JP2014041184A - Imaging lens, image reading apparatus, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve good imaging performance at a low angle and at the periphery of an image at a low angle while reducing the size of a lens.
An imaging lens includes, in order from an object side to an image side, a first lens that is a positive meniscus lens having a convex surface facing the object side, a second lens that has concave both lens surfaces, A third lens 3 having a convex lens surface, a fourth lens 4 having both concave surfaces, a positive fifth lens 5 having a convex lens surface on the image surface side, and a convex surface facing the image surface side A negative meniscus sixth lens 6, the distance between the fifth lens 6 and the sixth lens 6 is d11, the combined focal length from the first lens 1 to the fifth lens 5 is ff, and the sixth lens 6 Where f6 is the focal length and f is the focal length of the entire system,
(1) 0.15 <d11 / f <0.28
(2) −0.73 <ff / f6 <−0.48
Satisfied.
[Selection] Figure 1

Description

  The present invention relates to an imaging lens, an image reading apparatus using the imaging lens, and an image forming apparatus using the image reading apparatus. In particular, the image information of a document is arranged in a line shape. The image forming apparatus is used in a digital copying machine, a facsimile, or the like in which reduced image formation is performed on an image sensor and image information is read.

  An image reading apparatus such as an image reading unit of a digital copying machine or a facsimile, or an image scanner reduces an original information to be read by an imaging lens and forms an image on an image pickup device such as a CCD (Charge Coupled Device). Signal information.

  The image reading apparatus uses a so-called three-line CCD in which image sensors each having red, green, and blue filters, for example, are arranged in three rows on one substrate in order to read document information in color. There is. An image reading apparatus using a three-line CCD has an optical system that converts the original document information into signals by separating the three primary colors by forming the original document image on each image sensor.

  In the imaging lens used in the image reading apparatus as described above, a high contrast in a high spatial frequency region is generally required on an image sensor that is an image plane, and the aperture efficiency is 100 up to the periphery of the angle of view. It is required to be near%.

  In addition, with the imaging lens, it is necessary to match the imaging positions of red, green, and blue colors on the image plane in the optical axis direction in order to read a color document well, so that the chromatic aberration of each color is corrected well. There is a need to.

  In addition, in recent years, in order to reduce the size and cost of the image reading apparatus, it is desired to reduce the diameter and wide angle of the imaging lens.

  Various imaging lenses are known (see, for example, Patent Documents 1 to 3). For example, the imaging lens described in Patent Document 1 has been proposed as a small-diameter imaging lens having a six-lens configuration and a half field angle of around 24 °, which suppresses field curvature and astigmatic difference.

  However, in general, a telephoto type, a final lens as described in Patent Document 1, and an imaging lens having a negative power in the lens group, the final lens group is used for field curvature correction as the angle of view increases. Tend to be larger. Therefore, in the case where both the fifth lens and the sixth lens in the final lens group are negative lenses as in the imaging lens described in Patent Document 1, it is necessary to increase the diameter of both lenses when the angle of view is further increased. There is. For this reason, in the imaging lens described in Patent Document 1, if the angle is increased, the cost is increased.

  The present invention has been made in view of the above problems, and an image forming lens having a good image forming performance around an image even at a wide angle at a low cost while reducing the size of the lens. An object of the present invention is to provide an image reading apparatus using an image lens and an image forming apparatus using the image reading apparatus.

The imaging lens according to the present invention includes, in order from the object side to the image side, a first lens that is a positive meniscus lens having a convex surface directed toward the object side, a second lens in which both lens surfaces are concave surfaces, and both lens surfaces are A third lens that is a convex surface, a fourth lens that is concave on both lens surfaces, a positive fifth lens that has a convex lens surface on the image surface side, and a negative meniscus lens with the convex surface facing the image surface side In the imaging lens composed of the sixth lens, the distance between the fifth lens and the sixth lens is d11, the combined focal length from the first lens to the fifth lens is ff, the focal length of the sixth lens is f6, When the focal length is f,
0.15 <d11 / f <0.28
−0.73 <ff / f6 <−0.48
It is characterized by satisfying.

  According to the present invention, it is possible to reduce the size of the lens, and to have good imaging performance around the image even at a wide angle at a low cost.

It is an optical arrangement | positioning figure which shows embodiment of the imaging lens which concerns on this invention. FIG. 2 is an optical layout diagram of Example 1 of the imaging lens. FIG. 6 is an aberration diagram of Example 1 of the imaging lens. FIG. 6 is an optical layout diagram of Example 2 of the imaging lens. It is an aberration diagram of Example 2 of the imaging lens. FIG. 6 is an optical layout diagram of Example 3 of the imaging lens. It is an aberration diagram of Example 3 of the imaging lens. FIG. 6 is an optical layout diagram of Example 4 of the imaging lens. It is an aberration diagram of Example 4 of the imaging lens. FIG. 6 is an optical layout diagram of Example 5 of the imaging lens. It is an aberration diagram of Example 5 of the imaging lens. FIG. 10 is an optical layout diagram of Example 6 of the imaging lens. FIG. 10 is an aberration diagram of Example 6 of the imaging lens. 1 is a cross-sectional view in the sub-scanning direction showing an embodiment of an image reading apparatus according to the present invention. It is sectional drawing of the subscanning direction which shows another embodiment of the image reading apparatus which concerns on this invention. 1 is a cross-sectional view in the sub-scanning direction showing an embodiment of an image forming apparatus according to the present invention.

  Hereinafter, embodiments of an imaging lens according to the present invention, an image reading apparatus using the imaging lens, and an image forming apparatus having the image reading apparatus will be described with reference to the drawings.

● Embodiment of imaging lens ●
Embodiments of an imaging lens according to the present invention will be described.

  FIG. 1 is an optical arrangement diagram showing an embodiment of an imaging lens according to the present invention.

  In the following description, the left side (contact glass 8 side in FIG. 1) of the optical layout diagram showing the embodiment of the imaging lens 10 is the object side, and the right side (cover glass 9 side in FIG. 1) is the image. On the side.

  The imaging lens 10 according to the present invention includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a sixth lens in order from the object side to the image side. It consists of a lens 6. Here, all the lenses from the first lens 1 to the sixth lens 6 are glass lenses, and can be made of, for example, optically stable glass that is chemically stable and does not contain environmental load substances such as lead and arsenic.

  On the object side of the first lens 1, a contact glass (original table glass) 8 on which an original is placed is disposed. A cover glass 9 of an image sensor (not shown) is disposed on the image side of the sixth lens 6.

  A diaphragm 7 is disposed between the second lens 2 and the third lens 3.

  The first lens 1 is a positive meniscus lens having a convex surface facing the object side. The second lens 2 is concave on both lens surfaces.

  The third lens 3 is convex on both lens surfaces. Further, the fourth lens 4 is concave on both lens surfaces.

  The fifth lens 5 is a positive lens having a convex surface on the image side. The sixth lens 6 is a negative meniscus lens having a convex surface facing the image surface side.

The imaging lens 10 has a lens interval between the fifth lens 5 and the sixth lens 6 as d11, a combined focal length from the first lens 1 to the fifth lens 5 as ff, and a focal length of the sixth lens 6 as f6. The focal length of the entire system is f, the radius of curvature of the first surface of the second lens 2 is r4, the radius of curvature of the first surface of the sixth lens 6 is r12, and the radius of curvature of the second surface of the sixth lens 6 is r13. The following conditional expression is satisfied.

(1) 0.15 <d11 / f <0.28

(2) −0.73 <ff / f6 <−0.48

(3) -5.2 <r4 / f <-1.6

(4) -3.9 <(r12 + r13) / (r12-r13) <-1.7

  Conditional expression (1) defines the ratio of the lens interval between the fifth lens 5 and the sixth lens 6 and the focal length of the entire system. That is, the conditional expression (1) defines a range in which the size of the imaging lens 10 and the astigmatic difference are satisfactorily suppressed.

  Note that when the value of conditional expression (1) increases, the sixth lens 6 tends to move away from the fifth lens 5 to the image sensor side (image side). If the upper limit value of conditional expression (1) is exceeded, the sixth lens 6 becomes large in diameter and it becomes difficult to reduce the size of the imaging lens 10.

  On the other hand, when the lower limit value of conditional expression (1) is exceeded, the astigmatic difference of the intermediate image becomes large, so that good imaging performance cannot be obtained.

  Conditional expression (2) defines the ratio of the combined focal length from the first lens 1 to the fifth lens 5 and the focal length of the sixth lens 6. That is, the conditional expression (2) mainly corrects widening of the imaging lens 10 and coma aberration well.

  If the focal lengths of both lens groups are deviated beyond either the upper limit value or lower limit value of conditional expression (2), it becomes difficult to cancel each other's aberrations, and the resolving power around the image is reduced. Therefore, conditional expression (2) is a necessary condition for widening the angle.

  Conditional expression (3) defines the ratio of the radius of curvature of the first surface of the second lens 2 to the focal length of the entire system. That is, the conditional expression (3) defines a range in which coma aberration is favorably suppressed.

  When the conditional expression (3) exceeds the upper limit value, the coma aberration of the lower light ray falls to the negative side, and the image forming position around the image moves to the negative side. For this reason, the resolving power decreases due to the influence of the introverted coma.

  On the other hand, when the conditional expression (3) exceeds the upper limit value, the coma aberration of the lower light ray falls to the positive side, and the imaging position around the image moves to the positive side. For this reason, the resolving power is reduced due to the influence of the extroverting coma.

  Therefore, the conditional expression (3) is a condition necessary for obtaining a resolving power around the image of the imaging lens 10.

  Conditional expression (4) defines the ratio of the curvature radii of the first surface and the second surface of the sixth lens 6. That is, conditional expression (4) defines a range in which spherical aberration is satisfactorily suppressed.

  If conditional expression (4) exceeds the upper limit, the spherical aberration falls to the negative side, the spherical aberration increases, and the resolution of the entire image area decreases.

  On the other hand, if the conditional expression (4) exceeds the lower limit, the spherical aberration is excessively corrected and the imaging performance is improved, but the imaging position shift between the on-axis and the periphery of the image becomes large. On the other hand, if conditional expression (4) exceeds the lower limit, good imaging performance cannot be obtained over the entire image area.

  Therefore, the conditional expression (4) is a condition necessary for obtaining the imaging performance in the entire image region.

Actions / Effects According to Embodiment According to the embodiment described above, the two lenses of the fifth lens 5 and the sixth lens 6 are enlarged by the conditional expression (1) and the conditional expression (2). In addition, it is possible to provide an imaging lens having good imaging performance even at the periphery of the image at a low cost and at a wide angle.

  In addition, according to the embodiment described above, by providing the diaphragm 7 between the second lens 2 and the third lens 3, it is possible to provide an imaging lens that achieves both good distortion and miniaturization. it can.

  Further, according to the embodiment described above, it is possible to provide an imaging lens that can further suppress coma aberration and spherical aberration more favorably by conditional expression (3) and conditional expression (4).

  In addition, according to the embodiment described above, for example, all lenses are made of optical glass that is chemically stable and does not contain substances that cause environmental load such as lead and arsenic, while considering the global environment. An imaging lens can be provided in a small size and at low cost. Here, consideration for the global environment means that materials can be recycled and there is no water pollution due to waste liquid during processing.

  Furthermore, according to the embodiment described above, the imaging lens that has conventionally been constituted by six lenses is constituted by five lenses, thereby saving resources of the lens material and generating carbon dioxide during lens processing. Carbon and the like can be reduced.

  In the embodiment described above, the imaging lens 10 has been described using a circular lens, but the shape of each lens constituting the imaging lens according to the present invention is not limited to a circle. That is, the imaging lens according to the present invention may be a substantially oval lens in which the upper and lower sides of the lens are cut in order to reduce the size of the lens, particularly the height direction of the image reading apparatus. it can.

  Next, specific examples (numerical examples) 1 to 6 of the imaging lens according to the present invention will be described.

  In addition, the meaning of the symbol in each Example is as follows.

f: Total focal length of e-line total system FNo: F number m: Reduction ratio ω: Half angle of view (degrees)
Y: Object height r: Radius of curvature of lens surface d: Surface spacing nd: Refractive index νd of lens material νd: Abbe number of lens material C1: First surface C2 of contact glass 8: Second surface of contact glass 8 C3: First surface of the cover glass 9 of the image sensor C4: Second surface of the cover glass 9 of the image sensor

f: 28.4, FNo = 5.4, m = 0.1654, Y = 110, ω = 28.8 °

  FIG. 2 is an optical arrangement diagram of Example 1 of the imaging lens. FIG. 3 is an aberration diagram of Example 1 of the imaging lens.

  In the astigmatism in the aberration diagrams after FIG. 3, the broken line represents the meridional section, and the solid line represents the astigmatism of the sagittal section.

  FIG. 3 shows that various aberrations, particularly astigmatism and coma aberration, are well controlled by the imaging lens having the optical arrangement of Example 1 shown in FIG.

f: 28.2, FNo = 5.6, m = 0.1654, Y = 110, ω = 29.0 °

  FIG. 4 is an optical arrangement diagram of Example 2 of the imaging lens. FIG. 5 is an aberration diagram of Example 2 of the imaging lens.

  FIG. 5 shows that various aberrations, particularly astigmatism and coma aberration, are well controlled by the imaging lens having the optical arrangement of Example 2 shown in FIG.

f: 28.2, FNo = 5.5, m = 0.1654, Y = 110, ω = 29.0 °

  FIG. 6 is an optical layout diagram of Example 3 of the imaging lens. FIG. 7 is an aberration diagram of Example 3 of the imaging lens.

  FIG. 7 shows that various aberrations, particularly astigmatism and coma aberration, are well controlled by the imaging lens having the optical arrangement of Example 3 shown in FIG.

f: 28.2, FNo = 5.6, m = 0.1654, Y = 110, ω = 29.0 °

  FIG. 8 is an optical layout diagram of Example 4 of the imaging lens. FIG. 9 is an aberration diagram of Example 4 of the imaging lens.

  FIG. 9 shows that various aberrations, particularly astigmatism and coma aberration, are well controlled by the imaging lens having the optical arrangement of Example 4 shown in FIG.

f: 28.1, FNo = 5.5, m = 0.1654, Y = 110, ω = 29.0 °

  FIG. 10 is an optical arrangement diagram of Embodiment 5 of the imaging lens. FIG. 11 is an aberration diagram of Example 5 of the imaging lens.

  FIG. 11 shows that various aberrations, particularly astigmatism and coma aberration, are well controlled by the imaging lens having the optical arrangement of Example 5 shown in FIG.

f: 28.3, FNo = 5.8, m = 0.1654, Y = 110, ω = 28.9 °

  FIG. 12 is an optical layout diagram of Example 6 of the imaging lens. FIG. 13 is an aberration diagram of Example 6 of the imaging lens.

  FIG. 13 shows that various aberrations, particularly astigmatism and coma aberration, are well controlled by the imaging lens having the optical arrangement of Example 6 shown in FIG.

Summary of Examples For each example described above, the calculation results of conditional expressions (1) to (4) are shown in the following table.

Embodiment of image reading apparatus (1)
Next, an embodiment of an image reading apparatus according to the present invention will be described.

  FIG. 14 is a sectional view in the sub-scanning direction showing an embodiment of an image reading apparatus according to the present invention. In FIG. 14, the image reading apparatus 200 includes a document placement glass 31, a first traveling body 33, a second traveling body 34, an imaging lens 35, and an image sensor 36.

  A document 32 that is a target for reading a document image by the image reading device 200 is placed on the upper surface of the document placement glass 31.

  In FIG. 14, the first traveling body 33 moves at a constant speed: V from the initial position indicated by the solid line to the position of the first traveling body 33 ′ indicated by the broken line.

  The first traveling body 33 includes a mirror 33c whose longitudinal direction is the direction penetrating the paper surface of FIG. 14 and whose mirror surface is inclined 45 degrees with respect to the document placement surface of the document placement glass 31.

  Moreover, the 1st traveling body 33 is provided with the fluorescent lamp 33a and the reflective mirror 33b which are long in the direction which penetrates the paper surface of FIG. 14 as an illumination means.

  The fluorescent lamp 33 a emits light when the first traveling body 33 moves from the left to the right in FIG. 14 as a light source of the illumination means, and illuminates the document 32 on the document placement glass 31. That is, the document 32 is illuminated and scanned while the first traveling body 33 moves to the position of the first traveling body 33 '.

  Here, as the light source, a tube lamp such as a halogen lamp, a xenon lamp, or a cold cathode tube can be used instead of the fluorescent lamp 33a. Further, as the light source, instead of the fluorescent lamp 33a, point light sources such as LEDs (Light Emitting Diodes) can be arranged in a line and used.

  In addition, when using a point light source as a light source, a point light source can also be converted and used for a linear light emission mode using a light guide.

  Furthermore, instead of the fluorescent lamp 33a, a surface light source such as an organic EL (Electro Luminescence) can be used as the light source.

  The second traveling body 34 includes a pair of mirrors 34a and 34b which are long in the direction penetrating the paper surface of FIG. 14 and whose mirror surfaces are inclined orthogonally to each other. The second traveling body 34 moves at a constant speed: V / 2 to the position of the second traveling body 34 ′ indicated by a broken line in synchronization with the movement of the first traveling body 33.

  When the document 32 is illuminated and scanned, the reflected light from the illuminated portion (illuminated portion) of the document 32 is reflected by the mirror 33 c of the first traveling body 33. Then, the reflected light from the illuminated portion of the document 32 is sequentially reflected by the mirrors 34 a and 34 b of the second traveling body 34 and enters the imaging lens 35 as an imaging light beam. Here, the imaging lens 35 is the imaging lens according to the present invention described above.

  At this time, since the speed ratio between the first traveling body 33 and the second traveling body 34 is 2: 1, the optical path length from the illuminated portion of the document 32 to the imaging lens 35 is kept constant.

  The imaging light beam incident on the imaging lens 35 forms a reduced image of the document 32 on the light receiving surface of the image sensor 36 by the imaging action of the imaging lens 35. Here, the image sensor 36 is a CCD line sensor, and minute photoelectric conversion units (not shown) are closely arranged in a direction penetrating the paper surface of FIG. The image sensor 36 outputs a document image as an electrical signal in units of pixels as the document 32 is illuminated and scanned.

  This electrical signal undergoes signal processing such as A / D (Analog / Digital) conversion to become an image signal, and is stored in storage means such as a memory (not shown) as necessary.

  Note that the image sensor 36 can read color information using the image sensor 36a, the image sensor 36b, and the image sensor 36c corresponding to the three colors by separating the formed image into three colors (red, green, and blue). . The image sensor 36 can read a color original by synthesizing the electrical signals converted by the photoelectric conversion units.

  According to the embodiment described above, the image reading apparatus 200 uses the image forming lens according to the present invention as the image forming lens 35, so that the image reading apparatus 200 can be reduced in size and cost at the periphery of the image at the time of widening the angle. Even if it exists, it can have favorable imaging performance.

● Embodiment of image reader (2) ●
Next, another embodiment of the image reading apparatus according to the present invention will be described focusing on differences from the above-described embodiment.

  FIG. 15 is a sectional view in the sub-scanning direction showing another embodiment of the image reading apparatus according to the present invention.

  The image reading apparatus 200 </ b> A includes a document placement glass 41, an image reading unit 43, an imaging lens 44, and an image sensor 45.

  A document 42 that is a target for reading a document image by the image reading apparatus 200 </ b> A is placed on the upper surface of the document placement glass 41.

  The image reading unit 43 includes a mirror 43e, a mirror 43f, and a mirror 43g that are arranged with the direction penetrating the paper surface of FIG. 15 as the longitudinal direction and the mirror surface inclined with respect to the document placement surface of the document placement glass 41. .

  In FIG. 15, the image reading unit 43 moves at a constant speed: V from the position indicated by the solid line to the position of the image reading unit 43 ′ indicated by the broken line.

  Further, the image reading unit 43 includes a fluorescent lamp 43a, a fluorescent lamp 43c, a reflecting mirror 43b, and a reflecting mirror 43d that are long in the direction penetrating the paper surface of FIG.

  The fluorescent lamp 43a and the fluorescent lamp 43c emit light when the image reading unit 43 is displaced from the left to the right in FIG. 15 as the light source of the illuminating means, and illuminates the original 42 on the original placement glass 41. That is, the document 42 is illuminated and scanned while the image reading unit 43 moves to the position of the image reading unit 43 '.

  Instead of the fluorescent lamp 43a and the fluorescent lamp 43c, various light sources may be used as in the above-described embodiment.

  When the original 42 is illuminated and scanned, the reflected light from the illuminated portion of the original 42 is sequentially reflected by the mirror 43e, the mirror 43f, and the mirror 43g and enters the imaging lens 44 as an imaging light beam. Here, the imaging lens 44 is the imaging lens according to the present invention described above. At this time, the mirror 43e, the mirror 43f, and the mirror 43g are integrally held by the image reading unit 43. Therefore, during the illumination scanning of the document 42, the optical path length from the illuminated portion of the document 42 to the imaging lens 44 is constant.

  The imaging light beam incident on the imaging lens 44 forms a reduced image of the document 42 on the light receiving surface of the image sensor 45 by the imaging action of the imaging lens 44. In the image reading apparatus 200A, the document information can be read by converting the document image into an electrical signal by the image pickup element 45 as in the image reading apparatus described above.

  According to the embodiment described above, the image reading apparatus 200A uses the imaging lens according to the present invention as the imaging lens 44, so that the image reading apparatus 200A can be reduced in size and cost and around the image at the time of widening the angle. Even if it exists, it can have favorable imaging performance.

● Embodiment of image forming apparatus ●
An embodiment of an image forming apparatus according to the present invention will be described.

  FIG. 16 is a sectional view in the sub-scanning direction showing the embodiment of the image forming apparatus according to the present invention.

  The image forming apparatus 300 includes an image reading device 200 provided in the upper part of the apparatus, an image forming unit 100 provided in the lower part, and an image processing unit 120.

  An image signal output from the image sensor 36 that is a three-line CCD line sensor of the image reading apparatus 200 is sent to the image processing unit 120.

  The image processing unit 120 converts the image signal into a writing signal (a signal for writing each color of yellow, magenta, cyan, and black).

  The image forming unit 100 includes a photoconductive photoconductor 110 formed in a cylindrical shape as a latent image carrier.

  The image forming unit 100 includes a charging roller 111 as a charging unit, a revolver type developing device 113, a transfer belt 114, and a cleaning device 115 around the photoreceptor 110.

  Note that a corona charger can be used as the charging means instead of the charging roller 111.

  The image forming unit 100 includes a fixing device 116, a cassette 118, a registration roller 119, a paper feed roller 122, a tray 121, and a transfer sheet S as a recording medium.

  The optical scanning device 117 receives a writing signal from the image processing unit 120 and writes on the photoconductor 110 by optical scanning. Here, the optical scanning device 117 performs optical scanning of the photoconductor 110 between the charging roller 111 and the developing device 113.

  In the image forming unit 100, when performing image formation, the photoconductive photoconductor 110 rotates at a constant speed in the clockwise direction. The surface of the photoconductor 110 is uniformly charged by the charging roller 111. At this time, an electrostatic latent image is formed on the surface of the photoconductor 110 by exposure by optical writing of the laser beam of the optical scanning device 117. The formed electrostatic latent image is a so-called negative latent image, and the image portion is exposed.

  The image writing is performed in the order of yellow image, magenta image, cyan image, and black image in accordance with the rotation of the photoconductor 110. The formed electrostatic latent image is developed by each developing unit Y (developing with yellow toner), M (developing with magenta toner), C (developing with cyan toner), K of the revolver type developing device 113. (Developing with black toner) is sequentially reversed and developed to be visualized as a so-called positive image.

  Each color toner image obtained as a positive image is sequentially transferred onto the transfer belt 114 by a transfer voltage application roller 114A. Each color toner image is superimposed on the transfer belt 114 to form a color image.

  The cassette 118 storing the transfer paper S is detachable from the image forming apparatus 300. In the state where the cassette 118 is mounted on the image forming apparatus 300, the uppermost sheet of the transfer sheet S is fed by the sheet feeding roller 122. The leading edge of the fed transfer paper S is held by a registration roller 119.

  The registration roller 119 feeds the transfer sheet S to a transfer unit constituted by the transfer belt 114, the transfer roller 114B, and the like at the timing when the color image by the toner on the transfer belt 114 moves to the transfer position.

  The transfer sheet S sent to the transfer unit is superimposed on the color image of the transfer belt 114, and the color image is electrostatically transferred by the action of the transfer roller 114B. The transfer roller 114B presses the transfer sheet S of the transfer belt 114 against the color image at the time of transfer.

  The transfer sheet S on which the color image is transferred is sent to the fixing device 116. The transfer paper S is fixed with a color image by the fixing device 116. The transfer sheet S passes through a conveyance path by a guide unit (not shown) and is discharged onto the tray 121 by a discharge roller (not shown).

  Each time each color toner image is transferred to the transfer paper S, the surface of the photoconductor 110 is cleaned by the cleaning device 115 to remove residual toner, paper dust, and the like.

  In the above description, the image forming apparatus 300 has been described as forming a color image. However, the image forming apparatus 300 may be configured to form a monochrome image.

  According to the embodiment described above, since the image reading apparatus 200 can be downsized, the space between the image reading apparatus 200 and the image forming unit 100 is widened so that the user can easily see the output paper. can do. That is, according to the embodiment described above, the image forming apparatus 300 can provide good workability to the worker.

1: 1st lens 2: 2nd lens 3: 3rd lens 4: 4th lens 5: 5th lens 6: 6th lens 7: Aperture 8: Contact glass 9: Cover glass 10: Imaging lens 200: Image reading Apparatus 300: Image forming apparatus

Japanese Patent No. 3740370 JP 2002-31753 A JP 2011-81371 A

Claims (6)

In order from the object side to the image side, a first lens which is a positive meniscus lens having a convex surface facing the object side, a second lens whose both lens surfaces are concave surfaces, a third lens whose both lens surfaces are convex surfaces, An imaging lens including a fourth lens having a concave lens surface, a positive fifth lens having a convex surface on the image side, and a sixth lens being a negative meniscus lens having a convex surface facing the image side. ,
The distance between the fifth lens and the sixth lens is d11, the combined focal length from the first lens to the fifth lens is ff, the focal length of the sixth lens is f6, and the focal length of the entire system is f. When
0.15 <d11 / f <0.28
−0.73 <ff / f6 <−0.48
An imaging lens characterized by satisfying Having a diaphragm between the second lens and the third lens;
The imaging lens according to claim 1. When the radius of curvature of the first surface of the second lens is r4, the radius of curvature of the first surface of the sixth lens is r12, and the radius of curvature of the second surface of the sixth lens is r13,
−5.2 <r4 / f <−1.6
−3.9 <(r12 + r13) / (r12−r13) <− 1.7
Meet,
The imaging lens according to claim 1 or 2. The lenses used for the first lens to the sixth lens are all glass lenses and do not contain arsenic and lead.
The imaging lens according to claim 1. An illumination system for illuminating the document placed on the document placement surface;
An image reading device that reads document information illuminated by the illumination system using an imaging lens that forms an image on a line-shaped imaging device,
The imaging lens is an imaging lens according to any one of claims 1 to 4.
An image reading apparatus. An image forming apparatus that forms an image by exposing the surface of an image carrier according to document information read by an image reading apparatus,
The image reading apparatus is the image reading apparatus according to claim 5.
An image forming apparatus.

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