JP4972432B2 - Illumination unit, image reading apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to an illumination unit, an image reading apparatus, and an image forming apparatus.

Conventionally, tube lamps such as xenon lamps and halogen lamps that are generally used as a light source of an image reading apparatus consume a large amount of power and generate a large amount of heat, which increases the temperature of the entire apparatus. The rise in temperature in the image reading apparatus has become a problem that the conjugate relationship of the optical system is broken, the focus is shifted from the photoelectric conversion element, no image is formed, and a good image cannot be obtained.
Therefore, as a new illumination light source that replaces a tube lamp such as a xenon lamp, an illumination unit that uses an LED light source that consumes less power and generates heat has attracted attention.
As an illumination unit using an LED light source, for example, in the technique of Patent Document 1, an illumination unit that illuminates a document through a light guide with LEDs arranged in a line is disclosed.

As another known technique, in the technique disclosed in Patent Document 2, a long lens system is arranged in front of the arranged LEDs to increase the concentration of illumination in a direction perpendicular to the arrangement of the LEDs. A lighting unit is disclosed.
As another known technique, Patent Document 3 discloses an illumination unit that irradiates a document after the illumination light from an LED is once reflected by a reflection mirror.

FIG. 6 is a cross-sectional view showing the document 2 placed on the glass 1 from the contact of the image reading apparatus. In the same figure, even when the illumination unit 10 using a tube lamp and an LED is used, in the illumination in the image reading apparatus, the direction in which the reflected light from the original is large as shown in the figure in the light reflected on the original. That is, it is common not to read in the regular reflection direction. This is because the regular reflection direction reflects not only the reflection from the document but also the reflection from the back side of the document table, and the reflected light component on the back side also enters the photoelectric conversion element. It is because it becomes impossible to read.
Accordingly, the illumination unit 10 illuminates the original by being arranged obliquely with respect to the original surface as shown in the figure, and among the reflected light from the original, the reflected light in the direction perpendicular to the original is first. In general, the light is reflected by a mirror 3C and read by a photoelectric conversion element. By doing so, the influence of reflected light from the back surface of the contact glass 1 can be eliminated.

Patent Document 4 below discloses a line illumination system that efficiently adapts light emitted from an LED to an original reading apparatus in an illumination system that surrounds an LED light source, and the illumination light amount distribution on the original surface is changed from the central portion to the peripheral portion. An increased document illumination device is disclosed.
Further, Patent Document 5 below describes a line light source device in which irradiation unevenness in a direction along a line of a plurality of light emitting element chips is small.

JP 2006-025303 A JP-A-2005-278132 JP 2005-241681 A JP-A-2005-234109 Japanese Patent No. 3649939

  However, even when the light is illuminated obliquely as described above, for example, when reading the binding portion of the book b, as shown in FIG. As shown in FIG. 7A, the light applied to the bent portion of the binding portion of a book b emits specularly reflected light in the direction perpendicular to the document table surface at a specific angle. For this reason, the specular reflection light is directly taken into the photoelectric conversion element, and the amount of the light is too much larger than the amount of the reflected light when the document is normally read.

  Furthermore, in an illumination unit using an LED, an image of the LED itself is read by an image reading device. As shown in FIG. 7B, an image near the binding portion of a document such as a book b is There is a problem that white dots are missing and the original information cannot be read satisfactorily.

  This phenomenon is unlikely to occur due to the fact that tube lamps such as xenon lamps are diffused light sources, and are likely to occur with highly directional LEDs, etc. When the focal depth of the double imaging element itself is shallow, this phenomenon is unlikely to occur even when a highly directional LED or the like is used, and is a phenomenon seen in a reduction optical system with a deep focal depth. This phenomenon is prominent in the case of a strong original.

Here, Patent Document 5 discloses an illumination unit using a light source unit and a reflection unit. However, the illumination unit described here is arranged on a document surface arranged in contact with a document table. This is intended to reduce the unevenness of illumination. In addition, the degree of parallelism near the center of the light source unit is not shown, and the degree of divergence is also not shown for the divergence near the periphery, and it is also shown how far the center is near the center. Not. Therefore, there is no disclosure of means for reducing the influence of the regular reflection component of the document surface away from the document table even if the illumination unevenness on the document surface in contact with the document table is eliminated satisfactorily.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image reading apparatus and an image forming apparatus that are capable of satisfactorily suppressing condensing of a light source and obtaining a good image even when a part of the original is floating from the original table. Is to provide.

The invention according to claim 1 includes a plurality of light source units arranged in a line on a single substrate, and the light source unit reflects light from the light emitting element and the light emitting element and covers the light from the exit surface. A light reflecting unit that emits light to the irradiated object, and emits light from the emitting surface to the irradiated object, wherein the length of the emitting surface in the arrangement direction of the light source unit is D [mm], and the light source unit When the intensity distribution of the light emitted from the light source is measured, an angle half-value angle that is an angle when the direction of the intensity of the light becomes half of the maximum value when viewed from the direction perpendicular to the exit surface of the light source unit is A [ rad]

を満たすことを特徴とする照明ユニットである。

It is the lighting unit characterized by satisfy | filling.

According to a second aspect of the present invention, in the illumination unit according to the first aspect, the reflective portion has a reflective surface including a parabolic surface, and reflects the light emitted from the light emitting element by the reflective surface. The light is emitted to the object to be irradiated, and the light emitting element is arranged at a focal position of a paraboloid included in the reflecting surface.
According to a third aspect of the present invention, in the illumination unit according to the first or second aspect, the reflective surface of the reflective portion is a diffusing surface.
The invention according to claim 4 is characterized in that in the illumination unit according to any one of claims 1 to 3, a plurality of light source units emitting light of different colors are arranged as the light source unit. To do.
The invention according to claim 5, prior SL and lighting unit according to any one of claims 1-4 for radiating light to the document as an object to be irradiated, the photoelectric conversion element, in the document And an imaging element that forms an image of the reflected light on the photoelectric conversion element, and reads an image of the original .
The invention according to claim 6 is an image forming apparatus comprising: an image reading device that reads an image of a document; and an image forming unit that forms an image based on image data read by the image reading device. The image reading apparatus is an image forming apparatus according to claim 5.

According to the first aspect of the present invention, even when specularly reflected light that hits a folded document such as a binding portion of a book and enters the imaging element, data loss such as white spots is prevented and an abnormal image is obtained. Good image reading is possible without occurrence.
According to the second aspect of the present invention , the specularly reflected light can be imaged near the focal length of the imaging element, and the specularly reflected light diverges on the photoelectric conversion element, and the amount of light incident on each pixel is reduced. Since it can be reduced, it is possible to prevent data from being lost such as white spots and to read an image without causing an abnormal image . Further, a so-called reflective LED as described in claim 2 can emit light in one direction without emitting light from the entire circumference unlike a tube lamp such as a xenon lamp. However, the light utilization efficiency is high, and the power consumption can be reduced.
According to the third aspect of the present invention, since the surface of the reflecting portion is a diffusing surface, the direction of the light beam from the reflecting portion is irradiated in an irregular direction, so that it is almost the same as a tube lamp such as a xenon lamp. To the same extent, it is possible to suppress the occurrence of defective images due to the influence of regular reflection light. The light emitted from the light source unit is irradiated almost perpendicularly to the document, and the light use efficiency is reduced. However, compared to tube lamps such as xenon lamps, it is possible to achieve high light use efficiency and low power consumption. Is possible .
According to the invention described in claim 4 , by using a light source unit of a plurality of colors, a light source of a color corresponding to each of the red (R), green (G), and blue (B) filters of the photoelectric conversion element is used. Thus, it is possible to increase the light utilization efficiency and read full color image information. Since LEDs generally have a narrow wavelength band, the light source unit is not limited to three colors, and it is possible to increase the reproducibility of the color information of the document information by increasing other colors.

Embodiments of the present invention will be described below.
FIG. 1 is an explanatory diagram of an image reading apparatus according to the present embodiment. In FIG. 1, an image reading apparatus 100 has a document 2 having an image to be read placed in a plane on a contact glass 1 as a document table, and an illuminating unit is disposed below the contact glass 1. As a means, an illumination unit 10 described later is used to illuminate the document 2 from obliquely below.
The reflected light from the illuminated portion of the document 2 (reflected light from the image) is reflected by the first mirror 3C provided on the first traveling body 3, and then the second mirror provided on the second traveling body 4. 4A and the third mirror 4B are sequentially reflected, pass through the image reading lens 5, and form a reduced image of the original image on the imaging surface of the line sensor 6 as a photoelectric conversion element. These first, second, and third mirrors 3C, 4A, and 4B constitute a reflection optical system.

The first traveling body 3 and the second traveling body 4 are caused to travel in the direction of the arrow (to the right in FIG. 1) by driving means (not shown). The traveling speed of the first traveling body 3 is V, and the traveling speed of the second traveling body 4 is V / 2. By this traveling, the first traveling body 3 and the second traveling body 4 are displaced to the positions indicated by broken lines in FIG.
The illumination unit 10 moves integrally with the first traveling body 3 and performs illumination scanning of the entire document 2 on the contact glass 1.
Since the moving speed ratio between the first and second traveling bodies is “V: V / 2”, the optical path length from the original scanned portion to the image reading lens is kept unchanged.
The line sensor 6, which is a photoelectric conversion element, includes three rows of photoelectric conversion elements ( 6A, 6B, 6C ) having red (R), green (G), and blue (B) filters as color separation means on one chip. The three-line CCD (three-line line sensor) arranged in the above-described manner is used to convert the original image into an image signal as the original 2 is illuminated and scanned. In this way, reading of the document 2 is executed, and the color image of the document 2 is read by color separation into three primary colors of red, green, and blue.
The image reading apparatus 100 is an apparatus that reads an image in full color, and includes color separation means (red, green, and blue provided in the three-line CCD) provided in the imaging optical path of the image reading lens 5. Filter).

As another form of the image reading apparatus 100, an illumination unit that illuminates a document on the contact glass in a slit shape, a line sensor, and a plurality of mirrors that form an imaging optical path from the illuminated part of the document to the line sensor And a reading unit in which the image reading lens disposed on the image-forming optical path is integrated with each other, and the document is read and scanned by causing the driving unit to move relative to the document. Also good.
For color separation, separately from the above, a color separation prism or filter is selectively inserted between the image reading lens and the line sensor (CCD), and colors R (red), G (green), and B (blue). A method of disassembling and a method of illuminating a document by sequentially turning on R, G and B light sources can be used.

FIG. 2 is an explanatory diagram of the image forming apparatus of the present embodiment using the image reading apparatus shown in FIG.
This image forming apparatus is a copying machine. The image forming apparatus includes an image reading apparatus 100 positioned at the upper part of the apparatus and an image forming unit 200 positioned at a lower position. The portion of the image reading apparatus 100 is configured as described with reference to FIG.
The image signal output from the three-line line sensor (imaging means) 6 of the image reading apparatus 100 is sent to the image processing unit 1200, where it is processed by the image processing unit 1200 to generate an optical writing signal (yellow, magenta, cyan, Signal for writing each color of black).
The image forming unit 200 includes a photoconductive photosensitive member 1100 formed in a cylindrical shape as a latent image carrier, around which a charging roller 1110 as a charging unit, a revolver type developing device 1130, and a transfer belt 1140 are provided. A cleaning device 1150 is provided. As a charging unit, a corona charger can be used instead of the charging roller 1110.
An optical scanning device 1170 that receives a signal for writing from the signal processing unit 1200 and writes on the photosensitive member 1100 by optical scanning performs optical scanning of the photosensitive member 1100 between the charging roller 1110 and the developing device 1130.
Reference numeral 1160 denotes a fixing device, reference numeral 1180 denotes a cassette, reference numeral 1190 denotes a registration roller pair, reference numeral 1220 denotes a paper feed roller, reference numeral 1210 denotes a tray, and reference numeral S denotes a transfer sheet as a recording medium.

When image formation is performed, the photoconductive photoreceptor 1100 is rotated at a constant speed in the clockwise direction, the surface thereof is uniformly charged by the charging roller 1110, and is subjected to exposure by optical writing of the laser beam of the optical scanning device 1170. An electrostatic latent image is formed. The formed electrostatic latent image is a so-called negative latent image, and the image portion is exposed.
Image writing is performed in the order of a yellow image, a magenta image, a cyan image, and a black image in accordance with the rotation of the photoreceptor 1100, and the formed electrostatic latent image is stored in each developing unit Y (yellow toner) of the revolver type developing device 1130. ), M (development with magenta toner), C (development with cyan toner), K (development with black toner) in order to be reversely developed and visualized as a positive image. The color toner images are sequentially transferred onto the transfer belt 1140 by the transfer voltage application roller 114A, and the color toner images are superimposed on the transfer belt 1140 to form a color image.
The cassette 1180 storing the transfer paper S is detachable from the main body of the image forming apparatus, and in the mounted state, the uppermost sheet of the stored transfer paper S is fed by the paper feed roller 1220 and fed. The transferred transfer paper S is caught by the registration roller pair 1190 at its leading end.
The registration roller pair 1190 means a position where the transfer paper S is transferred to the transfer portion (the transfer belt 1140 and the transfer roller 114B are opposed to each other) in synchronization with the movement of the color image by the toner on the transfer belt 1140 to the transfer position. The same in) . The transferred transfer paper S is superimposed on the color image at the transfer portion, and the color image is electrostatically transferred by the action of the transfer roller 114B. The transfer roller 114B presses the transfer sheet S against the color image during transfer.
The transfer sheet S on which the color image is transferred is sent to the fixing device 1160, where the color image is fixed in the fixing device 1160, passes through a conveyance path by a guide means (not shown), and is discharged onto the tray 1210 by a pair of paper discharge rollers (not shown). The Each time each color toner image is transferred, the surface of the photoreceptor 1100 is cleaned by a cleaning device 1150 to remove residual toner, paper dust, and the like.
The configuration of the image forming unit 200 may be a well-known configuration for forming a single color image (such as one color of K).

Next, the illumination unit 10 of the image reading apparatus 100 will be described with reference to FIG.
FIG. 3A shows a light source unit 13, which is a reflection type LED that reflects light from the LED light emitting element 11 at the reflecting portion 12 and irradiates light on the document surface side, in a row on a single substrate 14. It is explanatory drawing of the lighting unit 10 arranged.
In this illumination unit 10, the LED light-emitting element 11 is arranged at the focal position of the reflecting portion 12 constituted by a substantially paraboloid, so that the light emitted from the focal point of the paraboloid is parallel to the document surface direction, that is, the document surface. The light emitted from the LED light emitting element 11 having a slight area but with a substantially Lambertian distribution can be emitted substantially perpendicularly to the document surface. The light emitted from the LED light emitting element 11 can be effectively used as illumination light.
Here, in the image reading apparatus using the reduction optical system, in order to reduce the influence of the light of the specularly reflected light component described above with reference to FIG. 7, it is necessary that the light is not condensed on the photoelectric conversion element. is there.

The conditions for not condensing light on the photoelectric conversion element will be described with reference to FIG.
The line sensor 6 shown in FIG. 4 includes a plurality of CCD pixels 15 arranged on a substrate 16.
The convergent rays 20 and 21 represent a state in which the regular reflection light from the book b as the document described with reference to FIG. 7 is collected by an imaging element (not shown). When this convergent light beam is collected on the CCD pixel 15, the amount of light incident on that pixel becomes too large, and the read image becomes white. The state in which the convergent rays 20 and 21 are collected on the CCD pixel 15 is a state in which the imaging element forms a conjugate relationship with the CCD pixel 15 when the light source is in the vicinity of the original surface. That is. Therefore, when the light source irradiates from a position farther from the vicinity of the original surface, the image formation position of the convergent light beam can be brought toward the focal position of the image formation element (left side in FIG. 4).
That is, if the light source is set to infinity, that is, the light beam applied to the document can be made parallel light, the convergent light beams 20 and 21 in the figure are collected at the focal position of the imaging element, The amount of light that diverges and greatly blurs on the CCD pixel 15 and enters each pixel of the CCD pixel 15 can be reduced, and the image can be prevented from being whitened.
[Delta] L _B in FIG. 4 when away arbitrary distance of the light source from the original surface, indicating the distance to the condensing position from on the line sensor 6.
Δ in Figure 4, the width of the collecting of light spread on the line sensor 6 when the light-condensing position is deviated [Delta] L _B.
Here, the focal length of the imaging element is f, the F number is F, the magnification of the imaging optical system is m 2 , the light beam divergence angle (convergence angle in FIG. 4) is μ ′, and the image-side numerical aperture is NA _img . putting the relationship of [Delta] L _B and δ can be represented by the number 2.

'When, m' the magnification of the imaging optical system for imaging at a position deviated from the line sensor 6 only [Delta] L _B m relationship with δ can be shown by the number 3.

Several third magnification m ', obtaining the displacement amount [Delta] L _A from the document surface to the light source position to be able to indicate the number 4.

Thus, by illuminating the document from a light source at the position of [Delta] L _A shown in Equation 4, it is on the line sensor 6, the condenser of the specular reflection light is seen to spread [delta]. If δ is expanded to 6 times the pixel size P in the arrangement direction of the line sensors 6, the area ratio becomes 36 times, so that the light quantity ratio becomes 1/36 and the regular reflection light can be reduced to about 3% or less. The image can be read satisfactorily.
from the relationship between the pixel size P of δ to the arrangement direction (the number 5), [Delta] L _A is Kakiarawaseru to 6.

数６で示したΔＬ_Ａまで光源位置をずらせば、ラインセンサ６上では画像読み取りにおいて影響のない程度までボケさせることが可能となる。
以下に結像素子のｆ、Ｆ、ｍと画素サイズＰとΔＬ_Ｂ、ｍ’、ΔＬ_Ａの計算結果を表１に示す。

If shifting the light source position to the [Delta] L _A shown in Equation 6, it is possible to blur extent not affecting the image reading on the line sensor 6.
Table 1 shows the calculation results of f, F, and m of the imaging element, pixel size P, and ΔL _B , m ′, and ΔL _A.

As shown in Table 1, if bright F number of the imaging optical element, the depth of focus of the imaging optical system becomes narrow, it found that requires even shorter required [Delta] L _A, the imaging optical element in the opposite the focal length of the depth of the imaging optical system becomes wider the longer it can be seen that it is necessary to increase also [Delta] L _a.
Also proportional to the magnification used, the smaller the ratio, it can be seen that the need also short Likewise [Delta] L _A for the depth becomes narrow.
From the above example calculation results, by setting [Delta] L _A far more 15 mm, it is possible to satisfactorily reduce the condensing of the specularly reflected light.
Note that lengthening the [Delta] L _A is the width of the spread of the light beam emitted from the divergence angle (LED light-emitting element 11 of the light source unit 13 of the lighting unit 10, refers to a divergence angle A from the false emission point 3 to.) it can be considered to narrow to be synonymous with the.
FIG. 3B shows an enlarged view of the light source unit. Since the light irradiated at an arbitrary angle A from the emission surface of the light source unit 13 in FIG. 3B can be considered to be equivalent to the light emitted from the pseudo light emission position O, from the emission surface of the light source unit 13. distance L _O to the pseudo emission position O is the relationship of the light source unit 13 and the length D of the exit surface of the array direction,

Can be expressed as
By setting L 2 _O to 15 mm or more (Equation 8), the relationship between the half-value angle A [rad] and the length D [mm] can be expressed by Equation 1.

Therefore, by using the illumination unit 10 that satisfies this number 1, it is possible to satisfactorily reduce the concentration of specularly reflected light from the document.
Here, the half-value angle A is a direction in which the intensity of light becomes half of the maximum value when the intensity distribution of light emitted from the light source unit 13 is measured, as shown in FIG. An angle measured with reference to (perpendicular to the exit surface of the light source unit 13).
For example, when the length D is 7 mm, the amount of light incident on the line sensor 6 is formed by forming the reflecting portion 12 of the light source unit 13 so that the half-value angle is 0.23 rad (13 °) or less from Equation 1. It can be reduced to the extent that there is no problem.
As shown in FIG. 3, if the reflecting portion 12 is a diffusing surface, an irregular light beam is emitted from the light emitting surface of the light source unit 10, and thus the light of the specularly reflected light itself as described with reference to FIG. 7. It is effective for reducing the strength.
Further, if a phosphor emitting fluorescence that is complementary to the color of the light source unit 11 is arranged between the light source unit 11 and the reflection unit 12 of the light source unit 10, white light can be easily obtained. This enables full color image reading.
Further, a plurality of single-color light source units 10 that emit light of different colors may be arranged to form white illumination synthesized on the document surface by the multiple color light source units 10. It is also possible to sequentially read the image every time .
In the present invention, regardless of the image reading apparatus using the contact glass 1 serving as a document table, the first and second traveling bodies 3 and 4 are fixed at arbitrary positions, and the image reading method using an image reading method for reading while feeding the document. Even if it is applied to the apparatus, the same effect as described above can be expected when the document being conveyed is warped and specularly reflected light can be generated.

It is explanatory drawing of the image reading apparatus which is one embodiment of this invention. 1 is an explanatory diagram of an image forming apparatus according to an embodiment of the present invention. FIG. It is explanatory drawing of an illumination unit. It is explanatory drawing of a line sensor. It is explanatory drawing of a half angle of view. It is explanatory drawing of the subject of this invention. It is explanatory drawing of the subject of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Contact glass 2 Document 6 Line sensor 10 Illumination unit 11 Light source part 12 Reflection part 13 Light source unit

Claims (6)

A plurality of light source units arranged in a line on a single substrate;
The light source unit includes a light emitting element, and a reflection unit that reflects light from the light emitting element and emits light from an emission surface to an irradiation object.
The length of the emission surface of the light source unit in the arrangement direction is D [mm], and when the intensity distribution of the light emitted from the light source unit is measured, the direction when the intensity of the light becomes half of the maximum value is An illumination unit characterized by satisfying the following mathematical formula (1) when an angle half-value angle, which is an angle when viewed from a direction perpendicular to an emission surface of the light source unit, is A [rad].

The reflective portion has a reflective surface including a parabolic surface, reflects light emitted from the light emitting element on the reflective surface, and emits light to the irradiated object,
The lighting unit according to claim 1, wherein the light emitting element is disposed at a focal position of a paraboloid included in the reflecting surface.   The illumination unit according to claim 1, wherein the reflection unit has a reflection surface that is a diffusion surface.   The lighting unit according to any one of claims 1 to 3, wherein a plurality of light source units emitting different colors of light are arranged. An illumination unit as claimed in any one of claims 1-4 for radiating light to the document as a pre-Symbol irradiated object,
A photoelectric conversion element;
An imaging element that images reflected light from the original on the photoelectric conversion element ;
An image reading apparatus for reading an image of the original . An image reading apparatus according to claim 5;
An image forming unit that forms an image based on image data read by the image reading device;
An image forming apparatus comprising:

Images