JPH03120509A - Light deflector - Google Patents

Abstract

PURPOSE:To provide a large amount of displacement with high accuracy with a high frequency by combining an electromagnetic actuator which displaces a lens located at a laser beam source or between the laser beam source and a deflecting means in an optical axial direction with a piezoelectric actuator which displaces the laser beam source or the lens in a subscan direction. CONSTITUTION:A laser beam from the laser beam source 10 is reflected on a rotary polygonal mirror 20 via the lens 14, and is image-formed on a plane to be scanned. The large amount of displacement can be obtained with a low driving force by limiting movable parts in the optical axial direction to only the lens 14, a lens holder 20, and a coil 21, and furthermore, setting a resonance point in the optical axial direction of an optical axial direction supporting spring 15 in the neighborhood of the driving frequency of the lens 14. Also, the amount of displacement is small in the subscan direction, however, the lens is driven integrally with the movable part in the optical axial direction and a supporting body 16, therefore, it is possible to efficiently displace the lens in the subscan direction with a supporting spring 18 in the subscan direction by mounting a laminate type piezoelectric element 17 with a large driving force on the supporting body 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical deflection device for scanning a laser beam using a deflection means in, for example, a laser printer or a laser copying machine.

2. Description of the Related Art Deflection devices using laser light sources have been known. FIG. 4 is a schematic diagram showing a known deflection device for a laser printer. In the figure, a laser beam emitted from a laser light source 1 passes through a collimator lens 2, is reflected by a rotating polygon mirror 3 serving as a deflecting means, and is transmitted to a scanned surface such as a photoreceptor drum by an fθ lens group 4 having a toric surface. 5.

The fθ lens group 4 allows the laser beam to scan the surface to be scanned at a constant speed, and also functions to always form an image on the surface to be scanned. In addition, the fθ lens group 4 corrects blurring of the laser beam in the sub-scanning direction (direction perpendicular to the scanning direction) due to the tilting of the rotating polygon mirror 3.

However, increasing the number of optical elements like the fθ lens group 4 poses problems in terms of cost and assembly accuracy. Furthermore, the fθ lens group 4 has a problem in that it is impossible to correct all fluctuations in the scanning direction and the sub-scanning direction.

For this reason, a method of directly displacing a lens or a laser light source has been considered, for example, as disclosed in Japanese Patent Laid-Open No. 59-116603. This will be explained below with reference to the drawings. FIG. 5 is a sectional view of the structure of the light source moving actuator. 6 is a lens, 7 is a laser light source, and 8 is a movable part in which the laser light source 7 is attached approximately to the center. FIG. 6 is a perspective view showing the main parts of the movable part 8. Movable part 8
A piezoelectric element 9 is attached to the top. A driving voltage is applied to the piezoelectric element 9 from the outside, and the expansion and contraction of the piezoelectric element 9 is used to displace the laser light source 7 in the optical axis direction so that an image is always formed on the surface to be scanned. The above-mentioned light source movement actuator makes it possible to correct the imaging position error, which is one of the main functions of the fθ lens group.

Problems to be Solved by the Invention However, with the recent increase in speed and resolution of laser printers, in order to convert the fθ lens group to a method of displacing the laser light source or lens, the amount of displacement must be 10 in the optical axis direction. It is necessary to secure about 50 μm or about 1 μm in the sub-scanning direction.

When the piezoelectric element 9 is used, the amount of displacement changes greatly with the same applied voltage due to hysteresis and temperature, and a plate-shaped piezoelectric element has a small driving force, so a plurality of piezoelectric elements 9 are required. The problem was that the mass of 8 was further increased.

In addition, when displacing a lens or a laser light source in the sub-scanning direction, although the amount of displacement required is small, it is necessary to add a drive mechanism to the movable part to displace it in both the optical axis direction and the sub-scanning direction. There was a problem in terms of power.

Means for Solving the Problems In order to solve the above problems, the present invention provides an electromagnetic actuator that displaces a laser light source or a lens located between the laser light source and the deflection means in the optical axis direction, and the laser light source. Alternatively, the image forming apparatus may include a piezoelectric actuator that displaces the lens in the sub-scanning direction.

According to the present invention, the optical axis direction can be precisely driven by the electromagnetic actuator with the minimum necessary mass of the movable part consisting of the laser light source or lens, its holder, and the coil, and furthermore, the piezoelectric element, In particular, by driving the movable part in the optical axis direction and the support of the movable part together in the sub-scanning direction using a laminated piezoelectric element, correction in the scanning direction and the sub-scanning direction can be performed using a lens or a laser. This can be done using a light limit, and an fθ lens group is not required.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of an optical deflection device according to the present invention.

10 is a laser light source, 11 is a lens actiniator, 12
1 is a rotating polygonal mirror, and 13 is a scanned surface of a photosensitive drum or the like. FIG. 2 is a perspective view showing a schematic configuration of an actuator section of the optical deflection device of the present invention. 14 is a lens; 15 is an optical axis support spring that allows displacement of the lens 14 in the optical axis direction; 16
is a support body that supports the lens 14 through a support spring 15;
17 is a laminated piezoelectric element that drives the support 16 in the sub-scanning direction; 18 is a support spring in the sub-scanning direction that supports the support 16 by allowing displacement in the sub-scanning direction; and 19 is a component that drives the lens 14 in the optical axis direction. This is an electromagnetic actuator.

FIG. 3 is a sectional view of the electromagnetic actuator 19 that drives the lens 14 in the optical axis direction. The lens 14 is held by a lens holder 20, and a coil 21 is attached to the side surface of the lens holder 20, and is positioned so as to interlink with the magnetic flux generated by the magnetic circuit 22.

The optical axis direction support springs 15 are two plate-shaped springs, and are attached to the lens holder 20 so as to support the center of gravity perpendicularly to the optical axis direction and spaced apart so that the lens 14 is displaced in the optical axis direction. installed. Sub-scanning direction support spring 1
8 are also two plate-shaped support springs, which are attached perpendicularly to the sub-scanning direction so that the lens 14 is displaced in the sub-scanning direction, and at a distance therebetween to support the center of gravity.

In the above configuration, the laser light emitted from the laser light source 10 passes through the lens 14, is reflected by the rotating polygon mirror 20, and forms an image on the surface to be scanned. In order to ensure that an image is formed on the scanned surface, the lens 14 is displaced in the optical axis direction by the lens actuator 11, and the laser beam in the sub-scanning direction is caused by the surface tilt of the rotating polygon mirror and the temperature and vibration of other components. The lens actuator 11 adjusts the displacement of the lens 14.
This can be corrected by displacing in the sub-scanning direction.

However, in order to accurately displace the lens 14 in the optical axis direction at a high frequency of 500 Hz or more and by about 10 to 50 μm, it is necessary to suppress the mass of the movable part as much as possible and to make the drive direction small in hysteresis and temperature dependence.

Therefore, in this embodiment, the only movable parts in the optical axis direction are the lens 14, lens holder 20, and coil 21, and the resonance point of the optical axis support spring 15 in the optical axis direction is set near the driving frequency of the lens. A large amount of displacement can be obtained with a small driving force.

In addition, although the amount of displacement in the sub-scanning direction is small, in order to drive the movable part in the optical axis direction and the support body 16 together, a laminated piezoelectric element with a large driving force is attached to the support body 16 using a support spring in the sub-scanning direction. 18 allows efficient displacement in the sub-scanning direction.

In addition, in the above embodiment, the support body 16 was made into a U-shape.
It goes without saying that it may be a box shape that wraps around the movable part, or that the sub-scanning direction support springs may be arranged around the support body 16 in a plane perpendicular to the sub-scanning direction.

Alternatively, the laser light source may be driven without driving the lens.

Effects of the Invention As described above, the present invention includes an electromagnetic actuator that displaces a laser light source or a lens located between the laser light source and a deflecting means in the optical axis direction, and an electromagnetic actuator that displaces the laser light source or the lens in the sub-scanning direction. By combining it with a piezoelectric actuator for displacement, it is possible to accurately apply a large displacement at zero and high frequencies, and it is possible to realize an optical deflection device without using an fθ lens group.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the optical deflection device of the present invention;
Fig. 2 is a perspective view showing a schematic configuration of a lens actuator, Fig. 3 is a sectional view of an electromagnetic actiniator, Fig. 4 is a perspective view showing a schematic structure of a conventional optical deflection device, and Fig. 5 is a perspective view of a conventional piezoelectric element. Cross-sectional view of the lens actuator used, No. 6
The figure is a perspective view of the main parts. 10... Laser light source, 11... Lens actuator, 12... Rotating polygon mirror, 13.
...Scanned surface, 14... Lens, 15.
... Optical axis direction support spring, 16 ... Support body, 17 ... Piezoelectric element, 18 ... Sub-scanning direction support spring, 19 ...・Electromagnetic actuator. 2(-11 coil-1+?

Claims (2)

[Claims] (1) In an optical deflection device including a laser light source, a deflection means for deflecting a light beam emitted from the laser light source, and an optical scanning position detection means for the light beam, the laser light source or the laser light source and the an electromagnetic actuator that displaces a lens located between the deflection means in the optical axis direction;
An optical deflection device comprising: a piezoelectric actuator that displaces the laser light source or the lens in a sub-scanning direction. (2) The piezoelectric actuator for displacing in the sub-scanning direction integrally drives a movable portion including the laser light source or the lens that is displaced in the optical axis direction and a support portion of the movable portion. 1. The optical deflection device according to 1.