JPH0196622A - Scanning optical device - Google Patents

Abstract

PURPOSE:To prevent the subscanning direction of a scanning beam from deviating by displacing either of a lens which collimates a light beam into parallel light and a lens which converges a light beam in the direction of subscanning on a surface to be scanned. CONSTITUTION:A beam position in a direction (subscanning direction) perpendicular to a main scanning direction on the surface 7 to be scanned nearby a position equivalent to the surface of a photosensitive drum as the surface 7 to be scanned is detected. Namely, a position sensor 8 is arranged which generates a deviation signal as the quantity D of a shift in set position, a displacement member 9 is put in operation with this deviation signal, and the collimator lens 2 is displaced on the surface 7 to be scanned in the direction where deviation in the subscanning direction is eliminated, thereby correcting the scanning deviation. Simultaneously, the signal of the position sensor 8 is used to detect the scanning start end of scanning line, thereby synchronizing an image signal. Consequently, the deviation of the scanning beam on the surface 7 to be scanned in the subscanning direction is securely corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is applied to laser beam printers and laser copying machines, and relates to a scanning optical device that scans a light beam emitted from a laser light source using a polarizing means.

(Prior Art) Conventionally, this type of scanning optical device has been disclosed in, for example, US Pat.
There is one disclosed in No. 47,112, which is constructed as shown in FIG. That is, in the same figure, 1
01 is a laser light source, which forms a substantially point light source and emits laser light in a divergent manner. This laser beam is converted into parallel light by a collimator lens 102 and guided to a cylindrical lens 103. The cylindrical lens 103 is a rotating polygon mirror 1 as a polarizing means.
The light is focused on the reflective surface 104a of 04. The light beam is reflected by the rotating polygon 1ia 104, becomes a diverging beam again on the X-Z plane, and is imaged on the scanned surface 107 such as a photoreceptor drum by the f-θ lens group 106 having a toric surface. . Therefore, in the X-Z plane, the optical system
A conjugate relationship is established with the scanned surface 107, and the one-rotation polygon mirror 10
The tilting and rotation of each reflecting surface 104a constituting the polygon mirror 1
The deviation of the focal spot on the scanned surface 107 due to the inclination of the shaft supporting the 04 is optically corrected.

Next, the beam in the x-y plane enters the f-theta lens group 106 including a toric surface as a parallel beam, and is focused onto the scanning surface 107 by the rotating polygon mirror 104 with a focusing function of 0 or more. As the scanning line rotates, a scanning line can be formed in a straight line on the scanned surface 107 (main scanning).On the other hand, since the scanned surface 107 moves in two directions (arrow directions) as shown in FIG. It becomes possible to record two-dimensional information virtually.

At this time, the photosensor 113 detects the scanning start end of the scanning line and synchronizes the image signal.The photo sensor 113 transfers the recorded information such as 0 or more onto the transfer paper using, for example, a known electrophotographic process. It becomes possible to play.

(Problems to be Solved by the Invention) However, in such a conventional example, since only the surface tilt of the rotating polygon mirror is corrected, there are the following problems.

That is, firstly, the scanning optical device has many elements that generate vibrations, such as a rotating polygon mirror and a photoreceptor drum. 101
It is not possible to correct the blurring of the scanning beam on the scanned surface 107 in a direction perpendicular to the main scanning direction (sub-scanning direction) due to such vibrations, resulting in pitch unevenness. Secondly, the refractive index of each lens changes and eccentricity occurs due to the influence of temperature and humidity, causing the position of the scanning beam to deviate from a predetermined position.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional example, and its purpose is to solve the above problems.

The object of the present invention is to provide a scanning optical device that can reliably prevent deviation of a scanning beam in the sub-scanning direction.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a laser light source that emits a light beam, and a laser light source that polarizes the light beam into a scanning beam to scan a surface to be scanned. In a scanning optical device having a polarizing means for scanning and an optical scanning position detecting means for determining a start point of modulation of the scanning beam, the light beam disposed between the laser light source and the polarizing means is converted into a parallel beam. The apparatus includes means for displacing either a lens for condensing the light beam or a lens for condensing the light beam in the sub-scanning direction on the surface to be scanned.

(Function) In the present invention having the above configuration, means is provided for displacing either the lens for collimating the light beam or the lens for condensing the light beam in the sub-scanning direction on the surface to be scanned. Accordingly, one of the lenses is displaced in a direction that eliminates the deviation in the sub-scanning direction on the surface to be scanned.

(Example) The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a perspective view showing a schematic configuration of a first embodiment of a scanning optical device according to the present invention, in which l is a semiconductor laser as a laser light source that emits a light beam modulated by an information signal; 2 is a collimator lens that converts the light beam emitted from the semiconductor laser l into parallel light; 3 is a cylindrical lens that focuses the light beam on the reflecting surface 4a of a rotating polygon mirror 4 serving as a deflecting means; and 6 has a toric surface. f-theta lens group, 7 is a scanned surface such as a photoreceptor drum, 8 is an optical scanning position detection device that detects the beam position in the direction perpendicular to the main scanning direction (sub-scanning direction) and determines the start point of modulation of the scanning beam. A position sensor 9 is a means for displacing the collimator lens 2 in the sub-scanning direction on the surface 7 to be scanned. Further, the one-rotation polygon mirror 4 deflects the light beam into a scanning beam and scans the surface to be scanned 7 .

As shown in FIG. 2, the displacement member 9 includes a lens holder 12 that holds the collimator lens 2, and the lens holder 12.
It consists of permanent magnets 10a, 10b that are provided integrally with the permanent magnets 10a, 10b, and electromagnets 11a, 11b that are installed facing the permanent magnets 10a, 10b at a predetermined distance. 11a or flb operates to attract permanent magnet 10a or lOb. Then, the collimator lens 2 rotates around the support shaft 13 and is displaced.

In the above configuration, the light beam emitted from the laser light source 1 is made into parallel light by the collimator lens 2, and the cylindrical lens 3 converts the light beam into a rotating polygon mirror in a plane that includes the optical axis of the laser beam and is parallel to the rotation axis of the rotating polygon mirror 4. The reflected light is focused onto a scanning surface 7 such as a photoreceptor drum by an f-theta lens group 6 having a toric surface, and the rotating polygon mirror 4 is rotated. is scanned in a straight line. At this time, the shift of the focal spot on the scanned surface 7 due to the inclination of the reflecting surface 4a of the rotating polygon mirror 4 and the inclination of the shaft supporting the rotating polygon mirror 4 is corrected by the f-θ lens group 6 having a toric surface. This is corrected by the surface tilt correction system of the rotating polygon mirror 4.

However, the deviation of the scanning beam on the scanning surface 7 in the sub-scanning direction due to the vibration of the laser light source 1, the collimator lens 2, the cylindrical lens 3, and the f-0 lens group 6 including the toric surface, and the collimator due to temperature, humidity, etc. lens 2%
f-θ including cylindrical lens 3 and toric surface
The deviation in the sub-scanning direction of the scanning beam on the scanned surface 7 due to changes in the refractive index or eccentricity of each lens in the lens group 6 is corrected by the surface tilt of the rotating polygon mirror 4 by the f-theta lens group 6 having a toric surface. It cannot be corrected by the system.

Therefore, in this embodiment, the beam position in the direction perpendicular to the main scanning direction (sub-scanning direction) on the surface to be scanned 7 is set near the equivalent position to the photoreceptor drum surface, which is the surface to be scanned 7, as shown in FIG. To detect. That is, a position sensor 8 that generates a deviation signal as a measure of change in the set position is arranged, and the displacement member 9 is actuated by this deviation signal, and the collimator lens is moved in a direction to eliminate scanning deviation in the sub-scanning direction on the scanned surface 7. 2 to correct the scanning deviation. At the same time, a signal from the position sensor 8 detects the scanning start end of the scanning line and synchronizes the image signals.

FIG. 4 shows a second embodiment of the present invention, in which the same parts as in the first embodiment are given the same reference numerals. In this embodiment, a displacement member 9' is attached to the cylindrical lens 3. The displacement member 9' displaces the cylindrical lens 3 in the sub-scanning direction based on the deviation signal from the position sensor 8, and corrects the scanning deviation in the sub-scanning direction on the scanned surface 7. The other configurations and functions are the same as those of the first embodiment, so their explanation will be omitted.

(Effects of the Invention) The scanning optical device according to the present invention has the above-described configuration and operation, and can reliably correct the deviation of the scanning beam in the sub-scanning direction on the surface to be scanned without increasing the manufacturing cost. can. As a result, when applied to a laser beam printer, it is possible to obtain accurate images without scanning deviation.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing a first embodiment of a scanning optical device according to the present invention, FIG. 2 is a front view of a displacement member in the same embodiment, and FIG. 3 is a front view of a position sensor in the same embodiment. FIG. 4 is a schematic perspective view showing a second embodiment of the present invention;
FIG. 5 is a schematic perspective view showing an example of a conventional scanning optical device. Explanation of symbols 1...Semiconductor laser 2...Collimator lens 3...Cylindrical lens 4...Rotating polygon ta (deflection means) 7...Scanned surface 8...Position sensor (optical scanning position detection means) 9
... Displacement member agent Patent attorney Oku 1) Ki Mi-(
: ; Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) A laser light source that emits a light beam, a polarizing means that polarizes the light beam into a scanning beam and scans the surface to be scanned, and an optical scanning position detection means that determines the point at which modulation of the scanning beam starts. In the scanning optical device, either a lens for collimating the light beam or a lens for condensing the light beam, which is disposed between the laser light source and the polarizing means, is connected to the surface to be scanned. 1. A scanning optical device comprising means for displacing in the sub-scanning direction. (2) The scanning optical device according to claim 1, wherein the displacement means is operated by a deviation signal sent from the optical scanning position detection means.