JP2008141405A - Image sensor and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image sensor capable of reducing illuminance differences on a reading object and inexpensively preventing picture quality from being degraded. <P>SOLUTION: The image sensor 10 for radiating light to an original 2 uses EL light emitting elements 24, 25 which emit light by organic electroluminescence as a light source. The EL light emitting elements 24, 25 are formed like lines each of which includes first and second end parts 36, 37 separated from each other in a scanning direction and an intermediate part 38 existing between the first and second end parts 36, 37. The EL light emitting elements 24, 25 have such a characteristic that the distribution of luminance intensity is changed so that the luminance intensity of the first and second end parts 36, 37 becomes higher than that of the intermediate part 38. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image sensor using an EL light emitting element that emits light by organic electroluminescence as a light source, and an image forming apparatus equipped with the image sensor.

  For example, a multifunctional image forming apparatus called a so-called multifunction peripheral (MFP) having a scanner function, a printing function, a copying function, a network connection function, and the like is used to read characters, images, etc. from a reading object such as a document. It is equipped with a line scanning image sensor that optically reads this information.

  This type of image sensor includes a light source that irradiates a reading target with light. As this light source, an LED light emitting element is widely used. However, in recent years, an attempt has been made to use an EL light emitting element as shown in Patent Document 1 instead of the LED light emitting element.

  The EL light emitting element includes a strip-shaped glass substrate extending in the scanning direction and a light emitting portion formed on the surface of the glass substrate. The light emitting portion emits light by electroluminescence when an electric field is applied, and extends in a straight line along the longitudinal direction of the glass substrate.

  By the way, when the light from the EL light emitting element is irradiated onto the light irradiation surface of the reading object, the central portion of the light irradiation surface facing the intermediate portion along the longitudinal direction of the EL light emitting element is along the longitudinal direction of the EL light emitting element. Light can be received from a wide range. On the other hand, since the edge part of a light irradiation surface leaves | separates from the center part of EL light emitting element, the light irradiated from EL light emitting element reduces compared with the center part of light irradiation surface. For this reason, an illuminance difference arises between the center part and edge part of a light irradiation surface.

  Furthermore, when an image sensor using an EL light emitting element as a light source is incorporated in an image forming apparatus, it is inevitable that the EL light emitting element is affected by heat from the image forming apparatus. Since the EL light-emitting element has an elongated shape, the EL light-emitting element is not heated uniformly over the entire length, and an intermediate portion thereof may be locally heated. As a result, the temperature distribution along the longitudinal direction of the EL light emitting element becomes non-uniform, and a temperature difference occurs in the EL light emitting element itself.

  Usually, the EL light emitting element has a characteristic that the luminous intensity increases as the temperature increases. For this reason, variation occurs in the luminous intensity distribution along the longitudinal direction of the EL light emitting element, and this is one factor that causes an illuminance difference on the light irradiation surface of the reading object.

  When an illuminance difference occurs on the light irradiation surface, there arises a problem that the image quality of a portion with low illuminance is deteriorated as the output of the image sensor than the image quality of a portion with high illuminance.

In order to prevent image quality deterioration due to this variation in luminous intensity, the conventional line scanning image sensor detects the luminous intensity of the light source using a light receiving sensor and corrects the image signal based on the detected luminous intensity. (For example, refer to Patent Document 2).
JP 2003-87502 A JP-A-6-225077

  However, the image sensor disclosed in Patent Document 2 requires a complicated signal processing circuit for correcting the light intensity detected by the light receiving sensor. For this reason, even if a good image signal can be obtained by correcting the luminous intensity, the cost of the signal processing circuit is unavoidably increased, resulting in a problem that the price of the image sensor increases.

  An object of the present invention is to obtain an image sensor which can suppress the difference in illuminance on a reading object and prevent deterioration in image quality, and can reduce cost by eliminating a complicated signal processing circuit.

  Another object of the present invention is to obtain an image forming apparatus equipped with the image sensor.

  In order to achieve the above object, an image sensor according to an embodiment of the present invention is an image sensor that irradiates light to an object to be read using an EL light emitting element that emits light by organic electroluminescence. Is formed in a line shape including first and second ends spaced apart in the scanning direction and an intermediate portion located between the first and second ends, and the first and second ends The luminous intensity distribution of the EL light emitting element is changed so that the luminous intensity of the portion is higher than the luminous intensity of the intermediate portion.

In order to achieve the above object, an image forming apparatus according to an aspect of the present invention includes a conveyance path that conveys an object to be read, and an image that is installed in the conveyance path and optically reads image information from the reading object. And a sensor.
The image sensor includes a light source that emits light toward the reading object. The light source is an EL light emitting element that emits light by organic electroluminescence. The EL light emitting element is a first light emitting element that is spaced apart in the scanning direction. And a second end portion and an intermediate portion located between the first and second end portions, and the luminous intensity of the first and second end portions is the luminous intensity of the intermediate portion. The luminous intensity distribution of the EL light emitting element is changed so as to be higher than that.

  According to the present invention, since the luminous intensity of the first and second end portions of the EL light emitting element is higher than the luminous intensity of the intermediate part, when the reading object is irradiated with light from the EL light emitting element, the reading object is The difference in illuminance on the light irradiation surface can be suppressed.

  Therefore, it is possible to prevent deterioration of image quality without using a complicated signal processing circuit, and to stably read image information from a reading object.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows an outline of the image forming apparatus 1 expanded linearly. The image forming apparatus 1 includes a hopper table 3 on which a document 2 as a reading object is placed. The document 2 placed on the hopper table 3 is sent to the conveyance path 5 via the paper feed roller 4. The conveyance path 5 connects the hopper table 3 and a stacker (not shown).

  A plurality of rollers 6 are arranged on the conveyance path 5. The rollers 6 are arranged at intervals in the feeding direction of the document 2 and are rotated in synchronization with each other. By the rotation of the roller 6, the document 2 is sequentially conveyed from the start end to the end of the conveyance path 5.

  A contact image sensor 10 is arranged in the middle of the conveyance path 5. The contact image sensor 10 is for optically reading information such as characters and images from the document 2 conveyed along the conveyance path 5, and is installed below the conveyance path 5.

  As shown in FIGS. 2 to 4, the contact image sensor 10 has a housing 11 made of synthetic resin. The housing 11 has an elongated bar shape along the scanning direction, and extends in a direction orthogonal to the conveyance direction of the document 2.

  A first recess 12 is formed on the upper surface of the housing 11. The first recess 12 extends in the longitudinal direction of the housing 11. The first recess 12 has an opening 13 that opens to the upper surface of the housing 10, and a bottom surface 14 that faces the opening 13. The opening 13 is closed with a glass plate 15 as a transparent plate. The glass plate 15 is exposed to the conveyance path 5, and the document 2 passes through the glass plate 15.

  A second recess 16 is formed on the bottom surface of the housing 11. The second recess 16 extends in the longitudinal direction of the housing 11. The second recess 16 communicates with the first recess 12 through a communication hole 17 formed inside the housing 11. The communication hole 17 is located at the center along the width direction of the housing 11 and extends in the longitudinal direction of the housing 11.

  A lens unit 18 is held inside the communication hole 17. The lens unit 18 extends in the longitudinal direction of the housing 11, and its upper end protrudes into the first recess 12. The lens unit 18 has a central axis O1 that stands up perpendicular to the scanning direction.

  A sensor substrate 19 is attached to the second recess 16. The sensor substrate 19 extends in the longitudinal direction of the housing 11 so as to close the second recess 16. A plurality of light receiving elements 20 such as CCDs are mounted on the upper surface of the sensor substrate 19. The light receiving elements 20 are arranged in a line at intervals in the longitudinal direction of the housing 11 and are positioned on the central axis O <b> 1 of the lens unit 18.

  The first recess 12 of the housing 11 houses an organic EL light source unit 22 as shown in FIG. The organic EL light source unit 22 of the present embodiment includes a rigid printed wiring board 23, a pair of EL light emitting elements 24 and 25, and four flexible wiring boards 26.

  As shown in FIGS. 3 and 5, the printed wiring board 23 has a pair of EL support portions 27a and 27b. The EL support portions 27a and 27b extend in a line shape in the longitudinal direction of the housing 11 along the scanning direction. The EL support portions 27a and 27b have one end 28 and the other end 29, respectively. The one end 28 and the other end 29 are separated from each other in the longitudinal direction of the EL support portions 27a and 27b.

  One end 28 of one EL support portion 27 a and one end 28 of the other EL support portion 27 b are connected to each other via a bridge portion 30. Similarly, the other end 29 of one EL support portion 27 a and the other end 29 of the other EL support portion 27 b are connected to each other via another bridge portion 31. For this reason, the EL support portions 27a and 27b of the printed wiring board 23 are arranged in parallel with a space between each other.

  As shown in FIGS. 4 and 7, each EL support portion 27 a, 27 b has a first surface 32 and a second surface 33 located on the opposite side of the first surface 32. The first surface 32 faces the direction of the glass plate 15. A pair of first electrodes 34 is formed on the first surface 32 at positions corresponding to the one end 28 and the other end 29 of the EL support portions 27a and 27b. As shown in FIG. 6, the first electrodes 34 are arranged in the width direction of the EL support portions 27a and 27b.

  As shown in FIG. 4, the second surfaces 33 of the EL support portions 27 a and 27 b face the bottom surface 14 of the first recess 12 of the housing 11. A pair of second electrodes 35 (only one is shown) is formed on the second surface 33 of one EL support portion 27a. The second electrode 35 is located at one end 28 of the EL support portion 27 a and is electrically connected to the first electrode 34 through a conductor layer (not shown) formed on the printed wiring board 23.

  The EL light emitting elements 24 and 25 are mounted on the first surfaces 32 of the EL support portions 27a and 27b. The EL light emitting elements 24 and 25 extend in a line shape along the scanning direction. The EL light emitting elements 24 and 25 have a first end portion 36, a second end portion 37, and an intermediate portion 38. The first end portion 36 and the second end portion 37 are separated from each other in the longitudinal direction of the EL light emitting elements 24 and 25. The intermediate portion 38 is located between the first end portion 36 and the second end portion 37.

  As shown in FIG. 7, the EL light emitting elements 24 and 25 each include a transparent glass substrate 39 and a light emitting unit 40. The glass substrate 39 extends in a line along the scanning direction, and is bonded to the first surface 32 of the EL support portions 27a and 27b via, for example, a double-sided adhesive tape 41.

  A pair of third electrodes 42 is formed on one end and the other end of the glass substrate 39, respectively. The third electrode 42 is, for example, an ITO (Indium Tin Oxide) electrode made of an oxide film of indium and tin. As shown in FIG. 6, the first and second end portions 36, 36 of the EL light emitting elements 24, 25 are provided. In FIG. 37, the glass substrates 39 are arranged in the width direction.

  The light emitting unit 40 is formed on the lower surface of the glass substrate 39. The light emitting section 40 emits light by electroluminescence when an electric field is applied, and has a strip-shaped light emitting surface 40 a extending in the longitudinal direction of the glass substrate 39. One end and the other end of the light emitting unit 40 along the longitudinal direction are electrically connected to the third electrode 42. For this reason, the light emitting section 40 is configured to emit light in a band shape by applying an electric voltage to both ends along the longitudinal direction to apply an electric field.

  As shown in FIG. 7, the flexible wiring board 26 is for electrically connecting the EL light emitting elements 24 and 25 and the printed wiring board 23. Each flexible wiring board 26 has a fourth electrode 43 and a fifth electrode 44.

  The fourth electrode 43 is thermocompression bonded to the first electrode 34 of the printed wiring board 23 via an anisotropic conductive film 45. The fifth electrode 44 is thermocompression bonded to the third electrode 42 of the glass substrate 36 via another anisotropic conductive film 46.

  As shown in FIGS. 3 and 4, the second surfaces 33 of the EL support portions 27a and 27b are fixed to the bottom surface 14 of the first recess 12 with the metal plate 47 interposed therebetween. In a state where the EL light emitting elements 24 and 25 are fixed to the first recess 12, the EL light emitting elements 24 and 25 are arranged in two rows with the lens unit 18 interposed therebetween. At the same time, the EL light emitting elements 24 and 25 are covered with the glass plate 15 over their entire length.

  Accordingly, the glass plate 15 is interposed between the document 2 and the EL light emitting elements 24 and 25 when reading information from the document 2.

  As shown in FIGS. 2 and 3, a circuit board 50 that controls driving of the EL light emitting elements 24 and 25 is supported by the housing 11. The circuit board 50 has a rectangular shape extending in the longitudinal direction of the housing 11, and a plurality of locations along the longitudinal direction are fixed to a plurality of boss portions 51 protruding from the side surface of the housing 11 via rivets 52. Further, the circuit board 50 is laminated on the lower surface of the sensor substrate 19 and is electrically connected to the sensor substrate 19.

  A plurality of electronic circuit components 53 are mounted on the lower surface of the circuit board 50. The electronic circuit component 53 includes an LSI 54 that generates heat during operation. The LSI 54 is located directly below the intermediate portion 38 of the EL light emitting elements 24 and 25. The heat generated by the LSI 54 is transmitted from the circuit board 50 to the housing 11 through the sensor substrate 19 and the rivet 52 and from the housing 11 to the EL light emitting elements 24 and 25. Therefore, when the EL light emitting elements 24 and 25 are affected by the heat from the LSI 54, the intermediate portion 38 tends to be locally heated.

  As shown in FIG. 4, the circuit board 50 is electrically connected to the printed wiring board 23 of the organic EL light source unit 22 via two cables 56. The cable 56 is wired through a cable passage 57 formed in the housing 11 and a through hole 58 opened in the sensor substrate 19.

  When the organic EL light source unit 22 is operated, the light emitting units 40 of the EL light emitting elements 24 and 25 emit light. The light emitted from the light emitting surface 40 a of the light emitting unit 40 is applied to the document 2 through the glass plate 15. The light irradiated on the document 2 is reflected by the lower surface (light irradiation surface) of the document 2 and then guided to the light receiving element 20 through the lens unit 18. The light receiving element 20 outputs a signal having a level corresponding to the amount of received light. Thereby, information such as characters and images drawn on the document 2 is optically read.

  When optically reading information from the document 2, the illuminance distribution on the light irradiation surface is aligned along the longitudinal direction of the EL light emitting elements 24 and 25 so that no illuminance difference occurs on the light irradiation surface of the document 2. It is desirable to equalize.

  The central portion of the light irradiation surface of the document 2 along the scanning direction faces the intermediate portion 38 of the EL light emitting elements 24 and 25 and can receive light from a wide range along the longitudinal direction of the EL light emitting elements 24 and 25. . On the other hand, light is received from a wide range along the longitudinal direction of the EL light emitting elements 24 and 25 at the end portions of the light emitting surfaces facing the first and second end portions 39 and 40 of the EL light emitting elements 24 and 25. I can't. Therefore, the illuminance at the end of the light irradiation surface of the document 2 is lower than that at the center of the light irradiation surface.

  Further, according to the present embodiment, the temperature of the intermediate portion 38 of the EL light emitting elements 24 and 25 is increased due to the thermal effect of the LSI 54, so that the luminous intensity of the intermediate portion 38 of the EL light emitting elements 24 and 25 is the first and first. It becomes higher than the end portions 36 and 37 of the second.

  As a result, on the light irradiation surface of the document 2, the illuminance at the central portion facing the intermediate portion 41 of the EL light emitting elements 24 and 25 becomes higher and the illuminance distribution on the light irradiation surface becomes longer in the longitudinal direction of the EL light emitting elements 24 and 25. It becomes non-uniform along (scanning direction).

  In order to improve the variation in the illuminance distribution, in the first embodiment, light shielding as shown in FIGS. 5 and 8 is performed on the upper surface of the glass substrate 39 located on the light emitting surface 40a of the EL light emitting elements 24 and 25. Layer 61 is formed. As the light shielding layer 61, for example, a black resin can be used. This black resin is affixed to the upper surface of the glass substrate 39 with a thickness of, for example, 0.2 mm, and has a characteristic capable of completely blocking light transmission.

  The light shielding layer 61 has a width dimension L along a direction orthogonal to the longitudinal direction of the EL light emitting elements 24 and 25. The width dimension L of the light shielding layer 61 gradually decreases as it proceeds from the intermediate portion 38 of the EL light emitting elements 24 and 25 toward the first and second end portions 36 and 37. In other words, at the position corresponding to the intermediate portion 38 of the EL light emitting elements 24 and 25, the light emitting surface 40a is largely covered with the light shielding layer 61, and the area contributing to light emission is reduced. On the contrary, at positions corresponding to the first and second end portions 36 and 37 of the EL light emitting elements 24 and 25, much of the light emitting surface 40 a is exposed and the area contributing to light emission is larger than that of the intermediate portion 38. .

  FIG. 9 shows the luminous intensity distribution along the longitudinal direction of the EL light emitting elements 24 and 25 having the light shielding layer 61. As is clear from FIG. 9, the luminous intensity is lower in the intermediate portion 38 of the EL light emitting elements 24 and 25 than in the first and second end portions 36 and 37.

  Therefore, the light shielding layer 61 has a light intensity distribution along the longitudinal direction of the EL light emitting elements 24 and 25 so that the light intensity of the first and second end portions 36 and 37 of the EL light emitting elements 24 and 25 exceeds the light intensity of the intermediate portion 38. Is changing.

  According to the first embodiment of the present invention as described above, the luminous intensity of the first and second end portions 36 and 37 of the EL light emitting elements 24 and 25 is higher than the luminous intensity of the intermediate portion 38. When the original 2 is irradiated with light from 24, 25, the illuminance difference between the central portion and the end portion of the light irradiation surface is reduced.

  That is, the light emitted from the EL light emitting elements 24 and 25 is reduced at the edge of the original 2 as compared with the central part of the original 2, but the luminous intensity distribution of the EL light emitting elements 24 and 25 is as described above. By changing the amount, the amount of light applied to the end portion of the document 2 and the amount of light applied to the center portion of the document 2 are balanced with each other. Therefore, the difference in illuminance between the end portion and the center portion of the document 2 is reduced.

  Further, even if the intermediate portion 38 of the EL light emitting elements 24 and 25 is affected by the heat of the LSI 54 and the luminous intensity of the intermediate portion 38 increases, the increase in luminous intensity is offset by the presence of the light shielding layer 61.

  As a result, when the light from the EL light emitting elements 24 and 25 is irradiated onto the document 2, the illuminance on the light irradiation surface of the original 2 is such that the first and second end portions 36 and 37 of the EL light emitting elements 24 and 25. It is possible to prevent a sudden drop at a position facing the.

  FIG. 10 shows the illuminance distribution on the light irradiation surface of the document 2 with respect to the longitudinal direction (scanning direction) of the EL light emitting elements 24 and 25. In FIG. 10, A indicates the illuminance distribution on the light irradiation surface when the original 2 is irradiated with light using the EL light emitting elements 24 and 25 having the light shielding layer 61, and B indicates the luminous intensity distribution over the entire length. Shows the illuminance distribution on the light irradiation surface when the original 2 is irradiated with light using a uniform EL light emitting element.

  When an EL light emitting element having a uniform light intensity distribution is used, the illuminance on the light irradiation surface of the document 2 is highest at the center of the document 2 as shown by the characteristic B, and gradually increases from there to the edge of the document 2. Along with the decrease, the illuminance tends to decrease rapidly in the vicinity of the edge of the document 2. This is because the light of the EL light emitting element guided to the edge of the original 2 is reduced compared to the central part of the original 2, and the luminous intensity of the intermediate part of the EL light emitting element is increased by the temperature rise of the intermediate part of the EL light emitting element. This is because it is high.

  On the other hand, when the EL light emitting elements 24 and 25 whose light intensity distribution is changed by the light shielding layer 61 are used, the illuminance at the center of the document 2 slightly decreases as shown by the characteristic A, but the edge of the document 2 is reduced. The illuminance drop at the edge of the document 2 is reduced, and the illuminance distribution from the edge to the center of the document 2 is substantially uniform. This is because the amount of light applied to the end portion of the document 2 and the amount of light applied to the center portion of the document 2 are balanced with each other due to the presence of the light shielding layer 61.

  FIG. 11 compares the outputs of the contact image sensor 10 using the EL light emitting elements 24 and 25 having the light shielding layer 61 and the contact image sensor using the EL light emitting element having a uniform light intensity distribution over the entire length. Shows the results.

  In FIG. 11, the characteristic A shows the output of the contact image sensor 10 using the EL light emitting elements 24 and 25 having the light shielding layer 61, and the characteristic B shows an EL light emitting element having a uniform light intensity distribution as a comparative example. The output of the contact type image sensor used is shown.

  As can be seen from FIG. 11, in the contact type image sensor 10 according to the first embodiment, the output drop at the end of the document 2 is suppressed to a small extent, whereas in the contact type image sensor of the comparative example, As the distance from the edge of the document 2 approaches, the drop in output becomes larger than that in the contact image sensor 10 according to the first embodiment.

  Therefore, it can be seen that in the contact type image sensor of the comparative example, the output at the portion corresponding to the end portion of the document 2 with low illuminance is deteriorated.

  From the above, according to the first embodiment of the present invention, the illuminance difference on the light irradiation surface of the document 2 is consciously changed by the luminous intensity distribution along the longitudinal direction of the EL light emitting elements 24 and 25. Can be reduced. Therefore, in comparison with the case where the image signal is corrected using a light receiving sensor or a complicated signal processing circuit, the image quality read by the contact image sensor 10 can be prevented with a simple configuration.

  Therefore, it is possible to obtain an inexpensive contact image sensor 10 that can stably read image information from the document 2 and an image forming apparatus 1 equipped with the image sensor 10.

  Note that the present invention is not limited to the first embodiment, and can be variously modified without departing from the spirit of the invention.

  12 and 13 disclose a second embodiment of the present invention.

  The second embodiment is different from the first embodiment in that a light shielding layer 71 is formed on the glass plate 15 of the contact image sensor 10. Other basic configurations of the contact image sensor 10 are the same as those in the first embodiment. Therefore, in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As schematically shown in FIG. 13, the glass plate 15 has a pair of regions 72 a and 72 b that cover the EL light emitting elements 24 and 25 from above. The regions 72a and 72b extend in the longitudinal direction (scanning direction) of the EL light emitting elements 24 and 25, and a light shielding layer 71 is formed on each of the regions 72a and 72b. The light shielding layer 71 has the same material and characteristics as the light shielding layer 61 in the first embodiment.

  The light shielding layer 71 has a width dimension L along a direction orthogonal to the longitudinal direction of the EL light emitting elements 24 and 25. The width dimension L of the light shielding layer 71 gradually decreases as it proceeds from the intermediate portion 38 of the EL light emitting elements 24 and 25 toward the first and second end portions 36 and 37. As a result, at the position corresponding to the intermediate portion 38 of the EL light emitting elements 24 and 25, the light emitting surface 40a is largely covered with the light shielding layer 71, and the area contributing to light emission is reduced. On the contrary, at positions corresponding to the first and second end portions 36 and 37 of the EL light emitting elements 24 and 25, much of the light emitting surface 40 a is exposed and the area contributing to light emission is larger than that of the intermediate portion 38. .

  Also in the second embodiment, the light intensity of the first and second end portions 36 and 37 of the EL light emitting elements 24 and 25 is made higher than the light intensity of the intermediate portion 38 due to the presence of the light shielding layer 71. Can do. Therefore, when light is emitted from the EL light emitting elements 24 and 25 to the original, the difference in illuminance between the central portion and the end of the light irradiation surface of the original is reduced.

  Therefore, as in the first embodiment, there is an advantage that the image quality read by the contact image sensor 10 can be prevented with a simple configuration in which the light shielding layer 71 is simply provided on the glass plate 15.

  The light shielding layer is not limited to completely blocking light, and may have a characteristic of transmitting light to some extent.

  Further, a light shielding layer may be formed on both the light emitting surface of the EL light emitting element and the glass plate.

  Further, since the luminous intensity can be represented by the luminance and the light emitting area, the luminous intensity may be changed by changing the luminance.

  In addition, the image sensor according to the present invention is not limited to the contact type but can be similarly applied to a reduction imaging type image sensor. In this case, in the reduced imaging type image sensor, the EL light emitting element can be used as a light source of the light emitting unit.

1 is a side view schematically showing an image forming apparatus according to a first embodiment of the present invention. 1 is a perspective view of a contact image sensor according to a first embodiment of the present invention. Sectional drawing which follows the width direction of the contact | adherence image sensor which concerns on the 1st Embodiment of this invention. 1 is a cross-sectional view along the longitudinal direction of a contact image sensor according to a first embodiment of the present invention. The top view of the organic electroluminescent light source unit which concerns on the 1st Embodiment of this invention. The top view of the organic electroluminescent light source unit which shows the structure of the connection part of EL light emitting element and a printed wiring board in the 1st Embodiment of this invention. Sectional drawing of the organic electroluminescent light source unit which shows the structure of the connection part of EL light emitting element and a printed wiring board in the 1st Embodiment of this invention. The top view which shows schematically the state which covered the light emission surface of EL light emitting element with the light shielding layer in the 1st Embodiment of this invention. The characteristic view which shows the luminous intensity distribution along the longitudinal direction of EL light emitting element in the 1st Embodiment of this invention. FIG. 3 is a characteristic diagram showing an illuminance distribution on a light irradiation surface of a document in the first embodiment of the present invention. FIG. 3 is a characteristic diagram showing an output ratio of the contact image sensor in the first embodiment of the present invention. The perspective view of the contact type image sensor which concerns on the 2nd Embodiment of this invention. The top view which shows roughly the state which covered the glass plate of the organic electroluminescent light source unit with the light shielding layer in the 2nd Embodiment of this invention.

Explanation of symbols

  2 ... read object (original), 5 ... conveying path, 10 ... image sensor (contact image sensor), 24, 25 ... EL light emitting element, 36 ... first end, 37 ... second end, 38 ... the middle part.

Claims (8)

An image sensor that irradiates a reading object with light using an EL light emitting element that emits light by organic electroluminescence,
The EL light emitting element has a line shape including first and second ends spaced apart in the scanning direction and an intermediate portion located between the first and second ends, and the first and second ends. An image sensor, wherein the luminous intensity distribution of the EL light emitting element is changed so that the luminous intensity of the second end is higher than the luminous intensity of the intermediate part.   2. The image according to claim 1, wherein the EL light emitting element has a light emitting surface extending in a scanning direction, and a light shielding layer for changing a luminous intensity distribution of the EL light emitting element is provided on the light emitting surface. Sensor.   3. The light shielding layer according to claim 2, wherein the light shielding layer has a width dimension along a direction orthogonal to the scanning direction, and the width dimension of the light shielding layer is from the middle portion of the EL light emitting element to the first and second end portions. An image sensor characterized by decreasing sequentially as it progresses in the direction.   2. The light-shielding layer according to claim 1, further comprising a transparent plate interposed between the EL light emitting element and the reading object, and a light shielding layer for changing a luminous intensity distribution of the EL light emitting element on the transparent plate. An image sensor characterized by being provided.   The image sensor according to claim 4, further comprising a housing that supports the EL light emitting element, wherein the transparent plate is supported by the housing so as to cover the EL light emitting element.   6. The light shielding layer according to claim 4, wherein the light shielding layer has a width dimension along a direction orthogonal to the scanning direction, and the width dimension of the light shielding layer is first and second from the intermediate portion of the EL light emitting element. An image sensor characterized by decreasing sequentially as proceeding in the direction of the end of the image sensor.   7. The circuit board according to claim 1, further comprising a circuit board that controls driving of the EL light emitting element, and the circuit board includes a circuit part that generates heat during operation. Is provided at a position corresponding to an intermediate portion of the EL light emitting element. A conveyance path for conveying an object to be read; and
An image sensor that is installed in the conveyance path and optically reads image information from the reading object,
The image sensor includes a light source that emits light toward the reading object. The light source is an EL light emitting element that emits light by organic electroluminescence. The EL light emitting element is a first light emitting element that is spaced apart in the scanning direction. And a second end portion and an intermediate portion located between the first and second end portions, and the luminous intensity of the first and second end portions is the luminous intensity of the intermediate portion. An image forming apparatus, wherein the luminous intensity distribution of the EL light emitting element is changed so as to be higher.

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