JP2014032418A - Imaging lens, image reading device using the same, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging lens holding a plurality of lens with one lens barrel, configured to reduce displacement of the lenses and to obtain excellent imaging performance by reliably pressing the posture of the held lenses.SOLUTION: An imaging lens 8 comprises a plurality of lenses having different outer diameters, and a lens barrel holding the lenses. The lens barrel has different inner diameters corresponding to the lenses having different outer diameters, and a plurality of projection parts formed on a periphery of the inner diameter of the lens barrel for each of the different inner diameters. The lenses are inserted from one side of the lens barrel. The lenses are brought into pressure contact with the projection parts to hold the lenses.

Description

  The present invention relates to an imaging lens, an image reading apparatus and an image forming apparatus using the imaging lens, and more specifically, image information of an original is reduced and imaged on image sensors arranged in a line, and an image is obtained by the image sensor. The present invention relates to an imaging lens for use in a digital copying machine, a facsimile, or the like that reads information.

  As the lens barrel that holds the imaging lens, a resin material-based lens barrel is mainly used. Among them, there is one that inserts a plurality of lenses into one lens barrel (for example, Patent Document 1). When holding a plurality of lenses in a lens barrel made of resin material, as a characteristic of the resin material, if the thickness of the resin is not constant, a dimensional error due to a shape change such as warping or bending will generally occur. It is necessary to keep the thickness of the resin material constant. Therefore, when the lens barrel holds a plurality of imaging lenses, it is necessary to set the outer diameter of the lens barrel according to the size of the diameter of each imaging lens. An outer wall portion having a constant diameter is provided around the lens barrel.

  The lens barrel in the invention described in Patent Document 1 is intended to fix a plurality of lenses against the inner peripheral surface thereof. However, even if the thickness of the resin material of the plurality of lenses is kept uniform, it is difficult to make the roundness of the inner diameter of the lens barrel equal to the roundness of the outer periphery of the plurality of lenses over the entire circumference. It is. For this reason, even if an attempt is made to hold a plurality of lenses with a single lens barrel, it has been difficult to stably maintain the position between the plurality of lenses. In addition, the imaging lens cannot obtain good imaging performance due to the positional shift of the plurality of lenses.

  In the invention described in Patent Document 1, an outer cylinder having a uniform diameter is provided on the outer periphery of the lens barrel, but the portion connecting the lens barrel and the outer cylinder is only in one cross section in the optical axis direction of the lens. Since it does not exist, it is difficult to match the optical axis of the lens with the central axis of the outer cylinder. Depending on the arrangement of the imaging lens, the center axis of the lens barrel may deviate from the central axis of the outer cylinder due to the weight of the imaging lens, or it may be bent due to a shape change when the temperature environment changes. was there.

  Further, as a method for fixing the lens after assembling the lens to the lens barrel, a method of pressing the press ring by fitting it into the lens barrel with a screw is used. However, in order to form a screw in a resin lens barrel, a complicated mold structure is required, or a screw must be manufactured by secondary processing after molding. Therefore, the above method is difficult to ensure accuracy and increases costs. As another method for fixing a plurality of lenses to a lens barrel, there is a method using thermal caulking. However, if thermal caulking is performed, it becomes impossible to reassemble the plural lenses. After checking the performance, the method using heat caulking cannot be adopted for the lens barrel that needs to adjust the air space of the lens.

  The present invention has been made to solve the above-described problems of the prior art. In an imaging lens in which a plurality of lenses are held by a single lens barrel, the positional deviation of each lens is reduced, and the present invention is excellent. An object of the present invention is to provide an imaging lens capable of obtaining imaging performance.

  The present invention is an imaging lens that includes a plurality of lenses having different outer diameters and a lens barrel that holds the plurality of lenses, and the lens barrel corresponds to a plurality of lenses having different outer diameters. And having a plurality of protrusions for each of the different inner diameter portions, the plurality of lenses being inserted from one side of the lens barrel, and the plurality of lenses and the plurality of protrusions being in pressure contact with each other, Is held by the lens barrel, the lens barrel has an outer cylinder on the outer side, the lens barrel and the outer cylinder are connected by a plurality of ribs, and the plurality of ribs have a diameter of the lens barrel. The most important feature is that it is arranged at the same position as the protrusion in the direction.

  According to the present invention, in an imaging lens in which a plurality of lenses are held by a single lens barrel, the positional deviation of each lens can be reduced and good imaging performance can be obtained.

It is a longitudinal cross-sectional view which shows the Example of the imaging lens which concerns on this invention. The 1st resin-made lens barrel in the said Example is shown, (a) is a longitudinal cross-sectional view, (b) is a front view. It is a longitudinal cross-sectional view which shows the state rotated 22.5 degrees of said 1st resin-made lens barrels. It is a front view which expands and shows a part of said 1st resin-made lens-barrel. It is a front view which shows the other aspect of said 1st resin-made lens-barrel. The 2nd resin-made lens-barrel in the said Example is shown, (a) is a front view, (b) is side sectional drawing, (c) is a right view, (d) is bottom sectional drawing. It is a front view which expands and shows the principal part of the modification of the 1st resin barrel which can be used for the lens barrel which concerns on this invention. It is a front view which shows the other aspect of said 1st resin-made lens-barrel. It is an optical arrangement | positioning figure which shows the lens system in the Example of the said lens barrel. FIG. 4 is a spherical aberration diagram, astigmatism diagram, distortion diagram, and coma aberration diagram of the lens system. It is sectional drawing which shows the Example of the image reading apparatus which concerns on this invention. 1 is a cross-sectional view showing an embodiment of an image forming apparatus according to the present invention.

In FIG. 1, the imaging lens 8 includes a plurality of lenses having different outer diameters and a resin barrel that holds the plurality of lenses. The lens barrel 8 is coupled to the first resin barrel 6 and the right end of the first resin barrel 6 in FIG. 1, and a plurality of lenses are placed in the first resin barrel 6. A second resin barrel 7 that is pressed and held is provided. The first resin barrel 6 includes an inner cylinder 13 and an outer cylinder 11 which are integrally formed. The inner cylinder 13 has different inner diameters corresponding to a plurality of lenses having different outer diameters. The first resin lens barrel 6 includes a first lens 1 that is a convex meniscus lens, a second lens 2 that is a biconcave lens, an aperture 3, and a third lens that is a biconvex lens in order from the left in FIG. 4. A plurality of lenses including the fourth lens 5 which is a concave meniscus lens is held. That is, in order from the left side of FIG. 1, the first lens 1 having a positive refractive power, the second lens 2 having a negative refractive power, the diaphragm 3, the third lens 4 having a positive refractive power, and the negative refractive power. The fourth lens 5 has a four-group four-lens configuration.
The first resin lens barrel 6, in particular its inner cylinder 13, forms the main body of the lens barrel. The second resin barrel 7 functions as a pressing member for fixing a plurality of lenses in the inner cylinder 13.

  The outer diameters of the first lens 1, the second lens 2, the third lens 4, and the fourth lens 5 are increased in this order, and the inner diameter of the inner peripheral portion that holds the lenses of the inner cylinder 13 is also increased in order. Yes. Further, the thickness of the inner cylinder 13 is substantially uniform over the entire length, and therefore the outer diameter of the inner cylinder 13 is also increased in order. Reference numeral 19 denotes a lens receiver integrally formed at the end portion on the minimum diameter side of the inner cylinder 13 in the inner diameter direction. As shown in FIGS. 2 to 5, a plurality of protrusions 14, 15, 16, and 17 for holding the outer periphery of each lens are integrated with the inner periphery of the inner cylinder 13 where the lenses are held. Is formed. The first lens 1, the second lens 2, the third lens 4, and the fourth lens 5 are inserted in this order from the opening end of the inner cylinder 13 on the maximum diameter side. The outer peripheral surface of each lens is held in pressure contact with the protrusion on the inner diameter portion of the corresponding inner cylinder 13. More specifically, the first lens 1 is in pressure contact with the protrusion 14, the second lens 2 is in pressure contact with the protrusion 15, the third lens 4 is in pressure contact with the protrusion 16, and the fourth lens 5 is in pressure contact with the protrusion 17. A second resin lens barrel 7 to be described later in detail is fitted to the opening end on the maximum diameter side of the inner cylinder 13. The first lens 1 is in contact with the lens receiver 19 of the first resin lens barrel 6, and hereinafter, the first lens 1, the second lens 2, the diaphragm 3, the third lens 4, and the fourth lens 5 are close to each other near the outer periphery. Abutting in a line contact state, the holding portion 22 of the second resin barrel 7 abuts in the vicinity of the outer periphery of the fourth lens 5, thereby positioning each lens and the diaphragm 3 in the optical axis direction.

  The structure of the first resin barrel 6 will be further described with reference to FIGS. FIG. 2 is a front view and a cross-sectional view of the first resin barrel 6, and FIG. 3 is a rib portion that rotates the first resin barrel 6 to integrally connect the inner cylinder 13 and the outer cylinder 11. It is sectional drawing cut | disconnected. FIG. 4 is an enlarged front view showing a portion including a plurality of protrusions of the first resin lens barrel 6.

  2 to 4, the first resin lens barrel 6 has a plurality of protrusions on the periphery of the inner cylinder 13 for each of different inner diameter portions. The first resin barrel 6 includes an outer cylinder 11 having a substantially uniform outer diameter, the inner cylinder 13, and a plurality of ribs 12 that connect the outer cylinder 11 and the inner cylinder 13. As described above, the first protrusion 14, the second protrusion 15, the third protrusion 16, and the fourth protrusion 17 are formed on the inner peripheral surface of the inner cylinder 13. The protrusions 14 to 17 are arranged at substantially equal intervals in the circumferential direction along the inner peripheral surface of each inner diameter part, and are arranged at substantially the same position along the lens optical axis in each inner diameter part. The first resin barrel 6 has a coupling portion 18 that engages with the notch 21 of the second resin barrel 7 and couples the second resin barrel 7 to the first resin barrel 6. Have.

  The ribs 12 are formed at substantially equal intervals in the circumferential direction as shown in FIG. 2B and extended over the entire length of the outer cylinder 11 as shown in FIG. The misalignment of the central axis of the outer cylinder 11 with respect to the axis is suppressed. Further, the first to fourth projecting portions 14 to 17 are formed at three positions at intervals of about 120 ° along the inner peripheral surface of the inner cylinder 13, respectively, and overlap with the formation position of the rib 12 in the radial direction. Is formed. By providing the protrusions 14 to 17 at positions that are parallel to the lens optical axis and overlap with the positions where the ribs 12 are provided in the radial direction, the holding force of the plurality of lenses can be increased. By configuring the three projections 14 to 17 in this way, the plurality of lenses 1, 2, 4, and 5 are held by the projections at the respective locations, and the lens is disposed at other portions. Will not win. Therefore, the positional deviation of the plurality of lenses can be reduced by obtaining the roundness of the three protrusions 14 to 17.

  Furthermore, the imaging performance can be kept good by aligning the centers of the circles connecting the tips of the projections 14 to 17 corresponding to the respective lenses with the optical axis of the imaging lens corresponding to each lens. It becomes possible. The protrusions 14 to 17 have an arc surface that is concentric with the inner peripheral surface, but the same effect can be obtained even if the shape is not an arc shape but a flat surface.

  The width in the inner circumferential direction of each of the protrusions 14 to 17 is desirably formed according to the outer diameter of the plurality of lenses. Thereby, it can hold | maintain in the state which applied the substantially same pressure with respect to any lens. By reducing the width of each of the projections 14 to 17, the gaps generated between the lens barrel 8 and the plurality of lenses, which are caused by the difference in thermal expansion coefficient between the resin material and the glass lens when the temperature fluctuates, are reduced. Can do. Further, the positional deviation of the plurality of lenses caused by the gap can be reduced. However, if the width of each of the protrusions 14 to 17 is too wide, it becomes difficult to accurately obtain the roundness of the inner diameter. Therefore, the width of the protrusions 14 to 17 is 10 ° of the circumference. It is preferable that the protrusions 14 to 17 are formed in three places.

  In the present embodiment, three projecting portions 14 to 17 are formed for each different inner diameter portion, but the above three locations are the minimum number constituting a perfect circle and may be more than that. However, if it is too large, it will be difficult to produce a perfect circle, so at most about six locations are desirable.

  Further, the distance from the inner peripheral surface of the inner cylinder 11 constituting the lens barrel 8 to the apexes of the projections 14 to 17, that is, the heights of the projections 14 to 17 are the same for all lenses. By aligning, the holding force of the lens can be made uniform. As a result, even if the temperature fluctuates, it is possible to obtain an imaging lens in which the holding force is kept uniform with respect to any lens and the influence of environmental fluctuation is small.

  An imaging lens that is less susceptible to temperature fluctuations and vibrations can be obtained by making the outer diameter of the lens larger by about 10 to 20 μm than the diameter of the circle formed by each of the three protrusions. In the above embodiment, the positions of the protrusions 14 to 17 are adjusted so as to overlap with the positions of the ribs 12 formed along the optical axis of the lens in the radial direction. However, as in the example shown in FIG. The protrusions 14 to 17 may be provided at positions shifted from the positions of the ribs 12, that is, positions that do not overlap the ribs 12. By providing the projections 14 to 17 at positions where there are no ribs 12 in the radial direction, a gap is formed between the outer cylinder 11 of the first resin barrel 6 and the inner cylinder 13. Thereby, the fluctuation | variation of the retention strength of the lens which arises by expansion / contraction of the lens-barrel 8 which consists of resin materials can be reduced.

  As described above, the ribs 12 are formed at substantially equal intervals in the circumferential direction and over the entire length of the outer cylinder 11, and it is possible to suppress misalignment of the axis of the outer cylinder 11 with respect to the axis of the inner cylinder 13. . As shown in FIGS. 1 and 2, etc., the inner cylinder 13 and the outer cylinder are located at the central portion in the optical axis direction of the third lens 4 and at the substantially central portion in the optical axis direction of the lens barrel 8. It has the connection part 25 which connects 11 over the perimeter. By providing the connecting portion 25, it is possible to suppress deformation of the lens barrel 8 in the entire circumferential direction. Further, the lengths of the ribs 12 in the optical axis direction can be distributed approximately symmetrically in the vicinity of the center of the lens barrel 8, and the deformation of the front side and the rear side of the imaging lens 8 can be suppressed to be evenly small. .

  In the embodiment shown in FIGS. 2 to 4, the number of the ribs 12 is three, but the three places are the minimum number constituting a perfect circle and may be more than that. If the number is too large, it becomes difficult to produce a perfect circle. Therefore, at most about six places are desirable as in the modification shown in FIG.

  FIG. 6 shows a second resin barrel 7 which is a resin pressing member. In FIG. 6, the second resin barrel 7 has a holding portion 22 for holding down the fourth lens 5 and a notch 21 coupled to the coupling portion 18 of the first resin barrel 6. Yes. The holding part 22 protrudes in an inward flange shape from the inner peripheral surface near the outer end (right end in FIG. 1) of the second resin barrel 7. The notches 21 are formed in a window hole shape that is long in the circumferential direction through the circumferential wall of the first resin barrel 6 at three locations at equal intervals in the circumferential direction. However, the edge of the notch 21 on the holding portion 22 side is parallel to the holding portion 22, while the opposite edge is inclined with respect to the circumferential direction. One end in the circumferential direction of each notch 21 is a groove in the optical axis direction formed on the inner peripheral surface of the second resin barrel 7 to guide the coupling portion 18 of the first resin barrel 6. 26. In addition, each notch 21 is formed with the inclined edge so that the groove 26 side is the widest and becomes narrower in the circumferential direction.

  In the second resin barrel 7, the coupling portions 18 of the first resin barrel 6 are aligned with the grooves 26 and pushed in the optical axis direction. The second resin lens barrel 7 is rotated in the circumferential direction with respect to the first resin lens barrel 6 in a state where the coupling portions 18 reach the notches 21. Each connecting portion 18 moves while being in sliding contact with the inclined edge of each notch 21, whereby a force for attracting the second resin barrel 7 toward the first resin barrel 6 acts. In this way, the holding portion 22 of the second resin barrel 7 presses the fourth lens 5 toward the first lens 1, and the lenses 1, 2, 4, 5 and the diaphragm 3 are moved. It can be held in the inner cylinder 13.

  As shown in FIG. 2, FIG. 7, etc., the connecting portions 18 of the first resin lens barrel 6 are arranged at three locations at intervals of about 120 ° on the outer periphery of one end of the inner tube, and in the radial direction with the ribs 12 respectively. It is formed at the overlapping position. The rib 12 extends along the optical axis of the lens. By providing the coupling portion 18 at a position where the rib 12 is provided, the rigidity of the coupling portion is increased and the holding force of the lens can be increased.

  In the illustrated embodiment, the tip of the coupling portion 18 is a flat surface, but the same effect can be obtained even with an arc surface that is concentric with the inner peripheral surface on which the projections 14 to 17 are formed. I can expect.

  When the second resin barrel 7 is rotated to hold down the plurality of lenses, a force that twists the coupling portion 18 of the first resin barrel 6 is applied to the periphery of the first resin barrel 6. At this time, if the fourth lens 5 and the first resin barrel 6 are in contact with each other, the force is transmitted to the fourth lens 5 and the posture of the lens changes. Therefore, as shown by the dotted line in FIG. 1, the inner diameter of the inner cylinder 13 in the vicinity of the protrusion 17 is increased so that a gap is provided between the inner peripheral surface of the inner cylinder 13 and the fourth lens 5. To do. By doing so, even if the second resin barrel 7 is tightened, only the first resin barrel 6 is deformed and can be held without changing the posture of the plurality of lenses.

  In the embodiment described above, the coupling portion 18 is provided at a position overlapping with the projections 14 to 17 in the radial direction. However, as illustrated in FIG. 8, the coupling portion 18 is provided on the first resin barrel 6. The protrusions 14 to 17 may be provided at positions shifted in the radial direction. By doing so, the influence of the deformation of the first resin barrel 6 due to the rotation of the second resin barrel 7 does not reach each of the plurality of lenses.

The imaging lens can be used in an image reading apparatus. Examples of imaging lenses designed for use in an image reader are shown in Table 1. The configuration of the lens system in this embodiment is shown in FIG.
The meanings of symbols used in Table 1 are as follows.
f: Focal length of the entire image reading lens system (e line: 546.07 nm)
FNo: F number m: Magnification ω: Half angle of view (degrees)
Y: Object height j: Surface number _rj : Radius of curvature of _jth lens surface _dj : Surface distance of _jth lens surface ndj: Refractive index of lens (d line: 587.56 nm)
νd _j : Abbe number of the lens [(nd-1) / (nF-nC)]
ne _i : Refractive index of lens (e-line)

表１の符号は図９に示すとおりである。 (Table 1)
Imaging Lens Example f = 47.652, F = 4.5, m = 0.16535, Y = 111, ω = 18.3 °

The symbols in Table 1 are as shown in FIG.

  FIG. 10 shows a spherical aberration diagram, an astigmatism diagram, a distortion diagram, and a coma aberration diagram of the imaging lens configured as the numerical values shown in Table 1. The aberration diagrams are as follows: a glass having a thickness of 3.2 mm (S-BSL7 (OHARA)) as a contact glass in front of the imaging lens and a glass having a thickness of 0.7 mm as a cover glass for the line sensor behind the imaging lens. S-BSL7 (OHARA)) was inserted and calculated. In FIG. 10, the line E is an e-line, the line G is a g-line (435.84 nm), the line C is a c-line (656.27 nm), and the line F is an F-line (486.13 nm) aberration curve. The broken line in the spherical aberration diagram is the sine condition, the solid line in the astigmatism diagram is the sagittal ray, and the broken line is the meridional ray.

FIG. 11 shows an embodiment of an image reading apparatus according to the present invention.
In FIG. 11, a document 112 having an image to be read is placed flat on a contact glass 111 as a “document table”, and an illuminating means using an Xe lamp, an LED light source or the like is disposed below the contact glass 111. , “Illuminate the slit-like portion long in the direction orthogonal to the drawing” The reflected light from the illuminated portion of the document 2 (reflected light from the image) is reflected by the first mirror 113B provided on the first traveling body 113 and then the second mirror provided on the second traveling body 114. 114A and the third mirror 114B are sequentially reflected, pass through the image reading lens 115, and form a reduced image of the original image on the imaging surface of the line sensor 116 as a photoelectric conversion element. The image reading lens 115 is an imaging lens for forming an object image, that is, an image of the original 112 on the imaging surface of the line sensor 116, and for reading the image of the original 112 by the line sensor 116. The imaging lens according to the present invention is used.

  The first to third mirrors 113B, 114A, and 114B constitute a “reflection optical system”. The first traveling body 113 and the second traveling body 114 each travel in the direction of the arrow (the right direction in the figure) by driving means (not shown). The traveling speed of the first traveling body 113 is “V”, and the traveling speed of the second traveling body 14 is “V / 2”. By this traveling, the first traveling body 113 and the second traveling body 14 are each displaced to the “position indicated by the broken line”. The illumination unit 113 </ b> A and the first mirror 113 </ b> B move integrally with the first traveling body 113 to “illuminate and scan” the entire document 112 on the contact glass 1. Since the moving speed ratio of 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 116 that is an “imaging unit” has “a photoelectric conversion element (116A, 116B, 116C) having red (R), green (G), and blue (B) filters as color separation means on one chip. 3 line CCD (3 line sensor) arranged in 3 rows. Along with illumination scanning of the original 112, the original image is converted into an image signal. In this way, the reading of the document 2 is executed, and the color image of the document 112 is separated and read into the three primary colors of red, green, and blue.
The image reading apparatus of the present embodiment is an apparatus for reading an image in full color, and “color separation means (red, green provided in the three-line CCD” provided in the imaging optical path of the image reading lens 15 is used. , Blue filter).

  As another form of the image reading apparatus, an illuminating unit that illuminates the original 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 original to the line sensor, The reading unit in which the image reading lens disposed on the image forming optical path is integrated with each other is moved relative to the original by the driving means so as to read and scan the original. You can also.

  In the “color separation”, separately from the above example, a color separation prism or filter is selectively inserted between the image reading lens and the line sensor (CCD), and R (red), G (green), B ( Blue) or a “method of illuminating a document by sequentially turning on R, G, and B light sources” can be used.

  Next, an embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. In FIG. 12, the image forming apparatus includes an image reading apparatus 200 positioned at the upper part of the apparatus and an “image forming unit” positioned at the lower part thereof. The part of the image reading apparatus 200 is the same as that described with reference to FIG. 11, and the same reference numerals as those in FIG.

  The image signal output from the three-line line sensor (imaging means) 16 of the image reading apparatus 200 is sent to the image processing unit 1200 and processed by the image processing unit 1200 to obtain a “writing signal (yellow, magenta, cyan, Signal for writing each color of black) ”.

  The image forming unit has a photoconductive photosensitive member 1100 formed in a cylindrical shape as a “latent image carrier”, and around it, a charging roller 1110 as a charging unit, a revolver type developing device 1130, a transfer belt. 1140 and a cleaning device 1150 are provided. As the charging means, a “corona charger” can be used instead of the charging roller 1110. An optical scanning device 1170 that receives a writing signal 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. ing.

  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 photoconductor 1100, and the formed electrostatic latent image is stored in each developing unit Y ( Development with yellow toner), M (development with magenta toner), C (development with cyan toner), K (development with black toner) are sequentially reversed and visualized as a positive image. The respective color toner images are sequentially transferred onto the transfer belt 1140 by the transfer voltage application roller 114A, and the respective color toner images are superimposed on the transfer belt 1140 to form a color image.

  The cassette 1180 containing the transfer paper S is detachable from the main body of the image forming apparatus, and the uppermost sheet of the stored transfer paper S is fed by the paper feed roller 1220 when mounted as shown in the figure. The leading edge of the fed transfer paper S is caught by the registration roller pair 1190.

  The registration roller pair 1190 feeds the transfer sheet S to the transfer unit at the timing when the “color image by toner” on the transfer belt 1140 moves to the transfer position. 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.
In the image forming apparatus shown in FIG. 12, the latent image corresponding to each color is sequentially developed on one photoconductor 1110 by the revolver-type developing device 1130. The image forming apparatus may be a so-called tandem type in which a latent image is formed and developed for each color on each photoconductor.

  As described above, the image forming apparatus according to the present invention forms an image by the electrophotographic process, and the exposure apparatus that executes the exposure process in the electrophotographic process is an image according to the present invention as shown in FIG. The exposure is performed based on the image signal read by the reading device.

DESCRIPTION OF SYMBOLS 1 1st lens 2 2nd lens 3 Aperture 4 3rd lens 5 4th lens 6 1st resin barrel 7 2nd resin barrel (pressing member)
8 imaging lens 11 outer cylinder 12 rib 13 inner cylinder 14 first projection 15 second projection 16 third projection 17 fourth projection 18 coupling portion 21 notch 22 holding portion

JP-A-9-61689

Claims (19)

A plurality of lenses having different outer diameters;
A lens barrel for holding the plurality of lenses;
An imaging lens comprising:
The lens barrel has a different inner diameter corresponding to the plurality of lenses having different outer diameters and a plurality of protrusions for each different inner diameter part,
The plurality of lenses are inserted from one side of the lens barrel, the plurality of lenses and the plurality of protrusions are in pressure contact, and the plurality of lenses are held by the lens barrel,
The lens barrel has an outer cylinder on the outside, and the lens barrel and the outer cylinder are connected by the plurality of ribs,
The plurality of ribs are disposed at the same position as the protrusion in the radial direction of the lens barrel.
An imaging lens characterized by that.   The plurality of protrusions that the lens barrel has at different inner diameter portions have the same distance from the inner peripheral surface on which the protrusions are formed to the apex portions of the protrusions. The imaging lens according to claim 1.   The imaging lens according to claim 1, wherein the protrusions are arranged at equal intervals along an inner peripheral portion of each inner diameter portion.   4. The imaging lens according to claim 1, wherein the protrusion is disposed at the same position along the lens optical axis for each inner diameter portion. 5.   The imaging lens according to claim 1, wherein three or more protrusions are provided for each of the different inner diameter portions.   The imaging lens according to claim 1, wherein three or more protrusions provided for each different inner diameter portion are arranged along a circle concentric with each inner diameter portion.   The imaging lens according to claim 1, wherein the outer cylinder is concentric with the lens barrel.   The imaging lens according to claim 1, wherein the imaging lens has six or more ribs.   9. The imaging lens according to claim 1, wherein the ribs are arranged at equal intervals along the outer periphery of the lens barrel.   A holding member for fixing the plurality of lenses to the lens barrel; and the projections formed on the outer periphery of the lens barrel and the notches formed on the pressing member are fitted together to hold the plurality of lenses. The imaging lens according to claim 1, wherein the imaging lens is fixed.   11. The imaging lens according to claim 10, wherein the lens is held in tension in the optical axis direction by fitting the notch portion of the pressing member and the projection of the lens barrel.   12. The imaging lens according to claim 10, wherein a gap is formed between an inner diameter side of a portion of the lens barrel where the protrusion is formed and an outer periphery of the reading lens.   The imaging lens according to claim 1, wherein the lens barrel is made of resin.   The imaging lens according to claim 10, wherein the lens barrel and the pressing member are made of resin.   The plurality of lenses are, in order from the object side, a first lens having a positive refractive power, a second lens having a negative refractive power, a diaphragm, a third lens having a positive refractive power, and a first lens having a negative refractive power. The imaging lens according to claim 1, wherein the imaging lens has a four-group four-lens configuration including four lenses.   The imaging lens according to claim 15, wherein the lens barrel and the outer cylinder are integrally connected at a position of the third lens in the optical axis direction.   The imaging lens according to claim 15, wherein the plurality of lenses have a lens outer diameter that is the smallest from the object side and the fourth lens is the largest, and the lens is pressed by a pressing member from the fourth lens side.   An image reading apparatus for reading an object image by forming an object image on an imaging surface with an imaging lens, wherein the imaging lens is the imaging lens according to any one of claims 1 to 17. Image reading device. 19. An image forming apparatus for forming an image by an electrophotographic process, wherein an exposure apparatus that performs an exposure process in the electrophotographic process performs exposure based on an image signal read by the image reading apparatus according to claim 18. An image forming apparatus.

Images