JP4118435B2 - Optical writing apparatus and color image output apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical writing device and a color image output device using the optical writing device. More specifically, the present invention scans a bright spot by a luminous flux whose intensity is emphasized by dividing an image into a number of minute pixels on an image recording medium or the like. The present invention relates to an optical writing device that writes an image by sequentially exposing each pixel region, and a color image output device that includes a plurality of these and outputs a color image.
[0002]
[Prior art]
Conventionally, when reproducing a halftone image in an image output device that reproduces an image by scanning a luminescent spot on a photoconductor, such as an electrophotographic printer, the pixels constituting the image are spotted further finely. The density change was created by reproducing the data as a set of spots and increasing or decreasing the number of spots.
[0003]
As this type of image output device, for example, “High-quality matrix printing for electrophotographic printing devices” disclosed in Japanese Patent Laid-Open No. Hei 6-133156, “Specific Rotating Screen for Digital Halftone”, and Japanese Patent Laid-Open No. 8-506704 There are those disclosed in “Method and apparatus for generating” and the like. According to these publications, in order to reproduce a smooth halftone, it is necessary to divide the image more finely than the resolution necessary to reproduce the finest line drawing contained in the image. For example, when the pixel density necessary for reproducing the line drawing information of the image is 600 dpi (the number of pixels per inch is 600 dots), the smooth gradation has 65 levels for one pixel as one standard. In order to realize the gradation property that can provide the density change, it is necessary to divide one pixel into an 8 × 8 matrix, so that the writing resolution necessary for writing is 600 × 8 = 4800 dpi. Optical writing with this resolution is not impossible at present, but the image output apparatus having such high resolution is an optical writing apparatus having the highest level of accuracy (state-of-the-art) at present. .
[0004]
[Problems to be solved by the invention]
However, such an optical writing apparatus has the following problems when used in general.
That is, since it is necessary to divide the image into extremely fine regions, there is a problem that the time required for image processing calculation increases. Therefore, in order to shorten the calculation time of image processing, it is necessary to incorporate an electronic computer equipped with a faster processor, but at present, the processing capacity is limited in a small electronic computer that can be incorporated in an image output device. Therefore, it is difficult to perform pixel division of 4800 dpi within a time as high as 600 dpi. Of course, in the future, it is conceivable that a high-speed processor capable of shortening the above-mentioned calculation time will be used in a small electronic computer that can be incorporated in an image output device due to progress in technological development, but by using such a high-speed processor A new problem of an increase in equipment cost arises.
[0005]
In addition, it is necessary to focus the light spot for writing to a size of 5 μm or less in the entire writing area. In order to realize such a spot size with a polygon scanner, it is made of a glass lens with very little birefringence. It is necessary to use an optical system, and it becomes impossible to use a polygon scanner using a plastic lens mainly used in general applications at present. However, since an optical system using a glass lens is very expensive compared to a plastic optical system, there is a problem that the apparatus cost increases.
[0006]
In the case of a polygon scanner, the spot is likely to collapse at the end of the scanning width. Therefore, the deflection angle by the polygon mirror cannot be increased too much in order to reduce the spot size to 5 μm or less at the end of the image. It was. For this reason, when writing an image of the same size, the optical path length becomes longer when a writing device with a small deflection angle is compared with a writing device with a low resolution, so that there is a problem that the image output device using this becomes large. It was.
[0007]
In the case of a polygon scanner, if the optical path length is increased, the optical spot is likely to be displaced due to mechanical distortion of the optical system. Therefore, the variation of the spot position on the photosensitive member is made sufficiently small with respect to the spot size. There is a need. Therefore, in order to suppress the distortion of the optical system casing to a negligible level with respect to a spot size of 5 μm, it is necessary to increase the rigidity of the apparatus very much, but this increases the size and weight of the apparatus. There was a problem that.
[0008]
Furthermore, in the case of a printer head using a light emitting diode (LED) array as a light source for writing, there is a problem that the cost of the device increases because the number of LEDs is extremely large.
[0009]
In addition, in the case of the four-drum color writing method normally used in a high-speed color image output apparatus, the image positional deviation between the four drums must be made small enough to be ignored with respect to the spot size. Since only a positional deviation of about 1 μm is allowed, it is necessary to extremely increase the medium conveyance accuracy. For this reason, there is a problem that the apparatus becomes large and heavy, and the cost becomes high. Particularly, in the case of the four-drum system, since four optical writing devices are used, there is a problem that when the size of each optical writing device is increased, the entire device is further increased in size.
[0010]
In this way, at present, an image is divided into sufficiently fine pixels at the stage of electronic information, and a halftone matrix is written on an image recording medium or the like by a high-definition optical writing device, so that a smooth half without any visual problems is obtained. Although it is possible to make a prototype image output device that reproduces the tone, the device becomes large and expensive, and it has been difficult to widely disseminate it as an industrial product.
[0011]
In addition, there is a limitation on the mechanism as described above in order to increase the writing speed, and the number of pixels to be written becomes enormous due to the small spot size, so even if a simple line drawing is output, it is long. There was a problem that writing time was required.
[0012]
The present invention has been made in view of the above problems, and an optical writing apparatus and a color that can reproduce a beautiful halftone image at high speed and low cost and can also reproduce a line drawing at high speed and well. An object is to provide an image output apparatus.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, an image is decomposed into a large number of minute pixels, and a luminous flux having an intensity corresponding to the pixel density is emitted from one or a plurality of light sources. The bright spot is exposed to light with a light density greater than the threshold value, and a latent image such as a surface potential change or chemical change is formed, or an image with a density change is formed immediately by exposure. In an optical writing device that scans an image recording medium to be written and writes an image by sequentially exposing each pixel region, a light focusing element unit that focuses a light beam between the light source and the image recording medium And a first minute opening provided at a position where the light beam is focused, and a light beam emitted from the first minute opening is diffused into a limited region that is approximately the same as the size of the pixel. A light diffusing element part; A second minute opening group composed of a plurality of openings for emitting light diffused by the light diffusing element part, and a plurality of light beams emitted from the second minute opening group are the image recording medium. Are arranged from the light source side in the order of the imaging element unit that forms an image as a separate bright spot on The second minute opening group includes an opening disposed substantially at the center of the first opening and one or a plurality of openings disposed around the opening. The light intensity density of the luminescent spot emitted from the opening arranged approximately at the center of the first opening in the group of the minute openings is determined by the luminescent spot emitted from the other second minute opening. Higher than light density It is a thing.
[0014]
According to this, an image is decomposed into a large number of minute pixels, a light beam having an intensity corresponding to the pixel density is emitted from one or a plurality of light sources, and a light focusing element is disposed between the light source and the image recording medium. The first spot, the first minute opening, the light diffusing element part, the second minute opening group, and the imaging element part in this order. Dividing into aggregates, the total area on the image recording medium that is exposed by the divided small spots is changed according to the intensity of light to be written, so beautiful halftone images and line drawings can be printed at high speed and at low cost. Etc. can be written on.
[0015]
In finding such a configuration, the present inventors have studied in detail about a halftone image, and as a result, high-resolution image data is not necessarily required to generate a smooth halftone. We paid attention to the fact that the dot-like photosensitive areas recorded on the screen are sufficiently fine so that they can be visually smooth. For this reason, the conventional halftone generation method that relies on an electronic computer is not simply improved, but a light beam for writing pixels is converted into a number of minute light beams by optical means before reaching the surface of the image recording medium. A function that divides and an area that integrates a photosensitive area on an image recording medium exposed by a minute light beam, that is, a function that increases or decreases the average density of pixels in the generated image by changing the original light beam intensity. Thus, a smooth halftone is generated.
[0016]
The image recording medium or the like that is the target of the optical writing apparatus of the present invention includes a rewritable recording medium, a recording medium that cannot be rewritten once recorded, and a medium such as an image display on which images are continuously written. It includes almost all media including images formed by an optical writing device. For example, specific examples of the image recording medium include: (1) An image is formed by a phase change or a reversible chemical change of a material caused by exposure to visible light, ultraviolet light, or infrared light, An image recording medium that can be erased and used repeatedly by irradiating light of wavelength and intensity, applying a magnetic field of a specific intensity and direction, applying a specific temperature change, etc. (2) electrophotographic photoreceptors, (3) black-and-white and color films or photosensitive papers produced by silver salt photography, and (4) other so-called photoreceptors such as recording media using photosensitive materials produced by other photochemical reactions. In addition to this, (5) a photoconductive material layer is disposed between the liquid crystal material layer and the drive electrode, and the photoconductive material at that portion is made conductive by irradiation of writing light to the photoconductive material layer. For example, a liquid crystal display that writes an image with an electric field applied thereto, and a display that immediately forms an image having a density change with a photoconductive effect as an intermediate. The optical writing apparatus of the present invention can write a good halftone image on all these image recording media.
[0017]
According to a second aspect of the present invention, in the optical writing apparatus according to the first aspect, the second small opening group is an opening having a relatively large diameter disposed substantially at the center of the pixel region. And one or a plurality of openings arranged around the ring, and the openings belonging to the ring on the outer periphery have a relatively small diameter.
[0018]
According to this, in the case where the second minute opening group is composed of the opening arranged at the approximate center of the pixel region and the opening arranged around the opening, the opening on the outer periphery is relatively relatively Since it is formed to have a small diameter, the average density change in the pixel region becomes smooth, and excellent halftone reproducibility can be realized.
[0019]
According to a third aspect of the present invention, in the optical writing device according to the first or second aspect, a light emitting diode array in which light emitting diode elements are linearly arranged at the same density as the pixels is used as a light source for optical writing. As the light focusing element part, a spherical, hemispherical, super hemispherical, conical or other mirror array having an emission part at a position facing the light emitting area provided above the light emitting area of each light emitting diode element is used. The first minute opening is made up of a first pinhole array provided in the exit portion of the mirror array, and is provided as the light diffusing element portion corresponding to the first pinhole array. A spherical, hemispherical, super hemispherical, conical or other integrating sphere array, and the second minute opening group is provided at a position facing the first pinhole array on the integrating sphere array. Are, respectively, consist of a second pin hole array in which a plurality of pin hole group are arranged, as the imaging element section, in which with equal magnification imaging device array.
[0020]
According to this, when a light emitting diode array (LEDA) is used as a light source for optical writing, the emitting part is located at a position facing the light emitting area provided above the light emitting area of each light emitting diode element as the light focusing element part. A spherical, hemispherical, super hemispherical, conical or other mirror array having a first minute opening is used as the first pinhole array, and the light diffusing element unit corresponds to the first pinhole array. Spheres, hemispheres, super hemispheres, cones, etc. of the integrating sphere array, and the second minute opening group has a plurality of pins at positions facing the first pinhole array on the integrating sphere array. Since the second pinhole array in which the hole groups are arranged and the equal-magnification imaging element array is used as the imaging element unit, various image recording media can be used even when the light emitting diode array is used as an optical writing light source. Good halftone image to equal can be written.
[0021]
As the imaging element unit of the present invention, any one may be used as long as an appropriate one is selected according to the characteristics of the target image recording medium. For example, if the image recording medium is a sheet having a relatively narrow width and the sheet is sent in the longitudinal direction according to time to write an image, an equal-magnification imaging optical system combined with a normal optical lens Is used. When writing to an electrophotographic photosensitive member, most of the same-size imaging elements that are usually used in this field can be used. For example, as a lens array in which a large number of refractive index distribution type fiber-shaped equal-magnification imaging lenses are linearly arranged, for example, a SELFOC lens array manufactured by Micro Opto Corporation or a plurality of equal-magnification imaging micro optical systems are used. For example, a roof mirror lens array manufactured by Ricoh Co., Ltd. can be used.
[0022]
According to a fourth aspect of the present invention, in the optical writing device according to the first or second aspect, as a light source for optical writing, a collimated laser beam is deflected by a rotating polygon mirror and scanned on an image recording medium. A polygon scanner that is arranged in the main scanning direction, which is a direction in which laser light is scanned by the polygon mirror, as the light focusing element portion, and has an emission portion at a position facing the laser light incident portion. The light incident portion uses a substantially conical mirror array having a larger diameter than the exit portion, and the first minute opening is a first pinhole array provided in the exit portion of the mirror array. As the light diffusing element part, a spherical, hemispherical, super hemispherical, conical or other integrating sphere array provided corresponding to the first pinhole array is used. The second minute opening group is provided at a position facing the first pinhole array on the integrating sphere array, and includes a second pinhole array in which a plurality of pinhole groups are arranged, As the imaging element section, an equal magnification imaging element array is used.
[0023]
According to this, when a polygon scanner that scans an image recording medium with a laser beam is used as the light source for optical writing, the light focusing element units are arranged in the main scanning direction and are positioned opposite to the laser beam incident unit. A first concentric mirror array in which the laser beam incident portion has a larger diameter than the exit portion, and the first minute opening is a first pin provided in the exit portion of the mirror array It is a hole array, the light diffusing element portion is a spherical, hemispherical, super hemispherical, conical or other integrating sphere array provided corresponding to the first pinhole array, and the second minute aperture group is integrated. Since the second pinhole array is provided at a position opposite to the first pinhole array on the sphere array and each of the plurality of pinhole groups is arranged, and the equal-magnification imaging element array is used as the imaging element unit, Polygon ski Even in the case of using Na light source for optical writing, it can be written good halftone image to such various image recording medium.
[0024]
According to the configuration of the fourth aspect of the present invention, since the same-magnification imaging element array, which is conventionally unnecessary for optical writing by the polygon scanner, is newly required, the apparatus becomes complicated, but the polygon scanner used in this optical writing apparatus is Since optical accuracy is not so required, there is an advantage that the cost can be reduced as a whole as compared with the conventional optical writing apparatus using a highly accurate polygon scanner.
[0025]
In other words, in order to perform high-resolution optical writing using only a highly accurate polygon scanner as in the prior art, the deviation of the light beam trajectory from the straight line on the photosensitive member must be made small enough to cause no problem in the resolution. I must. For example, when optical writing at 2400 dpi is performed, the scanning line interval is about 10 μm, so the trajectory of the light beam must be within the width of ± 1 μm or less, which is approximately 1/5 of that. There wasn't. Therefore, it is required to make birefringence extremely small in the optical system, to make the refractive index distribution extremely small, and to greatly reduce the distortion and vibration of the casing that causes the positional deviation of the light beam, resulting in high cost. For these reasons, the polygon scanner is approaching its limit in terms of increasing the resolution.
[0026]
On the other hand, the polygon scanner used in the optical writing device according to the fourth aspect of the present invention is allowed to scan so that light enters a conical mirror or the like that is a light focusing element, so that 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 oblong diameter with 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 displacement is allowed. can do. Due to such characteristics, the polygon scanner used in claim 4 does not require high-precision scanning accuracy, and an inexpensive unit is sufficient. Further, if the positional deviation between the equal-magnification imaging element and the photoconductor in the optical writing device according to claim 4 is suppressed to be small, the deviation of the writing position of the image does not occur. Unlike the conventional optical writing device using a high-precision polygon scanner, it is not necessary to firmly manufacture the entire housing for holding the optical elements of the polygon scanner.
[0027]
For this reason, it seems that the same number of imaging elements are added and the apparent number of parts increases. However, in terms of overall cost, the conventional high-resolution polygon scanner is used. The cost is lower than that of the conventional optical writing device, and the halftone dots generated can be made as fine as previously difficult, so halftones can be reproduced with a smoother than before. It becomes possible.
[0028]
According to a fifth aspect of the present invention, in the optical writing device according to any one of the first to fourth aspects, each of the first microscopic opening or the second microscopic opening group. Microlenses are formed in the opening or both.
[0029]
According to this, since the microlens is formed in each opening or both of the first minute opening or the second minute opening group, the use efficiency of the optical writing light source is increased. The image recording speed can be increased. However, since the manufacturing cost is added accordingly, if it is not necessary to increase the image recording speed, it is possible to choose not to provide the microlens.
[0030]
A sixth aspect of the present invention includes a plurality of the optical writing devices according to any one of the first to fifth aspects, wherein the color image is converted into yellow, magenta, cyan, black, red, green, or blue. After color separation, these are sequentially written on the same image recording medium or the like by an optical writing device for writing each color, or written on an individual image recording medium or the like for each color, and then the color images are superimposed by means of superimposing the images of each color. In the output color image output device, each of the second minute aperture groups of the optical writing device of each color of yellow, magenta, cyan, black, or red, green, and blue is an individual aperture. Placement pattern Between yellow, magenta, cyan, black, or red, green, and blue Same The arrangement position or the arrangement angle is shifted so as not to be formed.
[0031]
According to this, when a color image output device is configured using a plurality of optical writing devices, yellow, magenta, cyan, black (hereinafter also referred to as YMCK), or red, green, blue (hereinafter also referred to as RGB). ) The second minute opening group of each of the optical writing devices of the respective colors is formed into individual openings. Placement pattern Between each color of YMCK or RGB Same Since the screen position that forms the halftone of each color does not overlap each other and each color is difficult to be masked, the saturation and color turbidity are increased. It is possible to reproduce a beautiful color image with little.
[0032]
In a conventional color image output device, when generating a screen pattern, the degree of overlap of the patterns is reduced by changing the inclination angle in each color to reduce the calculation time of the image processing. However, in the case of the color image output device using the optical writing device of the present invention, the pattern of the second minute opening group of the optical writing device of each color is configured as a specific arrangement, so that special image processing is performed. Even if it is not performed, it is possible to suppress overlapping of dots of each color, and a color image with less color turbidity can be reproduced without reducing the image processing speed.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an optical writing apparatus and a color image output apparatus using the same according to the present invention will be described in detail in the order of (Embodiment 1) to (Embodiment 3) with reference to the accompanying drawings.
[0038]
(Embodiment 1)
1A and 1B are diagrams for explaining the configuration of a micro optical element unit 10 that mainly functions in the optical writing apparatus according to the first embodiment. FIG. 1A is a plan view, and FIG. It is A 'line sectional drawing. As shown in FIG. 1B, the micro optical element unit 10 includes a light focusing element unit 12 that focuses a light beam from a light source such as a conical mirror, and a top on which the light beam is focused by the light focusing element unit 12. A first minute opening 14 which is provided at a position and generates a writing light beam collected by the light focusing element unit 12 into a minute light spot, and an emission emitted from the first minute opening 14. A light diffusing element portion 16 having a small integrating hemisphere 18 for making light incident and diffusing into a limited volume corresponding to one pixel, and a light diffusion facing the first minute opening 14. A diffused light provided at the top position of the element unit 16 and diffused by the light diffusing element unit 16 is emitted from a plurality of minute openings (pinholes), so that a plurality of minute light is written from a light beam for writing one pixel. Second to generate a light spot It is constituted by a small opening groups 20 and 22.
[0039]
FIG. 2 is an overall configuration diagram of the optical writing device 30 according to the first embodiment. As shown in FIG. 2, the optical writing device 30 includes a light focusing element unit 10 that generates a plurality of minute light spots from a light beam 32 that writes one pixel, and a plurality of light focusing element units 10 generated by the light focusing element unit 10. Are formed with the same-magnification imaging element 34 for imaging the light spot on the image recording medium 36.
[0040]
The optical writing device 30 is adapted to change the pattern generated by the intensity of the writing light beam 32 according to the image density by devising the shape and arrangement of the second minute opening groups 20 and 22. Can be.
[0041]
Next, the mechanism will be described. FIG. 3 is a diagram showing the light amount distribution of a light spot formed on the image recording medium when the light intensity of the writing light beam is high using the optical writing device of the first embodiment, and the horizontal axis represents The position on the line AA ′ is shown, and the vertical axis represents the light intensity density on the image recording medium on an arbitrary scale. FIG. 4 is a diagram showing a shape pattern of light spots formed on the image recording medium as a result of FIG. FIG. 5 is a diagram showing the light amount distribution of a light spot formed on the image recording medium when the light intensity of the writing light beam is small using the optical writing device of the first embodiment. FIG. 6 is a diagram showing a shape pattern of a light spot created on the image recording medium as a result of FIG. 5.
[0042]
Therefore, in order to simplify the description of the micro optical element unit 10 shown in FIG. 1, a second one in which four relatively small pinholes 22 are arranged around one relatively large pinhole 20. A structure including minute opening groups 20 and 22 is shown. The shape of the light spot irradiated on the image recording medium 36 by the optical writing device 30 using the micro optical element unit 10 is such that the light intensity distribution as shown in the diagram of FIG. 3 when the intensity of the writing light beam 32 is sufficiently large. Therefore, when an image generation process is set so as to be exposed in an area irradiated with a light density higher than the broken line indicated as the light quantity level of the image recording medium in the figure, the output pixel pattern is as shown in FIG. become that way. Thus, when the intensity of the writing light beam 32 is sufficiently large, a screen pattern that is generated by a screen matrix by image processing can be generated from the light beam that writes one pixel.
[0043]
Further, when the light intensity of the writing light beam is reduced, the light quantity distribution as shown in the diagram of FIG. 5 is obtained, and therefore, irradiation with a light quantity density higher than the broken line indicated as the light quantity level of the image recording medium in the figure is performed. When the image generation process is set so that light is received in the received area, the output pixel pattern is as shown in FIG. As described above, when the intensity of the writing light beam 32 is small, one minute dot pattern is generated from the light beam for writing one pixel.
[0044]
In the state where the above two intermediate light amounts are irradiated, the diameter of the light spot due to the surrounding pinhole gradually changes to change the total area of the photosensitive region, and the average density of the pixel region is continuous. Will change. This makes it possible to form a smooth halftone portion.
[0045]
In the case described above, a simple pattern aperture group has been described as an example to simplify the description. However, the pixel interval when a 600 dpi optical writing light source having a normal resolution is used is about 42.3 μm. In addition, it is not difficult for the opening system of the second minute opening group to have a diameter of about 1 μm by a photoresist process. Therefore, since a large number of openings can be included in one pixel region, it is possible to generate a screen pattern that is not visually recognizable, and is recognized as a smooth halftone by an image observer. It will be.
[0046]
Unlike the case where the screen pattern is written on the image recording medium by the optical writing device having a finer resolution, the optical writing device configured as described above cannot write a line drawing with the maximum resolution that can be separated by separate small spots. This is because in the optical writing apparatus of the first embodiment, the pixels of the optical writing apparatus having a normal level of resolution are divided into small writing spots.
[0047]
However, in practice, it is possible to reproduce almost all of the line drawing images that are necessary every day with a resolution of about 600 dpi, which is the current normal resolution, and even if line drawings are written with a resolution higher than this, care must be taken with the naked eye. Otherwise, the separated lines cannot be recognized and are meaningless except for very special uses. Nevertheless, 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, a conventional optical writing apparatus having a fine resolution is required to have a very high-accuracy production technique, is expensive, and requires a smooth half-time despite an increase in calculation time required for image processing. The tone was not fully reproduced.
[0048]
On the other hand, in the case of the optical writing apparatus according to the first embodiment, it is possible to generate a screen pattern that is fine enough to be visually unrecognizable while using an optical writing light source having a normal resolution as described above. Since the technology for producing the apparatus is almost completed at present, a smooth halftone that has been impossible in the past can be reproduced using a low-cost, normal-resolution optical writing light source.
[0049]
Further, since the inventors have found that the performance and the shape of the second minute opening group greatly influence the performance of the optical writing device according to the first embodiment, there are various points on this point. As a result of searching for a desirable shape and arrangement by conducting the above experiment, the following was found.
[0050]
That is, when the second group of minute openings is composed of an opening having a relatively large diameter arranged at the approximate center of the pixel area and an opening arranged around one or more annular zones around the opening. By forming the arrangement pattern so that the opening belonging to the annular zone on the outer periphery has a relatively small diameter, the average density change in the pixel region becomes smooth, and excellent halftone reproducibility is achieved. It turns out that it can be realized.
[0051]
As described above, according to the optical writing apparatus of the first embodiment, it is possible to reproduce beautiful halftones and line drawings at low cost without increasing the processing time.
[0052]
(Embodiment 2)
In the second embodiment, an optical writing device is created using a light emitting diode array (hereinafter also referred to as LEDA) as a light source for optical writing, and this is used for writing each color of YMCK to produce a color image output device. Is the case.
[0053]
First, the manufacturing process of the optical writing element used in the color image output apparatus of the second embodiment will be described. FIG. 7 is a plan view of the micro optical element array section 40 of the optical writing apparatus using the LEDA as the optical writing light source in the second embodiment as viewed from above, and FIG. 8 is a BB ′ line in FIG. It is sectional drawing.
[0054]
As shown in FIG. 8, individual light emitting regions arranged in the same density as the resolution required for the optical writing light source are formed in an array to constitute the LEDA light emitting unit 56. And the conical mirror array 54 as a light focusing element part each arrange | positioned on the LEDA light emission part 56 is produced in the following procedures.
[0055]
First, a quartz glass substrate is polished to a thickness of 40 μm, and is attached to a glass plate with good flatness with a thermoplastic resin, and a photoresist is applied on the quartz glass substrate. Here, “OFPR8600” manufactured by Tokyo Ohka Co., Ltd. is used for this photoresist, and the photoresist is applied by spin coating so as to have a thickness of 3 μm.
[0056]
Then, a pattern in which circular openings having a diameter of 20 μm are linearly arranged at a pitch of 42.3 μm (600 dpi) is baked on this photoresist, and a normal development process and a rinsing process are performed to form a resist having the same shape. A mask is formed. Here, the back surface and the periphery were masked so that the glass plate as a substrate was not attacked by the etching solution, and then etching was performed in a dilute hydrofluoric acid solution. The etching time in this case was determined by observing the time when the quartz glass substrate penetrated, an opening having a diameter of 5 μm was formed, and the glass plate of the substrate was exposed. At this time, an array in which tapered openings having an upper diameter of 40 μm and a lower diameter of 5 μm are linearly arranged at a pitch of 42.3 μm is obtained by utilizing the fact that the upper diameter is expanded by undercutting. Can do. The tapered shape obtained here was controlled by adjusting the temperature of the etching solution, the concentration of hydrofluoric acid, and the frequency of stirring.
[0057]
Next, the etching mask is removed while being attached to the glass plate to be the base, and gold (Au) is vapor-deposited on the quartz glass substrate to a thickness of 7000 angstrom by a vacuum vapor deposition apparatus. Thereafter, the glass plate is heated, the quartz glass substrate is removed, and the thermoplastic resin used for pasting is removed by washing with an organic solvent to complete the quartz glass substrate 42 on which the conical mirror array 54 is formed. Can be made. The quartz glass substrate 42 is bonded to a 600 dpi LEDA light emitting portion 56 by aligning the center of the light emitting portion with the center of the small opening portion, and the large opening portion is bonded to the substrate surface of the LEDA light emitting portion 56 with a thermosetting resin. The smaller opening of the conical mirror array 54 is used as the first minute opening 44.
[0058]
Next, the light diffusing element array unit 46 is created by the following procedure. That is, the quartz glass substrate is polished to a thickness of 40 μm, and is attached to a glass plate with good flatness using a thermoplastic resin, and a photoresist is applied on the quartz glass substrate. In this case, the same photoresist as above, “OFPR8600” manufactured by Tokyo Ohka Co., Ltd. is used, and the photoresist is applied by spin coating so as to have a thickness of 3 μm.
[0059]
9A to 9D show the second minute opening group formed corresponding to the optical writing device for each color of YMCK (because the patterns are different for each color in FIG. 7). This is an example of patterns 50 and 52 (displayed with black circles for convenience). Therefore, a pattern in which the circular pattern opening group of any of FIGS. 9A to 9D is linearly arranged at a pitch of 42.3 μm (600 dpi) is baked on the above-described photoresist, and a normal development process is performed. And a rinsing step to form a resist mask having the same shape. In this case, too, the back surface and the periphery are masked so that the glass plate serving as the substrate is not attacked by the etching solution, and then etching is performed in a dilute hydrofluoric acid solution. In this case, the etching time was set to a time for etching the quartz glass substrate to a depth of 2 μm.
[0060]
After that, the glass plate is heated to remove the quartz glass substrate and washed with an organic solvent to remove the thermoplastic resin used for attachment to the glass plate.
[0061]
Next, the quartz glass substrate is turned over, and is again attached to a glass plate with good flatness with a thermoplastic resin, and a photoresist is applied onto the quartz glass. This resist also uses the same photoresist as described above, and is applied by spin coating so as to have a thickness of 3 μm.
[0062]
This photoresist is baked with a pattern in which circular openings having a diameter of 20 μm are linearly arranged at a pitch of 42.3 μm (600 dpi), and subjected to a normal development process and a rinsing process to obtain the same shape. A resist mask is formed. In this case as well, the back surface and the periphery were masked so that the glass plate serving as the substrate was not attacked by the etching solution, and then etching was performed in a dilute hydrofluoric acid solution. The etching time in this case is determined by observing the point of time when the quartz glass substrate is etched and the previously formed openings on the back surface appear and pass through them. In this case, a recess having a shape close to a hemisphere having an upper diameter of 40 μm was created by utilizing the fact that the upper diameter was expanded by undercutting. The shape of the depression is controlled by adjusting the temperature of the etching solution, the concentration of hydrofluoric acid, and the frequency of stirring.
[0063]
Next, the etching mask was removed while being attached to the glass plate to be the base, and gold (Au) was vapor-deposited on the quartz glass substrate to a thickness of 7000 Å using a vacuum vapor deposition apparatus. At that time, the pressure during vapor deposition is increased by leaking argon gas, so that the surface of the vapor deposited gold has a satin finish suitable for diffusing light. Thereafter, the glass plate is heated, the quartz glass substrate is removed, the thermoplastic resin used for pasting is removed by washing with an organic solvent, and the quartz glass substrate on which the light diffusion element array portion 46 is formed is completed. I was able to. Then, with respect to the LEDA light emitting unit 56 to which the conical mirror array 54 that is a light focusing element unit is bonded to the quartz glass substrate, the first minute opening 44 and the second minute opening group 50, 52 are provided. The optical writing device 40 as shown in FIGS. 7 and 8 was completed by aligning the centers of the respective patterns and bonding them with a thermosetting resin.
[0064]
Since this optical writing device 40 can generate a light beam corresponding to an approximately 3 × 3 pattern for one pixel, halftone reproduction corresponds to an optical writing device of 1800 dpi. Here, an SLA 12D manufactured by Micro-Opt Co., Ltd. is used as a unit magnification imaging element (see the unit magnification imaging element 34 in FIG. 2) of the optical writing device. These are mounted on a copying machine (4-drum system) in which a YMCK image is formed on a transfer belt by an independent photoconductive drum, and is transferred and fixed on plain paper. Was output.
[0065]
As a comparative example for this, the same test pattern is output by mounting the LEDA having a resolution of 1800 dpi on the copying machine used in the second embodiment.
[0066]
The evaluation items for comparing and evaluating the output images of these two are items obtained by visually evaluating the manufacturing cost of the device and the reproduced halftone image, and the results are shown in FIG.
[0067]
In the image evaluation result of FIG. 10, the evaluation result when the high-resolution LEDA is used is that the light emission amount between the light emitting regions of the LEDA is small due to slight unevenness of the general manufacturing process in the LEDA. Since unevenness occurs, the amount of emitted light is corrected by current correction. However, in the high-resolution LEDA, the light-emitting area is extremely small. Therefore, the amount of emitted light of one pixel is small, and the amount of light caused by uneven manufacturing process is relatively small. This is considered to be because the fluctuation becomes larger and correction cannot be made sufficiently.
[0068]
On the other hand, in the case of a color image output device using a plurality of optical writing devices in the second embodiment, a low-resolution LEDA having stable characteristics is used, so that an image with less unevenness is obtained. Since a halftone screen can be generated with the same fineness as when high-resolution LEDA is used, it is considered that a better image evaluation was obtained than when high-resolution LEDA was used.
[0069]
(Embodiment 3)
In the third embodiment, an optical writing device is created using a polygon scanner as a light source for optical writing, and this is used for writing each color of YMCK to produce a color image output device. This apparatus is mainly suitable for optical writing on an electrophotographic photosensitive member.
[0070]
In order to realize an optical writing device having this configuration, it is usually sufficient to provide a light focusing element portion at the light beam focusing position of a polygon scanner on which a photoconductor is disposed. About others, it is substantially the same as the structure with respect to the LEDA light source of Embodiment 2 mentioned above.
[0071]
The optical writing device used for the color image output device of the third embodiment is created by the following procedure. First, the same-magnification imaging element 72 uses “SLA12D” manufactured by Micro-Opt Co., Ltd., and a glass plate 70 having a width of 10 mm having a thickness of 4 mm equal to the working distance of SLA12D by polishing both surfaces flatly. Prepared. Here, the light diffusing element array portion in which the pattern of the second minute opening portion group is formed by the same photolithography process as in the second embodiment, and these patterns are written into the optical writing device for each color of YMCK. It is made to use corresponding to. However, in the second embodiment, the patterns shown in FIGS. 9A to 9D are used. In the third embodiment, the patterns shown in FIGS. 12A to 12D are used. To do.
[0072]
As described above, after the surface on which the second minute opening group is formed is bonded to the glass plate 70, the light focusing element array portion is formed by the same photolithography process as that of the second embodiment, and the first The surface on which the minute openings are formed is directed to the above-described light diffusing element array section, and the centers thereof are made to coincide with each other to bond them, whereby the micro optical element array section 68 is completed.
[0073]
Next, the SLA 12D, which is the equal-magnification imaging element array 72, is bonded to the other surface of the glass plate so that the fine optical element array portion 68 and the center line thereof are aligned.
[0074]
In this way, a main unit of the optical writing device was produced in which the equal-magnification imaging element array 72 and the micro optical element array unit 68 were coupled to both surfaces of the rod-shaped glass plate 70 while maintaining a predetermined operating distance.
[0075]
Then, as shown in FIG. 11, an optical writing device 60 using a polygon scanner as a light writing light source is created, and laser light 76 emitted from a laser 62 is reflected by a polygon mirror 64 that rotates at high speed and deflected. Scanning is performed, and the light passing through the optical system 66 and the above units (the glass plate 70, the equal-magnification imaging element array 72, and the minute optical element array unit 68) is imaged on the surface of the image recording medium 74. Yes.
[0076]
As described above, the second microscopic aperture group formed in the microscopic optical element array unit 68 is configured in a 4 × 4 pattern as shown in FIG. 12, and thus this optical writing device is 2400 dpi. It is possible to reproduce a halftone screen corresponding to. This was incorporated into a copier similar to that of the above-described second embodiment, and a test pattern whose density continuously changes is output by applying scanning light from a polygon scanner to the light focusing element portion. Note that the polygon scanner used here is an inexpensive scanner that conforms to the normal 600 dpi resolution.
[0077]
As a comparative example, the same test pattern was output by mounting a polygon scanner having a resolution of 2400 dpi on the copying machine used in the second embodiment.
[0078]
Evaluation items for comparative evaluation of the output images of these two items are comparative evaluations of device manufacturing costs and device volumes, and the results are shown in FIG. Although the image evaluation results are not compared in FIG. 13, the reproduced halftone image was a smooth color image of the same degree as evaluated visually.
[0079]
Further, in the comparison of the manufacturing costs in FIG. 13, the manufacturing cost is extremely high in the case of the high resolution scanner, whereas the color image output apparatus of the third embodiment can use a stable and inexpensive polygon scanner. Therefore, it can be manufactured at low cost.
[0080]
Further, since the deflection angle of the polygon scanner can be increased, it is possible to reduce the size of each optical writing device, and it is possible to further reduce the size of a color image output device including a plurality of optical writing devices using YMCK.
[0081]
In each of the above embodiments, a microlens may be provided in one or both of the first minute opening and the second minute opening group, In this case, since the utilization efficiency of the writing light beam is increased, the image recording speed can be increased. However, whether or not to provide the microlens in the opening may be selected depending on whether the manufacturing cost or the image recording speed is prioritized according to the use of the optical writing device and the color image output device using the optical writing device. .
[0082]
In each of the above embodiments, each pattern in FIGS. 9 and 12 is applied to YMCK to form the second minute opening group, but the present invention is not limited to this. Even in this case, the present invention can be applied in the same manner. Of course, the present invention may be carried out using patterns other than those shown in FIGS.
[0083]
【The invention's effect】
As described above, according to the first aspect of the present invention, a smooth halftone image or line drawing is reproduced without using an expensive light source for high-resolution optical writing and without increasing the image processing time. can do.
[0084]
According to the second aspect of the invention, the average density change in the pixel region becomes smoother, and excellent halftone reproducibility can be realized.
[0085]
According to the third aspect of the present invention, even when the light emitting diode array is used as an optical writing light source, good halftone images can be written on various image recording media.
[0086]
According to the fourth aspect of the present invention, even when a polygon scanner is used as a light source for optical writing, good halftone images can be written on various image recording media and the like. Cost can be increased.
[0087]
According to the fifth aspect of the present invention, since the utilization efficiency of the optical writing light source is increased, the image recording speed can be increased.
[0088]
According to the sixth aspect of the present invention, the second minute opening group of each color optical writing device is divided into individual openings. Placement pattern Between each color of YMCK or RGB Same Since the arrangement position and the arrangement angle are shifted so as not to occur, a beautiful color image with little color turbidity can be reproduced.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams illustrating a configuration of a micro optical element part that mainly functions in the optical writing device according to the first embodiment, where FIG. 1A is a plan view, and FIG. FIG.
FIG. 2 is an overall configuration diagram of the optical writing device according to the first embodiment.
FIG. 3 is a diagram showing a light amount distribution of a light spot formed on an image recording medium when the light intensity of a writing light beam is high using the optical writing device according to the first embodiment.
4 is a diagram showing a shape pattern of light spots formed on the image recording medium as a result of FIG. 3; FIG.
FIG. 5 is a diagram showing a light amount distribution of a light spot formed on an image recording medium when the light intensity of a writing light beam is small using the optical writing device of the first embodiment.
6 is a diagram showing a shape pattern of a light spot created on the image recording medium as a result of FIG. 5. FIG.
FIG. 7 is a plan view of a micro optical element portion of an optical writing device using LEDA as an optical writing light source in the second embodiment as viewed from above.
8 is a cross-sectional view taken along line BB ′ of FIG.
FIG. 9 is a pattern of a second minute opening group formed corresponding to the optical writing device for each color of YMCK used in the second embodiment.
FIG. 10 is a diagram showing a comparison result between a color image output apparatus according to the second embodiment and a comparative example.
FIG. 11 is a diagram illustrating a schematic configuration of an optical writing device of a color image output device according to a third embodiment.
12 is a pattern of second minute opening portions formed corresponding to the optical writing device for each color of YMCK used in the third embodiment. FIG.
FIG. 13 is a diagram illustrating a comparison result between a color image output apparatus according to Embodiment 3 and a comparative example.
[Explanation of symbols]
10 Micro optical element
12 Light focusing element
14 First minute opening
16 Light diffusing element part
18 Integral hemisphere
20, 22 Second minute opening group
30 Optical writing device
32 Light beam
34 Magnification imaging element
36 Image recording media
40 Micro optical element array section
42 Quartz glass substrate
44 First minute opening
46 Light Diffusing Element Array
48 Integral hemisphere
50, 52 Second minute opening group
54 Conical mirror array
56 LEDA light emitting part
60 Optical writing device
62 laser
64 polygon mirror
66 Optical system
68 Micro optical element array section
70 glass plate
72 Magnification Imaging Element Array

Claims (6)

The image is decomposed into a large number of minute pixels, and a luminous flux with intensity corresponding to the pixel density is emitted from one or more light sources. Then, a latent image such as a surface potential change or a chemical change is formed, or an image having a density change is immediately formed by exposure, and scanning is performed on an image recording medium or the like, and each pixel area is sequentially exposed. In an optical writing device that writes an image by
Between the light source and the image recording medium, etc.
A light focusing element for focusing the light beam;
A first minute opening provided at a position where the light beam is focused;
A light diffusing element portion for diffusing a light beam emitted from the first minute opening into a limited region of approximately the same size as a pixel;
A second group of minute openings composed of a plurality of openings for emitting light diffused by the light diffusing element part;
An imaging element unit that images a plurality of light beams emitted from the second minute opening group as separate bright spots on the image recording medium or the like;
Are arranged from the light source side in the order of
The second minute opening group is composed of an opening disposed substantially at the center of the first opening, and one or a plurality of openings disposed around the opening,
The light intensity density of the bright spot emitted from the opening arranged at the center of the first opening in the second minute opening group is emitted from the other second minute opening. An optical writing device characterized in that it is higher than the light intensity density of a bright spot.   The second minute opening group is composed of an opening having a relatively large diameter disposed substantially at the center of the pixel region and an opening disposed in the shape of one or a plurality of ring zones around the opening. 2. The optical writing device according to claim 1, wherein the opening belonging to the annular zone on the outer periphery is formed to have a relatively small diameter. As a light source for optical writing, a light emitting diode array in which light emitting diode elements are linearly arranged at the same density as the pixels is used.
As the light focusing element portion, using a mirror array such as a spherical shape, a hemispherical shape, a super hemispherical shape, a conical shape having an emitting portion at a position facing a light emitting region provided above the light emitting region of each light emitting diode element,
The first minute opening is composed of a first pinhole array provided at an emission part of the mirror array,
As the light diffusing element part, using an integrating sphere array such as a spherical, hemispherical, super hemispherical, conical or the like provided corresponding to the first pinhole array,
The second minute opening group is provided at a position facing the first pinhole array on the integrating sphere array, and includes a second pinhole array in which a plurality of pinhole groups are arranged, respectively.
The optical writing device according to claim 1, wherein an equal-magnification imaging element array is used as the imaging element unit. As a light source for optical writing, a polygon scanner that scans the image recording medium by deflecting the collimated laser beam with a rotating polygon mirror is used.
The light focusing element portion is arranged in the main scanning direction, which is the direction in which laser light is scanned by the polygon mirror, and has an emission portion at a position facing the laser light incidence portion. Using a generally conical mirror array with a larger diameter than the exit,
The first minute opening is composed of a first pinhole array provided at an emission part of the mirror array,
As the light diffusing element part, using an integrating sphere array such as a spherical, hemispherical, super hemispherical, conical or the like provided corresponding to the first pinhole array,
The second minute opening group is provided at a position facing the first pinhole array on the integrating sphere array, and includes a second pinhole array in which a plurality of pinhole groups are arranged, respectively.
The optical writing device according to claim 1, wherein an equal-magnification imaging element array is used as the imaging element unit.   5. The microlens is formed in each of the first minute openings and / or each of the second minute openings, or both of them. 5. The optical writing device described. 6. An optical writing device comprising a plurality of the optical writing devices according to claim 1 and writing each color by separating a color image into yellow, magenta, cyan, black, or red, green, and blue. In the color image output device for sequentially writing these on the same image recording medium or the like, or writing them on the individual image recording medium or the like for each color, and then superimposing the images of each color by means of overlapping,
The second minute opening group of each of the optical writing devices of yellow, magenta, cyan, black, or red, green, and blue has an arrangement pattern of the individual openings of yellow, magenta, cyan, black, Alternatively, the color image output device is provided by shifting the arrangement position or the arrangement angle so that the colors of red, green, and blue are not the same.

Images