JP5216109B2 - Lens array and exposure apparatus, image forming apparatus and reading apparatus having the same - Google Patents

Description

  The present invention relates to a lens array and an exposure apparatus, an image forming apparatus, and a reading apparatus having the lens array.

  Conventionally, an image forming apparatus such as an electrophotographic printer, a facsimile machine, and a copying machine using an LED head in which a plurality of LEDs (Light Emitting Diode) are arranged, and a reading document on a light receiving portion in which a plurality of light receiving elements are arranged A rod lens array in which a plurality of rod lenses are arranged in a reading device such as a scanner or a facsimile machine that forms the image is used (see, for example, Patent Document 1). The rod lens array is an optical system that forms an erecting equal-magnification image of an object in a line shape.

JP 2003-341134 A

  However, the conventional rod lens array is not suitable for high resolution.

  The present invention solves the above-mentioned conventional problems and sets numerical values such as the distance between optical axes of lenses in lenses arranged to form a plurality of rows so as to satisfy a predetermined relationship. Accordingly, an object of the present invention is to provide a lens array having a high resolution and an exposure apparatus, an image forming apparatus and a reading apparatus having the same.

Therefore, in the lens array of the present invention, comprises a lens set member to have a plurality of lenses which are arranged to form one row of a light shielding member having a plurality of aperture are arranged adjacent to each other When the distance between the optical axes of the lenses is P, and the maximum value of the distance from the optical axis to the outer periphery of each lens is RL,
P <2RL
The heights of the curved surfaces of the adjacent lenses in the optical axis direction coincide with each other on the boundary line between the adjacent lenses , and there are two lens assembly members, and each of the plurality of lenses each has Each optical axis is disposed so as to coincide with each other, the light shielding member is disposed between the two lens assembly members, and the diaphragm of the light shielding member has a pair of linear long sides parallel to each other Each of which has a shape in which both ends thereof are connected by an arc to form a single row and the long sides of the respective apertures in the row are arranged so as to face a direction perpendicular to the extending direction of the row, each of the optical axis of the plurality of lenses Ru are arranged to pass through the center of the stop each.

  According to the present invention, the lens array has lenses arranged to form a plurality of rows, and numerical values such as the distance between the optical axes of the lenses are set so that a predetermined relationship is satisfied. Yes. Thereby, the resolution can be increased.

1 is a schematic diagram of a printer according to a first embodiment of the present invention. It is a schematic sectional drawing of the LED head in the 1st Embodiment of this invention. It is a figure which shows the lens array in the 1st Embodiment of this invention. It is the 1st sectional view which cut the lens array in a 1st embodiment of the present invention by the plane which is horizontal to the arrangement direction of a micro lens, and contains an optical axis, and the horizontal direction of a drawing is a direction parallel to the arrangement of a micro lens FIG. It is the 2nd sectional view which cut the lens array in a 1st embodiment of the present invention by the plane which is horizontal to the arrangement direction of a micro lens, and contains an optical axis, and the horizontal direction of a drawing is a direction parallel to the arrangement of a micro lens FIG. The positional relationship between the LED elements of the LED array and the optical axis of the microlens on the object surface of the lens array in which the microlenses according to the first embodiment of the present invention are arranged so as to form two rows It is the figure shown above. The positional relationship between the LED elements of the LED array on the object surface of the lens array and the optical axis of the microlens arranged on the lens array in which the microlenses according to the first embodiment of the present invention are arranged to form three rows It is the figure shown above. It is a figure which shows the image used for the evaluation in the 1st Embodiment of this invention. It is a figure which shows the lens array in the 2nd Embodiment of this invention. The positional relationship between the LED elements of the LED array and the optical axis of the microlens on the object surface of the lens array in which the microlenses according to the second embodiment of the present invention are arranged to form one row It is the figure shown above. It is a figure which shows the structure of the reader in the 3rd Embodiment of this invention. It is a figure which shows the structure of the read head in the 3rd Embodiment of this invention. It is a figure which shows the detailed structure of the microlens in the 4th Embodiment of this invention.

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

  FIG. 1 is a schematic diagram of a printer according to a first embodiment of the present invention.

  In the figure, reference numeral 10 denotes a printer as an image forming apparatus, which is an electrophotographic color printer, for example, but may be a monochrome printer. The printer 10 may be a multi-function machine having functions of a scanner, a facsimile machine, a copier and the like. In the present embodiment, the printer 10 forms an image by an electrophotographic method, and an image is formed on a sheet 11 as a print medium based on the image data by a toner made of a resin containing a pigment as a color material. In the following description, it is assumed that this is a color printer.

  A paper feed cassette 60 for storing the paper 11 is mounted inside the printer 10, and further, a paper feed roller 61 for taking out the paper 11 from the paper feed cassette 60 and a paper 11 taken out from the paper feed cassette 60. Conveying rollers 62 and 63 are disposed.

  The printer 10 is a so-called tandem color electrophotographic printer, and includes an image forming unit that forms a toner image of each color, and a transfer unit that transfers the toner image formed by the image forming unit to a sheet 11. .

  The image forming unit includes four process units that are arranged in tandem along the conveyance path of the paper 11 and that respectively form yellow, magenta, cyan, and black images. Each process unit further includes a photosensitive drum 41 as an electrostatic latent image carrier, a developer 50 that develops the electrostatic latent image formed on the photosensitive drum 41 with toner, and forms a toner image. A toner cartridge 51 for supplying toner to the device 50, a charging roller 42 for supplying and charging the surface of the photosensitive drum 41, a cleaning blade 43 for removing toner remaining on the surface of the photosensitive drum 41, and charging An LED head 30 is provided as an exposure device that selectively irradiates light on the surface of the photosensitive drum 41 based on image data to form an electrostatic latent image. The toner image is an image obtained by visualizing an electrostatic latent image with toner. The cleaning blade 43 is disposed in contact with the photosensitive drum 41 in order to scrape off the toner after the toner image is transferred to the paper 11.

  The transfer unit includes a transfer belt 81 that conveys the paper 11 and a transfer roller 80 that transfers a toner image formed on the photosensitive drum 41 onto the paper 11. The transfer roller 80 is disposed so as to face the photosensitive drum 41 of each process unit with the transfer belt 81 interposed therebetween. The cleaning blade 82 is disposed in contact with the transfer belt 81 in order to scrape off toner adhering to the transfer belt 81.

  A fixing device 90 that fixes the toner image transferred onto the paper 11 with heat and pressure is disposed on the downstream side of the image forming unit with respect to the conveyance direction of the paper 11. Further, a transport roller 64 that transports the paper 11 that has passed through the fixing device 90 and a discharge roller 65 that discharges the paper 11 are disposed in a discharge portion 70 that stores the paper 11.

  A predetermined voltage is applied to the charging roller 42 and the transfer roller 80 by a power source (not shown). The transfer belt 81, the photosensitive drum 41, and each roller are rotationally driven by a motor (not shown) and a gear (not shown) that transmits driving. Further, a power source and a control device (not shown) are connected to the developing device 50, the LED head 30, the fixing device 90, and each motor (not shown).

  The printer 10 is connected to a network (not shown) or the like, communicates with an external device, receives print data from a higher-level device, and receives print data from the external interface. And a control device that performs control.

  Next, the configuration of the LED head 30 will be described.

  FIG. 2 is a schematic cross-sectional view of the LED head according to the first embodiment of the present invention.

  As shown in the drawing, a lens array 20 is disposed on the LED head 30. The lens array 20 is fixed to the LED head 30 by a holder 34. Reference numeral 31 denotes an LED element as a light emitting unit. Reference numeral 32 denotes a driver IC which controls light emission of the LED element 31. The LED element 31 and the driver IC 32 are disposed on the wiring board 34 and are connected by wires 33. Then, the light emitted from the LED element 31 passes through the lens array 20, whereby an image is formed on the surface of the photosensitive drum 41.

  In the present embodiment, the LED head 30 has a resolution of 600 [dpi], and 600 LED elements 31 are arranged per inch (1 inch is about 25.4 [mm]). That is, the LED elements 31 are arranged at intervals of 0.0423 [mm] to constitute an LED array.

  Next, the configuration of the lens array 20 will be described.

  FIG. 3 is a diagram showing a lens array in the first embodiment of the present invention. In the figure, (a) is a plan view of the lens array, (b) is a plan view of the light shielding member, (c) is a cross-sectional view of the lens array, and is a cross-sectional view taken along line AA in (a). It is a principal part enlarged view which shows the detail of a light-shielding member.

  As shown in the figure, the lens array 20 includes a lens plate 21 and a light shielding member 23 as lens assembly members. The lens plate 21 is a lens group including microlenses 22 as a plurality of lenses, and is made of a light transmissive material that transmits light emitted from the LED element 31. As shown in FIG. 3C, the two lens plates 21 are parallel to each other with the light shielding member 23 interposed therebetween, and the optical axes of the corresponding ones of the microlenses 22 included in each of the lens plates 21 are arranged. Are arranged so as to match. The optical axis of each microlens 22 extends in the direction perpendicular to the plane of the lens plate 21. Further, as shown in FIG. 3C, the thickness of the lens plate 21 is LT at the thickest portion of the microlens 22.

  In each lens plate 21, the microlenses 22 are arranged so as to form two rows, and the microlenses 22 in each row have a pitch PY, that is, between the adjacent microlenses 22. Arranged so that the center interval is PY, and the pitch of each column is PX, that is, the interval between the central axes of each column is PX. In FIG. 3A, each row of microlenses 22 extends in the vertical direction.

  Further, between adjacent rows, the microlenses 22 are arranged so that the pitches of the microlenses 22 are shifted from each other by a half pitch, and are included in two rows in the plane of the lens plate 21 as shown in FIG. The microlenses 22 are arranged in a zigzag or zigzag shape as a whole. Each microlens 22 is densely arranged so as to overlap the microlenses 22 on both sides in the adjacent row.

  The planar shape of each microlens 22 is circular except for a portion that overlaps the microlenses 22 on both sides in the adjacent row, and the radius of the circle is RL. That is, in each microlens 22, the maximum value of the distance from the optical axis to the outer peripheral portion is RL. Further, the distance between the center of each microlens 22 and the centers of the microlenses 22 on both sides in the adjacent row is PN. In other words, the distance between the optical axes of the microlenses 22 in adjacent rows and between the microlenses 22 adjacent to each other is PN. Since each microlens 22 overlaps with the microlenses 22 on both sides in the adjacent row, the relationship 2RL> PN is established.

  Further, the light shielding member 23 is an elongated strip-like plate member extending in the vertical direction in FIG. 3B, and two sheets having openings as a plurality of apertures opened on one side edge. A comb-shaped member 23a and an elongated partition plate 23b extending in the vertical direction in FIG. 3B disposed between the two comb-shaped members 23a. In this case, the two comb-shaped members 23a are arranged so that the side edges where a plurality of openings are open face each other, the partition plate 23b has a width of TB, and both side edges thereof are the comb-shaped. It arrange | positions so that it may contact | abut to the side edge which the member 23a mutually faces. As a result, the light shielding member 23 as a whole is a single plate member having a planar shape that is substantially the same rectangle as the lens plate 21 and having a thickness LS as shown in FIG. 3C. The comb-shaped member 23a and the partition plate 23b are made of a material that blocks the light emitted from the LED element 31.

  Each of the openings has a planar shape in which a part of the circle is cut by a straight line corresponding to the side edge of the comb-shaped member 23a, as shown in FIGS. 3B and 3D. The radius of the edge is RA. In addition, the openings of each comb-shaped member 23a are arranged so as to form one row extending in the vertical direction in FIG. 3B, and therefore the openings in the light shielding member 23 have a total of two rows. Arranged to form. The openings in each row are arranged so that the pitch is PY, that is, the center of the circle between adjacent openings is PY, and the pitch of each row is PX. That is, they are arranged so that the distance between the central axes of each column is PX. Each opening can pass through the light shielding member 23 in the thickness direction and allow light to pass in a direction perpendicular to the plane of the light shielding member 23.

  Further, between adjacent rows of openings, like the microlens 22, the openings are arranged so that the pitch of the openings is shifted by a half pitch from each other. As shown in FIG. In the plane, the openings included in the two rows are arranged in a zigzag or zigzag shape as a whole. Each opening corresponds to each microlens 22 when the lens plate 21 and the light shielding member 23 are arranged so as to overlap each other, as shown in FIG. That is, the optical axis of each microlens 22, that is, the axis extending in the thickness direction through the center of the circle in the planar shape of each microlens 22 passes through the center of the circle in the planar shape of each opening. Coincides with the axis extending to Accordingly, the distance between the center of each opening circle and the center of each opening circle in the adjacent row is PN.

  Strictly speaking, the planar shape of the opening is cut by a semicircular portion and a straight line corresponding to the side edge of the comb member 23a as shown in FIG. 3 (d). The width of the part is (PX-TB) / 2. That is, the distance from the center of the circle to the straight line corresponding to the side edge of the comb-shaped member 23a is (PX-TB) / 2.

  Next, the lens array 20 will be described in detail.

  FIG. 4 is a first cross-sectional view of the lens array according to the first embodiment of the present invention cut along a plane that is horizontal to the arrangement direction of the microlenses and includes the optical axis. It is a figure which shows a parallel direction.

  The first microlens 22-1 is arranged at a position where the distance from the object plane of the lens array 20 (the light emitting surface of the LED element 31) is LO. Further, the second microlens 22-2 is disposed so as to face each other so that the optical axis thereof coincides with the optical axis of the first microlens 22-1, and is separated by a distance of LS. The imaging surface of the lens array 20 (the surface of the photosensitive drum 41) is located at a distance LI from the second microlens 22-2 in the optical axis direction.

  The first microlens 22-1 has a thickness of LT1, a front focal length of FO, and an image of an object located at a distance LO1 in the optical axis direction on a surface separated by a distance LI1 in the optical axis direction. Form. The second microlens 22-2 has an image of an object having a rear focal length FI and a distance LO2 at a position separated by LI2 in the optical axis direction.

  The distance LO from the object plane of the lens array 20 to the first microlens 22-1 is set to be equal to the distance LO1, and the distance between the first microlens 22-1 and the second microlens 22-2. LS is set to LS = LI1 + LO2, and the distance LI from the second microlens 22-2 to the imaging plane of the lens array 20 is set equal to LI2.

  Note that the first microlens 22-1 and the second microlens 22-2 can have the same configuration. In this case, both the first microlens 22-1 and the second microlens 22-2 have the thickness LT1, the front focal length is FO, and the object is located at the distance LO1 in the optical axis direction. Is formed on a surface separated by a distance LI1 in the optical axis direction, the distance LO from the object plane of the lens array 20 to the first microlens 22-1 is set equal to the distance LO1, and the first microlens is formed. The interval LS between 22-1 and the second microlens 22-2 is set to LS = 2 × LI1, and the surface having the same shape as the curved surface on the object plane side of the first microlens 22-1 is the second. The microlenses 22-2 are arranged so as to face each other so as to be a curved surface on the imaging surface side. The distance LI from the second microlens 22-2 to the imaging plane of the lens array 20 is set equal to LO1, and LI = LO.

  The material forming the lens plate 21 of the lens array 20 in the present embodiment is an optical resin (trade name: ZEONEX E48R, manufactured by Nippon Zeon Co., Ltd.) which is a cycloolefin resin. Using the optical resin, a plurality of microlenses 22 were integrally formed by injection molding. The light shielding member 23 is made of polycarbonate. The polycarbonate was used and molded by resin molding.

  Further, by configuring each curved surface of the microlens 22 with a rotationally symmetric high-order aspheric surface expressed by the following equation (1), high resolution can be obtained. The function z (r) represents a rotational coordinate system in which the direction parallel to the optical axis of the microlens 22 is an axis and the coordinate in the radial direction is r, the vertex of each curved surface of the microlens 22 is the origin, and the lens array 20 The direction from the object plane to the imaging plane is represented by a positive number. C represents a radius of curvature, A represents a fourth-order coefficient of the aspheric coefficient, and B represents a sixth-order coefficient of the aspheric coefficient.

  Next, the operation of the printer 10 having the above configuration will be described.

  As shown in FIG. 1, the surface of the photosensitive drum 41 is charged by a charging roller 42 to which a voltage is applied by a power source (not shown). Subsequently, when the surface of the charged photosensitive drum 41 reaches the vicinity of the LED head 30 due to rotation of the photosensitive drum 41, the surface is exposed by the LED head 30, and an electrostatic latent image is formed on the surface of the photosensitive drum 41. It is formed. The electrostatic latent image is developed by the developing device 50, and a toner image is formed on the surface of the photosensitive drum 41.

  On the other hand, the paper 11 set in the paper feed cassette 60 is taken out from the paper feed cassette 60 by the paper feed roller 61 and is transported to the vicinity of the transfer roller 80 and the transfer belt 81 by the transport rollers 62 and 63.

  When the photosensitive drum 41 rotates and the toner image on the surface of the photosensitive drum 41 obtained by development reaches the vicinity of the transfer roller 80 and the transfer belt 81, a voltage is applied by a power source (not shown). The toner image on the surface of the photosensitive drum 41 is transferred onto the paper 11 by the transfer roller 80 and the transfer belt 81.

  Subsequently, the sheet 11 on which the toner image is formed is conveyed to the fixing device 90 by the rotation of the transfer belt 81. The toner image on the paper 11 is melted by being heated while being pressed by the fixing device 90 and fixed on the paper 11.

  Further, the paper 11 is discharged to the discharge unit 70 by the transport roller 64 and the discharge roller 65, and the operation of the printer 10 is finished.

  Next, the operation of the LED head 30 of the present embodiment will be described.

  When the control device of the printer 10 transmits a control signal of the LED head 30 based on the received print data, the LED element 31 emits light with an arbitrary amount of light by the control signal of the driver IC 32 as shown in FIG. Light rays emitted from the LED elements 31 enter the lens array 20 and an image is formed on the photosensitive drum 41.

  Next, the operation of the lens array 20 configured as described above will be described.

  As shown in FIG. 4, the light beam from the LED element 31 is incident on the first microlens 22-1, and the intermediate image is formed at a position separated by the distance LI1 in the optical axis direction by the first microlens 22-1. Is formed. Further, the intermediate image is formed by the second microlens 22-2, whereby an image of the LED element 31 is formed on the imaging surface. The intermediate image is an inverted reduced image of the LED element 31, and the image of the LED element 31 on the imaging surface is an inverted enlarged image of the intermediate image by the second microlens 22-2. In addition, between the first microlens 22-1 and the second microlens 22-2, so-called telecentric, in which principal rays of light rays from each point on the object plane are parallel, is formed.

  In this way, the lens array 20 forms an erecting equal-magnification image of the LED element 31. Of the light rays from the LED element 31, light rays that do not contribute to image formation are blocked by the light shielding member 23.

  In addition, when the first microlens 22-1 and the second microlens 22-2 are lenses having the same configuration, the lens array 20 forms an erecting equal-magnification image of the LED element 31. Light rays from the LED element 31 enter the first microlens 22-1, and an intermediate image is formed at a position separated by LS / 2 in the optical axis direction by the first microlens 22-1. Further, an intermediate image is formed by the second microlens 22-2, whereby an image of the LED element 31 is formed on the imaging surface. Moreover, it is telecentric between the 1st micro lens 22-1 and the 2nd micro lens 22-2.

  Next, the optical characteristics of the microlens 22 will be described.

  FIG. 5 is a second cross-sectional view in which the lens array according to the first embodiment of the present invention is cut along a plane that is horizontal to the arrangement direction of the microlenses and includes the optical axis. It is a figure which shows a parallel direction.

  The front focal length of the first microlens 22-1 is FO, and the distance from the first principal plane of the first microlens 22-1 to the object plane is SO. Further, the rear focal length of the second microlens 22-2 is FI, and the distance from the second principal plane of the second microlens 22-2 to the imaging plane is SI.

  Here, the difference between SO and LO is inversely proportional to the curvature radius of the curved surface on the object plane side of the first microlens 22-1, and the difference between SI and LI is the result of the second microlens 22-2. It is inversely proportional to the radius of curvature of the curved surface on the image side. In the lens array 20 of the present embodiment, the radius of curvature of each curved surface of the microlens 22 is large, and the difference between SO and LO and the difference between SI and LI can be ignored, so SO≈LO and SI≈LI.

  Furthermore, between the first microlens 22-1 and the second microlens 22-2, the principal ray of light rays from each point on the object plane is parallel to the optical axis. The peripheral rays of the light rays (light rays shown in FIG. 5) that pass through the inner wall of the section are blocked by the light shielding member 23, and the light rays, the object surface, and the first microlens 22-1 shown in FIG. The field radius RV of the first microlens 22-1 is expressed by the following equation (2) from the similarity of figures created by one main plane.

  Next, the relationship between the arrangement of the microlenses 22 and the field radius RV when the microlenses 22 are arranged in two lines is described.

  FIG. 6 shows the positional relationship between the LED elements of the LED array on the object plane of the lens array and the optical axis of the microlens arranged so that the microlenses in the first embodiment of the present invention form two rows. Is a diagram showing on the object plane. In the figure, (a) is a diagram showing a condition in which all LED elements are included in the field of view of at least one microlens, and (b) is a condition in which all LED elements are included in the field of view of two microlenses. FIG. 4C is a diagram showing a condition in which all LED elements are included in the field of view of eight microlenses.

  In FIG. 6A, all LED elements 31 are included in the field of view of at least one microlens 22, and the image radius of all the LED elements 31 formed on the photosensitive drum 41 is the smallest. It is shown. That is, this is a condition in which the field radius RV of the microlens 22 on which the lens array 20 operates is the smallest. At this time, the visual field radius RV is defined as an interval in the arrangement direction of the microlenses 22, that is, a pitch PY of the microlenses 22 in each row, and an interval in the direction perpendicular to the arrangement direction of the microlenses 22, that is, a row pitch PX. And is represented by the following formula (3).

  From the expressions (2) and (3), the focal length of the microlens 22 is F, the distance between the lens array 20 and the object plane of the lens array 20 is LO, the optical axis of the microlens 22 and the opening of the light shielding member 23. When the maximum value of the distance from the inner wall is RA, the following equation (4) is obtained as the operating condition of the lens array 20.

  However, when an image of each LED element 31 is formed by one microlens 22, the LED element 31 close to the optical axis of the microlens 22 and the LED element 31 far from the optical axis of the microlens 22 are connected to each other. The shape of the image will be different. Therefore, by setting so that the image of each LED element 31 is formed by at least two microlenses 22, the image of all LED elements 31 can be formed in substantially the same shape.

  FIG. 6B shows a condition in which all the LED elements 31 are included in the field of view of the two microlenses 22. At this time, the visual field radius RV is expressed by the following equation (5) using the interval PY in the arrangement direction of the microlenses 22 and the interval PX in the arrangement direction and the vertical direction of the microlenses 22.

  On the other hand, the image formed by the microlens 22 becomes more distorted as the object moves away from the optical axis. When the field radius RV of the microlens 22 is increased, the influence of image distortion due to the object at the field edge of the microlens 22 being separated from the optical axis increases. According to the verification in the present embodiment, when the LED element 31 is included in the field of view of eight or more microlenses 22 and an image is formed, the resolution is affected by the influence of the image distortion caused by the object moving away from the optical axis. Was found to be significantly reduced.

  FIG. 6C shows a condition in which all LED elements 31 are included in the field of view of the eight microlenses 22. At this time, the visual field radius RV is expressed by the following equation (6) using the interval PY in the arrangement direction of the microlenses 22 and the interval PX in the arrangement direction and the vertical direction of the microlenses 22.

  From the expressions (2), (5) and (6), the focal length of the microlens 22 is F, the distance between the lens array 20 and the object plane of the lens array 20 is LO, the optical axis of the microlens 22 and the light shielding member. Assuming that the maximum value of the distance from the inner wall of the opening 23 is RA, the following equation (7) is obtained as a condition for improving the resolution of the lens array 20.

  Next, the relationship between the arrangement of the microlenses 22 and the field radius RV when the microlenses 22 are arranged so as to form three linear rows will be described.

  FIG. 7 shows the positional relationship between the LED elements of the LED array on the object plane of the lens array and the optical axis of the microlens arranged so that the microlenses in the first embodiment of the present invention form three rows. Is a diagram showing on the object plane. In the figure, (a) is a diagram showing conditions under which all LED elements are included in the field of view of two microlenses, and (b) is a condition where all LED elements are included in the field of view of eight or more microlenses. FIG.

  FIG. 7A shows a condition in which all the LED elements 31 are included in the field of view of at least two microlenses 22. By setting so that the image of each LED element 31 is formed by at least two microlenses 22, the image of all LED elements 31 can be formed in substantially the same shape. At this time, the field radius RV is expressed by the following equation (8) using the interval PY in the arrangement direction of the microlenses 22 and the interval PX in the arrangement direction and the vertical direction of the microlenses 22.

  In addition, when the LED element 31 is included in the field of view of eight or more microlenses 22 and an image is formed, the resolution is significantly lowered due to the influence of image formation distortion caused by the object moving away from the optical axis.

  FIG. 7B shows a condition in which the LED elements 31 are included in the field of view of eight or more microlenses 22. At this time, the visual field radius RV is expressed by the following formula (9) using the interval PY in the arrangement direction of the microlenses 22 and the interval PX in the arrangement direction and the vertical direction of the microlenses 22.

  From the expressions (2), (8) and (9), the focal length of the microlens 22 is F, the distance between the lens array 20 and the object plane of the lens array 20 is LO, the optical axis of the microlens 22 and the light shielding member. Assuming that the maximum value of the distance from the inner wall of the opening 23 is RA, the following equation (10) is obtained as a condition for improving the resolution of the lens array 20.

  Next, evaluation of an image formed by the printer 10 using the lens array 20 will be described.

  FIG. 8 is a diagram showing an image used for evaluation in the first embodiment of the present invention.

  The inventor of the present invention evaluated an image using the lens array 20 described in the present embodiment, using an actual color LED printer having the same configuration as the printer 10. The image is an image as shown in FIG. 8, in which dots are formed every other pixel out of the entire print area. When such an image was formed and the quality of the image was evaluated, it was possible to obtain a good image free of streaks and shading.

  In the present embodiment, the example in which the plurality of microlenses 22 are integrally formed on the lens plate 21 has been described. However, the microlenses 22 may be individually formed and arranged at a predetermined interval. .

  In the present embodiment, the lens array 20 in which the microlenses 22 are arranged so as to form two or three linear rows has been described. However, the arrangement of the microlenses 22 is limited to this. It may be arranged so as to form four or more rows.

  Furthermore, in the present embodiment, an example in which the surface of the microlens 22 is a rotationally symmetric high-order aspheric surface has been described. However, the shape of the surface of the microlens 22 is not limited to this, and is a spherical surface. Alternatively, it may be a curved surface such as an anamorphic aspherical surface, a paraboloid, an elliptical surface, a hyperboloid, or a conic surface.

  Further, in the present embodiment, the example in which the lens plate 21 is formed by molding is described, but the molding method of the lens plate 21 is not limited to this, and resin is used for the mold. It may be a conventional mold forming method, or may be formed by cutting. Furthermore, although the example in which the material of the lens plate 21 is resin has been described, the material of the lens plate 21 may be glass.

  In the present embodiment, an example in which an LED array in which a plurality of LED elements 31 are arranged is used as a light emitting member is described. However, the light emitting member is not limited to the LED array. Electroluminescence), a semiconductor laser, or a light emitting member such as a fluorescent lamp or a halogen lamp combined with a shutter formed of a liquid crystal element may be used.

  Thus, in the present embodiment, since the lens array 20 in which a plurality of microlenses 22 are arranged is used, the resolution can be improved with respect to the lens array in which a plurality of rod lenses are arranged.

  Further, by defining the arrangement of the microlenses 22, the resolution can be further increased.

  Further, by using the lens array 20, it is possible to obtain an LED head 30 having a high contrast and a sufficient exposure amount. In the printer 10, an image is formed on the paper 11 according to the print data. No image streaks, density spots, etc. are formed, and the image quality can be improved.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operations and effects as those of the first embodiment is also omitted.

  FIG. 9 is a diagram showing a lens array according to the second embodiment of the present invention. In the figure, (a) is a plan view of the lens array, (b) is a plan view of the light shielding member, (c) is a cross-sectional view of the lens array, and is a BB cross-sectional view in (a).

  In the lens array 20 in the present embodiment, as shown in the drawing, a plurality of microlenses 22 are arranged on each lens plate 21 so as to form a single row extending in the vertical direction in the drawing. Yes. The microlenses 22 in the row are arranged so that the pitch is P, that is, the center distance between adjacent microlenses 22 is P. The microlenses 22 are densely arranged so as to overlap the microlenses 22 on both sides in the same row.

  The planar shape of each microlens 22 is circular except for the portions that overlap the microlenses 22 on both sides, and the radius of the circle is RL. And since each micro lens 22 has overlapped with the micro lens 22 of both sides, the relationship of 2RL> P is materialized. The thickness of the lens plate 21 is LT at the thickest portion of the microlens 22 as shown in FIG.

  In addition, the light shielding member 23 is a plate member having an elongated strip shape extending in the vertical direction in FIG. 9B and having a thickness of LS, and a plurality of openings extend in the vertical direction in the drawing. They are arranged so as to form one row. And the opening part in the said row | line | column is arranged so that the pitch may be set to P, ie, the space | interval of the center of adjacent opening parts may be set to P. FIG. Moreover, each opening part is arranged so that it may not overlap with the opening part of the both sides in the same row | line | column.

  In addition, although the planar shape of each opening part is a substantially rectangular shape, the part corresponding to the short side of a rectangle is an oval type formed in circular arc shape. Then, 1/2 of the distance between the long sides facing each other, that is, the distance from the center of the opening to the long side is RY.

  Each opening corresponds to each microlens 22 when the lens plate 21 and the light shielding member 23 are disposed so as to overlap each other, as shown in FIG. 9C. That is, the optical axis of each microlens 22, that is, the axis extending in the thickness direction through the center of the circle in the planar shape of each microlens 22 extends in the thickness direction through the center in the planar shape of each opening. It matches the existing axis.

  The configuration of the lens array 20 in the present embodiment corresponds to a configuration in which the size RA of the opening of the light shielding member 23 in the first embodiment as shown in FIGS. 3 to 5 is replaced with RY.

  In the present embodiment, the micro lens 22 on the object plane side and the micro lens 22 on the image plane side can be lenses having the same configuration. At this time, the curved surface on the object plane side of the micro lens 22 on the object plane side and the curved surface on the imaging plane side of the micro lens 22 on the imaging plane side are disposed so as to face each other.

  Since the configuration of other points is the same as that of the first embodiment, description thereof is omitted.

  Next, the relationship between the arrangement of the microlenses 22 and the field radius RV when the microlenses 22 are arranged in a straight line will be described.

  FIG. 10 shows the positional relationship between the LED elements of the LED array on the object plane of the lens array and the optical axes of the microlenses arranged such that the microlenses according to the second embodiment of the present invention form one row. Is a diagram showing on the object plane. In the figure, (a) is a diagram showing a condition in which all LED elements are included in the field of view of at least one microlens, and (b) is a condition in which all LED elements are included in the field of view of two microlenses. FIG. 4C is a diagram showing a condition in which all LED elements are included in the field of view of eight microlenses.

  In FIG. 10A, all LED elements 31 are included in the field of view of at least one micro lens 22, and the image radius of all LED elements 31 formed on the photosensitive drum 41 is the smallest. It is shown. That is, this is a condition in which the field radius RV of the microlens 22 on which the lens array 20 operates is the smallest. At this time, the viewing radius RV is expressed by the following formula (11) using the arrangement interval P of the microlenses 22.

  The field radius RV, the focal length F of the microlens 22, the distance LO between the lens array 20 and the object surface of the lens array 20, and the optical axis of the microlens 22 and the opening of the light shielding member 23 in the arrangement direction of the microlens 22 The relationship between the distance RY and the inner wall of the lens array 20 is equal to that obtained by replacing RA in the expression (2) in the first embodiment with RY. From the expression (11), the following expression is given as the operating condition of the lens array 20. (12) is obtained.

  However, when an image of each LED element 31 is formed by one microlens 22, the LED element 31 close to the optical axis of the microlens 22 and the LED element 31 far from the optical axis of the microlens 22 are connected to each other. The shape of the image will be different. Therefore, by setting so that the image of each LED element 31 is formed by at least two microlenses 22, the image of all LED elements 31 can be formed in substantially the same shape.

FIG. 10B shows a condition in which all the LED elements 31 are included in the field of view of the two microlenses 22. At this time, the viewing radius RV is expressed by the following formula (13) using the arrangement interval P of the microlenses 22.
RV = P Formula (13)
On the other hand, the image formed by the microlens 22 becomes more distorted as the object moves away from the optical axis. When the field radius RV of the microlens 22 is increased, the influence of image distortion due to the object at the field edge of the microlens 22 being separated from the optical axis increases. According to the verification in the present embodiment, when the LED element 31 is included in the field of view of eight or more microlenses 22 and an image is formed, the resolution is affected by the influence of the image distortion caused by the object moving away from the optical axis. Was found to be significantly reduced.

  FIG. 10C shows a condition in which all the LED elements 31 are included in the field of view of the eight microlenses 22. At this time, the viewing radius RV is expressed by the following formula (14) using the arrangement interval P of the microlenses 22.

  From the formulas (2), (13) and (14), the focal length of the microlens 22 is F, the distance between the lens array 20 and the object plane of the lens array 20 is LO, and the microlens in the arrangement direction of the microlenses 22. Assuming that the distance between the optical axis 22 and the inner wall of the opening of the light shielding member 23 is RY, the following equation (15) is obtained as a condition for improving the resolution of the lens array 20.

  The inventor of the present invention uses the actual color LED printer having the same configuration as that of the printer 10 described in the first embodiment, and uses the lens array 20 described in the present embodiment. Images used were evaluated. The image is an image as shown in FIG. 8 in the first embodiment, in which dots are formed every other pixel out of the entire printing area. When such an image was formed and the quality of the image was evaluated, it was possible to obtain a good image free of streaks and shading.

  By the way, in the present embodiment, the lens array 20 in which the microlenses 22 are arranged so as to form one linear row has been described. However, the arrangement of the microlenses 22 is not limited to this. These may be arranged so as to form a plurality of rows.

  Thus, in the present embodiment, the configuration of the lens array 20 can be simplified compared to the lens array 20 in the first embodiment.

  Further, the resolution can be improved by the lens array 20 having a simpler configuration than that of the first embodiment.

  Further, by using the lens array 20, it is possible to obtain an LED head 30 having a high contrast and a sufficient exposure amount. In the printer 10, an image is formed on the paper 11 according to the print data. No image streaks, density spots, etc. are formed, and the image quality can be improved.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st and 2nd embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operations and effects as those of the first and second embodiments is also omitted.

  FIG. 11 is a diagram showing the structure of a reading apparatus according to the third embodiment of the present invention.

  In the figure, reference numeral 100 denotes a scanner as a reading device that reads a document and generates electronic data of a document image. The scanner 100 includes a movable read head 110 disposed therein. The reading head 110 includes a sensor such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor), an optical element such as the lens array 20, and the like. Convert. The read head 110 is slidably disposed along the rail 103.

  A document for which electronic data is generated is placed on the document table 102. The document table 102 is made of a material that transmits visible light.

  Reference numeral 101 denotes a lamp as an illuminating device, which is arranged so that light emitted from the lamp 101 is reflected on the surface of the document and taken into the reading head 110.

  Reference numeral 105 denotes a driving belt, which is stretched by a plurality of pulleys 104, and a part of the driving belt 105 is connected to a part of the reading head 110.

  Reference numeral 106 denotes a motor as a drive source, which drives the drive belt 105 and slides the reading head 110.

  Next, the configuration of the read head 110 will be described.

  FIG. 12 is a diagram showing the structure of the read head in the third embodiment of the present invention. In the figure, (a) is a sectional view of the reading head, and (b) is a schematic diagram of an optical system of the reading head.

  In FIG. 12A, reference numeral 112 denotes a mirror that bends the optical path of the light beam reflected by the document. The lens array 20 forms an image of the original image on the light receiving surface of the line sensor 111. The line sensor 111 includes a plurality of light receiving elements arranged in a straight line, and converts the image of the original image into an electrical signal.

  Here, the line sensor 111 has a resolution of 600 [dpi], and 600 light receiving elements are arranged per inch (1 inch is about 25.4 [mm]). That is, the light receiving elements are arranged at intervals of 0.0423 [mm].

  Further, the positional relationship between the lens array 20, the object plane (original) and the imaging plane (light receiving surface of the line sensor 111) in the reading head 110 of the present embodiment is as shown in FIG. Yes.

  Note that the configuration of the lens array 20 in the present embodiment is the same as that in the first and second embodiments, and a description thereof will be omitted.

  Next, the operation of the scanner 100 configured as described above will be described.

  First, as shown in FIG. 11, when the lamp 101 is turned on and the surface of the original is irradiated, the light beam reflected by the original is taken into the reading head 110. When the driving belt 105 is driven by the motor 106, the reading head 110 and the lamp 101 move in the horizontal direction in FIG. 11, and the reading head 110 can take in the light beam reflected from the entire surface of the document.

  Next, the operation of the read head 110 configured as described above will be described.

  First, as shown in FIG. 12, the light beam reflected by the document surface is transmitted through the document table 102, the optical path is bent using the mirror 112, and enters the lens array 20. The lens array 20 forms an image of the original image on the line sensor 111. The line sensor 111 converts the image of the formed document image into an electric signal.

  When the inventor of the present invention forms image data from a document using an actual scanner having the same configuration as the scanner 100 described in this embodiment, the same good image as the document is formed. I was able to get the data. In this case, the original image is an image as shown in FIG. 8 in the first embodiment, and dots are formed every other pixel out of all the pixels on the entire print area.

  In this embodiment, the example in which the reading device that converts the document image into electronic data is the scanner 100 has been described. However, the reading device includes a sensor or a switch that converts an optical signal into an electrical signal, and Also, an input / output device, a biometric authentication device, a communication device, a dimension measuring device, or the like using them may be used.

  As described above, in the present embodiment, it is possible to form an image of a document image having high contrast, high focal depth, and sufficient brightness. In addition, the same image data as the original can be obtained.

  Next, a fourth embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st-3rd embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operations and effects as those of the first to third embodiments is also omitted.

  FIG. 13 is a diagram showing a detailed structure of the microlens according to the fourth embodiment of the present invention. In the figure, (a) is a plan view of the microlens, (b) is a first sectional view of the microlens, and (c) is a second sectional view of the microlens.

  FIG. 13A shows two microlenses that overlap each other among the microlenses 22 arranged as shown in FIG. 3A in the lens array 20 described in the first embodiment. 22 is shown. Here, one microlens is 22i, and the other microlens is 22j.

  I and j are the vertices of the curved surfaces of the microlenses 22i and 22j, respectively. Further, k is a point that bisects the line segment ij, and the straight line pb is a perpendicular bisector of the line segment ij in the same plane as the line segment ij. Here, a plane parallel to the optical axes of the microlenses 22i and 22j and including the straight line pb is defined as a plane f. A plane including the optical axes of the microlenses 22i and 22j and the line segment ij is defined as a plane g.

  FIG. 13B shows a cross section of the microlenses 22i and 22j cut along the plane f. Here, an arbitrary point on the boundary line between the curved surface of the microlens 22i and the curved surface of the microlens 22j is n, and an intersection of a perpendicular drawn from the point n to the straight line pb and the straight line pb is m. The plane h is a plane perpendicular to the optical axes of the microlenses 22i and 22j.

  Further, FIG. 13C shows a cross section of the microlenses 22i and 22j cut along the plane g.

  As shown in FIG. 13A, in the triangle ikm and the triangle jkm, the line segment km is common, the straight line pb is a perpendicular bisector of the line segment ij, and the point k represents the line segment ij by 2 Since they are equally divided points, the lengths of the line segment ik and the line segment jk are equal, the line segment km and the line segment ik are perpendicular to each other, and the line segments km and jk are perpendicular to each other. Therefore, the lengths of the three sides of the triangle ikm and the triangle jkm are equal, and the lengths of the line segment im and the line segment jm are equal.

  If the length of the line segment im is Ri and the length of the line segment jm is Rj, the distance Di between the point n and the point m on the boundary line with the microlens 22j in the microlens 22i is It can be represented by formula (16).

  The distance Dj between the point n and the point m on the boundary line between the microlens 22j and the microlens 22i can be expressed by the following equation (17).

  From Ri = Rj, Di = Dj. That is, the height in the optical axis direction of the curved surfaces of the two microlenses 22i and 22j coincides on the boundary line, and the height in the optical axis direction of the curved surfaces of the two adjacent microlenses 22i and 22j overlaps with each other. They coincide on the boundary line of the microlenses 22i and 22j. The curved surfaces of the adjacent microlenses 22i and 22j overlap each other without a step in the optical axis direction.

  In this way, the microlens 22 is a straight bisector (straight line pb) of a straight line connecting a plane perpendicular to the optical axis (plane h) and the vertices of the curved surfaces of two adjacent microlenses 22 parallel to the optical axis. The height in the optical axis direction of the curved surfaces of the adjacent microlenses 22 matches on the boundary line between the adjacent microlenses 22, It can be made into the shape without the level | step difference of an axial direction.

  Therefore, by configuring the lens array 20 molded by resin molding as in the present embodiment, the lens array 20 can be shaped without a step in the direction parallel to the optical axis of the microlens 22, and the resin inside the mold The fluidity is improved and generation of internal stress of the resin can be suppressed in the molding process. As a result, the shape transferability in the molding process is improved and the shape accuracy of the microlens 22 is improved.

  For this reason, in the lens array 20 according to the present embodiment, there is no step in the direction parallel to the optical axis of the microlens 22 at the boundary portion between the adjacent microlenses 22, and the light beam incident on the boundary portion between the adjacent microlenses 22 is present. It is possible to suppress a decrease in resolution of the exposure image due to irregular reflection.

  Since the configuration and operation of other points are the same as those in the first embodiment, description thereof is omitted.

  As described above, in the present embodiment, it is possible to adopt a configuration in which a step does not occur in the direction parallel to the optical axis of the microlens 22 at the boundary portion between the adjacent microlenses 22. It is possible to suppress a reduction in the resolution of the exposure image due to irregular reflection of the light rays incident on the boundary portion of.

  In addition, by configuring the lens array 20 molded by resin molding as in the present embodiment, it is possible to make a configuration without a step in a direction parallel to the optical axis of the microlens 22, and the resin inside the mold The fluidity is improved and the generation of internal stress of the resin in the molding process can be suppressed. As a result, the shape transferability in the forming process is improved, the shape accuracy of the microlens 22 is improved, and the lens array 20 is improved. Resolution can be improved.

  Furthermore, by using the lens array 20 in the present embodiment, it is possible to configure the LED head 30 with high contrast and sufficient exposure. Furthermore, in the printer 10 according to the present embodiment, an image is formed on the paper 11 according to the image data, and image quality on the paper 11 without any streak or density spots is improved. Can do.

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

  The present invention can be used for a lens array and an exposure apparatus, an image forming apparatus, and a reading apparatus having the lens array.

DESCRIPTION OF SYMBOLS 10 Printer 20 Lens array 21 Lens board 22, 22i, 22j Micro lens 22-1 1st micro lens 22-2 2nd micro lens 23 Light-shielding member 30 LED head 100 Scanner

Claims (10)

(A) comprises one lens collecting members which have a plurality of lenses that are arranged to form a row of a light shielding member in which a plurality of diaphragm are arranged,
(B) When the distance between the optical axes of adjacent lenses is P, and the maximum value of the distance from the optical axis to the outer periphery of each lens is RL,
P <2RL
And
(C) The height in the optical axis direction of the curved surfaces of adjacent lenses coincides with each other on the boundary line between adjacent lenses ;
(D) The number of the lens assembly members is two, and each of the plurality of lenses is disposed so that the optical axes of the plurality of lenses coincide with each other.
(E) The light shielding member is disposed between the two lens assembly members, and the diaphragm of the light shielding member has a shape in which both ends of a pair of linear long sides parallel to each other are connected by an arc. An array is formed so that the long side of each stop in the row is oriented in a direction perpendicular to the extending direction of the row, and the optical axes of each of the plurality of lenses are lens array, wherein Rukoto arranged to pass through the center of. The lens includes a curved surface cut by a plane perpendicular to the optical axis and a plane including a perpendicular bisector of a straight line that connects the vertices of curved surfaces of lenses adjacent to each other and parallel to the optical axis. The lens array according to claim 1. When the focal length of the lens is F, the distance from the lens array to the object plane is LO, and the distance from the center of each stop to the long side is RY,

Lens array according to Der Ru claim 1 or 2. The lens array according to claim 3, wherein the lens forms an inverted reduced image, and the lens assembly member forms an erecting equal-magnification image. The lens array according to claim 1, wherein the curved surface of the lens is a rotationally symmetric surface. The lens array according to claim 1, wherein the plurality of lenses are integrally formed. The lens array according to claim 1, wherein the lens is formed by resin molding. (A) comprises one lens collecting members which have a plurality of lenses that are arranged to form a row of a light shielding member in which a plurality of diaphragm are arranged,
(B) When the distance between the optical axes of adjacent lenses is P, and the maximum value of the distance from the optical axis to the outer periphery of each lens is RL,
P <2RL
And
(C) The height in the optical axis direction of the curved surfaces of adjacent lenses coincides with each other on the boundary line between adjacent lenses ;
(D) The number of the lens assembly members is two, and each of the plurality of lenses is disposed so that the optical axes of the plurality of lenses coincide with each other.
(E) The light shielding member is disposed between the two lens assembly members, and the diaphragm of the light shielding member has a shape in which both ends of a pair of linear long sides parallel to each other are connected by an arc. An array is formed so that the long side of each stop in the row is oriented in a direction perpendicular to the extending direction of the row, and the optical axes of each of the plurality of lenses are exposure apparatus characterized by having a lens array that will be arranged to pass through the center of. (A) comprises one lens collecting members which have a plurality of lenses that are arranged to form a row of a light shielding member in which a plurality of diaphragm are arranged,
(B) When the distance between the optical axes of adjacent lenses is P, and the maximum value of the distance from the optical axis to the outer periphery of each lens is RL,
P <2RL
And
(C) The height in the optical axis direction of the curved surfaces of adjacent lenses coincides with each other on the boundary line between adjacent lenses ;
(D) The number of the lens assembly members is two, and each of the plurality of lenses is disposed so that the optical axes of the plurality of lenses coincide with each other.
(E) The light shielding member is disposed between the two lens assembly members, and the diaphragm of the light shielding member has a shape in which both ends of a pair of linear long sides parallel to each other are connected by an arc. An array is formed so that the long side of each stop in the row is oriented in a direction perpendicular to the extending direction of the row, and the optical axes of each of the plurality of lenses are an image forming apparatus, comprising an exposure apparatus having a lens array that will be arranged to pass through the center of. (A) comprises one lens collecting members which have a plurality of lenses that are arranged to form a row of a light shielding member in which a plurality of diaphragm are arranged,
(B) When the distance between the optical axes of adjacent lenses is P, and the maximum value of the distance from the optical axis to the outer periphery of each lens is RL,
P <2RL
And
(C) The height in the optical axis direction of the curved surfaces of adjacent lenses coincides with each other on the boundary line between adjacent lenses ;
(D) The number of the lens assembly members is two, and each of the plurality of lenses is disposed so that the optical axes of the plurality of lenses coincide with each other.
(E) The light shielding member is disposed between the two lens assembly members, and the diaphragm of the light shielding member has a shape in which both ends of a pair of linear long sides parallel to each other are connected by an arc. An array is formed so that the long side of each stop in the row is oriented in a direction perpendicular to the extending direction of the row, and the optical axes of each of the plurality of lenses are reader and having a lens array that will be arranged to pass through the center of.

Images