuminating apparatus having an arrangement configuration, wherein the original illuminating units are arranged mirror-symmetrically with respect to the center of the original reading surface in the sub-scanning direction.   The light emitting surface of the LED illumination light source is disposed in the opposite direction and obliquely downward with respect to the document reading surface, and the normal line of the light emitting surface of the LED illumination light source and the center of the document reading surface in the sub-scanning direction 2. An original illuminating apparatus according to claim 1, wherein an angle formed by the normal line is set to 90 degrees or less.   3. The document illumination device according to claim 1, wherein each of the document illumination units includes a light shielding member that shields illumination light from one document illumination unit to the other document illumination unit.   The light guide member of each document illumination unit converts the illumination light into a direction including a + Y component and a ± X component in the YZ section in the sub-scanning direction of the document reading surface using the illumination light as three-dimensional light in the XYZ directions. One or more reflecting surfaces that reflect, one or more reflecting surfaces that reflect the illumination light in a direction that includes a −Y component and a ± X component, and one surface that reflects the illumination light in a direction that includes a + Z component and a ± X component 4. The original illumination according to claim 3, comprising: the above reflecting surface; one or more reflecting surfaces that reflect the illumination light in a direction including a -Z component and an X component; and a light aperture. apparatus.   Reflection in which at least one of the light guide members of the document illumination unit has a function of guiding illumination light from the LED illumination light source to a document reading surface and a function of shielding light from the other document illumination unit. The document illumination device according to claim 4, further comprising a surface.   5. The document illumination device according to claim 4, wherein a light diffusing member is provided in the light opening.   7. The document illumination device according to claim 1, wherein an incident angle of illumination light on the document reading surface is set to 20 degrees or more.   8. The document illumination device according to claim 1, wherein an incident angle of illumination light on the document reading surface is set to 60 degrees or less.   A document illumination device according to any one of claims 1 to 8, wherein the document illumination device illuminates a document placed on a document table, and the document information illuminated by the document illumination device includes first to first document information. An image is formed on an image sensor via a third reflection mirror and an imaging lens, and a light reception signal from the image sensor is converted into an electrical signal to read image information. The document illumination device and the first reflection mirror Scanning the first traveling body holding the second traveling body and the second traveling body holding the second reflecting mirror and the third reflecting mirror at a speed ratio of 2: 1 to read the document information. An image reading apparatus.   9. A document illumination device according to claim 1, wherein the document illumination device illuminates a document placed on a document table, and at least one document information illuminated by the document illumination device. An image is formed on an image sensor through a reflection mirror and an imaging lens of the image, and a light reception signal from the image sensor is converted into an electrical signal to read image information. The document illumination device, the reflection mirror, and the imaging lens And the image sensor are held by a single traveling body, and the traveling body is scanned to read document information.

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