JPS59147319A - Optical scanner of image forming device - Google Patents

Abstract

PURPOSE:To obtain an optical scanner which has high dust-proof effect, outputs a flicker-free output image, and eliminates the need to adjust the optical axis when a component is replaced by arranging a light source, polarizer, image forming lenses, and horizontal synchronizing signal detecting means at specific positions in an optical box, and sealing the box with a cover. CONSTITUTION:Laser light projected from a semiconductor laser unit 11 illuminates a detection mirror through an image forming lens 4a, a polygon mirror 2, and image forming lenses 4b and 4c. Its reflected light scans on the incidence port of an optical fiber tube 5 horizontally and is converted into a horizontal synchronizing signal by a photodiode 34. The semiconductor laser unit 11 is driven by using a recorded information signal a specific time later after said synchronizing signal is detected, making a scan on a photosensitive drum 3. The lenses 4a-4c and polarizer 2 are arranged on the bottom surface 17a of the optical box 17 on a base 1a, a side plate 17b is fitted with the laser unit 11, etc., and the box is sealed with the cover 21 to obtain the optical scanner which has high dust-proof effect, outputs a flicker-free output image, and eliminates the need for optical-axis adjustment in the replacement of a component.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an optical scanning device for an image forming apparatus.

Generally, in an optical scanning device of an image forming apparatus as shown in FIG. 1, a rotating polygon mirror, which is a laser beam deflector, must be sealed to prevent surface deterioration, especially a decrease in reflectance. Must be.

Conventionally, the optical scanning device / has a long optical path length up to the photosensitive drum 3, which is an image carrier, and has not only a rotating polygon mirror λ but also a rotating polygon mirror f.
A detection mirror for detecting a horizontal synchronization signal to determine the writing position of an imaging lens with −θ characteristics and a laser beam,
If the entire mechanism, including the photodetector, were to have a sealed structure, it would be extremely difficult to handle it during device assembly and maintenance. In addition, if the dustproofing is insufficient, not only the surface of the imaging lens, but also the reflecting surface of the detection mirror 50 and the surface of the photodetector B will be contaminated with dust and chips in the air, resulting in a decrease in reflectance and transmittance. This decrease in reflectance and transmittance lowers the detection accuracy of the horizontal synchronizing signal, resulting in a drawback that fluctuations occur in the output image. Furthermore, when each component such as the above-mentioned rotating polygon mirror unit is replaced, the optical axis must be adjusted, which is time-consuming.

The present invention was proposed to eliminate the above-mentioned drawbacks, and has a high dawn prevention effect, does not cause fluctuations on both edges of the output, and
It is an object of the present invention to provide an optical scanning device for an image forming apparatus that does not require optical axis adjustment even when replacing each component.

Hereinafter, the present invention will be described based on its embodiments with reference to the drawings.
I will explain. 1 is a schematic oblique view of the first embodiment of the present invention, and FIG. 3 is a sectional view of the embodiment of FIG. 2. Semiconductor laser unit // is a light source unit that irradiates and generates laser light, and is used in computers, word processors,
A compact light source device consisting of a semiconductor laser that is modulated and driven in response to recording information signals from a facsimile transmitter, etc., and a shaping optical system that corrects the cross section of the laser beam from this semiconductor laser and converts the laser beam into a flat beam. It is a device. The rotating polygon mirror a is a polarizer that scans the laser light irradiated from the semiconductor laser unit //, and the rotating polygon mirror a is a polarizer that scans the laser light irradiated from the semiconductor laser unit //, and is connected to the imaging lenses lla, 4b, 4
c is for forming an image on the photosensitive drum 3 by laser light irradiated from the semiconductor laser unit //. The detection mirror on the left is a mirror that reflects the laser beam scanned by a rotating polygon mirror (rotating polygon mirror) to the horizontal synchronization signal detection position immediately before the laser beam scans the image forming area of the photosensitive drum 3. An entrance opening is provided at a position where the laser beam forms an image. Imaging lens 4a, #b, '@C, B, JP-A-S
As proposed in 7-/Da'13/Da, image formation 1 in which the laser beam is imaged as a line image and 1- on the deflection reflection surface of a rotating polygon mirror≠-
7a (cylindrical lens), and imaging lenses b and 4tc (spherical lens, 1-rick lens) that form an image of polarized laser light on the surface of the photosensitive drum 3 and scan it at a constant speed.

With such a simple and compact configuration, the inclination of the deflecting reflection surface of the rotating polygon mirror λ can be corrected.

Optical box /7 has a bottom surface /'7a of the required shape and this bottom surface /7
It consists of a side plate/7b disposed approximately perpendicularly to the side of a, and includes various parts such as a semiconductor laser unit//. Protective glass/g is photosensitive drum 3 of optical box/7
It is disposed on the side plate /'7b, and is used to transmit laser light and carry an image on the photosensitive drum 3.

The optical box/7 is made of materials such as glass fiber and reinforced polycarbonate resin, and is precisely molded with high precision. The optical box/7 has a positioning pin q3 molded on the lower surface of the bottom surface/7a, and is fitted into a positioning hole (not shown) of the base/a, and is positioned with high precision with respect to the photosensitive drum 3 and is attached/detached. Optical box/mounting seat molded on the bottom surface of 7/top surface of 7a/united to 7C
, LLC and the detection mirror are positioned and fixed by adhesive or by a fixing member (not shown). The slit plate /7 is for fitting the protective glass /g to the side plate /7b of the optical box /7 near the photosensitive drum 3, and the laser light passes through the provided slot toward the photosensitive drum 3. The cover 20 covers the top surface of the storage box/7, and includes a cover,
2/ is for cutting the laser light passage hole.

Also, the optical fiber tube/shio used for detecting the horizontal synchronization signal is mounted on the mounting seat 37 on the bottom of the optical box/7.
It is arranged and fixed at 32. It is positioned by the plane of the sharp edge 33 that covers about 4 mm of the cross section of the optical fiber tube/S, and is arranged and fixed by the fixing plate 23 without any adjustment. The drive motor 22 rotationally drives the rotating polygon mirror Ω. 2 and 5 are an enlarged partial plan view and a front view of the horizontal synchronizing signal generating means constituting the embodiment of FIG. 2, respectively. fixed plate,
23 is for fixing the optical fiber tube/S to the mounting seat 37. The seal part paulownia 2g is fitted between the optical box/7 and the optical fiber tube/shio, and
This is to prevent dust inside. Laser light passing hole 2; B is a hole through which the laser light passes to the photoreceptor 3. In this example, the optical fiber tube/S is the optical box/
7 through the seal member 2, but it may be fitted without using the seal member J.

Next, the operation will be explained. Semiconductor laser unit //
The laser beam irradiated from the mirror is irradiated via the imaging lens a to the reflective surface of a rotating polygon mirror rotating in the direction of arrow A, and is reflected. The reflected laser beam is first irradiated and reflected by the detection mirror S, and scans the vicinity of the center of the entrance cross section of the optical fiber tube 15 almost horizontally. The laser light incident on the optical fiber tube 75 is transmitted through the photodiode 3.
'1, it is photoelectrically converted and converted into a horizontal synchronizing signal. When the semiconductor laser unit // is started to be driven using the recorded information signal after a predetermined time has elapsed since the detection of this horizontal +V+ signal, a laser beam modulated in accordance with the information signal is emitted from a predetermined position on the photosensitive drum 3. Begin scanning. As a result, an electrostatic latent image is formed on the photosensitive drum 3. Incidentally, well-known electrophotographic processing equipment is arranged along the rotation path of the photosensitive drum 30.

As explained above, this embodiment is easy to handle because it is handled as an optical box unit during assembly and maintenance during production, so no optical axis adjustment is required. In addition, the parts inside the optical box are not contaminated with dust and dust in the air, and the detection accuracy of the horizontal synchronization signal is not degraded because the parts are not contaminated with dust and dirt in the air, and the detection accuracy of the horizontal synchronization signal is not degraded, and the output image does not fluctuate.

The detection accuracy of this horizontal synchronization signal, in other words,
The recording accuracy on the 0 surface is also determined by the processing accuracy of the optical box/7.Since the semiconductor laser unit// and the drive motor 22 are fitted to the optical box/7, the mounting position accuracy is high, so the optical High accuracy. In addition, since an optical fiber tube is used for the horizontal synchronization signal detection means, the horizontal synchronization signal is transmitted to the processing circuit in the form of laser light, which reduces the influence of electromagnetic waves and improves noise resistance. be effective.

The sectional view in FIG. 3 shows a third embodiment of the present invention.

The structure and operation are almost the same as those of the embodiment shown in FIG. 3, except that the refracting mirror /B is disposed at the refracting mirror seat Il/. As a result, the laser beam is refracted downward, passes through the laser beam passage hole, and scans the photosensitive drum 3 in the vertical direction. Refractive mirror/B is the bottom of optical box/7/7? It is fixed to the refraction mirror seat '17' 12 formed in L by adhesive or by a fixing member (not shown). Protective mirror in the embodiment of Fig. 3/
g and slit plate /9 are replaced with k -2/. This embodiment provides the same effects as the first embodiment, and has the advantage that it can also be applied to optical scanning devices in which the photosensitive drum 3 is disposed at a different position.

As explained above, the present invention has a light source inside the optical box, which improves the dust-proofing effect, prevents contamination of the detection mirror, etc., reduces the detection accuracy of the horizontal synchronization signal, and eliminates fluctuations in the output image. Furthermore, since the optical box is molded with high precision, this high precision state can be maintained for a long time. Furthermore, since the optical box can be handled as a unit during assembly and maintenance during production, there is no need to adjust the optical axis, resulting in easier handling.

[Brief explanation of the drawing]

, FIG. 1 is a schematic perspective view of a conventional optical scanning device of an image forming apparatus, FIG. Ω is a perspective view of a first embodiment of the present invention, and FIG. 3 is a portion of the embodiment of FIG. The sectional view, FIG.
FIG. S is a partially enlarged front view of the horizontal synchronizing signal generating means of FIG. 9, and FIG. 6 is an enlarged partial front view of the horizontal synchronizing signal generating means of FIG. FIG. 3 is a partial cross-sectional view of an example. /, /′...Optical scanning device. λ・・・・・・・・・Rotating polygon mirror. 3・・・・・・・・・・・・Photosensitive drum. ria, gub, guc...imaging lens. Left: Detection mirror. Otsu......Photodetector. /c... Semiconductor laser unit. 15......Optical fiber tube. /Otsu......Refraction mirror. /7...Optical box. 7g・・・・・・Protective glass. 2 Left, M...Laser beam passage hole. Figure 4 Figure 5 Figure 6 113-

Claims (1)

[Scope of Claims] A light source section, a deflector having a deflection reflecting surface that scans the light beam emitted from the light source section, an imaging lens group that forms an image of the light beam scanned by the deflector; An optical scanning device for an image forming apparatus comprising: a horizontal synchronizing signal detecting means for outputting a synchronizing signal in the main scanning direction of a light beam; means is arranged and fixed at a predetermined position, has a passage hole through which a light beam is emitted and passes through to the photoreceptor, and a transparent body that seals the passage hole, is sealed with a cover, and is attached to the base of the optical scanning device. An optical scanning device for an image forming apparatus, comprising an optical box that is detachably fitted.