JPS6315212A - Optical scanner - Google Patents

Abstract

PURPOSE:To suppress a deformation of a lens by using a plastic lens as the lens, and also, containing the lens in a warp preventing body. CONSTITUTION:A warp preventing body 80 is formed in a shape of a rectangu lar parallelepiped having almost the same shape as an external form of a long- sized plastic lens 36, and both the right and left side faces and the lower face are opened, respectively. Also, in roughly the center part of the front and the back, respectively, a slit 82 having prescribed width and length is formed along the longitudinal direction. The slit 82 functions as a transmission-hole of a laser beam. In this state, when the lens 36 is contained in the warp preventing body 80 so that a lens part 61 is opposed to the slit 82, the outside peripheral surface (the bottom face of the lens part 61 and each outside peripheral surface of ribs 62, 63) of the lens 36 is installed to the inside surface of the warp preventing body 80, in a state that it has adhered closely. In this way, a deforma tion such as warp and torsion, etc. of the lens 36 can be suppressed almost exactly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical scanning device suitable for application to electrophotographic color copying machines and the like.

[Background of the Invention] In electrophotographic color copying machines, photosensitive image forming bodies (
As means for forming an electrostatic latent image on a photoreceptor drum using an image signal corresponding to a document, there is a method using an optical scanning device using a semiconductor laser or the like.

FIG. 3 is a configuration diagram showing an example of such a color copying machine 10. As shown in FIG.

The figure shows an example of a simple color copying machine. This copying machine attempts to record a color image by separating the color information of a color original into approximately three types of color information. In this example, the color information to be separated is black BK, red R, and helmet B.
Illustrate colors.

In the figure, 11 indicates a drum-shaped image forming body,
A photoconductive photoreceptor surface layer made of selenium or the like is formed on its surface, so that an electrostatic image (electrostatic layer image) corresponding to an optical image can be formed.

The following members are sequentially arranged on the circumferential surface of the image forming body 11 in the direction of rotation thereof.

The surface of the image forming body 110 is uniformly charged by the charger 12, and the charged surface of the image forming body 11 is subjected to image exposure based on each color separation image (the optical signal thereof is indicated by 14).

After the image is exposed, it can be developed using a predetermined developing device.

The number of developing units corresponding to the color separation images is arranged.

In this example, developing device 1 filled with red toner developer
5, a developing device 16 filled with a blue toner developer,
The developing devices 17 filled with a black toner developer are sequentially arranged facing the surface of the image forming body 11 in this order in the rotational direction of the image forming body 11.

The developing devices 15 to 17 are sequentially selected in synchronization with the rotation of the image forming body 11. For example, by selecting the developing device 17, a black color separation image is developed.

A pre-transfer charger 19 and a pre-transfer exposure lamp 20 are provided on the developing device 17 side, and these make it easy to transfer a color image onto a recording medium P such as recording paper. However, the pre-transfer charger 19 and the pre-transfer exposure lamp 20 are provided as necessary.

The color image developed on the image forming body 11 is transferred onto the recording medium P by the transfer device 21.

The transferred recording material P is subjected to a fixing process by the fixing device 22 at the subsequent stage, and then the recording material P is discharged.

Note that the static eliminator 23 includes one or a combination of a static eliminator lamp and a corona discharger for static elimination.

The cleaning device 24 includes a cleaning blade and a fur brush, and is used to remove residual toner adhering to the drum surface after the color image of the image forming member 11 has been transferred.

As the charger 12 described above, a scorotron corona discharger or the like can be used. This is because stable charging can be applied to the image forming body 11 with less influence from previous charging.

As the image exposure, image exposure obtained by an optical scanning device (laser beam scanner) using laser light is used.

This is because when a laser beam scanning device is used, a small and inexpensive semiconductor laser can be used as the light source of the image recording device, and a clear color image can be recorded.

The image exposure means shown in FIG. 4 is an example of an optical scanning device 30 using a laser.

The optical scanning device 30 has a semiconductor laser 31, and the laser 3
1 can perform light modulation based on an image signal corresponding to a color separated image (for example, binary data).

A laser beam (optical signal) emitted from the laser 31 enters a deflection device consisting of a rotating polygon mirror, ie, a mirror scanner 34, via a collimator lens 32 and a cylindrical lens 33.

The collimator lens 32 is a lens that converts the laser beam into substantially parallel light. The cylindrical lens 33 is used to optically correct the inclination of the mirror surface of the mirror scanner 34.

Instead of mirror scanner 34, a deflection device such as a galvanometer may be used.

The laser beam is deflected by a mirror scanner 34,
The deflected laser beam is completely irradiated onto the surface of the image forming body 11 through the f-θ lens 35 and the cylindrical lens 36 for imaging. The cylindrical lens 36 is also for correcting the inclination of the mirror surface of the mirror scanner 34.
As will be described later, a long plastic lens is used for this purpose.

By rotating the mirror scanner 34 clockwise, the laser beam scans the surface of the image forming body 11 at a constant speed in a predetermined direction a, and by such scanning, image exposure corresponding to the color separation image is performed. Become.

Further, a photosensor 39 is provided on the starting end side of the cylindrical lens 36 (laser scanning start side) and outside the effective scanning area of the image. By receiving the laser beam reflected by the mirror 38 with the photosensor 39, an index signal indicating the start of laser beam scanning can be generated. The writing of image data on each line is synchronized based on this index signal.

Note that when using such an optical scanning device 30,
Since electrostatic images for each color separation image can be easily formed while being shifted, a clear color image can be formed.

By the way, as the elongated cylindrical lens 36 disposed close to the image forming body 11, a plastic lens is used in consideration of ease of machining the aspheric surface. ' This is because, in addition to the above-mentioned superior workability compared to glass lenses, plastic lenses have other advantages such as being low in cost, lightweight, and easy to handle.

The fifth surface shows an example of a plastic lens 36.

FIG. 5 is a plan view of the lens 36 when the scanning direction of the laser beam is taken in the horizontal direction, FIG. It is a central vertical sectional view (a sectional view taken along the line B-8).

As is clear from FIG. 6, this lens 36 includes a lens part 61 formed with a predetermined curvature, and a lens part 61 provided on the left and right and up and down directions of this lens part 61 so as to surround this lens part 61. It is composed of short side ribs 62 and long side ribs 63.

The short side ribs 62 and the long side ribs 63 are formed integrally with the lens portion 61 made of plastic in order to improve the strength of the lens portion 61 and to suppress warping, twisting, etc. of the lens portion 61. be.

In other words, plastic lenses are molded from resins such as polymethyl methacrylate (PMMA) and polycarbonate (PC), so they are weaker than glass lenses and are more susceptible to deformation such as warping. This is because it is easy to occur.

This is because if warpage or twisting is left unaddressed, the shape of the laser beam on the image forming body 11 will be deformed, resulting in image deterioration.

Of the pair of long side ribs 63.degree. 63 provided in the vertical direction, a protrusion 65 directed outward is integrally provided at the center of the long side rib 63 that is located at the bottom in FIG.

As shown in FIG. 8, the lens 36 is connected to the base plate 70 of the optical system.
When attaching to the base plate 7o, the recess 7 formed in the base plate 7o
By engaging the protrusion 65 with the lens 1, the relative position of the lens 36 to the image forming body 11 is determined.

Further, as shown in FIG. 9, this elongated lens 36 is
Both left and right ends in the longitudinal direction are fixed by fixing members provided on the base plate 70.

That is, as shown in FIG. 9, the base plate 70 has a pair of screens 72. '73 is planted and fixed, and a relatively elastic holding piece 7 faces the screen 72 and 73.
4.75 is attached, and the lens 36 is fixed to the base plate 70 by holding the lens 36 down from the front surface of the lens 36 while the lens 36 is in a vertical position (72.73). I have to.

[Problems to be solved by the invention] By the way, in the optical scanning device configured as described above,
As described above, when a plastic lens is used as the lens 36, deformation such as warping or twisting inevitably occurs due to the nature of the resin used.

In order to suppress this deformation, short side ribs 62 and long side ribs 63 are provided, but these ribs 62 and 63 cannot completely suppress the deformation of the lens portion 61.

Therefore, as shown in FIG. 9, when fixing the lens 36 to the base plate 70, the deformation of the lens portion 61 is suppressed by using spring holding pieces 74 and 75 to hold both ends of the lens 36. I'm trying to do that, but it's still not enough.

As a result, if the lens 36 is used for a long period of time, the lens 36 becomes deformed and the laser beam spot becomes distorted, causing a deterioration in recorded image quality.

Therefore, the present invention solves these problems and proposes an optical scanning device that has a simple structure and can suppress lens deformation.

TECHNICAL MEASURES FOR SOLVING THE PROBLEMS In order to solve the above-mentioned problems, in this invention, an optical signal modulated with an image signal is deflected by a deflection device, and the optical signal is transmitted through a lens based on the deflected optical signal. An optical scanning device configured to scan a photoreceptor drum using a lens is characterized in that a long plastic lens is used as the lens, and the lens is housed in a warp prevention body.

[Function] If the elongated lens 36 is accommodated in the warp prevention body, deformation such as warping or twisting of the lens 36 can be almost certainly suppressed.

[Example] Next, a case in which an example of the optical scanning device according to the present invention is applied to the above-mentioned image recording device will be described in detail with reference to FIG. 1 and subsequent figures. As described above, a semiconductor laser is used as the optical scanning device.

In this invention, a warp preventing body (warpage regulating body) 80 as shown in FIG. 1 is used.

The anti-warp body 80 has a rectangular parallelepiped shape having almost the same external shape as the long plastic lens 36, and both left and right side surfaces and the bottom surface in the figure are completely open. Roughly speaking, slits 82 having predetermined widths and lengths as shown in the drawings are formed along the longitudinal direction approximately at the center of the front and back surfaces, respectively. The slit 82 functions as a laser beam transmission hole.

so that the lens part 61 faces the slit 82,
When the lens 36 is housed in the anti-warp body 8o, the outer peripheral surface of the lens 36 (the bottom surface of the lens portion 61 and the outer peripheral surfaces of the ribs 62, 63) is in close contact with the inner surface of the anti-warp body 80, as shown in FIG. It is installed in the condition.

FIG. 2 also shows how the lens 36 is attached to the base plate 70. In this example, screw fixing portions 84 and 85 are provided on a portion of the front and back surfaces of the warp preventer 80, respectively, and the warp preventer 80 is firmly fixed to the base plate 7o by these.

By the way, this anti-warp body 80 is made so as not to be deformed by the pressure from the lens 36 that can be housed inside it.
The material, thickness, etc. can be selected. Therefore,
The warpage prevention body 80 may be made of a material that is resistant to deformation, such as hard plastic or metal.

As shown in FIG. 1, the left and right sides of the anti-warp body 80 are configured to be open so that the lens 36 can be freely expanded and contracted in the longitudinal direction when the lens is stored. It's for a reason.

This is because the length of the lens 36 is larger than the others, so if the lens 36 is not allowed to expand or contract,
This is because, on the contrary, the distortion in the longitudinal direction of the lens portion 61 increases, resulting in deformation.

Note that the above-described warpage prevention body 80 may be integrally configured with the base plate 70.

Further, in the above description, a rotating polygon mirror is used as the deflection device 34, but a galvano mirror may also be used. In this case, the lens 35 is preferably a lens with f-sin θ characteristics. In addition, when using this galvanomirror, by arranging the line index photo sensor also on the terminal side in the laser scanning direction, the fourth
Not only in the main scanning direction a in the figure, but also in the opposite scanning direction (
This makes it possible to perform scanning on the return path, thereby realizing a high-speed optical scanning device.

[Effects of the Invention] As explained above, according to the present invention, since the elongated cylindrical lens is surrounded by the warpage prevention body, deformation of the lens 36 can be reliably suppressed by the warpage prevention body 8o. Can be done.

Therefore, the deformation of the laser beam due to the deformation of the lens 36,
In other words, deterioration of recorded image quality can be effectively prevented.

Furthermore, scattered light at the ends of the cylindrical lens can also be prevented.

Therefore, the optical scanning device according to the present invention is applicable to an optical scanning system such as an electrophotographic copying machine or a laser printer that electrostatically records a predetermined image by performing optical scanning using a semiconductor laser or the like. It is extremely suitable for application to

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a main part of an optical scanning device according to the present invention, FIG. 2 is a central vertical sectional view thereof, and FIG. 3 is an electrophotographic color copying machine suitable for application to the present invention. FIG. 4 is a schematic configuration diagram of an optical scanning device suitable for applying the present invention, FIG. 5 is a plan view showing an example of a cylindrical lens that can be used in the optical scanning device, and FIG. FIG. 7 is a central cross-sectional view, FIG. 8 is a cross-sectional view in a used state, and FIG. 9 is a perspective view in an installed state. 1o...Color copying machine 11...Photosensitive drum 30 serving as an image forming member...Laser beam scanning device 31...Semiconductor laser 36...Cylindrical plastic lens 39...
・Sensor 61...Lens portion 62...Short side rib 63...Long side rib 70...Base plate 80...Warp prevention body 82...Slit Figure 1 Figure 4 βQ; Ray r Kubototore = [ Figure 9 Figure 8 King

Claims (3)

[Claims] (1) In an optical scanning device in which an optical signal modulated by an image signal is deflected by a deflection device, and a photosensitive drum is scanned via a lens based on the deflected optical signal, a plastic lens is used as the lens. An optical scanning device used in the present invention, wherein the lens is housed in a warp prevention body. (2) The optical scanning device according to claim 1, wherein the lens is a long cylindrical lens. (3) Claims 1 and 2 are characterized in that the lens is composed of a lens part and a rib that is provided integrally with the lens part so as to surround the lens part. optical scanning device.