JP2008193374A - Illumination device, image reading device, and image forming device - Google Patents

Abstract

Even when a light source in which point light sources are arranged in an array in the main scanning direction is used, light reflected on a document surface having a uniform density enters an image sensor by obtaining a good illuminance distribution on the document surface. At this time, the light is incident with uniform intensity in the main scanning direction.
A straight line which is arranged in an image reading apparatus 101 having a line image sensor 110 and which can be imaged by the line image sensor 110 in one main scan by an LED array 402 having a plurality of LED elements 401 arranged in a line. In the illuminating device that illuminates the imaging region, the contact glass 703 disposed between the LED element 401 and the imaging region is subjected to shading processing for reducing unevenness of the light amount in the main scanning direction on the line image sensor.
[Selection] Figure 4

Description

  The present invention relates to an illuminating device, an image reading device, and an image forming device, and more particularly to a lighting device, an image reading device, and an image forming device, and a plurality of light emitting elements arranged in a line. The present invention relates to an illuminating device that illuminates a linear imaging region that can be imaged by main scanning, an image reading apparatus including the same, and an image forming apparatus.

  As a reduction optical system image reading apparatus, there is an apparatus that irradiates a document with light and reads reflected light of the document with a line image sensor that is an image pickup device including a CCD element and a CMOS element. Such an image reading apparatus includes an illuminating device, and some of the illuminating devices have a cylindrical xenon lamp as a light source.

  In such an image reading apparatus, the irradiation light of the xenon lamp is applied to the original on the contact glass that allows the light from the light emitting element to pass, and the diffuse reflection light of the original is guided to the imaging element via an optical element such as a lens. Then, the image signal is converted into an electric signal by the image sensor.

  Further, in such an image reading apparatus, a first traveling body in which a first mirror for deflecting reflected light from the original is disposed, a second mirror for further deflecting light from the second mirror, and a third mirror are disposed. The first traveling body and the second traveling body travel on a rail provided in the image reading apparatus, thereby scanning the document. In the image reading apparatus, the first traveling body is provided with a reflecting plate for reflecting light from the xenon lamp to optimize the illuminance distribution and for eliminating shadows when reading a cut and pasted document. FIG. 8 is a schematic view showing a conventional lighting device. The first traveling body 301 of the lighting device is disposed below the contact glass 305, and guides the xenon lamp 302, the reflector 303 for improving the illuminance distribution on the document surface, and the reflected light on the document surface to the CCD. A first mirror (not shown) is provided.

  In Patent Document 1, in order to improve the image quality of a read image, a light emitting mechanism and transmitted light or reflected light obtained by irradiating light from the light emitting mechanism onto a document on which predetermined image information is recorded are detected. In an image reading apparatus having reading means for reading predetermined image information, the light emitting mechanism is a light that mixes a plurality of light sources and light emitted from the plurality of light sources to form light emitted in substantially the same direction. There is a description that includes a mixing unit and a light focusing unit that focuses the light mixed by the light mixing unit toward the original.

Further, in Patent Document 2, one end surface of the light guide is disposed close to the side of the light source that irradiates light on the image surface of the document that does not face the image surface of the document, and the other end surface of the light guide is Light directed toward the image plane of the light source is incident from one end face of the light guide toward the position directly illuminated by the light source on the image plane. This light propagates through the light guide and exits from the other end face. However, it is described that the image surface can be illuminated, thereby increasing the amount of light that illuminates the image surface and illuminating the image surface from two directions.
JP 2003-248274 A Japanese Patent Laid-Open No. 11-317842

  In recent years, there has been a demand for shortening the rise time, saving energy, and prolonging the life of the light source in the image reading apparatus, and a light source that employs a light emitting diode (LED) as an alternative light source for the xenon lamp has been put into practical use. . When the LED is used in the reduction optical system, the distance from the document surface to the image pickup device is longer than that in the equal magnification optical system, so that the attenuation of light between them is increased. Therefore, a higher document surface illuminance is required. Therefore, an attempt has been made to increase the illuminance on the document surface by arranging a plurality of LEDs in an array in the main scanning direction.

  An illumination device using such an LED will be described. 9A and 9B are schematic views showing the configuration of a lighting device using a conventional LED, where FIG. 9A is a side view and FIG. 9B is a perspective view. As shown in FIG. 12B, the illumination device is arranged using a LED array 402 in which a plurality of LED elements 401 are arranged as a light source. Here, when the LED array 402 is used, in order to obtain a good illuminance distribution in the sub-scanning direction on the document surface, the light-emitting surface is inclined with respect to the document surface like the xenon lamp.

  The illumination distribution of such an illumination device is as follows. 10A and 10B are diagrams illustrating illumination characteristics of the illumination device, where FIG. 10A is a diagram illustrating a case where a xenon lamp is used, FIG. 10B is a diagram illustrating a case where an LED is used, and FIG. 15 is an illumination using an LED array. It is a figure which shows the state of the illumination in an apparatus, (a) is a side view, (b) is a front view.

  An illumination device using a xenon lamp can emit substantially uniform diffused light in the main scanning direction by surface emission (FIG. 10A), whereas an LED array in which LEDs that are point emission are arranged in the main scanning direction. When 402 is used, ripple-shaped illuminance unevenness corresponding to the pitch of the LED elements 401 appears in the main scanning direction (FIG. 10B). In order to avoid this phenomenon, it is necessary to optimize the relationship between the three elements of the distance between the LED and the document surface, the pitch of the LED, and the directivity of the LED.

  On the other hand, in an image reading apparatus that irradiates light on a document and forms an image of part of the diffusely reflected light and reads an image, when the light is irradiated to a place other than the image reading position on the document surface, the light is After reflection on the original surface, the light reaches the CCD surface and the original cannot be read faithfully. For this reason, in order to obtain the best possible illuminance distribution on the document surface, the light-emitting surface of the light source is inclined with respect to the document surface, or a reflector is provided on the surface facing the optical axis of the light source.

  Further, for example, when the document is lifted off the contact glass, a phenomenon that unintentional regular reflection light enters the image sensor due to the floating angle of the document and the angle of incident light from the light source occurs. This phenomenon occurs when the light source is a surface emission like a xenon lamp and can emit almost uniform diffused light in the main scanning direction, while a strip-like area brighter than the original image is formed on the image. In the case of a light source in which a plurality of point light sources are arranged in the main scanning direction as in an array, the same number of bright areas as the arranged LEDs appear in the form of dots, and particularly in the case of LEDs, a light source with high directivity. Therefore, the influence on the image becomes large.

  The present invention has been made in view of such a background, and even when a light source in which point light sources are arranged in an array in the main scanning direction is used, a uniform illuminance distribution can be obtained by obtaining a uniform illuminance distribution on the document surface. It is an object of the present invention to provide an illuminating device in which light reflected by a document surface having a density is incident at a uniform intensity in the main scanning direction when entering an image sensor.

  According to a first aspect of the present invention, a linear imaging region that is arranged in an image reading apparatus including a line image sensor and that the line image sensor can capture in one main scan is arranged with a plurality of light emitting elements arranged in a line. In the illumination device, a correction member that reduces unevenness of the light amount in the main scanning direction on the line image sensor is disposed between the light emitting element and the imaging region.

  According to a second aspect of the present invention, in the illumination device according to the first aspect, the correction member is a transparent member on which a reading target of the image reading apparatus is arranged in close contact.

  According to a third aspect of the present invention, in the illuminating device according to the second aspect, the transparent member is subjected to a shading process for changing a transmittance at an arrangement pitch interval of the light emitting elements in the main scanning direction. Features.

  According to a fourth aspect of the present invention, in the illumination device according to the first aspect, the light emitting element is provided with a light guide member that guides light of the light emitting element to the illumination region, and the correction member is the light guide member. It is characterized by that.

  According to a fifth aspect of the present invention, in the illuminating device according to the fourth aspect, the light guide member is subjected to a shading process for changing the transmittance in the main scanning direction at an arrangement pitch interval of the light emitting elements. It is characterized by.

  According to a sixth aspect of the present invention, in the illuminating device according to the fourth aspect of the present invention, the light guide member is configured by changing the shape at a pitch interval of the light emitting elements on the light emitting elements arranged in a row. Features.

  A seventh aspect of the invention is an image reading device comprising the illumination device according to any one of the first to sixth aspects.

  According to an eighth aspect of the present invention, there is provided an image forming apparatus comprising the image reading apparatus according to the seventh aspect.

  According to the present invention, even when a light source in which point light sources are arranged in an array in the main scanning direction is used, unevenness in the amount of light in the main scanning direction is reduced by the correction member, and a good illuminance distribution can be obtained on the document surface. . Therefore, the light reflected from the document surface having a uniform density is incident at a uniform intensity in the main scanning direction when entering the image sensor.

  Embodiments as the best mode for carrying out the present invention will be described below with reference to the drawings.

  Hereinafter, an image forming apparatus according to an embodiment will be described. FIG. 1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment. The image forming apparatus 10 includes an image reading apparatus 101 that reads a document, an image forming unit 12 that forms an image, an automatic document feeder (ADF) 13, a document discharge tray 14 that stacks documents sent from the ADF 13, and a paper feed cassette 15. Are provided with a paper feed unit 19 provided with thru 18 and a paper discharge tray 20 for stacking recording paper.

  When the document D is set on the document table 21 of the ADF 13 and a print key is pressed by an operation unit (not shown), the uppermost document D is sent in the direction of the arrow B1 by the rotation of the pickup roller 22, and the document is conveyed. By the rotation of the belt 23, the belt 23 is fed onto the contact glass 102 fixed to the image reading apparatus 101, and stops there. The image of the document D placed on the contact glass 102 is read by the image reading device 101 positioned between the image forming unit 12 and the contact glass 102. The image reading apparatus 101 includes an illumination device including an LED array 402 that illuminates a document D on a contact glass 102, a first traveling body 103 having a single mirror, and two mirrors for turning a document image. The 2nd traveling body 106 provided with is provided. In addition, the image reading apparatus 101 includes a lens 109 and a line image sensor 110 including a CCD that forms an image of a document. After the image reading is completed, the document D is transported in the direction of the arrow B2 by the rotation of the document transport belt 23 and discharged onto the document discharge tray 14. In this way, the document D is fed one by one onto the contact glass 102 and the document image is read by the image reading device 101.

  On the other hand, inside the image forming unit 12, a photoconductor 30 as an image carrier is disposed. The photoconductor 30 is rotated in the clockwise direction in the figure, and the charging device 31 charges the surface to a predetermined potential. Further, the writing unit 32 emits a laser beam L that is light-modulated in accordance with image information read by the image reading apparatus 101, and the surface of the charged photoconductor 30 is exposed with the laser beam L, whereby the photosensitive unit 30 is exposed to light. An electrostatic latent image is formed on the surface of the body 30. When the electrostatic latent image passes through the developing device 33, the electrostatic latent image is transferred to the recording medium P fed between the photosensitive member 30 and the transfer device 34 by the opposing transfer device 34. The surface of the photoconductor 30 after the toner image is transferred is cleaned by a cleaning device 35.

  The plurality of paper feed cassettes 15 to 18 arranged at the lower part of the image forming unit 12 contain recording media P such as paper, and the recording media P is fed from any of the paper feed cassettes 15 to 18 in the direction of arrow B3. The toner image formed on the surface of the photoreceptor 30 as described above is transferred onto the surface of the recording medium P. Next, the recording medium P is passed through the fixing device 36 in the image forming unit 12 as indicated by an arrow B4, and the toner image transferred to the surface of the recording medium P by the action of heat and pressure is fixed. The recording medium P that has passed through the fixing device 36 is conveyed by the discharge roller pair 37, discharged to the discharge tray 20 as indicated by an arrow B5, and stacked.

  Next, an image reading apparatus according to the embodiment will be described. 2 is an enlarged cross-sectional view showing the configuration of the image reading apparatus shown in FIG. 1, and FIG. 3 is a perspective view of the image reading apparatus shown in FIG. The image reading apparatus 101 includes a light source 104 having an LED array 402 and a first traveling body 103 having a first mirror 105 supported at both ends, and a second mirror 107 and a third mirror 108 similarly supported at both ends. The second traveling body 106, a line image sensor 110 that is an image sensor such as a CCD, and a lens 109 that forms an image on the line image sensor 110 are provided. Then, the image reading apparatus 101 moves the first traveling body 103 and the second traveling body 106 along the document at a speed of 2: 1 in accordance with the image reading request signal for each line sent from the host computer. It is configured to move and sequentially read images.

  Thereby, the document D on the contact glass 102 is optically scanned. That is, the document D on the contact glass 102 is illuminated by the LED array 402 of the light source 104, and the reflected light image is guided to the lens 109 through the first mirror 105, the second mirror 107, and the third mirror 108. As a result, an image is formed on the line image sensor 110.

  The line image sensor 110 photoelectrically converts the formed reflected light image of the document D into an analog image signal, and reads the document. Then, after the reading of the document D is completed, the first traveling body 103 and the second traveling body 106 return to the home position. The analog image signal output from the image sensor is converted into a digital image signal by an analog / digital converter, and each image processing (binarization, multi-value conversion, floor conversion) is performed on a circuit board on which an image processing circuit is mounted. Key adjustment processing, scaling processing, editing processing, etc.).

  Next, the lighting device will be described. FIG. 4 is a schematic cross-sectional view showing the lighting apparatus according to the first embodiment of the present invention.

  In the illuminating device according to the present embodiment, when the LED array 402 including the LED elements 401 is used, the light transmittance in the main scanning direction changes in a predetermined pattern as the contact glass 701 arranged between the document surface. You are using

  In this example, the contact glass 701 is shaded so as to have a transmittance distribution in the main scanning direction. As shown in FIG. 4, the transmittance of the contact glass 701 by the shading process is such that the transmittance changes at the same pitch as the arrangement pitch p of the LED elements 401 of the LED array 402. That is, the transmittance is low on the chief ray of the LED 401 and the transmittance is highest between the LEDs 401 and 401.

  Here, the meaning that the light incident on the line image sensor 110 has a uniform illuminance distribution means that the light reflected by the document surface having a uniform density becomes uniform in the main scanning direction when entering the line image sensor 110. That is. That is, the light input to the line image sensor 110 once passes through the contact glass 701, is reflected by the document surface, and then passes through the contact glass 701 again. For this reason, the light from the LED array 402 must be corrected to be uniform by passing through the contact glass twice. Therefore, in this example, the light incident on the document surface is not uniform in the main scanning direction.

  In this example, the variation in the light transmittance of the contact glass 701 corrects the inherent main scanning direction illuminance unevenness caused by the arrangement of the LED elements 401 of the LED array 402, and the light incident on the line image sensor 110 is corrected in the main scanning direction. The illuminance distribution can be uniform.

  Note that the transmittance of the contact glass 701 can be changed by shading the contact glass 701 itself, or by attaching an ND filter film or the like whose transmittance gradually changes to the contact glass 701.

  Next, a lighting device according to a second embodiment will be described. FIG. 5 is a side view showing a second embodiment of the lighting device, and FIG. 6 is a plan view schematically showing the lighting device in the second embodiment.

  In this example, a light guide plate 702 is disposed in the LED array 402 of the illumination device as shown in FIG. The light guide plate 702 is an optical member for efficiently guiding the light emitted from the LED array 402 toward the document. The light emitted from the LED is repeatedly transmitted and reflected inside the light guide plate, and then emitted to the outside from the end face of the light guide plate. Is done. In this example, the light guide plate 702 is processed to have a transmittance distribution in the main scanning direction, thereby correcting the illuminance unevenness of the incident light quantity in the main scanning direction on the exit side. Note that the contact glass 703 arranged in this example has a uniform transmittance unlike the contact glass 701 of the first embodiment.

  That is, the light guide plate 702 is subjected to shading, and the transmittance of the contact glass 701 changes as shown in FIG. 6 at the same pitch as the arrangement pitch p of the LED elements 401 of the LED array 402. Yes, the transmittance is low on the chief ray of the LED 401, and the transmittance is highest between the LED 401 and the LED 401. Here, the meaning that the light incident on the line image sensor 110 has a uniform illuminance distribution means that the light reflected by the document surface having a uniform density becomes uniform in the main scanning direction when entering the line image sensor 110. That is.

In this example, the light from the LED array 402 passes through the light guide plate 702 only once. Therefore, unlike the first embodiment, the light from the LED array 402 is uniformly irradiated on the document surface through the contact glass 703. Then, the reflected light from the document surface passes through the contact glass 703 and is guided to the line image sensor 110. Therefore, in this embodiment,
The illuminance distribution in the main scanning direction of the LED array 402 is corrected well when input to the document surface and the image sensor, and high-quality read data can be obtained.

Next, a lighting device according to a third embodiment will be described. FIG. 7 is a plan view schematically showing the illumination device in the third embodiment. In this example, the shape of the surface 704a of the light guide plate 704 is changed in the main scanning direction, and the illuminance unevenness in the main scanning direction of the LED array 402 is corrected by the light distribution. In this example, as shown in FIG. 8, the density distribution of light due to the lens effect is set as shown in the figure at the period of the arrangement pitch p of the LEDs 401. That is, it is sparse on the principal ray of the LED, and is most dense between the LEDs. Thereby, the uneven illuminance on the original surface is reduced.
According to the present embodiment, the illuminance distribution in the main scanning direction of the LED array 402 is corrected well when input to the document surface and the image sensor, and high-quality read data can be obtained.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment. It is an expanded sectional view which shows the structure of the image reading apparatus shown in FIG. FIG. 2 is a perspective view of the image reading apparatus illustrated in FIG. 1. It is a top view which shows typically the illuminating device in a 1st Example. It is a side view which shows the 2nd Example of an illuminating device. It is a top view which shows typically the illuminating device in a 2nd Example. It is a top view which shows typically the illuminating device in a 3rd Example. It is a schematic diagram which shows the illuminating device using the conventional xenon lamp. It is the schematic which shows the structure of the illuminating device using the conventional LED, (a) is a side view, (b) is a perspective view. It is a figure which shows the illumination characteristic of an illuminating device, (a) is a figure which shows the case where a xenon lamp is used, (b) is a figure which shows the case where LED is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 12 ... Image forming part 13 ... Automatic document feeder (ADF)
14 ... Document discharge trays 15-18 ... Paper feed cassette 19 ... Paper feed unit 20 ... Paper discharge tray 21 ... Document stand 22 ... Pickup roller 23 ... Document transport belt 30 ... Photoconductor 31 ... Charging device 32 ... Writing unit 33 ... Developing device 34 ... Transfer device 35 ... Cleaning device 36 ... Fixing device 37 ... Discharge roller pair 101 ... Image reading device 102 ... Contact glass 103 ... First traveling member 104 ... Light source 105 ... First mirror 106 ... Second traveling member 107 ... Second mirror 108 ... third mirror 109 ... lens 110 ... line image sensor 401 ... LED element 402 ... LED array 701 ... contact glass 702 ... light guide plate 703 ... contact glass 704 ... light guide plate 704a ... surface

Claims (8)

In an illuminating device that is arranged in an image reading device including a line image sensor and illuminates a linear imaging region that the line image sensor can image in one main scanning with a plurality of light emitting elements arranged in a row,
An illumination device, wherein a correction member that reduces unevenness in the amount of light in the main scanning direction on the line image sensor is disposed between the light emitting element and the imaging region.   The illumination device according to claim 1, wherein the correction member is a transparent member that is placed in close contact with a reading target of the image reading device.   The lighting device according to claim 2, wherein the transparent member is subjected to a shading process that changes transmittance in the main scanning direction at an arrangement pitch interval of the light emitting elements.   The lighting device according to claim 1, wherein a light guide member that guides light of the light emitting element to the illumination region is disposed in the light emitting element, and the correction member is the light guide member.   The lighting device according to claim 4, wherein the light guide member is subjected to a shading process that changes transmittance in the main scanning direction at an arrangement pitch interval of the light emitting elements.   The lighting device according to claim 4, wherein the light guide member is configured to change a shape at a pitch interval of the light emitting elements on the light emitting elements arranged in a row.   An image reading apparatus comprising the illumination device according to claim 1.   An image forming apparatus comprising the image reading apparatus according to claim 7.