JP2012227943A - Illuminating device, document reading device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that: in a conventional document reading device, illuminance of a reading area is changed due to re-reflection caused by contrast of a document existing in an illumination portion outside the reading area, so that there is possibility that uniform image density cannot be obtained, because an area with wider width in a sub-scanning direction than a predetermined reading area is illuminated; and further, in a double purpose type reading device for a movable document type and a fixed document type, difference in the illuminance of the reading area is needed to be corrected, because, in the movable document type, a portion except the reading area is shielded from light, and thereby reducing the likelihood of the occurrence of re-reflection.SOLUTION: A light guide body 101 comprising a cylindrical lens is provided just in front of a light source 6 comprising a plurality of LEDs arranged in a main scanning direction. Two reflecting plates 102 are provided so as to block light leaked from a gap between the light source 6 and the light guide body 101. A luminous flux emitted from the light source 6 becomes a parallel luminous flux or a converging luminous flux as necessary and illuminates a document surface placed on contact glass 1 in cooperation with an opposite reflecting plate 10.

Description

  The present invention relates to an illumination device in a reading device such as a digital copying machine or a general-purpose scanner.

FIG. 18 is a diagram illustrating an example of an image forming apparatus having a document reading device.
In the figure, reference numeral 11 is a photosensitive drum, 12 is a charging device, 13 is a cleaning device, 14 is a developing device, 15 is a transfer device, 16 is a fixing roller, 17 is a pressure roller, 18 is a fixing belt, and 19 is a tension roller. , 20 is a paper feed tray, 21 is a paper feed roller, 22 is a transport roller, 23 is a registration roller, 24 is a paper discharge roller, 25 is a paper discharge tray, 90 is an exposure device, and 100 is a reading device.
The surface of the photosensitive drum 11 is uniformly charged by the charging device 12 while rotating in the sub-scanning direction. The photosensitive member 11 is exposed by scanning with a light beam L carrying image information from the exposure device 90 in the main scanning direction perpendicular to the paper surface, and an electrostatic latent image is formed. The electrostatic latent image is visualized by the toner of the developing device 14 and becomes a toner image.

  The transfer paper P at the uppermost position of the paper feed tray 20 is sent out toward the transport roller 22 by the paper feed roller 21 and is abutted against the registration roller 23 to stop. The transfer paper sent from the registration roller in synchronization with the formation of the toner image on the photosensitive member is transferred with the toner image by the transfer device 15, and the toner image is fixed between the fixing roller 16 and the pressure roller 17. The paper is discharged onto a paper discharge tray 25 by a paper discharge roller 24 and the like.

FIG. 19 is a schematic configuration diagram of the reading apparatus.
In the figure, reference numeral 1 is a contact glass serving as a document table, 2 is a first carriage, 3 is a second carriage, 4 is an imaging lens, 5 is a CCD as an image reading element, 6 is a light source, 7 is a first mirror, Reference numeral 8 denotes a second mirror, and 9 denotes a third mirror.
A document (not shown) is placed on the contact glass 1 with the document surface facing downward, the light source is turned on, and the first carriage 2 is moved in the direction of arrow A at a predetermined speed. At this time, the second carriage 3 is moved in the arrow B direction at a half speed of the first carriage 2. The image forming lens 4 is disposed in a positional relationship for forming an image on the original surface on the CCD 5 via the first to third mirrors 7, 8, and 9.
Since the contact glass 1 (original surface) and the CCD 5 always maintain a conjugate relationship with the imaging lens 4 even during the movement of the carriage, a clear image is always taken into the CCD 5.

FIG. 20 is a diagram showing the conjugate relationship between the document surface and the CCD 5.
In the figure, symbols R, G, and B on the CCD indicate the reading CCD lines for the three primary colors (red, green, and blue), and R, G, and B on the document surface indicate the reading positions corresponding to the CCD lines. Respectively.
If the reading width of the CCD is a and the interval between the CCD lines is b, the illumination light needs to be at least 2b + a in the sub-scanning direction in terms of the CCD position. When the imaging magnification by the imaging lens is m (m <1), the illumination width C on the document surface needs to be at least C = (2b + a) / m 2. When manufacturing errors are taken into consideration, it is better to make it slightly larger. On the other hand, if it is too large, the amount of light that is not effectively used increases and the illumination efficiency decreases.

FIG. 21 is a diagram showing the illuminance distribution in the sub-scanning direction of the document surface by a conventional light source.
In the figure, reference numeral 10 denotes a counter mirror, 11 a distribution curve of direct light by a light source and a counter mirror when there is no document, and 12 an illuminance distribution curve of an actual document surface including secondary reflection when a blank sheet is placed. Each is shown.
Conventionally, a discharge tube such as a fluorescent lamp or a xenon lamp has been used as a light source, but in this case, the state is as shown in FIG.
The illuminance distribution curve 11 is distributed almost symmetrically with respect to the range C, but the illuminance distribution curve 12 is slightly biased to the right. This is because the illumination range of the light source 6 is wide, so that light also strikes the document surface outside the range C, and the reflected light from the document surface strikes the tube wall of the light source 6 and re-reflects. It is thought to illuminate.

Such an illuminance distribution curve 12 not only causes a loss of light quantity, but also causes a further problem when a combined scanner for document fixing and document movement is configured.
FIG. 22 is a diagram for explaining the illuminance distribution of the combined scanner.
In the figure, reference numeral 13 is an ADF contact glass, 14 and 15 are opaque guide members, 16 and 17 are document feeding rollers, 18 is a sheet document, and 19 is an ADF side illuminance distribution curve.
At the time of reading with the original fixed, the first and second carriages move as shown in FIG. On the other hand, when reading the movement of the original, the sheet-like original 18 is sent to the surface of the ADF contact glass 13 by the original feeding rollers 16 and 17, and the image illuminated by the light source 6 and the counter mirror 10 is displayed. The image is read by the CCD 5 by the imaging optical system below the first mirror 7.
This figure shows the illuminance distribution curve at the moving document position and the illuminance distribution curve at the fixed document position in one figure.

The illuminance distribution curve 12 at the fixed document position is the same as the distribution shown in FIG. On the other hand, since the illuminance distribution 19 at the position for the moving document is almost covered by the guide member 15 which is an opaque member, the portion directly above the light source 6 is not reflected from the area, and therefore, unnecessary re-transmission. There is no reflection. For this reason, the area outside the ADF contact glass 13 has almost no illuminance distribution, and the illuminance distribution curve 19 is very close to the direct light illuminance distribution curve 11 shown in FIG.
These differences in illuminance distribution curves do not cause any particular problems when used alone, but when a scanner is configured using the same CCD as a dual-use type, two new problems arise.

  One of the problems is a difference in the amount of illumination light on the document surface and a difference in the light amount balance for each color. The illuminance distribution curve 19 is substantially symmetric with respect to the illumination range C, whereas the illuminance distribution curve 12 has a large amount of light as a whole and the peak value is biased to the right. Therefore, when receiving light with the same CCD while changing the reading method, the sensitivity to the light amount and the sensitivity balance for each color must be changed. Sensitivity to the amount of light can be electrically processed by AGC, but changing the sensitivity balance for each color requires separate consideration.

  Another problem occurs when the original is a document having a large difference in brightness with respect to the sub-scanning direction of the original. That is, the reason why the peak value of the illuminance distribution curve 12 is biased to the right is the re-reflection from the light source tube wall to the reflected light from the document surface. Therefore, the illuminance distribution curve 12 shown in FIG. 22 is obtained while there is a bright portion of the document directly above the tube wall. However, when the portion directly above the tube wall is a dark portion of the document, re-reflection as described above occurs. Rather, it becomes a curve close to the illuminance distribution curve 19. For such changes, the above-mentioned AGC cannot be used immediately. This is because the dark original part continues to enter the reading range after that, and if AGC is applied suddenly, the original part cannot be correctly recognized as a dark part, and faithful image reproduction cannot be performed. Because.

In order to solve the problem caused by re-reflection of light once hitting the document surface, there is a proposal to specify a ratio of the amount of light within a predetermined range (see, for example, Patent Document 1). According to this method, although the problem of re-reflection from the document placement glass is solved, re-reflection from the tube wall such as an Xe lamp used as a light source cannot be solved.
There is also a configuration in which the illumination light is collected in a narrow range and it is not necessary to consider the illuminance outside the reading range (see, for example, Patent Document 2). These are excellent in that the problem of re-reflection does not occur. However, unless special measures are taken, the illuminance distribution generally has a mountain shape. Therefore, when reading a color image using a three-line CCD, the illuminance between the three colors is There is a problem that they are not equal.

  Provided are an illuminating apparatus and an image reading apparatus that do not illuminate as much as possible outside a desired range and do not need to give special consideration to a difference in a reading method even in a document fixing / moving document scanner.

According to the first aspect of the present invention, document reading is performed by irradiating at least a predetermined illumination width including a reading area having a predetermined reading width extending long in the main scanning direction of the document, and reading reflected light from the document by the image reading element. In the illuminating device in the apparatus, a point light source and a light guide having an incident surface in the vicinity of the light beam exit surface of the point light source and having the exit surface directed to the reading region are provided, and illumination is performed by irradiation light from the point light source The area has a high illuminance distribution area having a substantially constant illuminance, and the high illuminance distribution area is substantially coincident with the reading area.
According to a second aspect of the present invention, in the illumination device according to the first aspect, the illumination device includes a plurality of point light sources arranged in the main scanning direction.

According to a third aspect of the present invention, in the illuminating device according to the first or second aspect, an outside of a region where a light beam from the point light source is incident on the incident surface of the light guide is covered with a reflecting plate. It is characterized by.
According to a fourth aspect of the present invention, in the illuminating device according to any one of the first to third aspects, the illuminance distribution in the illumination area has a half-value width of not more than three times, preferably not more than twice the predetermined illumination width. It is characterized by being.
According to a fifth aspect of the present invention, in the illuminating device according to any one of the first to fourth aspects, the light is blocked from blocking the light flux from the exit surface of the light guide to the original surface immediately above the light guide. A member is provided.

According to a sixth aspect of the present invention, in the illuminating device according to any one of the first to fifth aspects, an opposing reflecting plate is provided at a facing position beyond the reading area from the exit surface of the light guide. And
According to a seventh aspect of the present invention, in the illumination device according to any one of the first to sixth aspects, the light guide is a cylindrical lens.
According to an eighth aspect of the present invention, in the illuminating device according to the seventh aspect, the cylindrical lens has a focal line position on the incident surface side of the light beam substantially coincided with a central portion of the point light source in the sub-scanning direction. And
According to a ninth aspect of the present invention, in the illumination device according to the seventh aspect, the cylindrical lens is arranged so that the point light source and the reading area center position are in a conjugate relationship of a predetermined imaging magnification. Features.

According to a tenth aspect of the present invention, in the illuminating device according to any one of the first to ninth aspects, the light guide is a light reflecting surface other than the light incident / exiting surface.
According to an eleventh aspect of the present invention, in the illumination device according to any one of the first to tenth aspects, a plurality of the point light sources are arranged in the sub-scanning direction.
According to a twelfth aspect of the present invention, in the illumination device according to any one of the first to eleventh aspects, the point light source is an LED.
According to a thirteenth aspect of the present invention, in the illumination device according to any one of the first to twelfth aspects, the predetermined reading width is a width corresponding to a light receiving width in a sub-scanning direction of the image reading element. And

According to a fourteenth aspect of the present invention, in the illuminating device according to any one of the first to thirteenth aspects, the predetermined illumination width is set to a width corresponding to a light receiving width of the image reading element in the sub-scanning direction. It is characterized by a width obtained by adding a fluctuation range caused by manufacturing tolerances.
According to a fifteenth aspect of the present invention, in the illumination device according to any one of the first to fourteenth aspects, the image reading element is a CCD.
According to a sixteenth aspect of the present invention, in the illumination device according to any one of the first to fifteenth aspects, the image reading element is a PDA.
The invention of claim 17 is characterized by an original reading device using the illumination device according to any one of claims 1 to 16.

According to an eighteenth aspect of the present invention, in the document reading device according to the seventeenth aspect, the illumination device is used for both of a document fixed reading method and a document movement reading method.
According to a nineteenth aspect of the present invention, there is provided the original reading apparatus according to the seventeenth or eighteenth aspect, wherein the substantially constant illuminance has a flatness of 30% or less.
According to a twentieth aspect of the present invention, there is provided the original document reading device according to the seventeenth or eighteenth aspect, wherein the substantially constant illuminance has a flatness of 12% or less.
According to a twenty-first aspect of the invention, there is provided an image forming apparatus using the document reading device according to any one of the seventeenth to twentieth aspects.

  According to a twenty-second aspect of the present invention, an original is read by irradiating at least a predetermined illumination width including a reading area having a predetermined reading width extending long in the main scanning direction of the original and reading reflected light from the original by an image reading element. In the illuminating device of the apparatus, a set of two lenses comprising a point light source, a convex lens system cylindrical lens having an entrance surface in the vicinity of a light beam exit surface of the point light source, and a concave lens system cylindrical lens having an exit surface facing the reading area A light guide, and the center of the point light source in the sub-scanning direction is disposed at the combined focal line position of the light guide, and the illumination area irradiated with light from the point light source has a substantially constant illuminance. An illuminance distribution area is provided, and the outside of the area where the light beam from the point light source is incident on the incident surface of the light guide is covered with a reflector, and the high illuminance distribution area is Characterized in that is substantially equal to the reading area.

According to a twenty-third aspect of the present invention, an original is read by irradiating at least a predetermined illumination width including a reading area having a predetermined reading width extending long in the main scanning direction of the original and reading reflected light from the original by an image reading element. In the illuminating device in the apparatus, a point light source and a light guide having an incident surface in the vicinity of the light beam exit surface of the point light source and having the exit surface directed to the reading region are provided, and illumination is performed by irradiation light from the point light source The region has a high illuminance distribution region having a substantially constant illuminance, and the outer side of the region where the light beam from the point light source is incident on the incident surface of the light guide has a shape in a cross section in the sub-scanning direction. The high-illuminance distribution area is substantially coincident with the reading area.
According to a twenty-fourth aspect of the present invention, in the illuminating device according to the twenty-third aspect, at least a part of the light beam reaching the reflecting plate is emitted from between the light guide and the reflecting plate toward the document. Features.

According to a twenty-fifth aspect of the present invention, in the illumination device according to the twenty-fourth aspect, the illumination device includes a plurality of point light sources arranged in the main scanning direction.
According to a twenty-sixth aspect of the present invention, in the illumination device according to any one of the twenty-third to twenty-fifth aspects, the illuminance distribution in the illumination region has a half-value width of three times or less, preferably two times or less of the predetermined illumination width. It is characterized by being.
According to a twenty-seventh aspect of the present invention, in the illuminating device according to any one of the twenty-third to twenty-sixth aspects, a light shield that blocks a light flux from an emission surface of the light guide to the original surface immediately above the light guide. A member is provided.
In the invention of claim 28, in the illumination device according to any one of claims 23 to 27, an opposing reflector is provided at an opposing position beyond the reading area from the exit surface of the light guide. And

According to a twenty-ninth aspect of the present invention, in the illumination device according to any one of the twenty-third to twenty-eighth aspects, the light guide is a cylindrical lens.
According to a thirty-third aspect of the present invention, in the illuminating device according to the twenty-ninth aspect, the cylindrical lens is configured such that a focal line position on the incident surface side of the light beam is substantially coincident with a central portion of the point light source in the sub-scanning direction. Features.
According to a thirty-first aspect of the invention, in the illumination device according to the thirty-third aspect, the cylindrical lens has a complex shape having a convex lens system cylindrical lens portion having a convex surface facing the point light source and a flat plate portion, The axis of symmetry is made coincident with the optical axis of the cylindrical lens, and the light beam reaching the reflecting plate is directed to the document side via the flat plate portion of the cylindrical lens.
According to a thirty-second aspect of the present invention, in the illumination device according to any one of the twenty-third to thirty-first aspects, a plurality of the point light sources are arranged in the sub-scanning direction.

According to a thirty-third aspect of the present invention, in the illumination device according to any one of the twenty-third to thirty-second aspects, the point light source is an LED.
According to a thirty-fourth aspect of the invention, in the illumination device according to any one of the twenty-third to thirty-third aspects, the predetermined reading width is a width corresponding to a light receiving width in a sub-scanning direction of the image reading element. And
According to a thirty-fifth aspect of the present invention, in the illumination device according to any one of the twenty-third to thirty-fourth aspects, the predetermined illumination width is set to a width corresponding to a light receiving width in the sub-scanning direction of the image reading element. It is characterized by a width obtained by adding a fluctuation range caused by manufacturing tolerances.
According to a thirty-sixth aspect of the present invention, in the illumination device according to any one of the twenty-third to thirty-fifth aspects, the image reading element is a CCD.

According to a thirty-seventh aspect of the present invention, in the illumination device according to any one of the twenty-third to thirty-fifth aspects, the image reading element is a PDA.
In a thirty-eighth aspect of the invention, document reading is performed by irradiating at least a predetermined illumination width including a reading area having a predetermined reading width extending long in the main scanning direction of the document, and reading reflected light from the document by the image reading element. An adjustment device for an illuminating device in the apparatus, comprising: a point light source; and a light guide having an incident surface in the vicinity of a light beam exit surface of the point light source and having the exit surface facing the reading region, The illumination area by the irradiated light has a high illuminance distribution area having a substantially constant illuminance, and the first carriage for moving the illumination area in the sub-scanning direction, the point light source, and the light guide are integrated. A support substrate that is held and supported on the first carriage, the support substrate being attached to the first carriage so as to be adjustable in a sub-scanning direction, and the high-illuminance distribution area substantially matching the reading area. To.

According to a thirty-ninth aspect of the present invention, in the lighting device adjusting apparatus according to the thirty-eighth aspect, the illuminating device is the illuminating device according to any one of the first to seventeenth and twenty-second to thirty-seventh aspects. To do.
The invention of claim 40 is characterized by an original reading apparatus using the illumination device according to any one of claims 22 to 37.
The invention of claim 41 is characterized by an original reading device using the adjustment device for an illumination device according to claim 38 or 39.
According to the invention of claim 42, in the document reading apparatus according to claim 40 or 41, the illuminating device is used for both of a document fixed reading method and a document moving reading method.

The invention according to claim 43 is characterized in that in the document reading device according to any one of claims 40 to 42, the substantially constant illuminance has a flatness of 30% or less.
The invention according to claim 44 is characterized in that in the document reading device according to any one of claims 40 to 42, the substantially constant illuminance has a flatness of 12% or less.
The invention of claim 45 is characterized by an image forming apparatus using the document reading device according to any one of claims 40 to 44.

  ADVANTAGE OF THE INVENTION According to this invention, the illuminating device which can illuminate only a desired range intensively using the light source device of a simple structure which provides a light guide in front of LED is obtained.

It is a figure for demonstrating embodiment of this invention. It is a figure for demonstrating embodiment of this invention. It is a figure for demonstrating other embodiment of this invention. It is a figure which shows the main scanning direction cross section of this embodiment. It is the figure which showed the ideal type of the illumination intensity distribution in a subscanning direction cross section. It is a figure which shows the relationship of the reading width in a reading position corresponding to the reading width of an image reading element. It is a figure which shows the relationship of the reading width in a reading position corresponding to the reading width of an image reading element. It is a figure which shows the relationship of the reading width in a reading position corresponding to the reading width of an image reading element. It is a figure for demonstrating the change of the reading position by a manufacturing error. It is a figure which shows an example of the illumination intensity distribution by the light source device of the structure shown in FIG. It is a figure for demonstrating the effect of the light source device by this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. 1 is a diagram illustrating an example of an image forming apparatus having a document reading device. 1 is a schematic configuration diagram of a reading device. It is a figure which shows the conjugate relation of a manuscript surface and CCD. It is a figure which shows the illumination intensity distribution of the subscanning direction of the original surface by the conventional light source. It is a figure for demonstrating the illumination intensity distribution of a combined use type scanner.

Hereinafter, the present invention will be described according to embodiments.
1 and 2 are diagrams for explaining an embodiment of the present invention. 1 is a sectional view in the sub-scanning direction, and FIG. 2 is a partially exploded perspective view.
In both figures, reference numeral 101 denotes a light guide, 102 denotes a reflector, 106 denotes a light shielding member, and G denotes an illuminance distribution. Other codes are in accordance with the codes shown in FIG.
The light source 6 includes a plurality of point light sources LED 6 ′ arranged in the main scanning direction. The light guide 101 is a cylindrical lens having a constant width extending in the main scanning direction. The light entrance 101 faces the light exit surface of the LED 6 'and the exit surface faces the document reading area. The reflection plate 102 is arranged so that light beams other than the light beam directly incident on the light guide body 101 from the light source 6 are directed to the light guide body 101.

In FIG. 1, the cylindrical lens is shown in a plano-convex configuration, but a biconvex configuration or a meniscus configuration may be used as long as it has a positive refractive power. With this configuration, a substantially flat distribution can be obtained around the maximum illuminance, such as the illuminance distribution indicated by G, and the illumination area can also be accommodated in a width that is substantially close to the width of the predetermined reading area. An almost constant illuminance distribution area near the maximum illuminance is called a high illuminance distribution area. The high illuminance distribution area is made to substantially coincide with the reading area.
The number of LEDs 6 ′ arranged in the main scanning direction is determined by the relationship with the light amount unevenness in the main scanning direction. Unevenness can be reduced as the number increases, but since there is a relationship with cost, efforts are made to reduce the number so that the unevenness in the amount of light falls within the allowable range.

A light shielding member 106 is provided between the light guide 101 and the contact glass 1. The light shielding member 106 may be formed by extending a part of the casing of the first carriage. Since the light beam emitted from the light guide has good convergence, stray light is little even if it is as it is, but if the light shielding member 106 is provided so as to block the light beam reaching the document surface directly above the light guide, it is unnecessary for the document surface. Illumination light can be blocked.
The distance between the light guide 101 and the light source 6 is determined as follows. When viewed in the sub-scan section, the light guide 101 has a lens action. In the figure, the surface facing the light source 6, that is, the light incident surface is a flat surface, and the surface facing the contact glass, that is, the light exit surface is a convex surface. The light source 6 is placed in the vicinity of the focal position on the incident surface side of the light guide 101. Specifically, it is determined by the relative relationship between the reading width of the document, the width of the light guide 101, and the irradiation angle with respect to the document surface.

  Assuming that the irradiation angle is inclined by 60 ° with respect to the normal of the original surface, and the reading width is 3 mm, the light guide body has a width of 3 mm × √ (3) /2=2.6 mm. The luminous flux is exactly parallel light. Therefore, in this case, the light source 6 may be set so that the center in the sub-scanning direction is aligned with the incident surface side focal line position of the light guide 101, that is, the focal position in the cross section. In general, the size of the LED 6 'in the sub-scanning direction is about 0.5 mm, so that ignoring this size does not cause a large error.

In practice, it is quite difficult to manufacture a long light guide having a width of 2.6 mm. For example, it is assumed that a light guide having a width of 5.2 mm is used. If the light beam is converged so that the width of the light beam becomes 2.6 mm at the center of the reading position, the image of the LED 6 ′ is formed at a position twice the distance from the light guide 101 to the original surface. This is what should be set. This can be achieved by increasing the distance between the light guide 101 and the LED 6 'as compared to the case where the above-mentioned light beams are made parallel. Specifically, the amount to be increased is determined by the focal length of the light guide 101, the distance from the light guide 101 to the center of the reading position, and the like. However, since the focal length of the light guide in the above example is quite small, the amount of change from the focal position for the convergence of the light beam is not so large.
As another method, the arrangement of the cylindrical lenses may be selected so that the width of the point light source in the sub-scanning direction forms an image with a predetermined reading width. For example, regarding a cross section in the sub-scanning direction, if a point light source having a width of 0.5 mm is imaged to a width of 2.6 mm, the imaging magnification is 5.2 times. What is necessary is just to arrange | position LED6 'and the reading area center in conjugate relation so that it may become this magnification.

FIG. 3 is a diagram for explaining another embodiment of the present invention. 2A is a perspective view of the main part, and FIG. 2B is a sectional view in the main scanning direction.
In the figure, reference numeral 101 'denotes a light guide.
The light guide 101 ′ is basically a plano-convex cylindrical lens, and the convex surface side is arranged close to the reading area as the light exit surface 101′b.
In this embodiment, two LEDs 6 ′ are used as the light source 6, and a light beam is incident from the end face in the longitudinal direction of the light guide. When a light beam is incident from the end surface in the longitudinal direction of the light guide 101 shown in FIG. 2, the light beam that goes straight out from the opposite surface increases, and the light beam emitted from the light guide 101 to the reading region decreases. Therefore, as in the light guide body 101 ′ shown in FIG. 3, an inclined surface is provided on the side opposite to the light exit surface of the light beam at the end in the longitudinal direction to form a light incident surface 101′a.

The LED 6 ′ is placed so as to substantially face the incident surface 101′a, and a main light beam enters the light guide 101 ′ from the incident surface 101′a. Since the luminous flux diffuses and becomes weaker as it goes farther, it is easier to obtain uniform illumination by illuminating from both sides as shown. Although the illustration of the light flux leaking outside the entrance surface due to the space between the LED 6 'and the entrance surface 101'a is omitted, a reflector similar to the reflector 102 shown in FIG. 2 may be provided. In this case, since there is one LED 6 'per one end surface, it is preferable to surround the four reflecting plates along the four sides of the incident surface 101'a formed in a quadrangular shape.
In addition, it is preferable that the light guide body 101 ′ has all the surfaces other than the light incident surface 101′a and the light exit surface 101′b as reflecting surfaces. As a method for forming the reflective surface, for example, a reflective member such as high-luminance aluminum may be attached, or a reflective function may be provided by a method such as aluminum vapor deposition.

In the case of a method such as aluminum vapor deposition, it is possible to prevent partial vapor deposition by applying a mask during vapor deposition, and by using this method, the degree of reflection can be varied depending on the location. That is, it is possible to reduce the reflection capability at a portion close to the LED 6 'and increase the reflection capability as the distance increases. If a high-luminance LED can be used, a desired illuminance distribution can be obtained by this method even if illumination is performed with only one LED from one side of the longitudinal end surface of the light guide 101 ′. Or although it is illumination from one side, it is also possible to arrange two or more in the sub-scanning direction. This can be used when the predetermined reading width is wide.
On the side far from the LED 6 ′, the incident angle of the light beam with respect to the emission surface 101 ′ b becomes shallow, and there is a high possibility that it becomes a total reflection region. In order to avoid this, it is better to form an antireflection film such as a multilayer film on the emission surface 101′b.

FIG. 4 is a diagram showing a cross section in the main scanning direction of the present embodiment.
In the figure, reference numeral 103 denotes a reflector.
Regarding the main scanning direction, the arrangement density is taken into consideration so that the illumination light from the light fluxes of the plurality of LEDs 6 ′ is uniform so as not to cause image unevenness in reading a document. If the incident angle of the luminous flux from the LED 6 'with respect to the light guide 101 is too large, the position far from the LED 6' is illuminated as shown on the left side of the figure, and the distribution becomes difficult to control. As shown on the right side of the figure, it is preferable to place the reflector 103 so that the light beam is directed to the light guide 101. In the drawing, the reflector 103 is shown with a triangular cross section. However, if the top of the reflector 103 is formed in a flat trapezoidal shape and used as a receiving portion of the light guide 101, the light guide 101 can be easily attached.
Although not shown, the LED 6 ′ is not limited to one row, and when the predetermined reading width is wide, a plurality of rows may be provided in the sub-scanning direction.

FIG. 5 is a diagram showing an ideal type of illuminance distribution in the cross section in the sub-scanning direction.
In the figure, Wr indicates a predetermined reading width, W0 indicates a predetermined illumination width, and L indicates an illuminance sufficient for reading.
A graph Gi indicated by a solid line in the figure shows an ideal illuminance distribution for illuminating only a region necessary for reading. A graph Gr indicated by a broken line indicates a general form of illuminance distribution that is likely to occur in practice.
Since the illuminating device is configured by stacking a plurality of parts, even if the parts are within an allowable manufacturing error (tolerance), the illumination position is slightly shifted due to the error. In order to illuminate the reading position regardless of how the parts vary within the tolerance, the predetermined illumination width W0 must be larger than the predetermined reading width Wr. A method for determining the predetermined illumination width W0 will be described below.

6 to 8 are diagrams showing the relationship between the reading width in the sub-scanning direction of the image reading element, that is, the predetermined reading width at the reading position corresponding to the light receiving width. 6 is a relationship diagram corresponding to a CCD for three colors, FIG. 7 is a relationship diagram for a CCD for four colors including black, and FIG. 8 is a relationship diagram corresponding to a CCD for monochrome (single color). Each figure shows an example in which a document is read at 600 DPI.
In the CCD 5 shown on the right side of the imaging lens 4 in FIG. 6, three line sensors having a width of 0.01 mm are arranged with an interval of 0.04 mm. On the other hand, at the document position G shown on the left side of the imaging lens, one reading width is set to about 0.0423 mm, and the three colors including the lens are read so that three colors are read at intervals of four. The arrangement is determined. Therefore, the document position and the CCD position are conjugate positions with respect to the imaging lens 4. The predetermined reading width Wr is about 0.381 mm, and the imaging magnification viewed from the original side is 1/43.

In the case of FIG. 7, a line sensor dedicated for monochrome is added to a position slightly apart from the line sensor for three colors shown in FIG. The CCD shown here has a sensor width of 0.005 mm and an interval between line sensors of 8 times the sensor width. The monochrome sensor is located 12 times away from the sensor width.
When the reading width Wr is obtained in the same way as described above, Wr = 1.23 mm, and similarly, the imaging magnification is 1 / 8.47.
In the case of FIG. 8, a CCD having one line sensor of 0.0047 mm is used. In this case, the reading width is the smallest and Wr = 0.0423 mm is sufficient. In this example, the imaging magnification is 1/9.
Note that a line sensor other than a CCD, such as a PDA, can be used as the image reading element.

FIG. 9 is a diagram for explaining a change in reading position due to a manufacturing error.
In the figure, the symbol θ represents the angle error of the second mirror, x represents the vertical position error of the second carriage, and X represents the fluctuation range caused by the manufacturing tolerances of the components.
As an example, the drawing shows the deviation of the reading light beam when the second carriage 3 is displaced in the vertical direction from the designed position and the second mirror 8 is displaced from the designed angle. However, it is assumed that there are no errors in other parts.
In the figure, x1 and x2 are the maximum displacements in the vertical direction of the second carriage 3 itself, θ1 and θ2 are the maximum displacements of the angle of the second mirror, and Xa and Xb are the maximum deviations of the resulting reading position from the design position. Respectively. X = Xa + Xb corresponds to a margin for manufacturing error. That is, the predetermined illumination width W0 is defined by W0 = Wr + X.

When the second carriage 3 is moved upward by the maximum displacement x1 and the second mirror 8 is tilted by the maximum angle θ1, the reading position on the document surface G shows the maximum deviation amount Xa in the upward direction. Similarly, the maximum shift amount Xb is shown in the downward direction by a combination of x2 and θ2.
There are many other factors that deviate the reading position from the design. If the tolerances are left as they are, the amount of deviation of the reading position becomes unpractical. Therefore, an adjustment portion is usually provided in any one of the optical paths from the original to the CCD to absorb these errors. Still, the final error cannot be eliminated completely. For example, the tolerance of the reading position at the original position is Xa = Xb = 0.1 mm in the case of a color machine, and Xa = Xb = 0.5 mm in the case of a monochrome machine. It is determined as follows.

  The predetermined illumination width W0 including a margin for absorbing the allowable error with respect to the reading width Wr derived from the CCD size is determined by a combination of the CCD configuration, the reading resolution, and the like. When the above-described allowable error is applied to the example, the predetermined illumination width W0 = 0.581 is obtained in the case of FIG. In the case of FIG. 7, since the monochrome sensor is provided at one end, the tolerance on the color side is 0.1 mm and the tolerance on the monochrome side is 0.5 mm, so that W0 = 1.83 mm. In the case of FIG. 8, W0 = 1.0423 mm because the sum is simply obtained.

  Although it is ideal if the light source device can illuminate the predetermined illumination width W0 without excess or deficiency, there are several factors that cause errors on the light source side, such as the setting angle of the light guide and the relative position with the LED. Although it is a common practice to provide an adjustment mechanism to absorb these errors, it is still difficult to eliminate the final error. Therefore, the actual illumination width W1 sets a margin α for the above-mentioned error that cannot be absorbed, and the light source device is designed so that W1 = W0 + α.

  In the light source device as shown in FIG. 1, when a predetermined actual illumination width W1 is used as a high illuminance distribution area and illumination is performed with a substantially uniform illuminance L, the illuminance outside the range cannot be zero as ideal. However, as described in the description of the prior art, it is desired to prevent the illumination light from reaching as much as possible outside the above range. As indicated by the broken line in FIG. 5, the distribution may be such that the illuminance decreases sharply in the region exceeding the actual illumination width W1. The width connecting the positions at which the illuminance is half that of the maximum illuminance L, that is, L / 2 is called a half-value width. In this embodiment, the half-value width is suppressed within three times, preferably within twice the predetermined illumination width W0. The goal is that. In the case of three times, this means that the width of the protrusion amount on one side of the half-value level point from the predetermined illumination width W0 is equal to W0.

  In the example of FIG. 7, since W0 = 1.8 mm, the half-value width of the illuminance distribution in this case is 5.4 mm, and the width protruding from the predetermined illumination width W0 is 1.8 mm on one side. Thus, since the width is very small and the illuminance is half of the maximum illuminance L at this position, the difference in re-reflection caused by the difference in brightness of the document at this position has little effect on the illuminance at the reading position. Not give.

10 is a diagram showing an example of illuminance distribution by the light source device having the configuration shown in FIG.
In the figure, the solid line indicates the illuminance distribution according to the present invention, and the broken line indicates the illuminance distribution by the conventional xenon lamp. In this embodiment, the predetermined illumination width W0 = 2.5 mm, the actual illumination width W1 = 2.9 mm, the half-value width 7.5 mm, which is exactly three times W0. In the illuminance distribution of the conventional example shown by the broken line, the half width is 23.2 mm, which is 9 times or more the predetermined illumination width W0. In particular, in the document area directly above the light source, the amount protruding from the predetermined illumination width W0 is about 17 mm, which is 6.7 times W0 only on one side.

Up to now, the maximum illumination intensity is L, and the high illumination intensity distribution area of the actual illumination width W1 has been treated as if it showed a constant value. However, even if it is slightly constant as shown in the illumination intensity distribution of FIG. There are some fluctuations when you look closely. There are a plurality of maximum values and a plurality of minimum values in a range where the illuminance is almost constant. The maximum value among the maximum values is Lmax, and the minimum value among the minimum values is Lmin. Similar to the definition of the surface roughness of an object, the definition of the flatness δ of illuminance is defined as follows.
δ = (Lmax−Lmin) / Lmax
The brackets represent the range of fluctuation. The average value of illuminance within this range should be used as the denominator. However, since the average value cannot be easily obtained, the maximum value that can be measured most easily was used as the denominator.

  Since the flatness δ of the illuminance is smaller as the numerical value is smaller, the flatness is higher. However, since an actual value cannot be set to 0, an allowable value is set. In the case of color reading, if the flatness is poor, the color balance may be lost in some cases. It is desirable that δ is within 12% as a limit at which no apparent color balance is lost. In the case of monochrome reading, in many cases, the read data is binarized. Therefore, when the binarization threshold is set to 50%, no reading error occurs until δ is about 30%. However, if the goal is to recreate a photo, high flatness that is as good as or better than color is required.

FIG. 11 is a diagram for explaining the effect of the light source device according to the present invention.
In the figure, the graph of illuminance distribution is schematically shown.
According to the present invention, in the document movement type reading device, the illumination width of the light source device is substantially within the width of the ADF contact glass 13. The opaque members 14 and 15 slightly block the bottom of the illuminance distribution. However, since this region is outside the reading range, there is no influence on the reading and moving of the document.
When moving to the fixed document type reading method, the above-mentioned skirt portion of the illuminance distribution is directly above the light source device, and the same problem as the conventional re-reflection is likely to occur. Since the amount of light is very small relative to the total amount of light, the re-reflected light has little effect on the read light amount.

FIG. 12 is a view showing still another embodiment of the present invention.
In the figure, reference numeral 104 denotes a reflecting member.
The reflecting member 104 is provided on the side surface over the entire length of the light guide 101. The reflecting member 104 may be a member separated from the light guide 101, but may be a mirror surface by aluminum vapor deposition or the like.
By doing in this way, the light which comes out of the light guide side surface by an angle among the light beams from LED can be returned to the illumination area.

FIG. 13 is a view showing still another embodiment of the present invention.
In the figure, reference numeral 105 denotes a reflector / reinforcing member.
The present embodiment is characterized in that both side surfaces of the light guide 101 ′ are not parallel. The incident surface facing the LED has an opening width that is small enough to cover the light emitting surface of the LED, and the emission surface has an opening width larger than that width.
Originally, the divergent light from the LED continues to diverge even in the light guide and becomes a parallel light beam or a convergent light beam by exiting the exit surface, so that the main light beam is almost the same as in the configuration of FIG. Light rays that reach the reflective surface on the side of the light guide are reflected by the reflective surfaces, but the reflective surfaces on both sides have an opening angle with respect to the traveling direction of the light. The direction does not change so much and it is easy to reach the reading area.

A surface 105a of the reflector / reinforcing member 105 facing the LED serves as the reflector 102 in FIG. 1 and serves as a reinforcement of the LED substrate as a whole. The upper opening also serves as a cradle for the light guide 101 ′.
By doing so, the easiness of bending of the elongated LED substrate is eliminated, the positioning of the light guide 101 ′ is facilitated, the assembling accuracy can be guaranteed, and the assembling process becomes very easy.
In the drawing, two reflectors / reinforcing members 105 are shown because of the cross section, but the assembly accuracy is further improved if they are made of an integrated body in which the LEDs are not connected to each other.

FIG. 14 is a diagram showing still another embodiment of the present invention.
In the figure, reference numeral 201 denotes a light guide, 202 denotes a concave lens system cylindrical lens, 203 denotes a convex lens system cylindrical lens, and 204 denotes a reflecting member.
In the present embodiment, the light guide 201 is a composite of two sets of a convex lens cylindrical lens and a concave lens cylindrical lens, and has a positive refractive power when combined.
When viewed in a cross-section in the sub-scanning direction, a convex cylindrical lens (in the following description of the cross-section, a cylindrical lens is simply referred to as a lens for simplification) 203 is positioned far from the focal point on the point light source 6 ′ side. Place the light source 6 '. The divergent light beam that exits the point light source 6 ′ and enters the convex lens 203 exits from the exit surface as convergent light. The convergent light is incident on the concave lens 202. However, if the convergent light is arranged in a positional relationship such that the convergence point of the convergent light coincides with the focal point of the concave lens 202 on the original side, the light beam exiting the concave lens 202 is It is emitted as a parallel light beam parallel to the.

By adopting such a configuration, the light beam emitted from the point light source 6 ′ and diverging at a wide angle can be converted into a parallel light beam in a narrow range. Therefore, if the central ray is made to substantially coincide with the center of the reading area, the reading area can be illuminated almost uniformly. If a combination of a convex lens and a concave lens is selected so that the high illuminance distribution area substantially coincides with the reading area, the use efficiency of the light beam can be increased without illuminating an unnecessary area. Since the illumination light is incident on the contact glass at an angle, refraction occurs on the glass surface. Accordingly, when the high illuminance distribution area is matched with the reading area, this refraction is always taken into consideration.
In this embodiment, the position where the point light source is placed is, as a result, the focal position of the composite of the convex lens and the concave lens.
The reflection member 204 may serve as a holding member for holding the convex lens 203 and the concave lens 202.

FIG. 15 is a diagram showing still another embodiment of the present invention.
In the figure, reference numeral 301 denotes a cylindrical lens as a light guide, and 302 denotes a reflecting plate whose section in the sub-scanning direction forms a parabola.
In the embodiment shown in FIG. 13, the light that has exited from the point light source 6 ′ and reached the reflecting surface 105a may be reflected twice, but is always incident on the light guide 101 ′. However, the emission direction of these lights when emitted from the light guide 101 ′ cannot be sufficiently regulated.
Therefore, as in this embodiment, the reflecting surface of the reflecting plate 302 is a cylindrical parabolic mirror whose optical axis (symmetry axis) is directed substantially to the center of the reading region, and the focal point is pointed at the focal position in the cross section in the sub-scanning direction. It arrange | positions so that light source 6 'may correspond. In this way, all the light rays that have exited from the point light source 6 ′ and reached the reflecting plate 302 travel in parallel to the optical axis.

The cylindrical lens 301 is formed as a curved surface having a flat surface on one side and a convex surface on the other surface. Either may be used as a light incident surface, but in the figure, the plane side faces the point light source 6 '.
Since the light beam emitted inward from the opening of the reflecting plate 302 does not reach the reflecting plate, the incident surface of the cylindrical lens 301 is disposed so that all the light beams in this region are incident on the cylindrical lens 301. At this time, if the light emission center of the point light source 6 ′ is arranged so that it coincides with the focal line position of the cylindrical lens 301 and the optical axis coincides with the optical axis of the reflecting plate 302, all the light emitted from the cylindrical lens 301 is emitted. The light beam is parallel to the optical axis. Eventually, all the light beams emitted from the point light source 6 'reach the original surface as parallel light. The optical axis of the cylindrical lens here is a straight line that passes through the center of curvature of the convex surface and is perpendicular to the plane portion.

Since the luminous flux passes between the cylindrical lens 301 and the reflecting plate 302, it is necessary to keep it open. Therefore, the cylindrical lens 301 is held at the end in the longitudinal direction (main scanning direction).
The reflecting plate 302 may be a resin molded product having a paraboloid inner surface as shown by phantom lines in FIG.
Also in this configuration, in order to block unnecessary illumination light on the document surface, the light shielding member 106 may be provided immediately above the cylindrical lens 301, that is, between the cylindrical lens 301 and the contact glass 1. Further, an opposing reflector may be provided at an opposing position beyond the reading area from the exit surface of the cylindrical lens 301. By doing so, stray light generated unscheduled is almost returned to the reading area.

FIG. 16 shows still another embodiment of the present invention.
In the figure, reference numeral 401 denotes a light guide, and 402 denotes a reflecting plate whose cross section in the sub-scanning direction forms a parabola.
The reflector 402 has the same configuration and arrangement as the embodiment shown in FIG.
The light guide 401 in the present embodiment has a composite shape in which a flat lens portion 401b whose both surfaces are parallel planes is integrated with a convex lens system cylindrical lens portion 401a having a convex surface on the point light source 6 ′ side. In this case, the optical axis of the cylindrical lens in the cross section in the sub-scanning direction is defined as a straight line passing through the center of curvature of the convex surface and perpendicular to the parallel plane.

The light emitting point center of the point light source 6 ′ is arranged so as to coincide with the focal line of the cylindrical lens, and the optical axis thereof coincides with the optical axis of the reflector 402. All the light beams emitted inward from the opening of the reflecting plate 402 are configured to enter the cylindrical lens portion 401a. In the sub-scan section, since the point light source 6 ′ is at the focal position of the lens, all the emitted light becomes a parallel light beam.
The light beam emitted from the point light source 6 ′ and reaching the reflection plate 402 is reflected in parallel with the optical axis and enters the flat plate portion 401 b of the light guide body 401 vertically. Accordingly, the light beam travels straight and travels toward the document surface while remaining parallel to the optical axis after exiting the flat plate portion 401b.
Since the optical axis of the cylindrical lens is aligned with the optical axis of the reflecting plate 402, all the light beams emitted from the point light source 6 ′ become parallel light beams parallel to the optical axis and travel toward the document surface.

FIG. 17 is a diagram showing still another embodiment of the present invention.
In the figure, reference numeral 501 denotes a light source substrate, and 502 denotes a support substrate.
The point light source 6 ′ is held together with the light guide on the light source substrate 501, and the light source substrate 501 is supported on the support substrate 502. The support substrate 502 can be adjusted in the sub-scanning direction by a set screw 503 with respect to a screw hole 2b formed in the horizontal substrate 2a of the first carriage 2 through a long hole 502b formed in the bent portion 502a. It is attached. For example, when the illuminance distribution curve of the illumination light when initially attached is shifted from the center of the reading area as indicated by G ′, the support substrate 502 is moved to the first carriage with the set screw 503 loosened. 2 is moved in the sub-scanning direction, and the center of the high illuminance distribution area is made to coincide with the center of the reading area as indicated by the illuminance distribution curve G. When the adjustment is completed, the set screw 503 is tightened to fix the support substrate 502 to the first carriage 2.

1 Contact Glass 2 First Carriage 3 Second Carriage 5 CCD
6 Light source 7 First mirror 10 Opposing mirror 12 Illuminance distribution curve 100 Document reading device 101 Light guide body 102 Reflector plate 103 Reflector 104 Reflective member 105 Reflector / reinforcing member

JP-A-2001-2222076 (page 2, paragraphs 0007 to 0010, FIG. 6) Japanese Patent Laid-Open No. 2002-125098 (page 4, paragraph 0025, FIG. 3)

According to the first aspect of the present invention, document reading is performed by irradiating at least a predetermined illumination width including a reading area having a predetermined reading width extending long in the main scanning direction of the document, and reading reflected light from the document by the image reading element. a lighting device in the apparatus, and the point light source is provided with a light body guide toward the output surface to the reading area has an incident surface in the vicinity of the light beam emitting surface of the point light source, the point light source, the light guide The illumination surface is disposed at both ends in the main scanning direction of the body, the incident surface of the light guide is disposed to be inclined with respect to the reading region, and the illumination region by the light emitted from the point light source has a substantially constant illuminance. has a distribution area, the high illuminance distribution areas, is characterized in that substantially coincide with the reading area.
According to a second aspect of the present invention, in the illuminating device according to the first aspect, the point light source is disposed such that a light beam exit surface of the point light source faces an incident surface of the light guide, and the main point of the point light source A light beam is incident on the light guide .

According to a third aspect of the present invention, in the illuminating device according to the first aspect, the light guide body is a surface that reflects light other than the incident / exit surface, and an illumination area in the sub-scanning direction by the light emitted from the point light source Has a high illuminance distribution area having a substantially constant illuminance, and the high illuminance distribution area is made substantially coincident with the reading area .
According to a fourth aspect of the present invention, in the document reading device , the illumination device according to any one of the first to third aspects is used .
The invention according to claim 5 is characterized in that the document reading apparatus according to claim 4 is used in the image forming apparatus .

It is a reference view for explaining an embodiment of the present invention. It is a reference view for explaining an embodiment of the present invention. It is a figure for demonstrating one Embodiment of this invention. It is a figure which shows the main scanning direction cross section of this embodiment. It is the figure which showed the ideal type of the illumination intensity distribution in a subscanning direction cross section. It is a figure which shows the relationship of the reading width in a reading position corresponding to the reading width of an image reading element. It is a figure which shows the relationship of the reading width in a reading position corresponding to the reading width of an image reading element. It is a figure which shows the relationship of the reading width in a reading position corresponding to the reading width of an image reading element. It is a figure for demonstrating the change of the reading position by a manufacturing error. It is a figure which shows an example of the illumination intensity distribution by the light source device of the structure shown in FIG. It is a figure for demonstrating the effect of the light source device by this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. It is a figure which shows other embodiment of this invention. 1 is a diagram illustrating an example of an image forming apparatus having a document reading device. 1 is a schematic configuration diagram of a reading device. It is a figure which shows the conjugate relation of a manuscript surface and CCD. It is a figure which shows the illumination intensity distribution of the subscanning direction of the original surface by the conventional light source. It is a figure for demonstrating the illumination intensity distribution of a combined use type scanner.

Hereinafter, the present invention will be described according to embodiments.
1 and 2 are reference views for explaining an embodiment of the present invention. 1 is a sectional view in the sub-scanning direction, and FIG. 2 is a partially exploded perspective view.
In both figures, reference numeral 101 denotes a light guide, 102 denotes a reflector, 106 denotes a light shielding member, and G denotes an illuminance distribution. Other codes are in accordance with the codes shown in FIG.
The light source 6 includes a plurality of point light sources LED 6 ′ arranged in the main scanning direction. The light guide 101 is a cylindrical lens having a constant width extending in the main scanning direction. The light entrance 101 faces the light exit surface of the LED 6 'and the exit surface faces the document reading area. The reflection plate 102 is arranged so that light beams other than the light beam directly incident on the light guide body 101 from the light source 6 are directed to the light guide body 101.

Figure 3 is a diagram for explaining an embodiment of the present invention. 2A is a perspective view of the main part, and FIG. 2B is a sectional view in the main scanning direction.
In the figure, reference numeral 101 'denotes a light guide.
The light guide 101 ′ is basically a plano-convex cylindrical lens, and the convex surface side is arranged close to the reading area as the light exit surface 101′b.
In the present embodiment, two LEDs 6 ′ are used as the light source 6, and a light beam is incident from the end face in the longitudinal direction of the light guide. When a light beam is incident from the end surface in the longitudinal direction of the light guide 101 shown in FIG. 2, the light beam that goes straight out from the opposite surface increases, and the light beam emitted from the light guide 101 to the reading region decreases. Therefore, as in the light guide body 101 ′ shown in FIG. 3, an inclined surface is provided on the side opposite to the light exit surface of the light beam at the end in the longitudinal direction to form a light incident surface 101′a.

Claims (5)

In an illuminating device in an original reading apparatus that irradiates at least a predetermined illumination width including a reading area having a predetermined reading width extending long in the main scanning direction of an original and reads reflected light from the original by an image reading element.
A point light source, and a light guide having an incident surface in the vicinity of the light beam exit surface of the point light source and having the exit surface facing the reading region,
The point light sources are arranged on both ends of the light guide in the main scanning direction,
The incident surface of the light guide is arranged to be inclined with respect to the reading area,
The illumination area by the light emitted from the point light source has a high illuminance distribution area having a substantially constant illuminance,
The illuminating device characterized in that the high illuminance distribution area substantially coincides with the reading area. The lighting device according to claim 1.
The illumination device, wherein the point light source is disposed such that a light beam exit surface of the point light source faces an incident surface of the light guide, and causes a main light beam of the point light source to enter the light guide. The lighting device according to claim 1.
Other than the incident / exit surface of the light guide is a surface that reflects light, and the illumination region in the sub-scanning direction by the light emitted from the point light source has a high illuminance distribution region having a substantially constant illuminance,
The illuminating device characterized in that the high illuminance distribution area substantially coincides with the reading area.   An original reading apparatus using the illumination device according to claim 1.   An image forming apparatus using the document reading device according to claim 4.

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