JP2008083576A - Lens-array, exposure device, image forming apparatus and reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent resolution deterioration and reduction in the light amount. <P>SOLUTION: Plural pairs of lenses are disposed so that the optical axes thereof aligning with each other, are arrayed nearly linearly in a direction perpendicular to the optical axes, a light-blocking member for shielding each pair of lenses from light having passed through the adjacent pair of lenses is disposed on each pair of lenses. If the diameter of each lens is expressed as D, and the lens arrangement interval is expressed as P, P<D is established. In this case, the diameter D of the lens is made larger than the lens arrangement interval P, consequently, such failures are prevented so that the resolution is deteriorated and the light amount is reduced, in the cycle of the lens arrangement interval. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Conventionally, in a reading device such as a scanner, or an image forming apparatus such as a printer, a copying machine, or a multifunction device, for example, an LED printer in which a plurality of LEDs are arranged in an array, a plurality of LEDs are arranged adjacent to a light emitting unit. A lens array in which rod lenses are arranged in an array is used.

  In a scanner in which a plurality of light receiving elements are arranged in an array, a lens array in which a plurality of rod lenses are arranged in an array adjacent to the light receiving unit is used.

  The rod lens is an optical element in which a glass fiber is impregnated with ions so that the refractive index decreases from the central portion toward the peripheral portion, and forms an erect life-size image of an object. A lens array in which the rod lenses are arranged in a plurality of arrays is used as an optical system for forming an image of an object in a line shape.

Furthermore, as an example of a simple optical system, there is a lens array in which rod lenses are arranged in a single row array. In addition, a lens array similar to the rod lens array can be configured by arranging lens pairs in which a pair of microlenses are arranged at intervals corresponding to the focal length so that the optical axes coincide with each other (for example, patents) Reference 1).
JP 2002-107661 A

  However, in the lens array in which the conventional rod lenses are arranged in a single-row array, there is a difference between the optical characteristics in the vicinity of the optical axis of each rod lens and the surrounding optical characteristics. , The resolution is lowered and the light quantity is lowered. Similarly, in a lens array using microlenses, there is a difference between the optical characteristics in the vicinity of the optical axis of each microlens and the surrounding optical characteristics, so that the resolution decreases with the period of the arrangement interval of the microlenses. Or the amount of light decreases.

  It is an object of the present invention to provide a lens array, an exposure apparatus, an image forming apparatus, and a reading apparatus in which the resolution of the conventional lens array is not reduced and the light amount is not reduced. And

  For this purpose, in the lens array of the present invention, a plurality of lens pairs arranged so that the optical axes of the lenses coincide with each other are arranged in a substantially straight line in a direction perpendicular to the optical axis, The pair is provided with a light blocking member that blocks light from the adjacent lens pair.

And when the aperture of each lens is D and the arrangement interval of each lens is P,
P <D
To be.

  According to the present invention, in the lens array, a plurality of lens pairs arranged so that the optical axes of the respective lenses coincide with each other are arranged substantially linearly in a direction perpendicular to the optical axis. The pair is provided with a light blocking member that blocks light from the adjacent lens pair.

And when the aperture of each lens is D and the arrangement interval of each lens is P,
P <D
To be.

  In this case, since the diameter D of the lens is made larger than the lens arrangement interval P, it is possible to prevent the resolution and the amount of light from decreasing at the period of the lens arrangement interval.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a printer and a reading device as the image forming apparatus will be described. In this case, the printer uses a toner made of a resin containing a pigment constituting the color material as a developer, and forms an image such as a color image or a monochrome image on a sheet as a medium according to the image data.

  FIG. 2 is a conceptual diagram of the printer according to the first embodiment of the present invention.

  In the figure, reference numeral 10 denotes a printer as an image forming apparatus. In the printer 10, there is a substantially “S-shaped” shape, and a conveyance path 25 for conveying a sheet (not shown) as a medium is disposed. Then, conveying rollers 26 to 29 are disposed in the conveying path 25. In addition, image forming units Bk, Y, M, and C for forming toner images as developer images of the respective colors are disposed along the conveyance path 25, and the image forming units Bk, Y, M, and C are disposed. Below C, a transfer unit 34 is provided for conveying the paper and transferring the toner images onto the paper. Between the image forming units Bk, Y, M, C and the transfer unit 34, a transfer unit 34 is provided. The conveyance path 25 is formed. The transfer unit 34 constitutes a belt drive unit.

  Further, the printer 10 is provided with an LED head 23 as an exposure device and as a recording head so as to face the photosensitive drum 11 as an image carrier. A fixing unit 35 for fixing the transferred toner image on the sheet is disposed downstream of the transfer unit 34.

  In each of the image forming units Bk, Y, M, and C, the photosensitive drum 11 rotates at a predetermined rotation speed and can store charges on the surface, and the charges on the surface are removed by exposure by the LED head 23. As a result, an electrostatic latent image (not shown) is formed as a latent image. A charging roller 12 as a charging device is brought into contact with the photosensitive drum 11 with a constant pressure and rotated in a direction opposite to the photosensitive drum 11 to apply a predetermined voltage to the surface of the photosensitive drum 11.

  Reference numeral 45 denotes a developing unit which is disposed adjacent to the photosensitive drum 11 and develops an electrostatic latent image to form a toner image. The developing unit 45 is used as a developer on the photosensitive drum 11. A developing roller 16 as a developer carrying member for adhering the toner, a developing blade (not shown) as a regulating member for regulating the thickness of the toner on the developing roller 16, and a developer supplying member for supplying toner to the developing roller 16 Toner supply roller 18 and the like. The developing roller 16 is brought into contact with the photosensitive drum 11 at a constant pressure and rotated in a direction opposite to the photosensitive drum 11, and the toner supply roller 18 is brought into contact with the developing roller 16 at a constant pressure to develop. It is rotated in the same direction as the roller 16.

  The photosensitive drum 11, the charging roller 12, the developing device 45, and the like are accommodated in a casing 20 that constitutes the main body of the image forming unit, and above the casing 20 is a developer accommodating portion that accommodates toner. A toner cartridge 15 is detachably disposed on the housing 20.

  The transfer unit 34 includes a transfer belt 21 that is movably disposed, and a transfer roller 22 as a transfer member that is disposed to face each of the photosensitive drums 11. A predetermined voltage is applied to the transfer belt 21 and the transfer roller 22 by a power source (not shown), and each toner image on the photosensitive drum 11 is transferred to a sheet.

  Reference numeral 38 denotes a lower frame, and reference numeral 40 denotes an upper frame that is disposed so as to be swingable with respect to the lower frame 38 and includes a stacker 31 for stacking discharged sheets. Below the transfer unit 34, a paper feed cassette 30 as a medium storage unit for storing paper is disposed at the end of the transport path 25, and a feeding unit 32 that feeds the paper is provided in the paper feed cassette 30. Arranged.

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

  In each of the image forming units Bk, Y, M, and C, the charging roller 12 charges the surface of the photosensitive drum 11 uniformly and uniformly, and the LED head 23 exposes the surface of the photosensitive drum 11. An electrostatic latent image is formed. Subsequently, the developing device 45 develops the electrostatic latent image to form a toner image of each color.

  On the other hand, the sheet fed by the feeding unit 32 is transported by the transport rollers 26 and 27 and is attached to the transfer belt 21 by an electrostatic effect. As the transfer belt 21 travels, each image forming unit Bk, Y , M, and C and the transfer unit 34, and the toner images of the respective colors are transferred and overlapped between them to form a color toner image. Thereafter, the sheet passes through the fixing unit 35, and the color toner image is fixed, and a color image is formed. Subsequently, the sheet is further conveyed by the conveying rollers 28 and 29 and discharged to the stacker 31.

  The printer 10 is provided with an external interface (not shown) that communicates with an external device (not shown) and receives print data. The printer 10 receives the print data from the external interface and controls the entire printer 10. A control unit that is not performed is arranged.

  Next, the LED head 23 will be described.

  FIG. 3 is a cross-sectional view of the LED head according to the first embodiment of the present invention.

  As shown in the figure, a lens array 50 is disposed on the LED head 23, and the lens array 50 is fixed to the support 23 a by a holding member 46.

  Reference numeral 11 denotes a photosensitive drum, and 41 denotes a light emitting portion of the LED head 23. The light emitting portion 41 includes a plurality of LED elements as light emitting elements, and in this embodiment, 1 inch (about 2.5 [ cm]) is arranged linearly at equal intervals. A light shielding member (not shown) is disposed between the light emitting unit 41 and the lens array 50.

  Reference numeral 42 denotes a driver IC that controls light emission of the LED elements of the light emitting unit 41. The light emitting unit 41 and the driver IC 42 are disposed on a wiring board 44 and are connected to each other by a wire 43.

  Next, the operation of the LED head 23 having the above configuration will be described.

  First, when the control unit generates a control signal for the LED head 23 based on the image data and sends it to the driver IC 42, the driver IC 42 causes each LED element to emit light with a predetermined light amount in accordance with the control signal. Light rays from the LED elements are incident on the lens array 50, pass through the lens array 50 and form an image on the photosensitive drum 11, and an image formed by the light emitting unit 41 is formed on the photosensitive drum 11. Is done.

  Next, the lens array 50 will be described.

  FIG. 1 is a plan view of a lens array according to the first embodiment of the present invention, FIG. 4 is a longitudinal sectional view of the lens array according to the first embodiment of the present invention, and FIG. 5 is a diagram illustrating the first embodiment of the present invention. It is a cross-sectional view of the lens array in the form.

  As shown in the drawing, the lens array 50 is disposed between two lens plates 51a and 51b, is made of a material that blocks light, and has a light shielding portion 54 as a light shielding member in which a plurality of openings 55 are formed. Is provided. In the present embodiment, a plurality of microlenses 53 are arranged substantially linearly in the direction perpendicular to the optical axis at the center in the width direction of the lens plates 51a and 51b and are integrally formed. A lens pair 52 is constituted by the microlenses 53 arranged so that the optical axes coincide with each other. The microlens 53 is an optical system that forms a reduced inverted image, and the lens pair 52 constitutes an optical system that forms an erecting equal-magnification image.

  The curved surface of the micro lens 53 is rotationally symmetric with respect to the optical axis, and the curved surface of the micro lens 53 has a shape that is cut in a plane parallel to the optical axis in the vicinity of the boundary with the adjacent micro lens 53. At this time, the aperture (microlens aperture) D of the microlens 53 is a diameter of a circle circumscribing the microlens 53 with the optical axis of the microlens 53 as the center.

The lens plates 51 a and 51 b and the light shielding portion 54 are disposed so that the optical axis of the lens pair 52 and the central axis of the opening 55 coincide with each other. In the present embodiment, the arrangement interval (microlens arrangement interval) P of the microlenses 53 is relative to the aperture D of the microlenses 53.
P <D
Configured to be.

The size of the opening 55 of the light shielding portion 54 is defined as W _{X, which} is an opening width in the direction perpendicular to the arrangement direction of the microlenses 53 (width direction light shielding portion opening width). When the arrangement direction shading part opening width is W _Y
W _Y <W _X
Configured to be. The opening 55 has a substantially cylindrical shape with a central axis coinciding with the optical axis and a diameter equal to the opening width W _X , and an interval equal to the opening width W _Y, and is disposed in parallel with the optical axis. Further, it has a shape surrounded by two planes.

  Here, in order to verify the effect in the present embodiment, a lens array of a comparative example was created.

In the lens array 50 ′ of the comparative example, the arrangement interval P of the microlenses 53 is made equal to the aperture D of the microlenses 53, and the shape of the microlenses 53 viewed from the optical axis direction is circular. In the lens array of the comparative example, is equal to the opening width W _Y and the opening width W _X of the opening 55 of the light blocking part 54, the shape of the aperture 55 is a diameter of the center axis coincides with the optical axis of the W _Y cylindrical It is.

  In the lens array 50 according to the present embodiment and the lens array according to the comparative example, an optical resin (product name: ZEONEX E48R manufactured by Nippon Zeon Co., Ltd.) that is a cycloolefin resin is used as the lens plates 51a and 51b. And formed by resin molding.

  Moreover, in the lens array 50 in the present embodiment and the lens array in the comparative example, the light shielding portion 54 is formed by resin molding using polycarbonate.

  FIG. 6 is a schematic diagram of an optical system according to the first embodiment of the present invention.

As shown in the drawing, the distance (object surface-lens surface distance) _Lo between the lens array 50 and the light emitting unit 41 is a plane (object) where the apex of the external curved surface 53a of the microlens 53 and the light emitting unit 41 are arranged. The distance between the lens array 50 and the photosensitive drum 11 (imaging plane-lens surface distance) L _I is the distance between the apex of the external curved surface 53a of the microlens 53 and the photosensitive drum 11. the distance between the plane (image plane) to be set, the lens thickness L _T is the distance between the outer curved surface 53a and an inner curved surface 53b of the microlens 53, between the lens surface distance L _S is between the inner curved surface 53b The distance, the imaging plane-object plane distance TC is a distance between the photosensitive drum 11 and the light emitting unit 41.

  Further, each of the outer curved surface 53a and the inner curved surface 53b of the microlens 53 is a rotationally symmetric high-order aspheric surface and is represented by the following function z (r).

The function z (r) represents a rotational coordinate system in which the direction parallel to the optical axis of the microlens 53 is an axis, and the coordinate in the radial direction is r, and the vertexes of the outer curved surface 53a and the inner curved surface 53b of the microlens 53 are defined. The direction from the object plane of the lens array 50 toward the imaging plane is expressed as a positive number with the origin. C is a radius of curvature (external curved surface radius of curvature C _O , internal curved surface radius of curvature C _I ), A is an aspherical coefficient quartic (external curved surface aspherical coefficient quaternary A _O , internal curved surface aspherical coefficient quaternary A _I ), And B represents the coefficient of the aspherical coefficient 6th order (outer curved surface aspherical coefficient 6th order B _O , inner curved surface aspherical coefficient 6th order B _I ).

  A plurality of microlenses 53 are integrally formed on the lens plates 51a and 51b, but the microlenses 53 can be individually formed and fixed at a predetermined arrangement interval.

  In the present embodiment, each of the outer curved surface 53a and the inner curved surface 53b is formed of a rotationally symmetric high-order aspheric surface, but may be formed of a spherical surface. Further, it can be formed of a conic surface such as a paraboloid, an ellipsoid, or a hyperboloid, a toroid surface that is asymmetric in each direction perpendicular to the optical axis, a cylinder surface, or the like, or a known free-form surface.

  Further, the microlens 53 is configured by forming a predetermined curved surface on a transparent material having a uniform refractive index that transmits the light beam of the light source. It can be formed of a fiber or the like.

  And although the said light-shielding part 54 is formed by resin molding, it can be formed by cutting. Further, a light shielding pattern is formed on the material that transmits the light by a light shielding material that shields the light from the light source, or a light shielding pattern is formed by a light shielding material on a part of the lens plates 51a and 51b. It is possible to shield the light beam by cutting the lens plates 51a and 51b so that a part of the light beam does not enter.

  In the present embodiment, an LED array in which a plurality of LED elements are arranged as light emitting elements in the light emitting unit 41 is used. For example, an organic EL can be used as the light emitting element. Further, a semiconductor laser can be used as the recording head of the printer 10, or a recording head using a light source such as a fluorescent lamp or a halogen lamp in combination with a shutter composed of a liquid crystal element can be used.

  Next, the operation of the lens array 50 having the above configuration will be described.

  7 is a plan view of the lens array according to the first embodiment of the present invention, FIG. 8 is a cross-sectional view of the lens array according to the first embodiment of the present invention, and FIG. 9 is a first embodiment of the present invention. FIG. 10 is a cross-sectional view showing a comparative example of the lens array in the first embodiment of the present invention.

  The lens array 50 in the present embodiment and the lens array 50 ′ in the comparative example are configured as shown in Table 1.

  In the figure, reference numeral 41a denotes a light emitting portion near the boundary between adjacent microlenses 53 and 53 '.

  By the way, when the imaged image I of the light emitting portion 41a is formed using the lens arrays 50 and 50 ', the resolution and the light amount are lower in the lens array 50' of the comparative example than the lens array 50 of the present invention. .

8 and 10 show an optical path through which the light emitting section 41a passes through the lens arrays 50 and 50 'and reaches the photosensitive drum 11 to form the image I. Furthermore, the principal ray indicating the shortest path of the optical path and R _M, the peripheral light rays showing the outermost paths for main beam R _M and R _S.

  The light beam emitted from the light emitting unit 41a is incident on the microlenses 53 and 53 'on the light emitting unit 41a side of the lens pair 52 and 52', and then forms a reduced image of the light emitting unit 41a. Is incident on the side microlenses 53 and 53 '. The microlenses 53 and 53 'on the photosensitive drum 11 side form an inverted enlarged image of the reduced image of the light emitting portion 41a, and the image of the light emitting portion 41a is an erecting equal-magnification image in the entire lens pair 52 and 52'. The image is formed on the drum 11.

  As shown in FIGS. 8 and 10, in the lens array 50 according to the embodiment of the present invention, the light emitting portion 41 a is disposed closer to the optical axis of the microlens 53 than the lens array 50 ′ in the comparative example. Is done.

  By the way, in general, an object image formed by a lens has a smaller aberration and a larger amount of light in an object closer to the optical axis of the lens.

The lens array 50 according to the embodiment of the present invention has a larger angle α _O formed by the peripheral ray R _S of the light emitted from the light emitting unit 41a than the lens array 50 ′ in the comparative example, and thus is emitted from the light emitting unit 41a. Of the emitted light, more light enters the microlens 53. Therefore, the image I of the light emitting part 41a by the lens array 50 in the embodiment of the present invention is brighter than the image I of the light emitting part 41a by the lens array 50 'in the comparative example.

  As a result, the lens array 50 in the embodiment of the present invention has the light emitting portion 41a closer to the optical axis of each microlens 53 than the lens array 50 'in the comparative example, and the aberration of the image I is smaller. A clear image is formed, and an image I having a large amount of light can be obtained. And the resolution of the arrangement period of the micro lens 53 of the lens array 50 and the fall of light quantity can be improved.

  Next, with respect to the LED head 23 in the embodiment of the present invention and the LED head 23 'in the comparative example, the measurement results of MTF (Modulation Transfer Function) and light quantity will be described.

  Here, MTF represents the resolution of the image formed by the LED head 23 and represents the contrast of the light amount of the image formed by the LED elements lit in the LED head 23. The MTF in the case where the contrast of the light amount of the formed image is the largest and the resolution as the LED head 23 is the highest is 100 [%]. The smaller the MTF is, the smaller the contrast of the light amount of the formed image is. The resolution as the head 23 is lowered.

  FIG. 11 is a diagram showing the MTF of the lens array in the first embodiment of the present invention, FIG. 12 is a diagram showing the MTF of the lens array in the comparative example, and FIG. 13 is a lens array in the first embodiment of the present invention. FIG. 14 is a diagram showing the light amount of the lens array in the comparative example. 11 and 12, the horizontal axis represents the light emission point position, the vertical axis represents the MTF, and in FIGS. 13 and 14, the horizontal axis represents the light emission point position, and the vertical axis represents the amount of light.

In this case, when the maximum value of the light amount of the imaged image is I _max and the minimum value of the light amount between two adjacent imaged images is I _min , MTF [%]
MTF = ((I _max −I _min ) / (I _max + I _min )) × 100 [%]
Is defined as follows.

In the measurement of MTF and light quantity, the lens array 50 in the embodiment of the present invention and the lens array 50 'in the comparative example are mounted on the LED head of a color LED printer having a resolution of 600 [dpi], and the imaging surface An image formed at a position distant from the imaging surface-lens surface distance L _I [mm] from the external curved surface 53a on the side (photosensitive drum 11 side) is captured by a microscope digital camera, and the image of the LED element is captured from the captured image. Was analyzed, and the MTF and the light amount were measured. The values of the MTF and the light amount of each LED element are expressed as a percentage (percentage) with respect to the maximum value of the MTF and the maximum value of the light amount.

  For MTF, every other 600 LED elements arranged per 1 inch (about 2.5 cm) in the LED heads 23 and 23 ′ are allowed to emit light. Measurement was performed by causing all LED elements of the LED heads 23 and 23 'to emit light, and a range of 20 [mm] among the measurement results was shown.

  In the LED head 23 ′ using the lens array 50 ′ in the comparative example, as shown in FIG. 12, the MTF swing width is about 50%, whereas the embodiment of the present invention is used. In the LED head 23 using the lens array 50 in FIG. 11, the deflection width of the MTF is about 5% as shown in FIG.

  Further, in the LED head 23 ′ using the lens array 50 ′ in the comparative example, as shown in FIG. 14, the light intensity fluctuation width is about 40%, whereas the embodiment of the present invention is used. In the LED head 23 using the lens array 50 in FIG. 13, as shown in FIG. 13, the fluctuation amount of the light amount is about 20%.

  By the way, the LED head 23 can be controlled so that the light amount of each LED element is constant if the fluctuation amount of the light amount is 30% or less.

  In the LED head 23 in the embodiment of the present invention, when the driver IC 42 is controlled so that the light amount of each LED element is constant, the fluctuation amount of the light amount can be reduced to 1% or less. However, the LED head 23 ′ in the comparative example cannot be controlled so that the light amount of each light emitting unit is constant.

  When the image of the printer using the lens array 50 according to the embodiment of the present invention was evaluated for the color LED printer, streaks, stripes, and the like were not seen. On the other hand, in the printer using the lens array 50 'in the comparative example, fringes having a period of 1.6 [mm] corresponding to the arrangement interval P of the microlenses 53' occurred in the image.

  The image evaluation of the printer is performed by forming 600 [dpi] and 1 × 1 images (images in which every other dot among all 600 pixels per [inch]) is formed on a sheet of paper. Degradation was evaluated.

  As described above, in the present embodiment, the lens array 50 can prevent the resolution from being reduced or the amount of light from being reduced at the period of the arrangement interval P of the microlenses 53.

  Further, in the printer 10 according to the embodiment of the present invention, it is possible to form an image according to the image data on the paper without generating streaks, stripes, or the like in the image.

  By the way, in the embodiment of the present invention, the microlenses 53 are arranged on both sides of the light-shielding portion 54, but a compound lens formed by overlapping a plurality of microlenses 53 on both sides of the light-shielding portion 54. Can be arranged.

  Next, a second embodiment of the present invention in which compound lenses are arranged on both sides of the light shielding portion 54 will be described. In addition, about the thing which has the same structure as 1st Embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  FIG. 15 is a plan view of a lens array according to the second embodiment of the present invention, FIG. 16 is a longitudinal sectional view of the lens array according to the second embodiment of the present invention, and FIG. 17 is a second embodiment of the present invention. It is a cross-sectional view of the lens array in the form.

  In this case, the lens array 50 includes four lens plates 51a to 51d and a light shielding portion 54 as a light shielding member in which a plurality of openings 55 are formed, and the lens plates 51a and 51c are arranged so as to overlap each other. 51d and 51b are disposed so as to overlap each other, and the light shielding portion 54 is disposed between the lens plates 51c and 51d.

  In the present embodiment, in the present embodiment, a plurality of microlenses 53 are arranged in a substantially straight line in the direction perpendicular to the optical axis in the center of the lens plates 51a to 51d in the width direction. .

  A compound lens 61 is configured by the microlenses 53 of the lens plates 51a and 51c, and each microlens 53 of the lens plates 51d and 51b, and a lens pair 62 is configured by each compound lens 61.

In this case, when the diameter of each micro lens 53 of the lens plates 51a and 51c is D1, the diameter of each micro lens 53 of the lens plates 51d and 51b is D2, and the arrangement interval of the micro lenses 53 is P, the present embodiment In form,
D1 = D2
If the caliber D1 and D2 are different,
P <D1
P <D2
To be.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as the said 1st, 2nd embodiment, the same code | symbol is provided and the effect of the embodiment is used about the effect of the invention by having the same structure.

  FIG. 18 is a cross-sectional view of an LED head according to the third embodiment of the present invention.

  In this case, reference numeral 70 denotes a reading device that reads a document (not shown) and generates electronic data. The reading device 70 includes an optical lens array 50 that forms an image of a document at a predetermined position, and a received image. A light receiving element 71 for converting an image into an electrical signal, a light receiving element 71 and a control device (not shown) are arranged side by side, connected to a wiring board 72, a light source 73 for irradiating a document with light, and a light beam from the light source 73. An original platen 75 or the like on which a document is placed is formed by a transparent material. Reference numeral 74 denotes a holding member that holds each member of the reading device 70.

  FIG. 19 is a schematic diagram of an optical system according to the third embodiment of the present invention.

As shown in the figure, the distance (object surface-lens surface distance) _Lo between the lens array 50 and the document is the distance between the apex of the external curved surface 53a of the microlens 53 and the plane (object surface) on which the document is placed. The distance between the lens array 50 and the light receiving element 71 (imaging surface-lens surface distance) L _I is the plane (image forming) where the apex of the external curved surface 53a of the microlens 53 and the light receiving element 71 are arranged. the distance between the surface), the lens thickness L _T is the distance between the external curved surface 53a and the distance between the inner curved surface 53b, the lens surface distance L _S is the internal curved surface 53b, the image plane - the object plane distance TC is This is the distance between the document and the light receiving element 71.

  The configurations of the reading device 70 in the embodiment of the present invention and the reading device 70 'in the comparative example are the same as the configurations in Table 1 in the first embodiment.

  Next, the operation of the reading apparatus 70 having the above configuration will be described.

  First, the light beam irradiated by the light source 73 is reflected by the surface of the document placed on the upper surface of the document table 75. Subsequently, the lens array 50 forms a formed image on the surface of the light receiving element 71 by a part of the reflected light from the document, and the light receiving element 71 converts the formed image into an electrical signal. Then, the electrical signal is sent to a control unit (not shown) of the reading device 70, and image data is generated in the image processing unit of the control unit.

  When image data is generated from the same document using the reading device 70 in the embodiment of the present invention and the reading device 70 'in the comparative example, the reading device 70 in the embodiment of the present invention is the same as the document. Image data could be obtained. On the other hand, in the reading device in the comparative example, stripes having a period of 1.6 [mm] equal to the arrangement interval P of the microlenses 53 were generated.

  Note that the operation of the reading device 70 in the embodiment of the present invention and the reading device in the comparative example is as follows: 600 [dpi], 1 × 1 image (every other dot out of all 600 pixels per 1 inch). The original on which the image formed on the medium was formed was used.

  Thus, in the present embodiment, the reading device 70 can eliminate the resolution of the period of the arrangement interval of the microlenses 53 and the decrease in the amount of light, and streaks, stripes, and the like are generated in the formed image data. Can be prevented. Therefore, the image quality can be improved, and the same image data as the original can be obtained.

  In each of the above-described embodiments, examples of applying to a printer and a reading device as an image forming apparatus have been described. However, the present invention can be applied to a copying machine, a facsimile machine, a multifunction machine, and the like.

  The present invention is not limited to the above embodiments, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.

It is a top view of the lens array in the 1st Embodiment of this invention. 1 is a conceptual diagram of a printer according to a first embodiment of the present invention. It is sectional drawing of the LED head in the 1st Embodiment of this invention. It is a longitudinal cross-sectional view of the lens array in the 1st Embodiment of this invention. It is a cross-sectional view of the lens array in the 1st Embodiment of this invention. It is the schematic of the optical system in the 1st Embodiment of this invention. It is a top view of the lens array in the 1st Embodiment of this invention. It is sectional drawing of the lens array in the 1st Embodiment of this invention. It is a top view which shows the comparative example of the lens array in the 1st Embodiment of this invention. It is sectional drawing which shows the comparative example of the lens array in the 1st Embodiment of this invention. It is a figure which shows MTF of the lens array in the 1st Embodiment of this invention. It is a figure which shows MTF of the lens array in a comparative example. It is a figure which shows the light quantity of the lens array in the 1st Embodiment of this invention. It is a figure which shows the light quantity of the lens array in a comparative example. It is a top view of the lens array in the 2nd Embodiment of this invention. It is a longitudinal cross-sectional view of the lens array in the 2nd Embodiment of this invention. It is a cross-sectional view of the lens array in the 2nd Embodiment of this invention. It is sectional drawing of the LED head in the 3rd Embodiment of this invention. It is the schematic of the optical system in the 3rd Embodiment of this invention.

Explanation of symbols

50 Lens array 52, 62 Lens pair 53, 61 Micro lens 54

Claims (12)

(A) arranging a plurality of lens pairs arranged so that the optical axes of the lenses coincide with each other in a direction substantially perpendicular to the optical axis;
(B) Each of the lens pairs is provided with a light blocking member that blocks light from an adjacent lens pair,
(C) When the aperture of each lens is D and the arrangement interval of the lenses is P,
P <D
A lens array. (A) Each of the lens pairs forms an erect life-size image,
(B) The lens array according to claim 1, wherein each lens forms a reduced inverted image.   The lens array according to claim 1, wherein the curved surface of the lens is rotationally symmetric with respect to the optical axis.   The lens array according to claim 1, wherein the curved surface of the lens has a shape that is cut by a plane parallel to the optical axis in the vicinity of a boundary between adjacent lenses.   The lens array according to claim 1, wherein each of the lenses is integrally formed.   The lens array according to claim 1, wherein the lens is formed by resin molding. (A) The light blocking member is made of a material that blocks light, and includes a plurality of openings.
(B) The arrangement interval of the openings is made equal to the arrangement interval of the lenses,
(C) Among the opening widths of the openings, when the opening width in a direction perpendicular to the lens arrangement direction is W _X and the opening width in a direction parallel to the lens arrangement direction is W _Y ,
W _Y <W _X
The lens array according to any one of claims 1 to 6, wherein:   The lens array according to claim 1, wherein the lens is a compound lens system configured by a plurality of lenses. The opening of the light-shielding member is formed with the central axis coinciding with the optical axis, the diameter is equal to the opening width W _X , substantially cylindrical, and parallel to the optical axis with an interval equal to the opening width W _Y. The lens array according to claim 1, wherein the lens array has a shape surrounded by two arranged flat surfaces.   An exposure apparatus comprising the lens array according to claim 1.   An image forming apparatus on which the exposure apparatus according to claim 10 is mounted.   A reading apparatus comprising the lens array according to claim 1.

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