JP4091212B2 - Optical writing device - Google Patents

Description

【００５０】
この画像評価結果において、高解像度の発光ダイオードアレイを使用した場合の評価結果が不良であるのは、発光ダイオードアレイにおいては一般的に製造プロセスのわずかなムラにより発光ダイオードアレイの各発光領域の間で発光量にむらが生じるので電流補正により発光光量を補正するが、高解像度の発光ダイオードアレイでは発光領域が極めて小さくなっていることにより一つの画素の発光光量が小さく、相対的に製造プロセスのムラによる光量変動が大きく充分に補正できないためと考えられる。これに対して、本発明の光書込み素子を使用した画像出力装置では安定した特性を持つ低い解像度の発光ダイオードアレイを使用できるため、ムラの少ない画像が得られ、高解像度の発光ダイオードアレイを使用した場合と同じ細かさでハーフトーンスクリーンが生成されるので良好な画像が得られた。
【００５１】
［実験例２］
ポリゴンスキャナを光源とした請求の範囲4に示す構成の光書込み装置を作成しこれをＹＭＣＫ各色の書込みに用いたカラー画像出力装置を製作した。光書込み素子は次のような手順で作成した。
【００５２】
先ず、等倍結像素子はマイクロオプト株式会社製のＳＬＡ１２Ｄを用いることとし、両面を平坦に研磨して厚さをＳＬＡ１２Ｄの作動距離と等しい４ｍｍとした幅１０ｍｍのガラス板を用意した。実施例１と同様の方法で作成したホログラムアレイ基板をこのガラス板のＳＬＡと反対の面に紫外線硬化樹脂により接着した。更に実験例１と同様にしてマイクロレンズアレイ基板とミラーアレイ基板を作成しホログラムアレイ基板上に重ねて接着し、書込み装置の主要なユニットを作成した。これを実験例１と同様の複写機に組み込みポリゴンスキャナによる走査光をミラーアレイ部に当てて濃度の連続的に変化したテストバターンを出力した。ポリゴンスキャナは６００ｄｐｉの解像度に適合した安価なものを使用したが、この書込み装置では一つの画素について３×３のパターンが生成されるのでハーフトーンの再生については１８００ｄｐｉの光書込み装置に相当する。
【００５３】
［比較例２］
実験例１で使用した複写機に２４００ｄｐｉの分解能のポリゴンスキャナを搭載して同じテストパターンの出力を行なった。
【００５４】
これらの出力画像を比較評価した。評価は機器の製造コストと装置の容積を比較評価した。結果を下記の表２に示す。再現されたハーフトーン画像は視覚により評価したところ同等であった。
【００５５】
【表２】

【００５６】
本発明の光書込み素子を使用した画像出力装置では安定した安価なポリゴンスキャナの使用が可能になるので低コストであると共に、ポリゴンスキャナの偏向角度が大きく取れるので機器を小型にすることができる。
【００５７】
なお、本発明は上記実施例に限定されるものではなく、特許請求の範囲内に記載であれば多種の変形や置換可能であることは言うまでもない。
【００５８】
【発明の効果】
以上説明したように、本発明によれば、画像を多数の微小な画素に分割し、一つもしくは複数の光源から各画素の濃度に対応した強度の光束を射出し、この光束による輝点を、閾値以上の光量密度の光が照射されることにより、感光して表面電位変化や化学的変化等の潜像が形成される、又は感光して濃度変化を持つ画像が形成される画像記録媒体の上に走査して、各画素領域を順次感光させることにより画像を書込む光書込み装置において、光源と画像記録媒体との間であって光源側から順に、光束を集束させる光集束素子部と、光束が集束する位置に設けられた微小な光学的開口部と、該光学的開口部より射出した光束をおおむね平行な光束とするコリメータ部と、光束を複数の方向へ分解して放射すると共に複数の光束をおおむね同一の平面上に集束させるホログラム素子と、を配列された一つのユニットを、主走査方向に画素数と同数のアレイ状に配置したことに特徴がある。よって、画素を書き込む光ビームを画像記録媒体の表面に到達する前段階において光学的手段により多数の微小な光ビームに分割する機能と、微小な光ビームにより露光される画像記録媒体上の感光領域を総合した面積、すなわち生成された画像においては画素の平均濃度、を元の光ビームの強度を変化することにより増減する機能とにより、なめらかなハーフトーンを生成することができ、1つの画素を書き込む光スポットをより細かな輝点の集合体に分割すると共に、分割した輝点により感光する画像記録媒体上の総合の面積を書込み光の強度により変化させる働きをもった複合微少光学素子アレイを画像記録媒体の近傍に配置した新たな構造の光書込み装置を提供できる。
【００５９】
また、ホログラム素子と対向する前記画像記録媒体の前面に透明材料からなる保護板を設けたことにより、ホログラム素子が微粒子等で汚染されることを防ぐことができる。
【００６０】
更に、ホログラム素子により複数の方向に分解され、それぞれ集束された光束により画像記録媒体上に形成される輝点群が、一画素領域の概ね中心に位置する相対的に大きな直径の輝点と、その周りに一つもしくは複数の輪帯状に位置する相対的に小さな輝点とからなるように、ホログラム素子を形成したことにより、ホログラム素子により分割される輝点のパターンについて優れた画像を再現できる。
【００６１】
また、光源が、複数の波長の光を放射することのできる素子もしくは異なる波長を射出する複数の素子からの射出光をビームコンバイナ等により統合した光源であることにより、画像記録媒体上に生成される輝点のパターンを光源の射出光の波長を変えることにより変化させることができる。
【００６２】
更に、光集束素子部の入射側の開口部、射出側の光学的開口部又は両方の開口部にマイクロレンズを設けることにより、光源光の利用効率が高まりより高速の画像出力が可能になる。
【００６４】
更に、別の発明として、レーザ光を平行光束としたのち回転するポリゴンミラーにより偏向して画像記録媒体上を走査するポリゴンスキャナを用いた光源と画像記録媒体との間であって光源側から順に、基板上に形成された、ポリゴンミラーによりレーザ光が走査される方向に配列され、レーザ光の入射部と対向する位置に射出部を有し、レーザ光の入射部が射出部よりも大きな面積を持つ概ね円錐形状もしくは角錐形状のミラーアレイを用い、光束を集束させる光集束素子部と、ミラーアレイの射出部に設けられた、光学的に透明な微小な開口部が配列されたピンホールアレイからなる光学的開口部と、ピンホールアレイに相対して設けられた凸レンズが配列されたマイクロレンズアレイを用い、光学的開口部より射出した光束をおおむね平行な光束とするコリメータ部と、マイクロレンズアレイに相対させてホログラム素子をアレイ状に配置して、光束を複数の方向へ分解して放射すると共に複数の光束をおおむね同一の平面上に集束させるホログラム素子とを設けたことに特徴がある。よって、光源の一つであるポリゴンスキャナに対して適用できる。
【図面の簡単な説明】
【図１】本発明の第１の実施例に係る光書込み装置の基本的な構造を示す断面図である。
【図２】複数の輝点を作成する部分の詳細を示す図である。
【図３】本発明の第２の実施例に係る光書込み装置の基本的な構造を示す断面図である。
【図４】本発明の光書込み装置により光強度が大きい場合の複数のスポットが形成される状況を示す図である。
【図５】本発明の光書込み装置により光強度が小さい場合の単独のスポットが形成される状況を示す図である。
【図６】発光ダイオードアレイ光源に対応した構造の一例を示す図である。
【図７】ポリゴンスキャナに対応した構造の一例を示す図である。
【符号の説明】
１１，２１ 光集束素子部
１２，２２ 書込み光ビーム
１３ 開口部
１４ 光拡散素子部
１５ 開口部群
１６ 等倍結像素子
１７，２６，３６ 画像記録媒体
２３ 光学的開口部
２４ コリメータ部
２５ ホログラム素子
３１ 発光ダイオードアレイ
３２ ミラーアレイ
３３ ピンホールアレイ
３４ マイクロレンズアレイ
３５ ホログラムアレイ
４１ ポリゴンスキャナ
４２ 集光素子アレイ部
４３ コリメータ素子アレイ部
４４ ホログラムアレイ部
４５ 感光体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical writing device, and more particularly, an image is obtained by scanning a bright spot by a light beam whose intensity is modulated by decomposing an image into a number of minute pixels on an image recording medium and the like, and sequentially exposing each pixel area. It relates to a writing device.
[0002]
[Prior art]
Conventionally, when a halftone image is reproduced in an image output apparatus that reproduces an image by scanning a luminescent spot on a photoconductor, such as an electrophotographic printer, a set of finer spots for pixels constituting the image It reproduces as a body and creates changes in density by increasing or decreasing the number of spots. As such examples, there are those described in JP-A-6-133156, JP-A-8-506704, and the like. In these conventional methods, in order to reproduce a smooth halftone, it is necessary to divide the image much finer than the resolution required to reproduce the finest line drawing contained in the image. As an example, when the pixel density necessary for reproducing the line drawing information of the image is 600 dpi (number of dots per inch), the intermediate density area portion in the image, so-called halftone area, In order to realize a gradation property in which a density change of 65 levels is given to one pixel, which is one standard as a smooth gradation, it is necessary to divide one pixel into an 8 × 8 matrix. The writing resolution required for this is 600 × 8 = 4800 dpi. Optical writing with this resolution is not impossible even at present.
[0003]
[Problems to be solved by the invention]
However, such a device capable of high resolution is an optical writing device having the highest level of accuracy (state-of-the-art) at present, and is manufactured and used in the development departments and research institutions of manufacturers. However, there are the following various problems in mass production as industrial products and general use.
[0004]
First, since it is necessary to divide the image into extremely fine regions, the time required for image processing calculation is greatly increased. In order to shorten this time, it is necessary to incorporate an electronic computer equipped with a faster processor, which increases the cost of the apparatus. Moreover, at present, a small computer that can be built into an image output device has a limited processing capability, and it is difficult to perform 4800 dpi pixel division within 600 dpi even if a high-speed model is built in. is there.
[0005]
As a second point, since writing with a resolution of 4800 dpi, that is, the width of one pixel is approximately 5 μm, it is necessary to focus the writing light spot to a size of 5 μm or less in the entire writing region. In order to realize such a spot size in a polygon scanner, it is necessary to use an optical system composed of a glass lens with very little birefringence. Polygon scanners using plastic lenses that are currently used mainly in general applications cannot be reduced sufficiently even if the plastic lens birefringence is optimized. Can not. Since an optical system using a glass lens is very expensive compared to a plastic optical system, the cost of the writing device increases.
[0006]
Thirdly, in the case of a polygon scanner, the spot is likely to collapse at the end of the scanning width, so that the deflection angle by the polygon mirror can be made too large in order to make the spot size 5 μm or less at the end of the image. The limit is approximately 50 degrees. On the other hand, a polarization angle of about 100 degrees can be easily realized with a writing resolution of 600 dpi. Due to the small deflection angle, the optical path length becomes very long when writing images of the same size as compared with a low-resolution writing device. Therefore, the image output device becomes large.
[0007]
As a fourth point, in the case of a polygon scanner, the light path is liable to be displaced due to the mechanical distortion of the optical system due to the long optical path, and the variation of the spot position on the photoconductor is relative to the spot size. Must be small enough. In order to keep the distortion of the optical system casing small enough to be negligible with respect to 5 μm, it is necessary to greatly increase the rigidity of the apparatus. As described above, the point that the optical path length becomes longer is added, and the apparatus becomes larger and heavier.
[0008]
As a fifth point, in the case of a print head using an LED array as a light source, the number of LEDs is extremely increased and the cost of the element is increased.
[0009]
As a sixth point, in the case of a four-drum color writing method that is normally used in a high-speed color image output apparatus, the image position shift between the four drums must be made small enough to be ignored with respect to the spot size. With 4800 dpi, only a positional deviation of about 1 μm is allowed, so it is necessary to extremely increase the medium conveyance accuracy. From this point as well, the apparatus becomes larger and heavier and more expensive.
[0010]
As a seventh point, in the case of a four-drum device, since four optical writing devices are used, it is a further serious problem that individual optical writing devices cannot be reduced in size.
In this way, a smooth halftone image can be obtained by dividing a currently used image into sufficiently fine pixels at the electronic information stage and writing the halftone matrix on an image recording medium or the like with a high-definition optical writing device. Depending on the method of creation, it is possible to create an image output device that reproduces smooth halftones without visual problems, but it becomes a large and expensive device, but it is widely used as an industrial product. It is difficult to make it.
[0011]
In addition, since the spot size becomes small, the scanning speed of the light beam has a mechanical limit, the sub-scanning speed decreases by increasing the number of scanning lines, and the image frequency for modulating the light beam is limited. For example, the number of pixels to be written becomes enormous, and therefore, there is a problem that the writing time is greatly increased even when a simple line drawing having no halftone area and no high resolution is output.
[0012]
The present invention is intended to solve these problems, and in an image output apparatus using optical writing, it is possible to generate a halftone image more beautiful than the conventional one at a low cost, and at the same time, only a line drawing having no halftone. An object of the present invention is to provide an optical writing apparatus capable of high-speed output for the above image.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, the present invention divides an image into a large number of minute pixels, emits a luminous flux having an intensity corresponding to the density of each pixel from one or a plurality of light sources, and obtains a bright spot by this luminous flux. An image recording medium on which a latent image such as a surface potential change or a chemical change is formed by irradiation with light having a light density greater than or equal to a threshold, or an image having a density change is formed by exposure. An optical writing device for writing an image by sequentially exposing each pixel area to light, and a light focusing element unit for focusing a light beam in order from the light source side between the light source and the image recording medium; A minute optical opening provided at a position where the light beam is converged, a collimator unit that makes the light beam emitted from the optical opening part a substantially parallel light beam, and radiates the light beam by decomposing it in a plurality of directions. Multiple light beams are generally the same A hologram element for focusing on a plane, one of the units arranged to, is characterized in that arranged in the pixel as many array in the main scanning direction. Therefore, a function of dividing a light beam for writing pixels into a large number of minute light beams by optical means before reaching the surface of the image recording medium, and a photosensitive area on the image recording medium exposed by the minute light beam A smooth halftone can be generated by the function of increasing or decreasing the total area of the pixel, that is, the average density of the pixel in the generated image, by changing the intensity of the original light beam. A composite micro-optical element array that divides the light spot to be written into a collection of finer luminescent spots and changes the total area on the image recording medium that is exposed by the divided luminescent spots depending on the intensity of the writing light. An optical writing device having a new structure arranged in the vicinity of the image recording medium can be provided.
[0014]
Further, by providing a protective plate made of a transparent material on the front surface of the image recording medium facing the hologram element, the hologram element can be prevented from being contaminated with fine particles.
[0015]
Furthermore, a bright spot group which is decomposed in a plurality of directions by the hologram element and formed on the image recording medium by each of the converged light beams is a bright spot having a relatively large diameter, which is positioned at the approximate center of one pixel region, By forming the hologram element so as to be composed of relatively small bright spots located around one or more annular zones, an excellent image can be reproduced for the pattern of bright spots divided by the hologram element. .
[0016]
In addition, the light source is generated on an image recording medium by being a light source in which light emitted from an element capable of emitting light of a plurality of wavelengths or a plurality of elements emitting different wavelengths is integrated by a beam combiner or the like. The bright spot pattern can be changed by changing the wavelength of the light emitted from the light source.
[0017]
Furthermore, by providing microlenses in the entrance-side opening, the exit-side optical opening, or both of the openings of the light focusing element section, the utilization efficiency of the light source light is increased and higher-speed image output is possible.
[0019]
Furthermore, as another invention, the laser beam is converted into a parallel light beam, deflected by a rotating polygon mirror, and scanned on the image recording medium between the light source using the polygon scanner and the image recording medium in order from the light source side. The laser beam is arranged on the substrate in the direction in which the laser beam is scanned by the polygon mirror, and has an emission part at a position facing the laser beam incident part, and the laser beam incident part has a larger area than the emission part. A pinhole array in which a light converging element part for converging a light beam and an optically transparent minute opening are arranged in a substantially conical or pyramidal mirror array having And a microlens array in which convex lenses provided opposite to the pinhole array are arranged, and the light beam emitted from the optical opening is roughly A collimator section for forming a luminous flux and a hologram element arranged in an array so as to be opposed to the microlens array, the luminous flux is decomposed and emitted in a plurality of directions, and the plurality of luminous fluxes are generally focused on the same plane. It is characterized in that a hologram element is provided. Therefore, it can be applied to a polygon scanner which is one of the light sources.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
In order from the light source side between the light source and the image recording medium, a light converging element part for converging the light beam, a minute optical opening provided at a position where the light beam converges, and an emission from the optical opening part A unit in which a collimator unit that converts the luminous flux into a substantially parallel luminous flux, and a hologram element that decomposes and emits the luminous flux in a plurality of directions and focuses the luminous flux on the same plane, They are arranged in the same number of pixels as the number of pixels in the main scanning direction.
[0021]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing the basic structure of an optical writing apparatus according to the first embodiment of the present invention. In the figure, a writing light beam 12 is condensed on a first minute opening 13 by a light focusing element unit 11 such as a conical mirror to generate one minute light spot. The light emitted from the opening 13 is incident on the light diffusing element 14 and diffused into a limited volume corresponding to one pixel. A plurality of minute light spots are generated from a single light beam for writing one pixel by emitting the diffused light from the second minute aperture group 15 composed of a plurality of minute openings. That is, the light diffusing element portion 14 has a function of making the light density of the divided light beams uniform. Therefore, if the second opening group 15 is formed of openings having various diameters, it is possible to emit light having an intensity corresponding to the diameter. The generated light spots are imaged on the image recording medium 17 by the equal-magnification imaging element unit 16. The image recording medium 17 includes a rewritable recording medium, a recording medium that cannot be rewritten once recorded, a medium such as an image display on which images are continuously written, and the like. It refers to almost all media. Specific examples are images of liquid crystal material layers, organic and inorganic crystal material layers, organic and inorganic amorphous material layers, and the like caused by phase changes or reversible chemical changes caused by exposure to visible light, ultraviolet light, or infrared light. If necessary, the image can be erased by irradiating light of a specific wavelength and intensity, applying a magnetic field of a specific intensity and direction, applying a specific temperature change, etc. It is a so-called photoreceptor such as an image recording medium that can be used repeatedly, an electrophotographic photoreceptor, a black-and-white and color film or a photosensitive paper by silver salt photography, or a recording medium using a photosensitive material by other photochemical reaction. In addition to this, for example, a photoconductive material layer is arranged between the liquid crystal material layer and the drive electrode, and the photoconductive material at the site is irradiated by the write light irradiation to the photoconductive material layer. A display that immediately forms an image with a density change in the middle of the photoconductive effect, such as a liquid crystal display that writes the image by applying an electric field to the liquid crystal layer with the material in a conductive state. Including bowls.
[0022]
FIG. 2 shows details of a portion for creating a plurality of bright spots. The arrangement pattern of the second minute opening group 15 in the figure is shown as an example, and various arrangements can be applied. In this apparatus, the total area of the area to which the image recording medium is exposed can be increased or decreased by changing the light source light quantity. At an intermediate amount of light, the average image density in the pixel can be continuously changed, and smooth gradation can be obtained.
[0023]
The optical writing apparatus according to the first embodiment shown in FIG. 1 is equivalent to about 8 times the resolution, that is, about 4800 dpi by using a normal resolution LED array of about 600 dpi, a polygon mirror scanner, and the like. It is possible to write a halftone matrix to an image recording medium, and to reproduce an image with a smooth gradation that could not be realized until then, using a scanning mechanism with a normal resolution that operates inexpensively and stably. I was able to. However, as can be seen from FIG. 1, between the minute optical elements of adjacent pixels, optically opaque is avoided in order to avoid the influence of the light flux at the adjacent position during optical scanning on the exposure amount of other pixels. A partition is required. For this reason, the second opening is not provided near the boundary between the individual elements of the array, and an exposure spot cannot be formed at a position on the image recording medium corresponding to this portion. Therefore, there is a limit to the uniformity when trying to form a screen matrix having a uniform density distribution. In addition, in order to guide light uniformly to each of the second openings, a light diffusing element for diffusing the light is necessary, so there is a slight light loss at this portion, and the light amount of the light source needs to be increased accordingly. It was. In order to increase the writing speed and to enable the application of a light source with a lower output that is less expensive, it is desirable to realize a device that further reduces the loss of light.
[0024]
Therefore, the second embodiment of the present invention is an embodiment for realizing an optical writing apparatus that solves the problems of the first embodiment.
[0025]
FIG. 3 is a sectional view showing the basic structure of an optical writing apparatus according to the second embodiment of the present invention. In the figure, a writing light beam 22 is condensed on a minute optical opening 23 by a light focusing element portion 21 constituted by a conical mirror or the like to generate a minute light spot. The light beam emitted from the opening 23 is made incident on the collimator unit 24 arranged as necessary. A hologram element having a function of collimating the light emitted from the opening 23 by the collimator unit 24, separating the light beam into a plurality of directions and emitting the light beam, and condensing each light beam on substantially the same plane 25 is incident. The photosensitive surface of the image recording medium 26 is placed on a plane on which the light beam groups emitted from the hologram element 25 are focused.
[0026]
The collimator unit 24 is configured by a convex lens array that makes divergent light from the minute opening 23 substantially parallel. Further, the function of the collimator may be included in the function of the hologram element. Further, the hologram element 25 is formed on both surfaces of the substrate, and the surface close to the light source has a function of a convex lens as a collimator, and the function of separating the light beam into a plurality of light beams on the other surface and the respective light beams are almost on the same plane. You may give the function to condense. In such a structure, it is not necessary to provide a convex lens or the like as the collimator element portion, but the manufacture of the hologram element becomes complicated, so that an optimum structure is selected in each case. Further, the minute optical opening 23 may be actually formed with an opening or a pinhole on a light shielding mask formed on a transparent substrate. The hologram element 25 can be most easily a grating-like element in which parallel linear patterns made of a transparent material having a predetermined thickness and refractive index are repeatedly arranged on a transparent substrate. The linear pattern repeat interval, the refractive index of the transparent material, and the height from the substrate surface are set according to the deflection angle and the wavelength of the light source. In this case, the incident light beam is decomposed into three light beams of zero-order light and positive and negative primary light that are transmitted without being diffracted. If a lattice-like pattern is formed by arranging linear patterns orthogonally, it is decomposed into a total of five luminous fluxes of zero-order light and positive and negative primary light decomposed in two orthogonal directions. In order to focus these light beams on the image recording medium, the pitch of the diffraction pattern and the like are smoothly changed from the center to the outer periphery of the hologram element. In order to form an arbitrary arrangement pattern in the form of an image recording medium, a necessary diffraction pattern is calculated from an intensity pattern on the hologram element of each light beam by an electronic computer, and the hologram element is provided on the surface. Use a hologram element created by determining the refractive index distribution if the pattern is formed by a diffraction grating made of a transparent material, or if the hologram element is formed by a refractive index distribution provided in the substrate. . As a calculation procedure by an electronic computer, a bright spot array generated for a simple pattern is obtained based on the optical principle, and various patterns with slight changes in pattern interval, pattern shape, etc. are assumed from this. A procedure can be used in which the generated bright spots are calculated and repeated until the desired bright spot arrangement is achieved.
[0027]
In the optical writing apparatus of the second embodiment having such a configuration, there is no need for a portion that blocks light such as a partition between adjacent pixels, so that no region where a bright spot is not provided on the image recording medium does not occur. Therefore, it is possible to reproduce a halftone region having a more uniform density distribution as compared with the first embodiment. Further, since no light diffusing element is used, the incident light source light can be used effectively and the amount of light irradiated onto the image recording medium can be increased. Therefore, the optical writing apparatus of the first embodiment is improved, and an advantage that an image can be output at a higher speed than before can be obtained by an inexpensive apparatus. Further, since the optical writing apparatus of the second embodiment basically does not require the same magnification imaging element, there is an advantage that it is possible to provide an image output apparatus having a lower cost.
[0028]
Next, the halftone generation function of the optical writing device of the present invention will be described in detail. In the apparatus of the present invention, the pattern generated by the intensity of the writing light beam is changed according to the image density by devising the pattern of the bright spot group formed on the image recording medium with the light beam decomposed by the hologram element. be able to. For the sake of simplicity, a case will be described where a hologram element is used in which four bright spots having a relatively small diameter are generated around one relatively large bright spot.
[0029]
The shape of the light spot irradiated onto the image recording medium by this optical writing device is as shown in the characteristic diagram of FIG. 4A when the intensity of the writing light beam is sufficiently large. In this characteristic diagram, the horizontal axis indicates the position on the straight line where the light spots are arranged with the position of the 0th-order light as the center, and the vertical axis indicates the light intensity on an arbitrary scale. If the image generation process is set so that a region irradiated with light with a light density equal to or higher than the light density indicated by the horizontal line in the characteristic diagram is exposed, the output pixel pattern is as shown in FIG. Thus, it is possible to generate a screen pattern as generated by a screen matrix by image processing from a light beam for writing one pixel.
[0030]
Next, a state when the light intensity of the writing light beam is reduced will be described. The shape of the light spot irradiated onto the image recording medium by this optical writing device is as shown in the characteristic diagram of FIG. 5A when the intensity of the writing light beam is small. In this characteristic diagram, the horizontal axis indicates the position on the straight line where the light spots are arranged with the position of the 0th-order light as the center, and the vertical axis indicates the light intensity on an arbitrary scale. If the image generation process is set so that a region irradiated with light with a light density equal to or higher than the light density indicated by the horizontal line in the characteristic diagram is exposed, the output pixel pattern is as shown in FIG. Thus, one minute dot pattern is generated from the light beam for writing one pixel.
[0031]
In the state in which the two intermediate light quantities are irradiated, the diameter of the light spot that surrounds the light gradually changes, and the average density of the pixel region continuously changes. Therefore, a smooth halftone portion is formed.
[0032]
In the above description, for the sake of simplicity, the case of a simple pattern of bright spot arrangement has been shown. However, when an optical writing light source of 600 dpi, which is a normal resolution, is used, the interval is about 42.3 μm. It is not difficult to set the diameter of the condensed bright spot to a diameter of about 2 μm when a light source having a wavelength of about 670 nm is used. Therefore, since many minute bright spots can be individually irradiated in one pixel area on one image recording medium, a fine screen pattern that cannot be visually recognized can be generated. It is recognized as a smooth halftone. At this time, unlike when the screen pattern is actually written on the image recording medium by an optical writing device with high resolution, it is not possible to write a line image with the maximum resolution that can be separated by separate small spots. This is because in the optical writing device of the present invention, the pixels of the optical writing device having a normal level of resolution are decomposed into small writing spots. However, in practice, most line drawing images that are routinely used can be reproduced with a resolution of about 600 dpi, which is a normal resolution. In other words, even if a line drawing is drawn with a resolution higher than this, it cannot be recognized as a separated line or point unless it is carefully taken with the naked eye, and it is meaningless except for a very special purpose. However, the reason why an optical writing device of 600 dpi or more is required is that the density gradation of the image needs to be written with a screen pattern that cannot be visually recognized. For this reason, the conventional optical writing apparatus is required to have a very high-precision manufacturing technique and is high in cost. Even so, it cannot be said that it is sufficient for smooth halftone reproduction. In contrast, the optical writing apparatus of the present invention can generate a screen pattern fine enough to be visually undetectable while using an optical writing light source with a normal resolution. Based on a normal resolution optical writing light source that can be manufactured at a low cost, it is possible to reproduce a smooth halftone that could not be generated conventionally.
[0033]
Further, in the optical writing device of the present invention, since the hologram element is disposed in the vicinity of the image recording medium, it is not so clean that a large number of fine particles such as toner float as in the case where the image recording medium is an electrophotographic photosensitive member. In the environment, fine particles may adhere to the hologram element, reducing its diffraction efficiency or generating scattered light, which may adversely affect the written image. In order to prevent such an adverse effect, a transparent protective plate for isolating the space is provided in front of the image recording medium, and the hologram element is formed on the surface of the protective plate facing the image recording medium. According to such a structure, the surface on the image recording medium side of the protective plate can be made smooth, so that fine particles do not adhere easily, and even if it adheres, it can be wiped off with a soft cloth so that the user can clean it. It is easy and can maintain high image quality.
[0034]
Further, in the optical writing apparatus of the present invention, the arrangement of bright spots decomposed by the hologram element and condensed on the medium greatly affects the performance, and various experiments were conducted on this point to search for a desirable arrangement. As a result, it consists of a bright spot with a relatively large diameter arranged at the center of the pixel area and bright spots arranged around one or more ring zones around it. It has been found that if the bright spot belonging to a certain annular zone is made to have a relatively small diameter, the average density change in the pixel region becomes smooth and excellent halftone reproducibility is realized.
[0035]
Further, a light source capable of emitting light of various different wavelengths in the apparatus of the present invention is used for an image recording medium capable of outputting a single color even if the wavelength of the writing light is different, such as an electrophotographic photosensitive member. If the hologram element has a function to change the direction of splitting the light beam according to the wavelength, the halftone screen pattern generated on the image recording medium can be electrically changed by controlling the wavelength of the light source. Further, a highly functional optical writing device can be realized. For example, a near-infrared laser element is used as a light source having a relatively long wavelength, and a blue laser element is used as a light source having a relatively short wavelength, and the emitted light is matched by a beam combiner to produce blue light as writing light source light. On the other hand, the hologram element has a function of decomposing a light beam at an angle larger than that of red light. With this device, line images that do not require halftones are written with red light, and halftone areas are written with blue light. In addition, since the bright spots are largely dispersed in the halftone region, an intermediate density with good uniformity can be reproduced. According to such a configuration, the image quality can be improved because an image can be written with an appropriate bright spot according to each image characteristic as compared with the case where the light amount of the light source is simply modulated.
[0036]
Further, if a microlens is formed in the entrance-side opening and / or the exit-side opening of the light focusing element, the use efficiency of the writing light beam is increased, and the image recording speed can be increased. However, since the corresponding manufacturing cost is added, there is no need to provide a microlens unless particularly necessary.
[0037]
Further, in the optical writing device of the present invention, since the light beam is condensed by a hologram element having a width of approximately 40 μm or less, the distance from the hologram element to the image plane, that is, the working distance cannot be made too long. About 1 mm is a range in which good light collecting performance can be maintained. Depending on the usage of the optical writing device, a larger working distance may be required. In such a case, the above-described optical writing apparatus has a structure in which the same-magnification imaging element is arranged in focus on the image plane. According to such a structure, a long working distance can be obtained. As the unity imaging element here, almost all the unitary imaging elements that are normally used can be used. For example, a lens array in which a large number of refractive index distribution type fiber-shaped equal-magnification imaging lenses are arranged in a straight line, for example, a Selfoc lens array manufactured by Micro-Opt Co., Ltd. For example, a roof mirror lens array manufactured by Ricoh Co., Ltd. can be used.
[0038]
Next, the configuration of an actual optical writing apparatus corresponding to various optical writing light sources will be described.
One common light source for optical writing is a light-emitting diode array. FIG. 6 shows the configuration of the apparatus of the present invention against this. Since the light emitting diode array 31 is an array of individual light emitting regions arranged at the same density as the required resolution, the light writing light source is used as a light focusing element unit for focusing the light flux. A mirror array 32 having a spherical, hemispherical, super hemispherical, conical shape or the like having an emission part provided at the top and facing the light emitting region, and a fine optical opening provided in the emission part of the mirror array 32 A pinhole array 33, a convex lens microlens array 34 provided as a collimator portion relative to the pinhole array 33, and a hologram array 35 in which hologram elements provided relative to the microlens array 34 are arranged are used. The configuration was as follows. Any light source can be used as long as a minute light emitting area is arranged in an array. In addition to a light emitting diode array, a field emission type that operates in a minute low pressure space. An array light source in which a phosphor is caused to emit light by an electron source, an array light source of an electroluminescence light emitting element, and the like can also be used.
[0039]
Next, FIG. 7 shows the configuration of the optical writing apparatus of the present invention when a polygon scanner which is another general writing light source is used. This apparatus is mainly suitable for optical writing on an electrophotographic photosensitive member. In order to realize the optical writing device having this configuration, the light converging element array section 42 formed on the substrate may be provided at the light beam converging position of the polygon scanner 41 on which the photosensitive member is normally arranged. The other configuration is the same as that of the light emitting diode array described above with respect to the light source. According to this configuration, since writing by the polygon scanner requires a new optical element array that is conventionally unnecessary, the apparatus is complicated and it seems that there is no advantage. However, the polygon scanner used in the optical writing apparatus of the present invention may have a low optical accuracy. From this point, the overall cost can be reduced as compared with the conventional optical writing apparatus using a high-precision polygon scanner. It becomes possible. More specifically, in order to perform high-resolution optical writing using only a polygon scanner as in the prior art, the deviation of the light beam trajectory on the photosensitive member from the straight line must be reduced to such an extent that the resolution does not become a problem. I must. For example, at the time of optical writing at 2400 dpi, the scanning line interval is about 10 μm, so the trajectory of the light beam must be within a width with a positional deviation of ± 1 μm or less, which is approximately 1/5 of that. For this reason, it is required to reduce the birefringence in the optical system, to make the refractive index distribution extremely small, and to thoroughly reduce the distortion and vibration of the casing that cause the displacement of the light beam, resulting in high costs. For these reasons, the polygon scanner is approaching its limit in terms of increasing the resolution. On the other hand, since the polygon scanner used in the optical writing device of the present invention only needs to scan so that light enters a conical mirror or the like that is a light focusing element, a considerable positional deviation is allowed. For example, when a micro optical element array arranged at a density of 600 dpi is used and the light focusing element is a conical mirror, the light source side diameter of one conical mirror can be expanded to about 42 μm. When scanning with a polygon scanner, it is sufficient that a light beam is incident on the polygon scanner. Therefore, if the focused spot has a diameter of about 30 μm, a positional deviation of ± 6 μm is allowed. Further, if the conical mirror of the light focusing element has an opening with an ellipse having a long diameter in the direction perpendicular to the direction in which the light beam is scanned, that is, in the sub-scanning direction, a larger positional deviation is allowed. Can do. Due to such features, the polygon scanner used here does not require high-precision scanning accuracy and may be an inexpensive unit. Further, in the optical writing device of the present invention, if the positional deviation between the hologram element array and the photosensitive member is suppressed to be small, the positional deviation of the writing of the image does not occur. There is no need to manufacture the entire housing for holding the optical elements of the polygon scanner as in the case of a writing device using a polygon scanner. For these reasons, although an optical element array is added to increase the apparent number of parts, the overall cost is greatly reduced and generated compared to a conventional optical writing device using a high-resolution polygon scanner. Since the fineness of the halftone dots can be made as fine as previously difficult, it is possible to reproduce the halftone with a smoothness higher than that of the conventional case.
[0040]
Next, a color image forming apparatus using the optical writing device of the present invention will be described. A color image is color-separated into YMCK (yellow, magenta, cyan, black) or RGB (red, green, blue), and each color is separated. In a color image output device for writing a color image sequentially by means of an optical writing device for writing, or for writing each color separately on an image recording medium etc. If the screen patterns forming the halftones of the respective colors are not overlapped with each other, the respective colors are not easily masked, so that an image with higher saturation can be reproduced. In the case of an image output device using a plurality of the above-described optical writing devices, this can be realized extremely simply as follows. That is, the position of the pattern arrangement or the angle of arrangement of the bright spot patterns of the YMCK or RGB optical writing devices is set so that the centroids of the individual patterns do not overlap each other between the YMCK or RGB colors. What is necessary is just to provide by shifting. In a conventional electrophotographic apparatus or the like, when a screen pattern is generated, the degree of overlap is reduced by calculating by changing the inclination angle or the like in each color. This caused an increase in calculation time for image processing. However, in the case of an image output device using the optical writing device of the present invention, a hologram array having a specific arrangement of the bright spot patterns of the optical writing device of each color is used. By using it, it is possible to reproduce a color image with less color turbidity without overlapping dots of each color without performing special image processing or the like.
[0041]
Next, an experimental example to which the embodiment of the present invention is applied and a corresponding comparative example are shown.
[0042]
[Experiment 1]
An optical writing device using a light-emitting diode array as a light source was prepared, and a color image output device using this for writing each color of YMCK was manufactured. The optical writing element was prepared by the following procedure.
[0043]
First, a conical mirror array of the light focusing element portion was formed on the light emitting diode array by the following procedure. The quartz glass substrate was polished to a thickness of 40 μm, attached to a glass plate with good flatness with a thermoplastic resin, and a photoresist was applied on the quartz glass substrate. The photoresist used was 0FPR8600 manufactured by Tokyo Ohka Co., Ltd. with a viscosity adjusted to 200 cp, and was applied by spin coating so as to have a thickness of 3 μm. The photoresist film is pre-baked under the conditions described in the data sheet, and then exposed through a photomask in which circular openings having a diameter of 20 μm are linearly arranged at a pitch of 42.3 μm (600 dpi), and normal development and rinsing steps are performed. Then, a resist mask having the same shape as the photomask pattern was formed. The back surface and the periphery were masked so that the glass plate as a substrate was not attacked by the etching solution, and etching was performed in a dilute hydrofluoric acid solution. The etching time was determined by observing the time when the quartz glass substrate penetrated to form an opening having a diameter of 5 μm and the glass plate of the substrate was exposed. An array in which tapered openings having an upper diameter of 40 μm and a lower diameter of 5 μm were linearly arranged at a pitch of 42.3 μm was obtained by utilizing the enlargement of the upper diameter by undercutting. The taper shape was controlled by adjusting the temperature of the etching solution, the concentration of hydrofluoric acid, and the frequency of stirring. Next, the etching mask was removed as it was affixed to the glass plate to be the base, and gold was deposited on the quartz glass substrate to a thickness of 7000 mm using a vacuum deposition apparatus. After that, a dicing saw is used to cut the mirror array into strips, the glass plate is heated to remove the strip-shaped quartz glass substrate, washed with an organic solvent, and the thermoplastic resin used for pasting is removed. The strip-shaped glass substrate on which the conical mirror array was formed was completed. The mirror array substrate is attached to a 600 dpi light-emitting diode array, the center of the light-emitting area and the small opening is aligned, and the large opening is bonded to the substrate surface of the light-emitting diode array with a thermosetting resin, so that the conical mirror is small. One of the openings was used as a minute opening.
[0044]
Next, a microlens array serving as a collimator element portion was prepared by the following procedure. The quartz glass substrate was polished to a thickness of 200 μm, attached to a glass plate with good flatness with a thermoplastic resin, and a photoresist was applied onto the quartz glass. As the photoresist, 0FPR8600 (viscosity 300 cp) manufactured by Tokyo Ohka Co., Ltd. was used, and was applied by spin coating so as to have a thickness of 4 μm. After pre-baking the photoresist film, a circular pattern having a diameter of 40 μm is exposed through a photomask arranged in a straight line at a pitch of 42.3 μm (600 dpi), and subjected to normal development and rinsing processes, and then has the same shape as the photomask pattern. A cylindrical resist film was formed. Next, this sample was placed in a clean oven at 150 ° C. for 30 minutes, and a cylindrical photoresist film was fluidized to change into a convex lens shape. At this time, the height of the convex shape was 4.5 μm. The substrate provided with the convex resin pattern was etched from the surface provided with the resin pattern using an ECR dry etching apparatus, and the shape was engraved on the surface of the quartz glass substrate. Etching conditions are substrate temperature −40 ° C., microwave (2.54 GHz) power 670 W, ECR ion source coil current 19 A, substrate bias high frequency (13.56 MHz) power 450 W, and the etching gas and its supply amount are CHF 3: flow rate 15 SCCM, 02: The flow rate was 1.5 SCCM. The reaction pressure in the etching chamber was set to 0.013 Pa by controlling the opening degree of the variable orifice provided in the exhaust apparatus of the dry etching apparatus. Under these conditions, the etching rate of quartz glass was 120 nm / min, and the etching rate of the resin film was approximately 140 nm / min. Etching was performed until the resin pattern was completely etched under these conditions. The lens height transferred onto the surface of the quartz glass wafer was 2.9 μm. Like the mirror array, after cutting into a strip shape, the microlens array is separated, and the center of the opening and the center of the microlens are aligned so that the upper surface of the mirror array above the light emitting diode array chip is made of UV curable resin. Glued.
[0045]
Next, a hologram array was prepared by the following procedure. The quartz glass substrate was polished to a thickness of 100 μm, attached to a glass plate with good flatness with a thermoplastic resin, and a photoresist was coated on the quartz glass. As the photoresist, 0FPR8600 (viscosity 20 cp) manufactured by Tokyo Ohka Co., Ltd. was used, and was applied by spin coating so as to have a thickness of 0.3 μm. After pre-baking this photoresist film, it was exposed through a photomask on which a hologram pattern was created and subjected to normal development and rinsing steps to form a resist film having the same shape as the photomask pattern.
[0046]
Next, this sample was placed in a clean oven at 130 ° C. for 30 minutes and post-baked. This substrate was etched from the surface provided with the resin pattern using an ECR dry etching apparatus, so that the shape was engraved on the surface of the quartz glass substrate. Etching conditions are substrate temperature −40 ° C., microwave (2.54 GHz) power 670 W, ECR ion source coil current 19 A, substrate bias high frequency (13.56 MHz) power 450 W, and the etching gas and its supply amount are CHF 3: flow rate 15 SCCM, 02: The flow rate was 1.5 SCCM. The reaction pressure in the etching chamber was set to 0.013 Pa by controlling the opening degree of the variable orifice provided in the exhaust apparatus of the dry etching apparatus. The hologram pattern forms a lattice-like pattern in which patterns that are decomposed into three light beams of zero-order light and positive and negative primary light that are transmitted without being diffracted by the incident light beam are formed in a total of five patterns. It was supposed to be decomposed into luminous flux. In order to focus these light beams on the image recording medium, the pitch of the diffraction pattern was smoothly changed from the center to the outer periphery of the hologram element. This hologram was made into a hologram array in which a size of 42.3 μm × 42.3 μm was linearly arranged. The glass substrate engraved with the hologram array was cut out in the same manner as the mirror array, washed, and loaded onto the microlens array. At this time, a spacer is sandwiched around the substrate so that the convex portion of the microlens does not come into contact with the hologram array substrate, the surface on which the hologram is formed by the ultraviolet curable resin is directed toward the light emitting diode array, and the opening portion and the hologram pattern The optical writing device was completed by bonding with the centers aligned. Since this writing apparatus generates a 3 × 3 pattern for one pixel, halftone reproduction corresponds to an optical writing apparatus of 1800 dpi. This was mounted on a copying machine in which a YMCK image was formed on a transfer belt by an independent photoconductive drum, transferred to a plain paper, and fixed, and a test pattern with a continuously changing density was output.
[0047]
[Comparative Example 1]
The copying machine used in Experimental Example 1 was equipped with a light-emitting diode array with a resolution of 1800 dpi and output the same test pattern.
[0048]
These output images were compared and evaluated. The evaluation was performed by visually evaluating the manufacturing cost of the equipment and the reproduced halftone image. The results are shown in Table 1 below.
[0049]
[Table 1]

[0050]
In this image evaluation result, when the high-resolution light emitting diode array is used, the result of the evaluation is poor. In the light emitting diode array, the light emitting diode array generally has a slight unevenness in the manufacturing process. In this case, the light emission amount is corrected by current correction. However, in the high-resolution light emitting diode array, the light emission region is extremely small. This is thought to be due to the fact that fluctuations in the amount of light due to unevenness cannot be corrected sufficiently. In contrast, the image output device using the optical writing element of the present invention can use a low-resolution light-emitting diode array with stable characteristics, so that an image with less unevenness can be obtained and a high-resolution light-emitting diode array is used. As a result, a halftone screen was generated with the same fineness as the case, and a good image was obtained.
[0051]
[Experiment 2]
An optical writing device having a configuration shown in claim 4 using a polygon scanner as a light source was produced, and a color image output device was produced which used this for writing each color of YMCK. The optical writing element was prepared by the following procedure.
[0052]
First, SLA12D manufactured by Micro-Opt Co., Ltd. was used as the equal magnification imaging element, and a glass plate having a width of 10 mm was prepared by polishing both surfaces flatly and having a thickness of 4 mm equal to the working distance of SLA12D. A hologram array substrate prepared by the same method as in Example 1 was bonded to the surface of the glass plate opposite to the SLA with an ultraviolet curable resin. Further, in the same manner as in Experimental Example 1, a microlens array substrate and a mirror array substrate were prepared, and were superposed and bonded on the hologram array substrate to form a main unit of the writing apparatus. This was incorporated into the same copying machine as in Experimental Example 1, and a test pattern with a continuously changing density was output by applying scanning light from a polygon scanner to the mirror array section. The polygon scanner used is an inexpensive one adapted to a resolution of 600 dpi, but this writing device generates a 3 × 3 pattern for one pixel, so halftone reproduction corresponds to an optical writing device of 1800 dpi.
[0053]
[Comparative Example 2]
The copying machine used in Experimental Example 1 was equipped with a polygon scanner with a resolution of 2400 dpi, and the same test pattern was output.
[0054]
These output images were compared and evaluated. Evaluation was made by comparing the manufacturing cost of the device and the volume of the device. The results are shown in Table 2 below. The reproduced halftone images were comparable when visually evaluated.
[0055]
[Table 2]

[0056]
The image output apparatus using the optical writing element of the present invention can use a stable and inexpensive polygon scanner, so that the cost is low and the deflection angle of the polygon scanner can be increased, so that the apparatus can be downsized.
[0057]
In addition, this invention is not limited to the said Example, It cannot be overemphasized that various deformation | transformation and substitution are possible if it is described in a claim.
[0058]
【The invention's effect】
As described above, according to the present invention, an image is divided into a large number of minute pixels, a light beam having an intensity corresponding to the density of each pixel is emitted from one or a plurality of light sources, and a bright spot by this light beam is obtained. An image recording medium on which a latent image such as a surface potential change or a chemical change is formed by irradiation with light having a light density greater than or equal to a threshold, or an image having a density change is formed by exposure. An optical writing device for writing an image by sequentially exposing each pixel area to light, and a light focusing element unit for focusing a light beam in order from the light source side between the light source and the image recording medium; A minute optical opening provided at a position where the light beam converges, a collimator that converts the light beam emitted from the optical opening into a substantially parallel light beam, and radiates the light beam by decomposing it in a plurality of directions. Multiple light beams are generally the same A hologram element for focusing on a plane, one of the units arranged to, is characterized in that arranged in the pixel as many array in the main scanning direction. Therefore, a function of dividing a light beam for writing pixels into a large number of minute light beams by optical means before reaching the surface of the image recording medium, and a photosensitive area on the image recording medium exposed by the minute light beam A smooth halftone can be generated by the function of increasing or decreasing the total area of the pixel, that is, the average density of the pixel in the generated image, by changing the intensity of the original light beam. A composite micro-optical element array that divides the light spot to be written into a collection of finer luminescent spots and changes the total area on the image recording medium that is exposed by the divided luminescent spots depending on the intensity of the writing light. An optical writing device having a new structure arranged in the vicinity of the image recording medium can be provided.
[0059]
Further, by providing a protective plate made of a transparent material on the front surface of the image recording medium facing the hologram element, the hologram element can be prevented from being contaminated with fine particles.
[0060]
Furthermore, a bright spot group which is decomposed in a plurality of directions by the hologram element and formed on the image recording medium by each of the converged light beams is a bright spot having a relatively large diameter, which is positioned at the approximate center of one pixel region, By forming the hologram element so as to be composed of relatively small bright spots located around one or more annular zones, an excellent image can be reproduced for the pattern of bright spots divided by the hologram element. .
[0061]
In addition, the light source is generated on an image recording medium by being a light source in which light emitted from an element capable of emitting light of a plurality of wavelengths or a plurality of elements emitting different wavelengths is integrated by a beam combiner or the like. The bright spot pattern can be changed by changing the wavelength of the light emitted from the light source.
[0062]
Furthermore, by providing microlenses in the entrance-side opening, the exit-side optical opening, or both of the openings of the light focusing element section, the utilization efficiency of the light source light is increased and higher-speed image output is possible.
[0064]
Furthermore, as another invention, the laser beam is converted into a parallel light beam, deflected by a rotating polygon mirror, and scanned on the image recording medium between the light source using the polygon scanner and the image recording medium in order from the light source side. The laser beam is arranged on the substrate in the direction in which the laser beam is scanned by the polygon mirror, and has an emission part at a position facing the laser beam incident part, and the laser beam incident part has a larger area than the emission part. A pinhole array in which a light converging element part for converging a light beam and an optically transparent minute opening are arranged in a substantially conical or pyramidal mirror array having And a microlens array in which convex lenses provided opposite to the pinhole array are arranged, and the light beam emitted from the optical opening is roughly A collimator section for forming a luminous flux and a hologram element arranged in an array so as to be opposed to the microlens array, the luminous flux is decomposed and emitted in a plurality of directions, and the plurality of luminous fluxes are generally focused on the same plane. It is characterized in that a hologram element is provided. Therefore, it can be applied to a polygon scanner which is one of the light sources.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a basic structure of an optical writing device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing details of a portion for creating a plurality of bright spots.
FIG. 3 is a sectional view showing a basic structure of an optical writing device according to a second embodiment of the present invention.
FIG. 4 is a diagram showing a state in which a plurality of spots are formed when the light intensity is high by the optical writing device of the present invention.
FIG. 5 is a diagram showing a situation where a single spot is formed when the light intensity is low by the optical writing device of the present invention.
FIG. 6 is a diagram showing an example of a structure corresponding to a light emitting diode array light source.
FIG. 7 is a diagram illustrating an example of a structure corresponding to a polygon scanner.
[Explanation of symbols]
11, 21 Light focusing element
12,22 Writing light beam
13 opening
14 Light diffusing element
15 Openings
16 1x imaging element
17, 26, 36 Image recording medium
23 Optical aperture
24 Collimator section
25 Hologram element
31 Light emitting diode array
32 mirror array
33 pinhole array
34 Micro lens array
35 Hologram array
41 polygon scanner
42 Condensing element array part
43 Collimator element array
44 Hologram array section
45 photoconductor

Claims (6)

The image is divided into a large number of minute pixels, and a light beam having an intensity corresponding to the density of each pixel is emitted from one or a plurality of light sources. As a result, a latent image such as a surface potential change or a chemical change is formed by exposure to light or scanned on an image recording medium on which an image having a change in density is formed by exposure. In an optical writing device that writes an image by exposing it to light,
In order from the light source side between the light source and the image recording medium,
A light focusing element for focusing the light beam;
A minute optical opening provided at a position where the light beam is focused,
A collimator unit that converts the light beam emitted from the optical aperture into a substantially parallel light beam;
A hologram element that decomposes and emits a light beam in a plurality of directions and focuses the light beams substantially on the same plane;
An optical writing apparatus characterized in that one unit arranged in an array is arranged in the same number as the number of pixels in the main scanning direction.   2. The optical writing apparatus according to claim 1, wherein a protective plate made of a transparent material is provided on the front surface of the image recording medium facing the hologram element.   A bright spot group which is decomposed in a plurality of directions by the hologram element and formed on the image recording medium by each focused light beam is a bright spot having a relatively large diameter located at the approximate center of one pixel region, The optical writing device according to claim 1, wherein the hologram element is formed so as to be composed of relatively small bright spots located around one or a plurality of annular zones.   4. The light source according to claim 1, wherein the light source is a light source obtained by integrating light emitted from an element capable of emitting light of a plurality of wavelengths or a plurality of elements emitting different wavelengths by a beam combiner or the like. The optical writing device described.   5. The optical writing device according to claim 1, wherein microlenses are provided in an entrance-side opening, an exit-side optical opening, or both openings of the light focusing element unit. 6. The image is divided into a large number of minute pixels, and a light beam having an intensity corresponding to the density of each pixel is emitted from one or a plurality of light sources. As a result, a latent image such as a surface potential change or a chemical change is formed by exposure to light or scanned on an image recording medium on which an image having a change in density is formed by exposure. In an optical writing device that writes an image by exposing it to light,
In order from the light source side between the light source and the image recording medium using a polygon scanner that scans the image recording medium by deflecting the laser beam with a parallel light beam after being deflected by a rotating polygon mirror ,
The laser beam is arranged in the direction in which the laser beam is scanned by the polygon mirror formed on the substrate, and has an emission part at a position facing the laser beam incident part. The laser beam incident part has a larger area than the emission part. Using a generally conical or pyramid-shaped mirror array having a light focusing element unit that focuses a light beam,
Provided on the exit portion of the front you Raarei, an optical aperture optically transparent small opening is made from the pinhole array arranged,
Using a microlens array in which convex lenses are arranged, which is provided in opposition to the pinhole array, and a collimator unit configured so that a light beam emitted from the optical aperture is a substantially parallel light beam;
A hologram element is arranged in an array so as to be opposed to the microlens array, and a hologram element that decomposes and emits a light beam in a plurality of directions and focuses the plurality of light beams almost on the same plane is provided. A characteristic optical writing device.

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