JP4043701B2 - Optical writing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical writing apparatus and an image forming apparatus that expose an image recording medium such as an image carrier by scanning a light beam through a scanning optical system.
[0002]
[Prior art]
“Banding” means irregular or regular on an output sheet in a laser printer having an optical writing device structured to expose an image carrier such as a photosensitive drum by scanning a light beam through a scanning optical system. It is a term used to define striped image noise, which is a bright and dark area (band) that was not present in the original image that appears automatically. These bands are created as a result of the position of the scanning lines being not constant, dark bands appear when the pitch between the scanning lines is close to each other, and lighter bands are spaced apart from the scanning line. Occurs when
[0003]
In general, when the image (document) on the output sheet is only text, the “banding” is not clearly understood by the user. However, today, when the resolution that laser printers can use is greatly improved, the document is often a graphic image containing grayscale, in which case "banding" is clearly visible to the user's eyes. It will be.
[0004]
The variation in pitch between scan lines as described above is caused by various system errors. Various system errors that cause variations in pitch between scanning lines, which are the factors that cause such “banding”, will be described below with reference to a laser printer as an example.
[0005]
The first cause is variation in the moving speed (rotational speed) of an image carrier such as a photosensitive drum. The variation in the moving speed (rotational speed) of the image carrier is caused by a defect in mechanical parts including the image carrier driving system. These defects include the image carrier or mechanical parts not being perfect circles, poor gear accuracy, bearing wear, mechanical coupling errors, and the like.
[0006]
In the prior art, this “banding” problem is solved by using more accurate (and more expensive) parts when manufacturing the optical writing device. In fact, by applying a high-precision drive mechanism and high-accuracy position detection technology to the image carrier and other movable parts, “banding” due to uneven speed of the image carrier is reduced to an extent that does not cause any problems. Has been.
[0007]
The second cause is the vibration state of the structure that occurs as a result of mechanical resonance. When the structure is vibrated in this way, a relative movement is caused between the optical writing device and the image carrier, resulting in variations in the pitch between the scanning lines, and “banding” is applied to the image on the output sheet. Will occur.
[0008]
With respect to such a vibration problem, in the prior art, the “banding” problem is solved by preparing a harder structure.
[0009]
However, these harder structures usually have the problem of being heavier and more expensive. In addition, there is a problem that even if a harder structure is prepared and improved as described above, the “banding” cannot be completely removed. “Banding” that cannot be removed in this way is, for example, “banding” that occurs when the optical path of the scanning optical system expands or tilts when an impact is applied to the housing, and the position of the writing light spot changes. is there.
[0010]
Therefore, a feedback system that attempts to compensate for the mechanical movement of the image carrier or drive system is also considered, but this feedback system is fast enough to completely overcome the effects of such “banding” due to vibrations. no response. The high-bandwidth servo system is close to solving this “banding” problem, but mechanical elements usually have elasticity, and this elasticity is used to correct the system at high frequencies. Does not function well enough to prevent such “banding” to limit the response of As an example, a system for reducing the “banding” by controlling the rotational speed of the photosensitive member by a highly accurate feedback system is disclosed in Japanese Patent Laid-Open No. 09-34186. It cannot be reduced to "banding" due to the irregular vibration given to
[0011]
Therefore, a so-called LED printer in which an LED (Light Emitting Diode) array and an equal-magnification imaging optical system are combined is considered as an optical writing device having a method different from that of a laser printer. In this method, it is common to use a 1X imaging optical system with a short optical path length by a lens array. In such a short optical path, the fluctuation of the position of the light spot due to vibration of the housing can be suppressed, so "banding" The problem is easier to solve.
[0012]
[Problems to be solved by the invention]
However, since LED printers write with light beams from several thousand to 10,000 or more light emitting areas, it is difficult to ensure the uniformity of the amount of light emitted from these many light emitting areas. Therefore, at present, the current supply amount to each light emitting region is individually corrected to obtain an apparently uniform light emission amount. However, this method can cope with fluctuations in the amount of light due to changes over time of the LED. It has not been possible to realize a high-quality optical writing device.
[0013]
That is, for correcting such a change with time, an optical writing apparatus of a method of scanning and writing light from one or several semiconductor laser light sources is overwhelmingly advantageous. This is because the amount of light from the operating light source can be monitored and corrected in real time.
[0014]
An object of the present invention is to provide an optical writing apparatus and an image forming apparatus that can reduce the occurrence of “banding” at low cost and can improve image quality.
[0015]
[Means for Solving the Problems]
According to a first aspect of the present invention, in an optical writing apparatus that scans a light beam emitted from a light source via a scanning optical system onto an image recording medium and exposes the image recording medium, the openings arranged in an array are formed. A light focusing element unit that focuses the light beam emitted from the light source in units of one pixel and emits the light beam from a minute opening formed at a focusing position, and the minute opening part of the light focusing element unit A light diffusing member which is provided on the side and diffuses the light beam emitted from the minute opening to form a bright spot, and the bright spot formed on the light diffusing member is imaged on the image recording medium, etc. A double imaging element in the scanning optical system.
[0016]
Therefore, even if the irradiation position of the light beam fluctuates due to vibrations of the housing, the light beam incident on the light focusing element unit is converged at the same point in the openings arranged in an array, so that the angle variation of the light beam changes. It does not affect image formation. Further, by forming an image of the bright spot formed on the light diffusing member on the image recording medium by the equal magnification imaging element, the optical path becomes a short distance from the equal magnification imaging element to the image recording medium. Therefore, even if a slight fluctuation occurs in the positional relationship between the light focusing element portion and the image recording medium due to the vibration, the position fluctuation of the imaging position on the image recording medium can be ignored. It gets smaller. As a result, it is possible to reduce the occurrence of “banding” at a low cost compared to the case where the apparatus housing is manufactured firmly, and it is possible to improve the image quality.
[0017]
According to a second aspect of the present invention, in the optical writing device according to the first aspect, the opening of the light focusing element portion has a pyramid shape in which an optical path cross-sectional area gradually decreases from the light source side toward the minute opening or It has a conical shape, and a reflective film is formed on the inner surface thereof.
[0018]
Therefore, by applying manufacturing equipment and manufacturing processes used for manufacturing semiconductors and the like, it is possible to manufacture a high-precision light focusing element portion by a simple method.
[0019]
According to a third aspect of the present invention, in the optical writing device according to the first or second aspect, the light diffusing member is a single member that covers all the minute openings formed in the light focusing element portion.
[0020]
Therefore, it becomes possible to manufacture at low cost, and it becomes possible to provide an optical writing device at low cost.
[0021]
According to a fourth aspect of the present invention, in the optical writing device according to the first or second aspect, the light diffusing member is a plurality of members that individually and independently cover the minute openings formed in the light focusing element portion. It is.
[0022]
Therefore, since the spread of the bright spot in the light diffusing member is limited, the blur of the bright spot is limited to the area of each light diffusing member, and the resolution can be improved.
[0023]
According to a fifth aspect of the present invention, in the optical writing device according to the first or second aspect, the light diffusing member is provided inside each of the minute openings formed in the light focusing element portion.
[0024]
Therefore, it is possible to form a small light spot necessary for higher resolution on the image recording medium.
[0025]
According to a sixth aspect of the present invention, in the optical writing device according to the fifth aspect, the light focusing element portion is provided with a microlens that individually covers the minute openings.
[0026]
Therefore, by collecting the light emitted from the light diffusing member with the microlens, it becomes possible to increase the effective amount of light, and thus it is possible to increase the utilization efficiency of the light emitted from the light diffusing member. Thus, the image recording speed can be increased.
[0027]
According to a seventh aspect of the present invention, in the optical writing device according to the fifth aspect, light from a portion other than the minute openings is blocked around the minute openings formed in the light focusing element portion. A light shielding member is provided.
[0028]
Therefore, stray light is blocked because light that does not contribute effectively to image formation is blocked, including light having a certain angle with respect to the optical axis and light leaking from the inside of the element in the light emitted from the light diffusing member. It becomes possible to obtain an effect of improving the image quality such as improving the contrast.
[0029]
According to an eighth aspect of the present invention, in the optical writing device according to any one of the first to seventh aspects, the light diffusing member absorbs light having a specific wavelength λa and emits light having a wavelength λb different from the wavelength λa. It is a structure containing fibers or fine particles formed of a material to be emitted.
[0030]
Therefore, it becomes possible to emit light having a more effective wavelength by exposing the image recording medium using an easily available light source.
[0031]
According to a ninth aspect of the present invention, in the optical writing device according to any one of the first to eighth aspects, an opening shape on the light source side of the opening portion of the light focusing element portion is a direction in which the light beam is scanned. It has an elliptical shape or a rectangular shape with a long diameter in the perpendicular direction, that is, the sub-scanning direction.
[0032]
Therefore, by increasing the opening area on the light source side of the opening, it is possible to further increase the allowable range of the positional deviation of the locus of the light beam.
[0033]
According to a tenth aspect of the present invention, in the optical writing device according to any one of the first to ninth aspects, a pulse corresponding to the light beam being scanned in the vicinity of the opening of the light focusing element portion. A light receiving signal generator for generating a light receiving signal in the form of a ring.
[0034]
Therefore, since the scanning position of the light beam can be monitored, it is possible to control the light amount of the light beam with higher accuracy, and to obtain the effect of improving the image quality such as stabilizing the image density more uniformly.
[0035]
According to an eleventh aspect of the present invention, there is provided an image forming apparatus comprising: a latent image carrier; a charging device that uniformly charges a surface of the image carrier; 11. The optical writing device according to claim 1, which forms an image, a developing device that develops an electrostatic latent image formed on the image carrier, and a development image transferred from the image carrier to a sheet. A transfer device.
[0036]
Therefore, it is possible to provide an image forming apparatus that can reduce the occurrence of “banding” at low cost.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. The optical writing apparatus according to the present embodiment is used in a laser printer (image forming apparatus) that forms an image by an electrophotographic method, and in accordance with an electrophotographic process, together with a charging device, a developing device, a transfer device, a cleaning device, and the like, an image carrier. The present invention is applied to an optical writing device disposed in the periphery of the.
[0038]
FIG. 1 is a perspective view showing a schematic configuration of the optical writing device 1. As shown in FIG. 1, an optical writing apparatus 1 includes an LD (Laser Diode) 2 as a light source, an optical modulator 3, a collimating lens 4, a polygon scanner 5, a polygon motor 6 that rotationally drives the polygon scanner 5, An image bearing member (image carrier as an image recording medium) which is a characteristic component of the f-glow tower Y system 9 composed of the cylinder lens 7 and the toroidal lens 8, the reflecting mirror 10, and the optical writing device 1 of the present embodiment. The optical element 11 is provided in the vicinity of the photosensitive drum 13. A scanning optical system 12 is formed by the polygon scanner 5, the cylinder lens 7, the f excitation tower Y system 9, the reflecting mirror 10, and the optical element 11.
[0039]
Schematically, a light beam, which is a light beam emitted from the LD 2, is intensity-modulated by the light modulator 3, and then forms an image on the reflection surface 5 a of the polygon scanner 5 via the collimator lens 4. The light beam thus emitted from the LD 2 and imaged on the reflection surface 5 a of the polygon scanner 5 is deflected and scanned by rotating the polygon scanner 5 by the polygon motor 6. The light beam deflected and scanned by the rotation of the polygon scanner 5 in this way is corrected by the f excitation tower Y system 9 composed of the cylinder lens 7 and the toroidal lens 8, and is folded back by the reflecting mirror 10. The light beam folded back by the reflecting mirror 10 is imaged on the photosensitive drum 13 via the optical element 11 to be a writing light spot, as will be described in detail later.
[0040]
Next, the optical element 11 which is a characteristic component of the optical writing device 1 of the present embodiment will be described in detail. Here, FIG. 2 is a longitudinal side view schematically showing the configuration of the optical element 11. As shown in FIG. 2, the optical element 11 is provided on the transparent substrate 14, the micro optical element 15 provided on the LD2 side of the transparent substrate 14, and the photosensitive drum 13 side of the transparent substrate 14. And the same magnification imaging element 16.
[0041]
First, the micro optical element 15 will be described. Here, FIG. 3 is an enlarged view showing a part of the configuration of the micro optical element 15, (a) is a front view seen from the LD 2 side, and (b) is a longitudinal section on line AA in (a). It is a side view. As shown in FIG. 3, the micro optical element 15 is roughly divided into a light focusing element portion 17 provided on the LD2 side and a light diffusion member 18 provided on the photosensitive drum 13 side. It is configured.
[0042]
The light converging element portion 17 has a conical or pyramid-shaped opening portion 19 (in this embodiment, a conical shape) whose optical path cross-sectional area gradually decreases from the LD 2 side toward the photosensitive drum 13 side. Many are formed in an array over the entire writing width of the photosensitive drum 13. That is, the light diffusing member 18 side of the opening 19 is a minute opening 20, and the minute openings 20 are arranged on a straight line at a pitch of 42.3 μm corresponding to 600 dpi. A reflective film 21 is formed on the inner surface of the opening 19, and the openings 19 formed in a large number in an array form a conical mirror array having a micromirror configuration. In addition, a light shielding film 22 is formed on the LD 2 side of the light focusing element portion 17 and excluding the opening 19.
[0043]
Here, the manufacturing procedure of the optical element 11 will be described.
1. Production of light focusing element
After a quartz glass substrate polished to a thickness of 40 μm is bonded to a silicon wafer using a thermoplastic resin for fixing the sample, a chromium film serving as a light shielding film 22 is laminated on the surface of the quartz glass substrate to a thickness of 500 nm by a sputtering method. Provide. At this time, in order to improve the adhesion strength of the chromium film, a titanium film may be provided as a base layer with a thickness of 10 nm stacked by a sputtering method.
[0044]
Next, a photoresist is applied on the quartz glass substrate to form a photoresist film. For the photoresist, OFPR800 (viscosity 800 cp) manufactured by Tokyo Ohka Co., Ltd. is used, and the photoresist is applied to a thickness of 9 μm by spin coating. Thereafter, this photoresist film is pre-baked. 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 the pre-baked photoresist film, and then development and rinsing are performed to obtain a diameter of 20 μm. A resist mask in which cylindrical recesses having a depth of 9 μm are linearly arranged at a pitch of 42.3 μm (600 dpi) is formed on a quartz glass substrate.
[0045]
Subsequently, with the quartz glass substrate adhered to the silicon wafer, a thermal fluidization process is performed on the resist mask at 200 ° C. for 30 minutes. As a result, the upper diameter of the resist mask expands due to thermal deformation, so that the resist mask is linearly spaced at a pitch of 42.3 μm with tapered openings having an upper diameter of 40 μm, a lower diameter of 20 μm, and a depth of 5 μm. It becomes the shape arranged in the shape.
[0046]
Next, this tapered shape is engraved on a quartz glass substrate by dry etching. An ECR dry etching apparatus (ER-037 apparatus manufactured by Sumitomo Metal Industries, Ltd.) is used for the dry etching process, and CHF3 gas is used as the etching gas. The dry etching conditions are as follows: CHF3 gas supply amount: 20 SCCM, reaction pressure: 0.1 Pa, microwave (2.54 GHz) power: 800 W, substrate bias RF (13.56 MHz) power: 300 W, substrate temperature: −30 ° C. And Under this condition, the ratio of the etching rate between the quartz glass substrate and the resist mask is approximately “4.5: 1”, so that the taper shape of the resist mask is engraved by enlarging 4.5 times in the etching direction, and the minute opening An opening 19 having 20 is formed. Since the chromium film as the light shielding film 22 is very thin with a thickness of 500 nm, the exposed portion is removed in a short time at the initial stage of dry etching, so that the chromium film is an obstacle to dry etching of the quartz glass substrate. Never become. The dry etching is stopped when the quartz glass substrate penetrates and the resist mask remains on the chromium film.
[0047]
Thereafter, a gold film is deposited on the quartz glass substrate to a thickness of 7000 mm using a vacuum deposition apparatus. In order to improve the adhesion strength, a titanium film may be provided as a base layer with a thickness of 10 nm stacked by a sputtering method.
[0048]
Next, after the quartz glass substrate is heated, the quartz glass substrate is removed from the silicon wafer, and the thermoplastic resin used for bonding is removed by washing with an organic solvent. At this time, the resist mask remaining on the quartz glass substrate swells, and the gold film on the chromium film (resist mask) as the light shielding film 22 is removed by lift-off, and only the inner surface of the opening 19 serves as the reflective film 21. A gold film is formed.
[0049]
Through the above-described steps, the light focusing element portion 17 in which the conical mirror array which is the conical opening portion 19 having the micromirror structure including the minute opening portion 20 is formed.
[0050]
In addition, when manufacturing the light focusing element part 17 by such a procedure, about 120 mm is suitable for the length of the light focusing element part 17. When manufacturing an element longer than this, for example, when manufacturing the light focusing element portion 17 having a length of 297 mm corresponding to the short side of the A3 size, a large-scale dry etching apparatus and photolithography equipment are required. This is not a good idea. Therefore, it is considered that the concentric mirror array having a length of about 120 mm is arranged in a strip shape on a silicon wafer of about 6 inches to manufacture a plurality of light focusing element portions 17 and then the light focusing element portions 17 are separated. It is done. However, when a dicing saw or the like is used to separate the light focusing element portion 17, chipping at the end portion (so-called chipping) occurs, and the conical mirror array of the light focusing element portion 17 is damaged, resulting in a decrease in yield. Is inevitable. Therefore, in the stage of manufacturing the conical mirror array, it is considered to include a separation line of the conical mirror array in advance in the exposure pattern so that the quartz glass substrate is etched and separated in the dry etching process. It is done. According to this method, the end portion such as chipping is not damaged at all, so that the yield is not lowered.
[0051]
2. Bonding transparent substrate and light diffusion member
An opal glass plate polished to a thickness of 20 μm is bonded to one side of a transparent substrate 14 having an optical thickness shorter than the working distance of the equal-magnification imaging element 16 with an ultraviolet curable resin. This opal glass plate functions as the light diffusing member 18. Since the working distance of the equal-magnification imaging element 16 is usually several millimeters, the transparent substrate 14 only needs to have a thickness smaller than that. Further, when the light diffusing member 18 has a structure including fibers or fine particles formed of a material that absorbs light having a specific wavelength λa and emits light having a wavelength λb different from the wavelength λa, the light diffusing member 18 is easily available. By using an LD (Laser Diode: semiconductor laser), it is possible to emit light having an effective wavelength by exposing the photosensitive drum 13.
[0052]
3. Adhere the light focusing element onto the light diffusion member
The light focusing element portion 17 is bonded on the opal glass plate functioning as the light diffusion member 18, and the micro optical element 15 is formed on the transparent substrate 14. That is, the light diffusing member 18 is joined to the light focusing element portion 17 so as to cover all the minute openings 20. As described above, the structure in which the light diffusion member 18 is continuously formed so as to cover all the minute openings 20 allows the minute optical element 15 to be manufactured at low cost.
[0053]
4). Bonding the same magnification imaging element to a transparent substrate
An equal-magnification imaging element 16 is bonded to the transparent substrate 14 provided with the micro optical element 15. For example, an RPLA (roof prism lens array) element manufactured by Ricoh Co., Ltd. can be used as the equal magnification imaging element 16.
[0054]
Thus, the optical element 11 is completed. In the case where a transparent substrate 14 having an optical thickness just equivalent to the working distance of the equal-magnification imaging element 16 is used, the equal-magnification imaging element 16, the micro optical element 15, and the like are formed on both surfaces of the transparent substrate 14. By adhering and mounting, this portion can be made into a unit structure and can be easily fixed inside the apparatus.
[0055]
With such a configuration, as shown in FIG. 4, the light focusing element portion 17 of the micro optical element 15 condenses the light beam folded by the reflecting mirror 10 onto the micro aperture 20 and emits it from the micro aperture 20. To do. The light emitted from the minute opening 20 is diffused in the light diffusing member 18 of the minute optical element 15 to form minute dot-like bright spots on the light diffusing member 18. The bright spots formed in this way are imaged on the photosensitive drum 13 by the equal magnification imaging element 16 to become a writing light spot.
[0056]
According to such a configuration, even if the irradiation position of the light beam deflected by the polygon scanner 5 fluctuates due to vibration of a housing (not shown) of the laser printer, the light beam incident on the optical element 11 is not changed. Since the light focusing element portion 17 of the micro optical element 15 is focused at the same point, the angle variation of the writing light beam does not affect the image formation.
[0057]
Further, the writing light spot imaged on the photosensitive drum 13 is obtained by converting the image of the bright spot formed on the light diffusing member 18 of the micro optical element 15 disposed in the vicinity of the photosensitive drum 13 by the equal magnification imaging element 16. Since the image is formed, the optical path can be a short distance from the micro optical element 15 to the photosensitive drum 13. Specifically, the optical path length from the micro optical element 15 to the photosensitive drum 13 is about 4 mm to 8 mm, compared with the optical path of the writing light beam by the polygon scanner 5 ranging from about 20 cm to 40 cm. That is, due to the short optical path, even if a slight variation occurs in the positional relationship between the optical element 11 and the photosensitive drum 13 due to vibration, the positional variation of the writing light spot on the photosensitive drum 13 is Small enough to be ignored.
[0058]
As described above, since there is no position fluctuation in the writing light spot, there is no variation in the pitch between the scanning lines, so that “banding” that can be visually recognized in the image on the output sheet does not occur. Absent.
[0059]
In the configuration described above, when the light incident position on the light focusing element portion 17 changes slightly, the state of light emitted from the light focusing element portion 17 (for example, the far field pattern) changes. However, since the light emitted from the light focusing element portion 17 is always diffused by the light diffusing member 18 to have the same characteristics, such a problem does not occur. This means that the light diffusing member 18 is provided.
[0060]
Further, in the above-described configuration, since the same-size image forming element 16 and the like that are unnecessary for the conventional optical writing apparatus are newly required, the apparatus seems to be complicated and expensive. However, in actuality, the cost can be reduced overall. The reason will be described below.
[0061]
In order to suppress the occurrence of “banding”, the deviation of the trajectory of the light beam on the photosensitive drum 13 from the appropriate scanning position must be reduced to such an extent that the resolution does not become a problem. For example, in order to suppress the occurrence of “banding” at the time of optical writing with a resolution of 600 dpi (scan line interval (pitch between scan lines) of about 42.3 μm), the positional deviation allowed in the trajectory of the light beam is It is approximately ± 1 μm. Conventionally, in order to satisfy this condition, it has been required to specifically reduce distortion and vibration of the casing, and it has been unavoidable that the manufacturing requires a lot of cost. On the other hand, in the optical writing device 1 of the present embodiment, a relatively large positional deviation can be allowed by the action of the light focusing element portion 17. For example, when the opening 19 of the light focusing element 17 is a conical mirror, the diameter on the LD2 side of one opening 19 arranged at a density of 600 dpi can be expanded to about 42 μm. Therefore, it is sufficient that the light beam is incident upon scanning, so that when the writing light beam is narrowed to a diameter of about 20 μm, a positional deviation of ± 11 μm is allowed. That is, in order to suppress the occurrence of “banding” during optical writing, it is not necessary to manufacture the housing of the housing laser printer specially firmly, and the mutual position of the light diffusing member 18 and the photosensitive drum 13 is different. It will be good if it does not fluctuate.
[0062]
In addition, even if a minute position change occurs in the equal magnification imaging element 16, the writing light spot is not displaced due to the principle of the equal magnification imaging system, and the bright spot of the light source (here, The amount of positional deviation of the bright spot on the light diffusion member 18 is the same as the amount of positional deviation of the exposed point of the photosensitive drum 13. Further, since the light diffusing member 18 and the support point of the photosensitive drum 13 (here, the rotation center of the photosensitive drum 13) are provided close to each other, the unit structure is connected with high rigidity, and the positional relationship varies. It is relatively easy to keep the value below ± 1 μm.
[0063]
Further, since the 1 × imaging element 16 is an inexpensive part, the overall cost is higher than that of the conventional optical writing apparatus although the 1 × imaging element 16 is added as a component configuration and the number of parts is increased. Lower.
[0064]
For the reasons described above, according to the optical writing device 1 of the present embodiment, it is possible to suppress the occurrence of “banding” at a lower cost than when the device housing is firmly manufactured.
[0065]
In the present embodiment, the same-magnification imaging element 16 that linearly guides the optical path of the light beam as shown in FIG. 4 is used, but the present invention is not limited to this. An equal magnification imaging element that refracts the optical path of the light beam by 90 degrees and guides it may be used.
[0066]
Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those described in the first embodiment of the present invention are denoted by the same reference numerals, and description thereof is also omitted. This embodiment is different only in that a micro optical element 30 is provided instead of the micro optical element 15 of the first embodiment.
[0067]
6A and 6B are enlarged views of a part of the configuration of the micro optical element 30. FIG. 6A is a front view seen from the LD2 side, and FIG. 6B is a longitudinal side view taken along line AA in FIG. It is. As shown in FIG. 6, the micro optical element 15 according to the first embodiment includes the light diffusion member 18 having a structure continuously formed so as to cover all the micro openings 20. The micro optical element 30 of the form is configured to include a plurality of light diffusing members 31 formed so as to individually cover the micro openings 20.
[0068]
Here, the manufacturing procedure of the optical element 11 will be described. It should be noted that “1. Production of light focusing element” and “2. Adhesion of transparent substrate and light diffusing member” described in the first embodiment are not changed at all, and thus description thereof is omitted.
[0069]
In this embodiment, an opal glass plate is bonded to one side of the transparent substrate 14 with an ultraviolet curable resin, and then a photoresist film is applied on the opal glass plate, and a circular pattern having a diameter of 30 μm is arranged at a density of 600 dpi. A resist mask is formed. Then, the opal glass plate is dry-etched under the same conditions as the quartz glass substrate is dry-etched in the first embodiment, thereby forming the opal glass plate into a shape in which cylinders with a diameter of 30 μm are arranged. That is, the cylinders with a diameter of 30 μm formed in an island shape on the transparent substrate 14 each function as the light diffusing member 31.
[0070]
Thereafter, “3. Adhering the light focusing element portion on the light diffusing member” and “4. Adhering the same magnification imaging element to the transparent substrate” described in the first embodiment are the same as those in the first embodiment. By carrying out similarly, the optical element 11 which has the micro optical element 30 provided with the several light-diffusion member 31 formed so that each of the micro opening part 20 may be each covered is manufactured.
[0071]
According to the optical writing device 1 using the optical element 11 having such a micro optical element 30, the light diffusion member 31 individually covers the micro openings 20, thereby limiting the spread of bright spots in the light diffusion member 31. Therefore, the blur of the bright spot is limited to the area of each light diffusing member 31, and the resolution can be improved. That is, the light diffusing member 31 individually covers the minute openings 20 so that minute dots can be reproduced.
[0072]
Next, a third embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is used about the same part as the part demonstrated in 1st embodiment or 2nd embodiment of this invention, and description is also abbreviate | omitted. This embodiment differs from the second embodiment only in that a micro optical element 40 is provided instead of the micro optical element 30 of the second embodiment.
[0073]
7A and 7B are enlarged views of a part of the configuration of the micro optical element 40. FIG. 7A is a front view seen from the LD2 side, and FIG. 7B is a longitudinal side view taken along line AA in FIG. It is. As shown in FIG. 7, the micro optical element 30 of the second embodiment includes a plurality of light diffusion members 31 formed so as to individually cover the micro openings 20, but this embodiment The micro optical element 40 has a structure in which a light diffusing member 41 is provided inside the micro opening 20.
[0074]
The manufacturing procedure of the optical element 11 including such a micro optical element 40 is substantially the same as the manufacturing procedure of the optical element 11 including the micro optical element 30 of the second embodiment, and when patterning an opal glass plate. The only difference is that a circular pattern having a diameter of 15 μm is used. That is, the cylinders having a diameter of 15 μm formed in an island shape on the transparent substrate 14 each function as the light diffusion member 41.
[0075]
Then, in the step of adhering the light focusing element portion 17, the light diffusion member 41 having a diameter of 15 μm formed in an island shape on the transparent substrate 14 is aligned so as to enter the minute opening 20 of the light focusing element portion 17. It will be glued.
[0076]
According to the optical writing apparatus 1 using the optical element 11 having such a micro optical element 40, it is possible to form a small light spot necessary for high resolution on the photosensitive drum 13.
[0077]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The same parts as those described in any of the first to third embodiments of the present invention are denoted by the same reference numerals, and the description thereof is also omitted. The micro optical element 50 of this embodiment is different only in that a micro lens 51 is provided in each micro opening 20 of the micro optical element 40 of the third embodiment.
[0078]
8A and 8B are enlarged views showing a part of the configuration of the micro optical element 50. FIG. 8A is a front view seen from the LD2 side, and FIG. 8B is a longitudinal side view taken along line AA in FIG. It is. As shown in FIG. 8, the micro optical element 50 according to the present embodiment has a structure including microlenses 51 so as to individually cover the microopenings 20 each including the light diffusion member 41 therein. .
[0079]
According to the optical writing device 1 using the optical element 11 having such a micro optical element 50, the utilization efficiency of the light emitted from the light diffusing member 41 can be increased, and the image recording speed can be increased. . This is because the light reception angle range (NA) of the equal-magnification imaging element 16 is generally narrower than the light emission angle of the light diffusing member 41, and light having a certain angle or more with respect to the optical axis is used. This is because the effective amount of light can be increased by condensing the light emitted from the light diffusing member 41 by the microlens 51.
[0080]
Next, a fifth embodiment of the present invention will be described with reference to FIG. The same parts as those described in any of the first to fourth embodiments of the present invention are denoted by the same reference numerals, and the description thereof is also omitted. The micro optical element 60 of this embodiment is different only in that a light shielding member 61 is provided in each micro opening 20 of the micro optical element 40 of the third embodiment.
[0081]
9A and 9B show an enlarged view of a part of the configuration of the micro optical element 60. FIG. 9A is a front view seen from the LD2 side, and FIG. 9B is a longitudinal side view taken along line AA in FIG. It is. As shown in FIG. 9, the micro optical element 60 of the present embodiment includes a light shielding member 61 that blocks light from a portion other than the micro opening 20 around the micro opening 20 having the light diffusion member 41 therein. Each is equipped with a structure.
[0082]
According to the optical writing device 1 using the optical element 11 having such a micro optical element 60, the light or element having a certain angle or more with respect to the optical axis in the light emitted from the light diffusion member 41. Since light that does not contribute effectively to image formation, including leakage light from the inside, is blocked, stray light is eliminated and an effect of improving image quality such as an improvement in contrast can be obtained.
[0083]
Next, a sixth embodiment of the present invention will be described with reference to FIG. In addition, the same code | symbol is used about the part same as the part demonstrated in either of 1st Embodiment of this invention thru | or 5th Embodiment, and description is also abbreviate | omitted. The micro optical element 70 of this embodiment is different from the micro optical element of any one of the first embodiment to the fifth embodiment only in that a light receiving signal generation unit 71 is provided. In the present embodiment, the micro optical element 40 of the third embodiment provided with a light reception signal generator 71 will be described.
[0084]
10A and 10B are enlarged views showing a part of the configuration of the micro optical element 70, where FIG. 10A is a front view seen from the LD2 side, and FIG. 10B is a longitudinal side view taken along line AA in FIG. It is. As shown in FIG. 10, the received light signal generation unit 71 of the micro optical element 70 of the present embodiment is provided on the LD2 side of the light focusing element unit 17, and is a thin film element 72 (for example, amorphous) that generates photovoltaic power. A light receiving window 73 is provided corresponding to each opening 19 in a silicon PIN diode or the like. With such a configuration, the light reception signal generator 71 can generate a pulsed light reception signal in response to the scanning of the light beam.
[0085]
According to the optical writing device 1 using the optical element 11 having such a micro optical element 70, the scanning position of the light beam can be monitored, so that the light amount control of the light beam can be performed with higher accuracy and the image density can be further increased. The effect of improving image quality such as uniform stabilization can be obtained.
[0086]
In each embodiment, the LD2 side of the opening 19 (conical mirror) is a circular opening. However, the present invention is not limited to this, and the LD2 side of the opening (conical mirror) 80 shown in FIG. In addition, an elliptical opening having a long diameter in the direction perpendicular to the direction in which the light beam is scanned, that is, the sub-scanning direction, or a rectangular opening (not particularly shown) may be used. In this way, by increasing the opening area of the opening 19 on the LD2 side, it is possible to further increase the allowable range of positional deviation of the light beam locus.
[0087]
In each of the embodiments, the optical writing device used in the laser printer that forms an image by the electrophotographic method has been described. However, the present invention is not limited to this. Further, the image recording medium targeted by the optical writing device is not limited to the image carrier (photosensitive drum) 13 used in the laser printer for forming an image by the electrophotographic method. This includes almost all media on which images are formed by optical writing, including recording media that cannot be rewritten and media such as image displays on which images are continuously written. Specific examples thereof will be described below.
[0088]
First, the light transmittance of the display material, light due to the phase change, crystal state change, other state change, or reversible chemical change caused by irradiation of visible light, ultraviolet light or infrared light. The scattering state, the spectral reflectance, the refractive index, the birefringence, etc. change, and a visible image is formed, and if necessary, irradiating light of a specific wavelength and intensity, an electric field of a specific intensity and direction, or The image can be erased by applying a magnetic field, applying a specific temperature change, or the like, and an image recording medium that can be used repeatedly, so-called digital paper, can also be used as the image recording medium.
[0089]
Second, an electrophotographic photosensitive member made of an organic and inorganic single material or composite material or a laminate thereof can also be applied as an image recording medium.
[0090]
Thirdly, black-and-white and color films or photosensitive paper by silver salt photography can also be applied as image recording media.
[0091]
Fourthly, a recording medium using a photosensitive material by other photochemical reaction can also be applied as an image recording medium.
[0092]
In addition to the above, the image recording medium targeted by the optical writing device 1 described in each embodiment has a photoconductive material layer disposed between the liquid crystal material layer and the drive electrode, and writing light to the photoconductive material layer. Immediately change the concentration with the photoconductive effect in the middle, such as in a liquid crystal display that writes an image by applying an electric field to the liquid crystal layer with the photoconductive material in the conductive state by irradiation. It also includes a display that forms an image.
[0093]
The optical writing device 1 described in each embodiment can prevent the occurrence of “banding” and improve the image quality for all of them.
[0094]
【The invention's effect】
According to the first aspect of the present invention, in the optical writing apparatus that scans the light beam emitted from the light source via the scanning optical system onto the image recording medium and exposes the image recording medium, the openings arranged in an array form A light focusing element unit for focusing the light beam emitted from the light source by a unit of one pixel and emitting the light beam from a minute opening formed at a converging position, and the minute light of the light focusing element unit A light diffusing member that is provided on the opening side and diffuses the light beam emitted from the minute opening to form a bright spot, and the bright spot formed on the light diffusing member is imaged on the image recording medium The scanning optical system includes the same-magnification imaging element that allows the light beam incident on the light focusing element unit to be arranged in an array even when the irradiation position of the light beam fluctuates due to vibration of the housing. From being focused on the same point Angular variations of the light beam is no longer able to bring an influence on image formation. Further, by forming an image of the bright spot formed on the light diffusing member on the image recording medium by the equal magnification imaging element, the optical path becomes a short distance from the equal magnification imaging element to the image recording medium. Therefore, even if a slight variation occurs in the positional relationship between the light focusing element portion and the image recording medium due to vibration, the positional variation of the image forming position on the image recording medium is negligibly small. Become. As described above, it is possible to reduce the occurrence of “banding” at a low cost as compared with the case where the apparatus housing is firmly manufactured, and it is possible to improve the image quality.
[0095]
According to a second aspect of the present invention, in the optical writing device according to the first aspect, the opening of the light focusing element portion is a pyramid whose optical path cross-sectional area gradually decreases from the light source side toward the minute opening. Because it has a shape or conical shape and a reflective film is formed on its inner surface, it can be applied to manufacturing equipment and manufacturing processes used for manufacturing semiconductors, etc. Can be manufactured by a simple method.
[0096]
According to a third aspect of the present invention, in the optical writing device according to the first or second aspect, the light diffusing member is a single member that covers all the minute openings formed in the light focusing element portion. Since it can be manufactured at a low cost, an optical writing device can be provided at a low cost.
[0097]
According to a fourth aspect of the present invention, in the optical writing device according to the first or second aspect, the light diffusing member is a plurality of individually covering each of the minute openings formed in the light focusing element portion. By using this member, the spread of bright spots in the light diffusing member is limited, so that the blur of bright spots can be limited to the area of each light diffusing member, and the resolution can be improved.
[0098]
According to a fifth aspect of the present invention, in the optical writing device according to the first or second aspect, the light diffusing member is provided inside each of the minute openings formed in the light focusing element portion. As a result, a small light spot required for higher resolution can be formed on the image recording medium.
[0099]
According to a sixth aspect of the present invention, in the optical writing device according to the fifth aspect, the light focusing element portion is provided with a microlens that individually covers each of the minute openings, so Since the light emitted from the light diffusing member can be collected and the effective amount of light can be increased, the utilization efficiency of the light emitted from the light diffusing member can be increased, and the image recording speed can be increased. .
[0100]
According to a seventh aspect of the present invention, in the optical writing device according to the fifth aspect, light from a portion other than the minute openings is formed around the minute openings formed in the light focusing element portion. By providing a light-shielding member that shields light, light including light that has a certain angle with respect to the optical axis in the light emitted from the light diffusing member and leaked light from inside the element is imaged. Since light that does not contribute effectively is blocked, stray light is eliminated, and an effect of improving image quality such as an improvement in contrast can be obtained.
[0101]
According to an eighth aspect of the present invention, in the optical writing device according to any one of the first to seventh aspects, the light diffusing member absorbs light having a specific wavelength λa and has a wavelength λb different from the wavelength λa. With a structure including a fiber or fine particles formed of a substance that emits light, light having an effective wavelength can be emitted by exposing the image recording medium using an easily available light source.
[0102]
According to a ninth aspect of the present invention, in the optical writing device according to any one of the first to eighth aspects, the light source side opening shape of the opening portion of the light focusing element portion is scanned with the light flux. By increasing the opening area on the light source side of the opening, the tolerance of positional deviation of the locus of the light beam is further increased by being an elliptical shape or a rectangular shape having a long diameter in the direction perpendicular to the direction, that is, the sub-scanning direction. Can be bigger.
[0103]
According to a tenth aspect of the present invention, in the optical writing device according to any one of the first to ninth aspects, the light beam is scanned in the vicinity of the opening of the light focusing element portion. By providing a light receiving signal generator that generates a pulsed light receiving signal, the scanning position of the light beam can be monitored, so that the light amount of the light beam can be controlled with higher accuracy and the image density can be made more uniform. An effect of improving the image quality such as stabilization can be obtained.
[0104]
According to the image forming apparatus of the eleventh aspect of the invention, the latent image carrier, the charging device for uniformly charging the surface of the image carrier, and the image carrier after the uniform charging are exposed to static electricity. 11. The optical writing device according to claim 1, which forms an electrostatic latent image, a developing device that develops an electrostatic latent image formed on the image carrier, and a developed image from the image carrier to a sheet. By providing the transfer device for transferring the image, it is possible to provide an image forming apparatus capable of reducing the occurrence of “banding” at low cost.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a schematic configuration of an optical writing device according to a first embodiment of the present invention.
FIG. 2 is a longitudinal side view schematically showing a configuration of an optical element.
FIGS. 3A and 3B are enlarged views of a part of the configuration of a micro optical element, in which FIG. 3A is a front view seen from the LD side, and FIG. 3B is a longitudinal side view taken along line AA in FIG. is there.
FIG. 4 is a schematic front view schematically showing the operation of the optical writing device.
FIG. 5 is a schematic front view showing a modified example thereof.
6A and 6B are enlarged views showing a partial configuration of a micro optical element according to a second embodiment of the present invention. FIG. 6A is a front view seen from the LD side, and FIG. It is a vertical side view on line AA.
FIGS. 7A and 7B are enlarged views showing a partial configuration of a micro optical element according to a third embodiment of the present invention. FIG. 7A is a front view seen from the LD side, and FIG. It is a vertical side view on line AA.
FIGS. 8A and 8B are enlarged views showing a partial configuration of a micro optical element according to a fourth embodiment of the present invention. FIG. 8A is a front view seen from the LD side, and FIG. It is a vertical side view on line AA.
FIGS. 9A and 9B are enlarged views showing a partial configuration of a micro optical element according to a fifth embodiment of the present invention. FIG. 9A is a front view seen from the LD side, and FIG. It is a vertical side view on line AA.
FIGS. 10A and 10B are enlarged views showing a configuration of a part of a micro optical element according to a sixth embodiment of the present invention. FIG. 10A is a front view seen from the LD side, and FIG. It is a vertical side view on line AA.
FIG. 11 is a front view showing a modification of the opening of the micro optical element.
[Explanation of symbols]
1 Optical writing device
2 Light source
12 Scanning optical system
13 Image recording medium, image carrier
16 1x imaging element
17 Light focusing element
18, 31, 41 Light diffusing member
19,80 opening
20 Micro opening
21 Reflective film
51 micro lens
61 Shading member
71 Light reception signal generator

Claims (11)

In an optical writing apparatus that scans an image recording medium with a light beam emitted from a light source via a scanning optical system and exposes the image recording medium,
A light focusing element unit that has apertures arranged in an array and focuses the light beam emitted from the light source in units of one pixel, and emits the light beam from a minute aperture formed at a focusing position;
A light diffusing member that is provided on the side of the microscopic aperture of the light focusing element and diffuses the light beam emitted from the microscopic aperture to form a bright spot;
An equal-magnification imaging element that forms an image of the bright spot formed on the light diffusion member on the image recording medium;
Is included in the scanning optical system. The opening portion of the light focusing element portion has a pyramid shape or a cone shape in which an optical path cross-sectional area gradually decreases from the light source side toward the minute opening portion, and a reflection film is formed on an inner surface thereof. The optical writing device according to claim 1, wherein: 3. The optical writing apparatus according to claim 1, wherein the light diffusing member is a single member that covers all the minute openings formed in the light focusing element portion. 3. The optical writing device according to claim 1, wherein the light diffusing member is a plurality of members that individually cover each of the minute openings formed in the light focusing element portion. 3. The optical writing device according to claim 1, wherein the light diffusing member is provided inside each of the minute openings formed in the light focusing element portion. 6. The optical writing device according to claim 5, wherein the light focusing element portion is provided with a microlens that individually covers each of the minute openings. 6. The light according to claim 5, wherein a light shielding member that blocks light from a portion other than each of the micro openings is provided around each of the micro openings formed in the light focusing element section. Writing device. The light diffusing member has a structure including fibers or fine particles formed of a material that absorbs light having a specific wavelength λa and emits light having a wavelength λb different from the wavelength λa. 8. The optical writing device according to any one of 7. The opening shape on the light source side of the opening portion of the light focusing element portion is an elliptical shape or a rectangular shape having a long diameter in a direction perpendicular to the direction in which the light beam is scanned, that is, in the sub-scanning direction. The optical writing device according to claim 1. 2. A light receiving signal generating section for generating a pulsed light receiving signal corresponding to the scanning of the light beam is provided in the vicinity of the opening of the light focusing element section. The optical writing device according to any one of Items 9 to 9. A latent image carrier;
A charging device for uniformly charging the surface of the image carrier;
The optical writing device according to any one of claims 1 to 10, wherein the image bearing member after uniform charging is exposed to form an electrostatic latent image;
A developing device for developing an electrostatic latent image formed on the image carrier;
A transfer device for transferring a developed image from the image carrier to paper;
An image forming apparatus comprising:

Images