JPWO2010110016A1 - Image forming apparatus and lens array - Google Patents

Abstract

In an image forming apparatus and a lens array that form an image using light beams emitted from a plurality of light emitting points, the light emitted from a plurality of LEDs that are light emitting points in order to ensure a sufficient distance between the lens and the photosensitive member. Since the light beam passes through each lens unit LS corresponding to the light beam and is made into a substantially parallel light beam and is incident on the photosensitive member 201a (or 201b, 201c, 201d), the requirement for the focal position and the focal depth is alleviated, and the lens unit A high-quality image can be formed regardless of the distance from the LS to the photoconductor 201a.

Description

  The present invention relates to an image forming apparatus and a lens array, and more particularly to an image forming apparatus and a lens array that form an image using light beams emitted from a plurality of light emitting points.

  LED printers that form images using LED arrays have been developed. In such an LED printer, an optical element including a microlens is provided for each LED of the LED array in order to guide the light from the LED array to the photoreceptor, and the light collected by the optical element such as these microlenses. LED printer head configured to irradiate the photosensitive drum with light, and the light from each LED is guided to the microlens through the respective waveguides, and the light beam collected by these microlenses is applied to the photosensitive drum. It is comprised so that it may irradiate.

  At this time, the interval between the light emitting points of the LEDs is generally as narrow as several tens of μm. In order to efficiently collect the light emitted from one light emitting point on the photoconductor with the microlens, In this case, the LED, microlens, and photoconductor must be brought close to each other. However, since toner may scatter and adhere to the lens, which may adversely affect the light collecting performance, it is desirable to avoid the lens and the photoconductor as close as possible. For this reason, when the interval is increased, there is a problem that the amount of light collected on the photosensitive member is insufficient and darkened (underexposure).

  Therefore, a rod lens is provided between the LED and the photosensitive member, and without a shortage of NA necessary for condensing, the distance between the lens and the photosensitive member is secured to some extent, and the emitted light from the LED is An LED printer that converts light into convergent light through a rod lens and collects the light on a photosensitive member is known (see, for example, Patent Document 1).

  Further, there is also known one provided with two microlenses instead of using a rod lens (see, for example, Patent Document 2).

JP 2002-107661 A JP 2005-37891 A

  However, in the configuration described in Patent Document 1, since the convergent light is incident on the photoconductor, it is difficult to say that the distance from the rod lens to the photoconductor is still sufficiently long, and the toner adhered to the photoconductor. Is scattered and adheres to the lens, and it is still highly likely that the light collecting performance will be adversely affected.

  In addition, since the depth of focus is shallow, it is necessary to increase the manufacturing accuracy and assembly accuracy of the optical element, resulting in high costs, and the optical path length is likely to change due to thermal expansion / contraction of each component due to temperature change. There is also a problem that defocusing is likely to occur. Further, since the rod lens itself is relatively expensive, there is a problem that the cost increases.

  In addition, when a two-lens lens as described in Patent Document 2 is used, there is a problem that the cost increases due to the large number of lenses. At this time, if a single condenser lens is used to reduce the cost, the distance from the lens to the photosensitive member becomes shorter or the distance becomes darker as described above. There's a problem.

  In addition, since the photoconductor is rotated and used, the spot on the photoconductor deteriorates when the distance between the microlens and the photoconductor changes due to the eccentricity of the rotation of the photoconductor. There is also a problem.

  Furthermore, in many conventional techniques including the example using the rod lens of Patent Document 1, it is necessary to collect light emitted from the light emitting points onto the photosensitive member in a state where the light emitting point interval of the light source is as narrow as several tens of μm. In order to obtain a light amount, an optical system in which optical paths of adjacent light emitting points overlap is often used. That is, when the light emitting points are divided into groups and a condensing lens is used corresponding to each group (the number of light emitting points is larger than the number of lenses), the light paths of the light emitting points overlap each other, so that the light paths are complicated. There was also a problem that stray light countermeasures were difficult.

  In addition, as shown in Patent Document 2, even when a two-lens microlens is provided, the same problem may be caused. Furthermore, a similar problem may occur in an LD printer that uses an LD instead of an LED.

  The present invention has been made in view of such problems of the prior art, and can secure a sufficient distance between the lens and the photoconductor, is inexpensive, and can emit a sufficient amount of light onto the photoconductor. An object of the present invention is to provide an image forming apparatus and a lens array that form an image by using a light beam emitted from a lens.

The image forming apparatus according to claim 1,
An array light source comprising a plurality of light emitting points arranged in an array;
A lens array having a single lens portion that is equal to or more than the number of the light emitting points, and exposing the light beam emitted from the light emitting points onto the photoconductor via the lens portion. In the image forming apparatus to be formed,
The lens part is formed of a material having a uniform refractive index,
The light beam emitted from the light emitting point passes through the lens unit to become a parallel light beam or a substantially parallel light beam, and is incident on the photoconductor.

  As a result of earnest research, the present inventor has come up with the present invention that can solve all the above-mentioned problems. That is, according to the present invention, the light beam emitted from the light emitting point passes through the lens portion to become a parallel light beam or a substantially parallel light beam and enters the photoconductor, so that the distance from the lens unit to the photoconductor is sufficiently long. It is possible to prevent the toner adhering to the photoreceptor from being scattered and adhering to the lens, and it is possible to maintain good light collecting performance for a long time.

  Further, according to the present invention, it is not necessary to increase the manufacturing accuracy and assembly accuracy of the optical element, the cost can be reduced, and even if the optical path length changes due to thermal expansion / contraction of each component due to temperature change, it is parallel. Since the photosensitive member is irradiated with a light beam or a substantially parallel light beam, no defocusing problem occurs. The substantially parallel light beam referred to in the present invention is B / A ≧ 3, where A is the distance from the light emitting point to the first principal point of the lens unit, and B is the distance from the second principal point to the photosensitive member. The state of the emitted light beam that satisfies

  In addition, according to the present invention, since the lens portion can be a single lens having a uniform refractive index, the cost of the lens array itself can be reduced. Furthermore, since it is formed of a material having a uniform refractive index, it can be manufactured by injection molding or the like, and the manufacturing cost can be greatly reduced. Even if the lens unit is a single lens, the distance from the lens to the photosensitive member can be increased, and there is no problem of darkening.

  Furthermore, even if the distance between the microlens and the photoconductor changes due to the eccentricity of the rotation of the photoconductor, there is no problem that the spot on the photoconductor deteriorates.

  In addition, since the number of light emitting points is the same as or smaller than the number of lenses, the optical paths of the light emitting points are difficult to overlap, and the problem of stray light can be reduced.

  The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1, wherein the optical element that changes a divergence degree of a light beam arranged in an optical path between the array light source and the photosensitive member is the optical element. It is characterized by only a lens array.

  According to the present invention, since there is no optical element for changing the divergence other than the lens portion, the structure can be simplified and the degree of freedom of arrangement of each component can be increased. It becomes. However, an optical element that does not change the divergence may be disposed in the optical path between the lens unit and the photosensitive member. For example, a reflective optical element such as a mirror or an optical element that controls transmission and shielding of a light beam may be disposed between the lens unit and the photosensitive member.

  The image forming apparatus according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the number of light emitting points of the array light source is equal to the number of lens portions of the lens array. And

  The image forming apparatus according to claim 4 is the image forming apparatus according to claim 1 or 2, wherein the number of lens portions of the lens array is larger than the number of light emitting points of the array light source. To do.

  An image forming apparatus according to a fifth aspect is the image forming apparatus according to any one of the first to fourth aspects, wherein a stop is formed in the lens portion. With this configuration, there is no need to provide a separate diaphragm, and the number of parts can be reduced. Examples of the “aperture” include a step formed on the optical surface of the lens unit, a portion with increased roughness, a portion having an inflection point, and a light shielding film.

  An image forming apparatus according to a sixth aspect is the image forming apparatus according to any one of the first to fifth aspects, wherein a diaphragm separate from the lens section is provided between the light emitting point and the lens section. It is provided. With this configuration, even if stray light is generated, it is possible to reduce the risk that the adjacent stray light will enter the optical path. As the “diaphragm”, a flat diaphragm, a lens barrel diaphragm, an optical filter, a liquid crystal device, or the like can be used.

  The image forming apparatus according to claim 7 is the image forming apparatus according to any one of claims 1 to 6, wherein a shielding member is formed between the adjacent light emitting points. To do. With this configuration, generation of stray light can be reliably suppressed. Thus, for example, when a light beam emitted from a certain light emitting point is exposed on the photosensitive member, the light beam emitted from the adjacent light emitting point may be overlaid and exposed on at least a part of the exposure range. Disappear.

  The image forming apparatus according to claim 8 is the image forming apparatus according to any one of claims 1 to 7, wherein the light emitting point is an LD (laser diode) or an LED (light emitting diode). And

  The image forming apparatus according to claim 9 is the image forming apparatus according to any one of claims 1 to 8, wherein an optical path length between the light emitting point and the lens unit is between the lens unit and the photoconductor. It is characterized by being shorter than the distance between them. With this configuration, it is possible to more reliably prevent the toner on the photosensitive member from adhering to the lens unit, and it is possible to more reliably prevent stray light from an adjacent light emitting point from entering the lens unit.

The lens array according to claim 10,
An array light source having a plurality of light emitting points arranged in an array, and a lens array having a single lens part that is equal to or more than the number of the light emitting points, and a light beam emitted from the light emitting points, In a lens array of an image forming apparatus that forms an image by exposing on a photoreceptor via the lens unit,
The lens portion of the lens array is formed of a material having a uniform refractive index,
The lens array converts a light beam incident on the lens unit from the light emitting point into a parallel light beam or a substantially parallel light beam and emits the converted light beam.

  With the lens array according to the present invention, the same effect as that of the image forming apparatus of claim 1 can be obtained.

  The lens array according to an eleventh aspect is the lens array according to the tenth aspect, wherein the number of light emitting points of the array light source is equal to the number of lens portions of the lens array.

  A lens array according to a twelfth aspect is characterized in that in the lens array according to the tenth aspect, the number of lens portions of the lens array is larger than the number of light emitting points of the array light source.

  A lens array according to a thirteenth aspect is characterized in that in the lens array according to any one of the tenth to twelfth aspects, a diaphragm is formed in the lens portion.

  Examples of the material of the lens array include glass, thermoplastic resin such as cyclic polyolefin, thermosetting resin, photocurable resin, UV curable resin, and silicon. In the case of silicon, the lens portion may be formed by etching or the like. When a thermoplastic resin such as cyclic polyolefin is used, it can be manufactured by injection molding, so that the manufacturing cost can be greatly reduced.

  In general, when a fine powder is mixed with a transparent resin material, light scattering occurs and the transmittance decreases, so that it has been difficult to use as an optical material. It has been found that by making the wavelength smaller than the wavelength, it is possible to substantially prevent scattering.

  In addition, although the refractive index of the resin material decreases as the temperature increases, the refractive index of the inorganic particles increases as the temperature increases. Therefore, it is possible to make almost no change in the refractive index by using these temperature dependencies so as to cancel each other. Specifically, by dispersing inorganic particles having a maximum length of 30 nanometers or less, preferably 20 nanometers or less, more preferably 10 to 15 nanometers in a plastic material as a base material, temperature dependence is comprehensively achieved. A material with extremely low properties can be provided.

For example, by dispersing fine particles of niobium oxide (Nb ₂ O ₅ ) in an acrylic resin, the refractive index change with respect to the temperature can be reduced, so that the fluctuation of the image point position due to the temperature change is effectively reduced. Can be suppressed.

  According to the present invention, in an image forming apparatus and a lens array that form an image using light beams emitted from a plurality of light emitting points, it is possible to ensure a sufficiently long distance from the lens unit to the photosensitive member. The toner adhering to the photosensitive member can be prevented from being scattered and adhering to the lens, and good condensing performance can be maintained for a long time. In addition, it is not necessary to increase the manufacturing accuracy and assembly accuracy of the optical element, and the cost can be reduced. Furthermore, even if the optical path length changes due to thermal expansion / contraction of each component due to temperature change, parallel light is applied to the photoconductor. Irradiation can prevent defocusing problems from occurring. In addition, the cost of the lens array itself can be reduced. Further, even when the distance between the microlens and the photoconductor changes due to the eccentricity of the rotation of the photoconductor, there is no problem that the spot on the photoconductor deteriorates. In addition, it becomes difficult for the light paths of the respective light emitting points to overlap, and the problem of stray light can be reduced.

1 is a schematic diagram of an image forming apparatus of the present embodiment. It is a perspective view of the light source unit containing the lens array of this Embodiment. It is sectional drawing of a LED array and a lens array. It is a figure which shows the relationship between the LED array concerning a modification, and a lens array. It is a figure which shows the relationship between the LED array concerning a modification, and a lens array.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an image forming apparatus according to the present embodiment. FIG. 2 is a perspective view of a light source unit including the lens array of the present embodiment. FIG. 3 is a cross-sectional view of the LED array and the lens array. In the following description, an LED array is used for explanation, but an LD (laser diode) may be used.

  2 and 3, the LED array LAY which is an array light source is formed by arranging a plurality of LEDs as light emitting points in an array at intervals of several tens of μm. From the viewpoint that the effect of the present invention that the distance between the lens and the LED can be increased without darkening, the interval between the light emitting points is preferably 100 μm or less, and more preferably 50 μm or less. . A lens array (also referred to as a microlens array) MLY is disposed to face the LED array LAY. The microlens array MLY has a single lens portion LS arranged close to each LED in a one-to-one correspondence, and is a single resin injection molding or imprint technique (that is, having an equal refractive index). Can be formed. Here, the LEDs and the lens portions LS are arranged in one row, but may be arranged in a staggered manner. A lens array having a plurality of rows may be used. The LED array LAY and the microlens array MLY are held in the housing BX shown in FIG. 2 to constitute a light source unit OPU.

  Further, as shown in FIG. 3, a light shielding film SM that exhibits the function of a diaphragm is formed around the side surface of the light source of the lens portion LS. The light shielding film SM can be formed by CVD or sputtering, but is not limited thereto. However, instead of the light-shielding film SM, a surface with a deteriorated surface roughness of the mold may be transferred, or a step, an inflection point, etc. may be transferred to form a rough surface, a step, or a surface with a different curvature. Thus, the function of the diaphragm can be exhibited to narrow the luminous flux from the LED. The diaphragm may not be provided in the lens unit, but a diaphragm separate from the lens unit may be provided between each LED and the lens unit LS.

  Further, as shown in FIG. 3, a shielding plate (also called a shielding member) SH is arranged between adjacent LEDs between the LED array LAY and the microlens array MLY, so that the luminous flux generated from the LED is adjacent to the adjacent LED. The lens portion LS is prevented from entering. The shielding plate SH may have a diaphragm.

  The divergent light emitted from each LED of the LED array LAY is incident on each lens part LS of the microlens array MLY, converted into a parallel light beam or a substantially parallel light beam, and emitted. Light emitted from each lens unit LS is irradiated on the photosensitive member 201a (or 201b, 201c, 201d) without passing through an optical element that changes the divergence of the light flux, and an image MG corresponding to each LED is formed on the photosensitive member 201a. Will be formed. (In FIG. 2, the photoconductor is depicted as a flat surface to aid understanding, but in actuality it has a cylindrical shape as in FIG. 1.) According to the present embodiment, a plurality of LEDs that are light emitting points. 2 passes through the corresponding lens portions LS to become a parallel beam or a substantially parallel beam, respectively, and without passing through another optical element that changes the divergence of the beam, the photosensitive member 201a ( Or 201b, 201c, 201d), the requirement for the focal position and the focal depth is alleviated, and a high-quality image can be formed regardless of the distance from the lens unit LS to the photoconductor 201a. Further, since the optical path length between the LED, which is a light emitting point, and the lens unit LS is shorter than the distance between the lens unit LS and the photoconductor 201a, the toner on the photoconductor 201a is more likely to adhere to the lens unit LS. It is possible to reliably prevent the stray light from the adjacent light emitting point from being mixed into the lens unit LS more reliably.

  Next, the image forming apparatus of the present embodiment will be described in detail with reference to FIG. In FIG. 1, four photosensitive members 201a, 201b, 201c, and 201d corresponding to toners of four colors of yellow, magenta, cyan, and black necessary for color image formation are arranged vertically in the main body. Further, the intermediate transfer belt 202 stretched vertically is juxtaposed so as to come into contact with the photoconductors 201a, 201b, 201c, and 201d. On the opposite side of the intermediate transfer belt 202 of each photoconductor 201a, 201b, 201c, 201d, four light source units OPU that expose the surface of each photoconductor 201a, 201b, 201c, 201d to form an electrostatic latent image, and Developers 205a, 205b, 205c, and 205d that visualize electrostatic latent images with toner are stacked in the vertical direction.

  Around each photosensitive member 201a (201b, 201c, 201d), a charger (not shown) for charging the photosensitive member 201, a light source unit OPU, a developing device 205a (205b, 205c, 205d), an intermediate transfer belt 202, An erase lamp (not shown) for neutralizing the surface of the photoreceptor 201a (201b, 201c, 201d) and a photoreceptor cleaner (not shown) for cleaning residual toner are provided. On the outer periphery of the intermediate transfer belt 202, there are an image sensor 211 that detects the positional deviation of the toner images of the respective colors, a toner charger 212 that charges the toner, a transfer device 213 that transfers the toner image on the intermediate transfer belt 202 to the paper, a paper The sheet neutralizer 214 for peeling the toner from the intermediate transfer belt 202 and the intermediate transfer belt cleaner 215 for cleaning the toner on the intermediate transfer belt 202 are provided. Further, a paper cassette 216, a paper feed mechanism 217, and a fixing device 219 are arranged on the paper transport path.

  Next, a printing sequence of the image forming apparatus will be described. When a print command is first sent to a controller (not shown), driving and charging of the intermediate transfer belt 202 and the photosensitive members 201a, 201b, 201c, and 201d are started at a predetermined timing. Subsequently, the photosensitive member 201a that is in contact with the most upstream part is image-exposed by the light source unit OPU, the electrostatic latent image is developed by the developing unit 205a, and the toner image is transferred onto the intermediate transfer belt 202. After a predetermined time, the light source unit OPU also performs image exposure, development, and transfer on the photoreceptor 201b immediately below. The exposure of the photoconductor 201b is started at a timing at which the image formed on the photoconductor 201b accurately overlaps the image previously formed on the photoconductor 201a. In this process, an image in which toner images of two colors are superimposed on the intermediate transfer belt 202 is formed. Similarly, exposure, development, and transfer are performed using the light source unit OPU with the photoconductors 201c and 201d of the third color and the fourth color, and a full color image in which the respective color toner images are superimposed on the intermediate transfer belt 202 is formed. The full color image on the intermediate transfer belt 202 is transferred to a recording medium such as paper by a transfer device 213 and fixed by a fixing device 219.

  The image forming apparatus is a so-called tandem type color printer using four photoconductors corresponding to yellow, magenta, cyan, and black toners. Each color toner image formed by each photoconductor 201 is transferred to an intermediate transfer belt. After being overlaid on 202, the entire apparatus can be miniaturized in order to collectively transfer to a sheet or the like as a final recording medium.

  The example in which the number of light emitting points and the number of lens portions are equal has been described above, but the number of lens portions may be increased compared to the number of light emitting points.

  FIG. 4 is a diagram illustrating a relationship between the LED array and the lens array according to the modification. FIG. 4 shows an example in which the number of light emitting points and the number of lens parts are 1: 2, and in the direction in which the light emitting points are arranged, there are more lens parts than the number of light emitting points.

  With the arrangement as shown in FIG. 4, the same image data can be exposed as a latent image simultaneously on the two photoconductors 201a and 201b by the light emission control of each LED of the single LED array LAY.

  Although not shown, between the LED array LAY and the microlens array MLY, an aperture plate having an aperture is arranged for every other lens, and the aperture is only in the lens that is exposed to the photoconductor 201a. , The LED array LAY is controlled so that the image data is exposed to the photoconductor 201a, the aperture is moved only to the lens portion that exposes the aperture plate to the photoconductor 201b, and the image data is exposed to the photoconductor 201b. If the control of the LED array LAY is repeated so that the following results are obtained, different image data can be alternately exposed as latent images on different photoconductors.

  In addition, although not shown, an element (for example, PLZT for each lens unit) that can control transmission and shielding is arranged for each lens unit between the LED array LAY and the microlens array MLY. May be controlled. In this way, different image data can be exposed as a latent image on different photoconductors. In this case, the LED array is always in a light-emitting state, and an element capable of individually controlling transmission and shielding for each lens unit serves as a shutter.

  By doing in this way, it can be used also as a light source unit, and by this, reduction of a number of parts and compactization of a structure can be achieved. Furthermore, since a parallel light beam or substantially parallel light is emitted from the lens unit LS, the distance from one lens unit LS to the photoconductor 201a and the distance from the other lens unit LS to the photoconductor 201b can be arbitrarily changed. Thereby, the freedom degree of design, such as a layout, can be expanded.

  FIG. 5 is a diagram illustrating a relationship between the LED array LAY and the microlens array MLY according to the modification.

  FIG. 5 also shows an example in which the number of light emitting points and the number of lens portions are 1: 2, and is an example in which two lens portions are arranged in a direction different from the direction in which the light emitting points are arranged with respect to one light emitting point. .

  Even in such an arrangement, the same image data can be simultaneously exposed as a latent image on the two photoconductors 201a and 201b by the light emission control of each LED of the single LED array LAY.

  Similarly, a lens (not shown) between the LED array LAY and the microlens array MLY is provided with an aperture plate having an aperture on the lens unit side corresponding to one of the photoconductors to expose the photoconductor 201a. The LED array LAY is controlled so that the image data to be exposed to the photosensitive member 201a is associated with the opening portion, and the opening portion is moved to the lens portion side that exposes the opening plate to the photosensitive member 201b. If the control of the LED array LAY is repeated so as to obtain image data to be exposed, different image data can be alternately exposed as latent images on different photoconductors.

  Similarly, although not shown between the LED array LAY and the microlens array MLY, the lens unit side corresponding to the photoconductor 201a and the lens unit side corresponding to the photoconductor 201b are independently transmitted and shielded. Elements that can be controlled (for example, PLZT for each lens unit) may be arranged. In this case, the LED array LAY is controlled so that image data to be exposed on the photoconductor 201a is set with the lens unit side corresponding to the photoconductor 201a being in a transmissive state, and then the lens unit side corresponding to the photoconductor 201b is set in a transmissive state. By repeatedly controlling the LED array LAY so as to be image data to be exposed to the photoconductor 201b, different image data can be exposed as a latent image on different photoconductors.

  Even in this case, the light source unit can also be used, thereby reducing the number of parts and making the configuration compact. Furthermore, since a parallel light beam or substantially parallel light is emitted from the lens unit LS, the distance from one lens unit LS to the photoconductor 201a and the distance from the other lens unit LS to the photoconductor 201b can be arbitrarily changed. Thereby, the freedom degree of design, such as a layout, can be expanded.

  The configuration shown in FIG. 5 is more flexible than the configuration shown in FIG. 4 and the amount of exposure to the photosensitive member can be increased compared to the configuration shown in FIG. 4 when the amount of emitted light is the same. .

  In FIGS. 4 and 5, the example in which image data is exposed on two photoconductors using one LED array has been described. However, the present invention is not limited to this, and one LED array is formed by a similar method. Of course, it is also possible to expose image data on three or more photoconductors.

  According to the present invention, it is possible to provide an image forming apparatus and a lens array that form an image using light beams emitted from a plurality of light emitting points, but an LD may be used instead of an LED.

201a to 201d Photoconductor 202 Intermediate transfer belt 205a Developing device 211 Image sensor 212 Toner charger 213 Transfer device 214 Paper neutralizer 215 Intermediate transfer belt cleaner 216 Paper cassette 217 Paper feed mechanism 219 Fixing device BX Housing LAY LED array LED Light emitting diode LS lens part MG image MLY lens array (micro lens array)
OPU Light source unit SH Shield plate SM Shield film

Claims (13)

An array light source comprising a plurality of light emitting points arranged in an array;
A lens array having a single lens portion that is equal to or more than the number of the light emitting points, and exposing the light beam emitted from the light emitting points onto the photoconductor via the lens portion. In the image forming apparatus to be formed,
The lens part is formed of a material having a uniform refractive index,
The light beam emitted from the light emitting point passes through the lens unit to become a parallel light beam or a substantially parallel light beam, and enters the photoconductor.   The image forming apparatus according to claim 1, wherein an optical element that changes a divergence of a light beam disposed in an optical path between the array light source and the photosensitive member is only the lens array.   The image forming apparatus according to claim 1, wherein the number of light emitting points of the array light source is equal to the number of lens portions of the lens array.   The image forming apparatus according to claim 1, wherein the number of lens portions of the lens array is greater than the number of light emitting points of the array light source.   The image forming apparatus according to claim 1, wherein a diaphragm is formed in the lens unit.   The image forming apparatus according to any one of claims 1 to 5, wherein a diaphragm separate from the lens unit is provided between the light emitting point and the lens unit. .   The image forming apparatus according to claim 1, wherein a shielding member is formed between the adjacent light emitting points.   The image forming apparatus according to claim 1, wherein the light emitting point is an LD or an LED.   9. The optical path length between the light emitting point and the lens unit is shorter than a distance between the lens unit and the photoconductor, according to claim 1. Image forming apparatus. An array light source having a plurality of light emitting points arranged in an array, and a lens array having a single lens part that is equal to or more than the number of the light emitting points, and a light beam emitted from the light emitting points, In a lens array of an image forming apparatus that forms an image by exposing on a photoreceptor via the lens unit,
The lens portion of the lens array is formed of a material having a uniform refractive index,
The lens array is characterized in that a light beam incident on the lens unit from the light emitting point is converted into a parallel light beam or a substantially parallel light beam and emitted.   11. The lens array according to claim 10, wherein the number of light emitting points of the array light source is equal to the number of lens portions of the lens array.   The lens array according to claim 10, wherein the number of lens portions of the lens array is greater than the number of light emitting points of the array light source.   The lens array according to any one of claims 10 to 12, wherein a diaphragm is formed in the lens portion.