JP2010068412A - Lighting device and image reading unit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an illumination device capable of reducing the occurrence of bright spots in read image information and reading high-quality image information.
Image information of a document placed on a document table is imaged on a line sensor arranged in the main scanning direction via an imaging optical system, and the image information used in an image reading device for obtaining the image information is illuminated. In the lighting device for
The illumination device includes a light source unit in which a plurality of point light sources are arranged in the main scanning direction;
Diffusing means for diffusing and transmitting incident light along the main scanning direction, disposed in an optical path connecting the light source unit and the image reading position of the document;
The light flux region generated on the original reading surface of the original after the light flux from each point light source passes through the diffusion surface is longer in the main scanning direction than the sub scanning direction and has a curved shape curved in the sub scanning direction. Being.
[Selection] Figure 2

Description

  The present invention relates to an illumination device and an image reading device using the same.

  In particular, it is suitable for reading image information such as a monochrome image and a color image using a signal from a line sensor (imaging device) such as a CCD in an image scanner, a digital copying machine, a facsimile, or the like.

  Conventionally, various flatbed image scanners have been proposed as image reading devices (image scanners) that read image information on a document surface (Patent Documents 1 and 2).

  In Patent Document 1, an imaging lens (imaging optical system) and a line sensor (CCD) are fixed, and only the reflection mirror provided in the optical path is moved to perform slit exposure scanning on the document surface to read image information. A 2-to-1 mirror scanning system is used.

  In Patent Document 2, in order to simplify the structure of the image reading apparatus, a carriage-integrated scanning system that scans a document surface by moving a casing in which a reflecting mirror, an imaging lens, a line sensor, and the like are integrated, reads image information. Is used.

  FIG. 9 is a schematic view of a main part of an image reading apparatus using a conventional carriage-integrated scanning method.

  In the figure, the light beam emitted from the illumination light source 91 directly illuminates the original 97 placed on the original table (original table glass) 92.

  Then, the reflected light beam from the illuminated original 97 is bent in order inside the carriage 96 via the first, second, third and fourth reflecting mirrors 93a, 93b, 93c and 93d. An image is formed on the surface of a line sensor (imaging device) 95 by an imaging lens (imaging optical system) 94.

  Then, the line sensor 95 reads the image information of the original 97 by moving the carriage 96 in the direction of arrow A (sub-scanning direction) by a drive motor (not shown).

  The line sensor 95 in FIG. 9 has a configuration in which a plurality of light receiving elements are arranged in a one-dimensional direction in a direction perpendicular to the paper surface (main scanning direction).

  FIG. 10 is an explanatory diagram of a basic configuration related to imaging of the imaging optical system 94 of the image reading apparatus of FIG.

  In FIG. 10, 94 is an imaging lens.

  Reference numeral 145 denotes a line sensor group, which includes line sensors 145R, 145G, and 145B that read R (red), G (green), and B (blue) colors.

  Reference numerals 147R, 149G, and 147B denote reading ranges on the surface of the original 147 corresponding to the line sensors 145R, 145G, and 145B, respectively.

  By scanning the surface of the original 147 in the sub-scanning direction indicated by the arrow A, the same portion can be read with different colors by the line sensors 145R, 145G, and 145B at a certain time interval.

  In recent years, cold cathode tubes (so-called fluorescent lamps) have been used in place of halogen and xenon lamps conventionally used as illumination light sources. When a cold cathode tube is used, power consumption, the amount of heat generated, and the like can be reduced, and the structure can be simplified.

  When a cold cathode tube is used as an illumination light source in a carriage in which an illumination system and a reading optical system are integrated, the occupied volume is greatly reduced, and the amount of generated heat is greatly reduced.

  A cooling cathode tube is often used in an image reading apparatus of an A4 size original reading system.

  In recent years, LEDs (light emitting diodes) that can reproduce white color with a single element have appeared, and white color is obtained with only one type of LED.

  If a plurality of LEDs are used, it can be used as an illumination system for an image reading apparatus. For example, by using an LED array in which a large number of LEDs are arranged in the main scanning direction and illuminating the light flux from the LEDs toward the document surface using a reflector, a sufficient amount of light for reading can be obtained.

  When the 2: 1 mirror scanning method is employed, for example, in the A3 system, a long light path has been used, and thus a large amount of xenon lamp has been used as a conventional light source.

  A xenon lamp is easy to obtain a large amount of light instantaneously, but has the disadvantage of generating a large amount of heat.

  If the LEDs are arranged in an array in the main scanning direction and configured as an illumination system instead of a xenon lamp, the amount of light is sufficient, and the generated heat is considerably suppressed as compared to xenon.

If a conventional xenon lamp can be simply replaced with an LED array, it can be arranged without changing the occupied volume of the illumination system.
JP 2008-065234 A JP 2000-307800 A

  When an LED array is used in the illumination system of the image reading apparatus, bright spot reflection may occur in reading image information.

  This state will be described using the simple model shown in FIG. 11 and the illumination systems shown in FIGS.

  FIG. 11 is an explanatory diagram of the optical action of the illumination system and the imaging optical system of the image reading apparatus. In FIG. 11, the light beam from the reflecting mirror 123 of the illumination system and the light beam from the light source 122 reach the document surface of the document table glass 121 directly with respect to the document 120 on the document table glass 121.

  At this time, when the original 120 has a smooth surface such as glossy paper or plastic, the original 120 is folded back on the original surface so that the direct light from the light emission point 122a of the light source 122 is reflected by the mirror.

  When it is imaged by the imaging lens 124, it reaches the imaging surface 125 on which the imaging element is arranged, and a part of the image information is reflected as a bright luminescent spot, and the image quality deteriorates. .

  In order to prevent a bright spot from occurring in the image information, a diffusion plate 126 that diffuses the light beam may be disposed in the optical path connecting the LED 122 and the image reading position on the platen glass 121 as shown in FIG.

  As shown in FIG. 5, the light beam emitted from the LED 122 as the light source is diffused by the diffusion plate 126 arranged in the middle.

  At this time, the diffusion plate 126 used has different diffusivities in the main scanning direction and the sub-scanning direction so as to spread in the main scanning direction.

  This is because, when a diffuser plate having a uniform diffusivity is used, the central portion of the diffuser plate remains brightest, and although it is slightly blurred, a bright spot is eventually generated.

  For this reason, a large amount of diffusion acts in the main scanning direction so that the light beam is in a linear state as if it is transmitted through a cylinder lens having a refractive power in the main scanning direction and is too diffused in the sub scanning direction. This prevents the amount of light from decreasing more than necessary.

  At this time, when the diffusing plate is arranged in the optical path, the diffusing plate 126 is arranged so that the optical axis 122b of the light emitted from the LED 122 and the diffusing plate 126 intersect perpendicularly. Then, as shown in FIG. 6, the original 120 is illuminated in a state where the light beams 122c1, 122c2,... Linearly extended in the main scanning direction on the original 120 are folded.

  As a result, the region where the light beams 122c1, 122c2,.

  On the other hand, as shown in FIG. 7, the diffusion plate 126 is arranged with a certain finite angle that is not perpendicular to the optical axis 122 b of the light emitted from the LED 122.

  Then, due to the fact that the diffusion level of the diffusing plate 126 is different between the main scanning direction and the sub-scanning direction, illumination areas 122d1, 122d2,... Like field curvature appear on the original 120 as shown in FIG. . As a result, the diffused linear light beams are arranged in a curved shape for each light beam from each light emitting point.

  As shown in FIG. 8, when the light beams that have passed through the diffusion plate 126 have reached the original 120, the light beams become bright spots in the areas where the illumination light beams having independent curved shapes overlap. .

  When the image is captured in such a manner, the quality of the read image is greatly deteriorated even if the bright spot is blurred.

  The present invention reduces the occurrence of bright spots in read image information when a plurality of point light sources such as LEDs are used to illuminate image information of a document placed on a platen glass via a diffuser plate, thereby improving the quality of the image. An object of the present invention is to provide an illumination device capable of reading information and an image reading device using the same.

The illuminating device of the present invention forms the image information of the document placed on the document table on the line sensor arranged in the main scanning direction via the imaging optical system, and uses the image used in the image reading apparatus for obtaining the image information. In an illumination device for illuminating information,
The illumination device includes a light source unit in which a plurality of point light sources are arranged in the main scanning direction;
Diffusing means for diffusing and transmitting incident light along the main scanning direction, disposed in an optical path connecting the light source unit and the image reading position of the document;
When the angle formed by the center line of the light beam from the point light source toward the reading position and the normal line of the diffusion surface of the diffusion means is θ,
θ ≧ 45 °
And
The light flux region generated on the original reading surface of the original after the light flux from each point light source passes through the diffusion surface is longer in the main scanning direction than the sub scanning direction and has a curved shape curved in the sub scanning direction. And
In the luminous flux region formed by a single point light source, the curvature radius of the curved shape, the maximum luminous flux width in the sub-scanning direction, the distance from the center line in the curved shape to an arbitrary position in the main scanning direction, the main scanning direction , D, a _n , a _max in order,

The amount Py at any position a _n in the main scanning direction in the bent inner shape that is generated by the respective point light sources when placing the

Represented by

It is characterized by satisfying.

  According to the present invention, image quality deterioration due to bright spots is suppressed while making effective use of the diffusion effect, the amount of light is not reduced more than necessary, and conversely, the diffusion effect is too small to capture bright spots. Thus, an illuminating device capable of reading excellent image information is obtained.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The illumination device of the present invention forms image information of a document placed on a document table on a line sensor (reading unit) in which a plurality of sensors are arranged in the main scanning direction via an imaging optical system (reading optical system). And it is for illuminating the image information of the manuscript used in the image reading apparatus for obtaining the image information.

  The illuminating device is disposed in an optical path connecting a light source unit in which a plurality of point light sources are arranged in the main scanning direction and the light source unit and the image reading position of the document, and diffuses and transmits incident light along the main scanning direction. Means.

  In addition, there may be a reflection member that reflects and deflects the light beam from the light source unit toward the image reading position of the document.

  FIG. 1 is a schematic view of the essential portions of Embodiment 1 of an image reading apparatus using the illumination device of the present invention.

  In the following description, for convenience, only the plurality of mirrors are moved in the sub-scanning direction to read the image information on the document surface, and the image reading apparatus shown in FIG. 1 is used. Even when the device is mounted, the same effect can be obtained.

  Similarly, an “imaging lens” composed of a lens is used as the imaging optical system, but this also applies to an imaging optical system composed of a reflection system.

  In the following description, the main scanning direction is the direction in which the pixels of the line sensor are arranged, and the sub-scanning direction is the direction perpendicular to the direction in which the pixels of the line sensor are arranged.

  When reading the document 3 on the document surface glass 2 in the image reading apparatus 1 of FIG. 1, first, the first mirror base 4 having the mirror M1 is disposed immediately below the white reference plate 9 as a reading position.

  The first mirror stage 4 and the second mirror stage 5 having the mirrors M2 and M3 are driven by a drive system (not shown) so that the movement amount of the first mirror stage 4 in the sub-scanning direction: the movement amount of the second mirror stage 5 is 2: 1. It is set and is configured by a so-called 2: 1 mirror scanning method.

  A folding mirror M1 is mounted on the first mirror base 4, and mirrors M2 and M3 formed at an angle of 90 degrees are mounted on the second mirror base 5 in a C shape. The image information of the document 3 is guided to the imaging lens (reading optical system) 6 through the mirrors M1, M2, and M3, and formed on the CCD (reading means) 7 ahead.

  As shown in FIG. 10, the CCD 7 has three lines of RGB extending in the main scanning direction, and reading in the main scanning direction is performed at three positions of RGB by one reading. Then, the processing circuit (not shown) corrects the location and the time lag, and converts it into information as one reading line.

  The white reference plate 9 is a shading correction plate, and obtains an appropriate light amount and light amount uniformity in the main scanning direction, and also serves as a color reference. First, the white reference plate 9 is read by the CCD 7 through the imaging optical system 6, and information is sent to and stored in the storage means through a processing circuit (not shown) to obtain a reference (reference signal) for reading the document.

  Next, a series of operations for reading a document will be described.

  After reading the white reference plate 9, scanning of the document 3 in the sub-scanning direction (arrow direction in the figure) is started in such a manner that the second mirror table 5 follows the first mirror table 4.

  The document 3 is illuminated by the illumination system 8 mounted on the first mirror table 4, and image information at the reading position is sequentially sent to the CCD 7 through the mirrors M 1, M 2, M 3 and the imaging lens 6, so that the document 3 Reading is performed.

  FIG. 2 is a fragmentary cross-sectional view of a part of the illumination system 8. FIG. 3 is an explanatory diagram of the optical action in the main scanning direction of the illumination system of FIG.

  The illumination system 8 in the image reading apparatus 1 includes a substrate 8ab on which a light source unit 8a in which white LEDs 8aa are arrayed in the main scanning direction as a point light source and a reflecting member 8b, 8c that deflects a light beam emitted from the LED 8aa. have. Furthermore, it has the diffusion plate 8d which consists of optical resin arrange | positioned at the light emission side.

  As shown in FIG. 2, the illumination system 8 includes a plurality of white LEDs 8aa arranged and mounted on the substrate 8ab in an array at an appropriate interval in the direction perpendicular to the paper surface (main scanning direction).

  The LED used here adopts a type that emits a light beam from the side surface direction of the substrate 8ab, which is called a side view type, but the LED used in the present invention is not limited to this, and the light beam is directed upward of the substrate. The top view type that injects

  Reflecting members 8b and 8c are arranged at a suitable interval so as to face the substrate 8ab, and the light beams deflected by the reflecting members 8b and 8c are read positions 3a on the document surface 2a of the document surface glass 2 and It is injected around.

  The reflecting members 8b and 8c are made of a metal mirror, and the reflecting surface is made of an aluminum-deposited surface.

  The reflective surface may be a vapor-deposited or mirror-finished metal substrate.

  In this embodiment, the reflecting surface is a flat surface, but may be a concave surface if necessary.

As shown in FIG. 2, in this embodiment, the angle formed by the center line 8e of the light beam from the point light source 8aa toward the reading position 3a and the normal line of the diffusion surface of the diffusion means 8d is θ. At this time,
θ ≧ 45 ° (1)
It is.

  The luminous flux region generated on the original surface 2a of the original 3 after the luminous flux from each point light source 8aa passes through the diffusing surface 8d is longer in the main scanning direction than in the sub scanning direction and is curved in the sub scanning direction as shown in FIG. It has a curved shape (fan shape) 8aa11. That is, the diffusion plate 8d has different diffusion degrees in the main scanning direction and the sub-scanning direction.

  The diffusing plate 8d made of optical resin is arranged in parallel to the horizontal direction (in a plane parallel to the original surface glass 2), which is the center line 8e in the emission direction of the light beam from the illumination system 8 and the diffusing plate 8d. The angle θ formed with the normal line is about 50 degrees.

  The diffusing plate 8d is made of an optical resin made up of a plurality of protrusions having a fine projection structure, and each protrusion has an effect of prism action. The diffusivity 8d is set to a necessary diffusivity by devising the shape of this fine structure.

In this embodiment, in the light beam region formed by the single point light source 8aa, the radius of curvature of the curved shape 8aa11 and the maximum light beam width in the sub-scanning direction are r and d. Further, the distance to an arbitrary position in the main scanning direction from the center line in the curved shape and a _n. The maximum light flux width in the main scanning direction is a _max .

  And the angle ψ shown in FIG.

far.

Quantity Py at any position a _n in the main scanning direction in the curved shape that is generated by the point light sources are

It is represented by And in this example,

Meet.

  Next, the illumination state on the document surface 2a of the light beam emitted from the diffusion plate 8d will be described with reference to FIG.

  Consider a light beam emitted from two adjacent LED light emitting points 8aa1 and 8aa2.

  Here, a light beam emitted from the LED is considered to be a light beam that directly reaches the document surface 2a after passing through the diffusion plate 8d.

  A light beam emitted from a certain light emitting point 8aa1 passes through the diffusion plate 8d and is projected as a diffused light beam having a fan shape 8aa11 in the vicinity of the reading position 3a on the document surface 2a.

  At this time, the width in the sub-scanning direction is d, and the light flux appears in the main scanning direction up to the middle of the adjacent light emitting point 8aa2.

  Actually, it is naturally diffused beyond this point, but diffusion at positions other than directly above the light emitting point has a high degree of diffusion, so it is not reflected like a bright spot and can be ignored.

  Further, d, which is the sub-scanning width, is considered as a half-value width here, so the light quantity at the end of the width d is 0.5 at the fan center.

  This fan shape can be roughly regarded as a circular shape, and its radius of curvature is r.

  Of course, the reading line of the document 3 does not follow the fan shape, but is a direction extending in a straight line in the left-right direction as shown in FIG. 3, that is, a so-called main scanning direction.

  The angle formed by the line Sa connecting the arbitrary position s in the fan-shaped main scanning direction from the assumed center point (8aa1) of the circle of the sector 8aa11 with the center line So which is the front of the sector 8aa11 is ψ.

  Let h be the distance from the radius of curvature r at the position s. Let the distance from the center line So to the position s be an.

Expressing these relationships,
r + h = r + r (1 / cosφ-1) (formula a)
It becomes. The amount of light Py at the position s by illumination light is Py = 1−0.5 * (h / (d / 2)) = 1−h / d (Equation b)
Next, using Expression 6] the length of the main scanning direction to the position s as an, [Formula b] is Py = 1-r (1 / cos (Atan (a n / r)) - 1) / d [Formula c]
It becomes.

  Here, since the precautions in the above formula consider the light quantity at half value, the above formula does not consider the light quantity below half value.

Therefore, in order for the light quantity to be 0.5 or more at the maximum width a _max in the main scanning direction, r ≧ 1/2 * a _max
It is good to do. And d ≧ 0.42a _max
It is good to meet.

  If deviating from these conditions, the amount of light at the end portion in the sub-scanning direction, which is considered to be the light beam width, becomes insufficient, and a portion with a high amount of light is conspicuous as a bright spot in the read image, and the image quality deteriorates.

  The lighting device design method of the present invention includes a light source section 8a in which a plurality of point light sources are arranged in at least the main scanning direction.

  In the optical path connecting the point light source 8aa and the image reading position 3a of the document 2 or the vicinity thereof, there is a diffusion means for diffusing at least in the direction along the arrangement direction.

  The original surface of the illumination light generated by the spread of the illumination light derived from the angle θ formed by the light beam from the point light source 8aa toward the reading position 3a and the normal of the diffusion surface of the diffusion means 8d and the diffusion degree of the diffusion plate Consider the amount of curved shape above.

  The diffusion degree of the illumination light of the diffusion plate 8d in the main scanning direction and the sub-scanning direction is defined from the interval between the point light sources or the curved interval corresponding to each light emitting point on the original surface 2a. This facilitates illumination with bright spots.

  In the first embodiment, the effect on one optical path has been described.

  Actually, there are a light beam that reaches the original surface glass 2 directly from the illumination system 8 and a light beam that reaches the original surface glass 2 via the reflecting mirrors 8b and 8c as shown in FIG.

Of the light beams from the light emitting points 8aa1 to 8aan, the light beam that has directly passed through the diffusing surface 8b and the light beam that has been reflected and deflected by the reflecting members 8b and 8c and then passed through the diffusing surface 8b are incident on the original reading surface 2a. There is a luminous flux. The sub-scanning direction of the total width of composite curved shape light beam curved shape respectively generated on the document reading surface 2a is generated in the composite and d _all.

The maximum luminous flux width in the main scanning direction of the curved shape formed by the luminous flux from a single point light source is defined as a _max . At this time

Satisfied.

  In addition, the maximum light flux width in the sub-scanning direction of each curved shape constituting the composite curved shape is defined as d. At this time

Each element is set to be

  Here, a description will be given of the synthesis of three paths including the direct light from the LED 8aa and the two paths deflected by the reflecting mirrors 8b and 8c.

  Although the above-described curved shape (fan shape) has been described for one curve, the appearance conditions of the respective curves are almost the same even from the three paths.

  That is, a parallel curve appears as if it is slid and shifted in the sub-scanning direction. If this spreads too much in the sub-scanning direction, the required light intensity will not be collected and flare will appear, or if the curve is strong, the difference in light intensity between the position just above the light emitting point and the position slightly separated from the main scanning direction. Becomes larger and stands out as a bright spot.

Therefore, the inventor determined from the experimental results the combined total curvature width d _all occupying in the sub-scanning direction.

As limited. And the occupied width d in the sub-scanning direction for each curve.

As a result, it has been found that it is possible to reduce the image quality degradation level by suppressing it.

  If this embodiment is combined with this embodiment, an image with better image quality can be obtained. In this case, it is sufficient to satisfy the expression (4). In addition, it is preferable to configure each element so as to satisfy the expressions (4), (5), and (6).

  FIG. 4 is a schematic diagram of a main part of the illumination system according to the third embodiment of the present invention.

  In FIG. 4, the same members as those shown in FIG.

  Example 3 is a case where the freedom degree of arrangement | positioning of each member is comparatively large. In the third embodiment, the second diffusing plate 42 is arranged so as to cancel out the curved light flux region formed by the diffusing plate 41 arranged as shown in FIG.

  In this embodiment, there are two diffusing means 41 and 42 for diffusing and transmitting incident light with different diffusivities in the main scanning direction and the sub-scanning direction.

  The two diffusing units 41 and 42 are arranged so as to cancel the curved shape of the light beam region generated on the document reading surface 2a when the light beam from the point light source passes through one diffusing unit.

  In FIG. 4, the first diffusion plate 41 is given an angle θ1 by an angle formed by the optical axis (center axis) La from the LED and the diffusion plate.

  The second diffusing plate 42 is given in a form that cancels the curved shape generated in the first diffusing plate 41 by giving an almost opposite angle to the second diffusing plate 42 and allowing it to pass therethrough.

  As the angle θ2 given to the second diffusion plate 42, it is best to give only the same number of different signs as the first diffusion plate 41. If the absolute value of the angle cannot be made equal due to the arrangement of each member or the like, half of the absolute value of the angle θ1 given to the first diffusion plate 41 may be given. Cut in half.

It is the figure which showed the main structures of the image reading apparatus of 2: 1 mirror system which mounts the illuminating device of the Example of this invention. FIG. 2 is a sub-scanning sectional view showing an arrangement of a reflecting member and light source means shown in FIG. 1. It is a figure which shows the relationship of the curved shape of the illumination area | region on the original surface of FIG. It is a principal part schematic of Example 3 of this invention. It is the figure which showed the state which has arrange | positioned the diffuser plate perpendicular | vertical with respect to the optical axis from a light source means. It is a figure which shows the mode of the diffused light beam which appeared on the original surface by arrangement | positioning in FIG. It is the figure which showed the state which inclined and arrange | positioned the diffuser plate with respect to the optical axis of a light source means. It is a figure which shows the mode of the diffused light beam which appeared on the original surface by arrangement | positioning in FIG. It is a principal part schematic diagram which shows the conventional image reading apparatus. It is a figure explaining a mode that the image formation lens of FIG. 9 and the information of a manuscript surface image on a 3 line sensor. It is a figure explaining that the light emission point of a light source means reaches an image formation surface by the regular reflection from a document.

Explanation of symbols

1. 1. Image reading device Platen glass 2a. 2. Manuscript surface Original 3a. Reading position4. 4. First mirror stand Second mirror stand 6. Imaging optical system 7. CCD sensor8. Illumination system 8a. Light source unit 8aa. LED (point light source)
8aa11. Curved shape (fan shape)
8ab. Substrate 8b. Reflective member 8c. Reflective member 8d. Diffuser 9. White reference plates 41, 42. Diffusion plates M1 to M3. Folding mirror

Claims (7)

Illumination for illuminating the image information used in an image reading device for obtaining image information by imaging the image information of the document placed on the document table onto a line sensor arranged in the main scanning direction via an imaging optical system In the device
The illumination device includes a light source unit in which a plurality of point light sources are arranged in the main scanning direction;
Diffusing means for diffusing and transmitting incident light along the main scanning direction, disposed in an optical path connecting the light source unit and the image reading position of the document;
When the angle formed by the center line of the light beam from the point light source toward the reading position and the normal line of the diffusion surface of the diffusion means is θ,
θ ≧ 45 °
And
The light flux region generated on the original reading surface of the original after the light flux from each point light source passes through the diffusion surface is longer in the main scanning direction than the sub scanning direction and has a curved shape curved in the sub scanning direction. And
In the luminous flux region formed by a single point light source, the curvature radius of the curved shape, the maximum luminous flux width in the sub-scanning direction, the distance from the center line in the curved shape to an arbitrary position in the main scanning direction, the main scanning direction , D, a _n , a _max in order,

The amount Py at any position a _n in the main scanning direction in the bent inner shape that is generated by the respective point light sources when placing the

Represented by

An illumination device characterized by satisfying Illumination for illuminating the image information used in an image reading device for obtaining image information by imaging the image information of the document placed on the document table onto a line sensor arranged in the main scanning direction via an imaging optical system In the device
The illumination device includes a light source unit in which a plurality of point light sources are arranged in the main scanning direction;
A reflecting member that reflects the light beam from the light source unit toward the image reading position of the document;
Diffusing means for diffusing and transmitting incident light along the main scanning direction, disposed in an optical path connecting the light source unit and the image reading position of the document;
When the angle formed by the center line of the light beam from the point light source toward the reading position and the normal line of the diffusion surface of the diffusion means is θ,
θ ≧ 45 °
And
The light flux region generated on the original reading surface of the original after the light flux from each point light source passes through the diffusion surface is longer in the main scanning direction than the sub scanning direction and has a curved shape curved in the sub scanning direction. And
Of the light beams from each point light source, the curved shape generated on the original reading surface by the light beam that has directly passed through the diffusion surface and the light beam that has been reflected by the reflecting member and then passed through the diffusion surface. The total width in the sub-scanning direction of the compound curved shape generated by combining the light beams is d _all ,
When the maximum luminous flux width in the main scanning direction of the curved shape formed by the luminous flux from a single point light source is a _max

And when the maximum light flux width in the sub-scanning direction of each curved shape constituting the complex curved shape is d

A lighting device characterized by the above. Illumination for illuminating the image information used in an image reading device for obtaining image information by imaging the image information of the document placed on the document table onto a line sensor arranged in the main scanning direction via an imaging optical system In the device
The illumination device includes a light source unit in which a plurality of point light sources are arranged in the main scanning direction;
A reflecting member that reflects the light beam from the light source unit toward the image reading position of the document;
Diffusing means for diffusing and transmitting incident light along the main scanning direction, disposed in an optical path connecting the light source unit and the image reading position of the document;
When the angle formed by the center line of the light beam from the point light source toward the reading position and the normal line of the diffusion surface of the diffusion means is θ,
θ ≧ 45 °
And
The light flux region generated on the original reading surface of the original after the light flux from each point light source passes through the diffusion surface is longer in the main scanning direction than the sub scanning direction and has a curved shape curved in the sub scanning direction. And
In the luminous flux region formed by a single point light source, the curvature radius of the curved shape, the maximum luminous flux width in the sub-scanning direction, the distance from the center line in the curved shape to an arbitrary position in the main scanning direction, the main scanning direction , D, a _n , a _max in order,

The amount Py at any position a _n in the main scanning direction in the bent inner shape that is generated by the respective point light sources when placing the

Represented by

The filling,
Of the light beams from each point light source, the light beam that has directly passed through the diffusion surface, and the curved light beam generated on the original reading surface by the light beam that has been reflected by the reflecting member and then passed through the diffusion surface. D _all , the total width in the sub-scanning direction of the compound curved shape generated by _combining
When the maximum luminous flux width in the main scanning direction of the curved shape formed by the luminous flux from a single point light source is a _max

A lighting device characterized by the above.   4. The illuminating device according to claim 1, wherein the diffusing unit is a diffusing plate having a different degree of diffusion in the main scanning direction and the sub-scanning direction.   5. The illumination according to claim 1, further comprising a second diffusing unit that cancels a curved shape of a light beam region generated on the original reading surface after the light beam from the point light source passes through the diffusion surface. apparatus. Illumination for illuminating the image information used in an image reading device for obtaining image information by imaging the image information of the document placed on the document table onto a line sensor arranged in the main scanning direction via an imaging optical system In the device
The illumination device includes a light source unit in which a plurality of point light sources are arranged in the main scanning direction;
Two diffusing means disposed in an optical path connecting the light source unit and the image reading position of the document and diffusing and transmitting incident light with different diffusivities in the main scanning direction and the sub-scanning direction;
The two diffusing means are arranged so as to cancel the curved shape of the light beam region generated on the original reading surface when the light flux from the point light source passes through one diffusing means. .   The illumination device according to any one of claims 1 to 6, a reading optical system that forms image information of a document illuminated by a light beam from the lighting device, and image information formed by the reading optical system An image reading apparatus having a line sensor for reading image data.