JPH04118617A - Optical scanner - Google Patents

Abstract

PURPOSE:To set the center position of depth of focus on a drum surface and to enable excellent image formation by making an optical lens slantingly eccentric with its scanned surface by an eccentricity means and adjusting the spot diameter of luminous flux which is made incident on the scanned surface. CONSTITUTION:As for laser light which passing through the toric lens 5, laser light which passes the circumference of the slot B of the toric lens having large slanting eccentricity by the slight displacement of the toric lens 5, i.e. at an extremely small angle of rotation is used and a rotary shaft P which is inserted into the slot B is rotated on a fixed shaft O by rotating a jig driver 12 so that the laser light has an excellent spot diameter, e.g. minimum diameter at an equivalent position on the photosensitive drum 10. Namely, the toric lens 5 is rotated on a point A and made slantingly eccentric by a specific quantity. Then the laser luminous flux is so adjusted as to have the excellent laser spot diameter, namely, to be in the center of depth of focus at the equivalent position of the photosensitive drum 10. Consequently, the optical scanner which is tolerant to vibration and a shock is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical scanning device, and is used, for example, in a digital copying machine or an LBP (laser beam printer), to perform photosensitive scanning using a laser beam from a laser light source. The present invention relates to an optical scanning device suitable for forming an image on a drum surface.

(Prior Art) Conventionally, a laser beam from an optically modulated laser light source is guided to a rotating polygon mirror, and the laser beam reflected by the rotating polygon mirror is transmitted to a photosensitive drum through an optical system including an f-theta lens. An optical scanning device that guides light onto a scanning surface and performs optical scanning is widely used as an image input/output device.

FIG. 2 is a schematic diagram of the main parts of a conventional optical scanning device. In the figure, a parallel laser beam from a laser unit 8 is focused in a one-dimensional direction by a cylindrical lens 9, and is incident on a rotating polygon mirror 3. The rotating polygon mirror 3 is attached to the motor unit 2, and the laser beam reflected and deflected by the 0-rotation polygon mirror 3 rotating at a constant speed in one direction is f-
θ. The light is focused by a lens 31 and guided onto the surface of the photosensitive tram 10 via a mirror 31. The f-theta lens 31 consists of a spherical lens 4 and a toric lens 5, and is fixed in a predetermined position with an adhesive or the like, and the laser beam reflected and deflected by the rotating polygon mirror 3 that rotates at a constant speed is directed to the photosensitive drum surface. I am trying to scan at a constant speed above.

This is a 6118D folding unit and is used to obtain a horizontal synchronization signal when forming an image. Reference numeral 7 denotes an optical fiber, which introduces the laser beam reflected by the BD folding unit 6 through a light introducing portion 7a.

The light is guided to a photodetector (not shown).

Note that 1 is a housing that houses a motor unit 2, a laser unit 8, a cylindrical lens 9, and the like.

The optical scanning device in the figure adjusts the optical arrangement of the cylindrical lens 9 so that the laser beam from the laser unit 8 has a good laser spot shape and laser light intensity on the surface of the photosensitive tram 10, and then glues the cylindrical lens 9. The material is firmly attached to the housing 1.

(Problems to be Solved by the Invention) Recently, digital copying machines, LBPs, etc. There is a demand for an optical scanning device in which the diameter of the laser spot incident on the laser beam (above) is smaller than that of conventional devices.

In order to reduce the diameter of the laser spot incident on the photosensitive drum surface, for example, the effective F number of the f-theta lens can be reduced, but generally speaking, when the laser spot diameter on the photosensitive drum surface is reduced, the depth of focus becomes shallower. Therefore, optically and mechanically, it becomes difficult to keep the laser spot diameter within the depth of focus over the entire scanning surface on the photosensitive tram surface.

- In particular, the mounting precision of optical lenses for optical scanning has become stricter, and it has become difficult to maintain a uniform laser spot diameter over the entire horizontal scanning range with the same mounting precision as before. A problem arises in that the amount of change increases and it becomes very difficult to maintain the depth of focus over the entire scanning range.

Furthermore, it becomes difficult to locate the center position of the depth of focus on the surface of the photosensitive drum, resulting in problems such as, for example, the position on the surface of the photosensitive drum may deviate from the depth of focus due to slight vibrations or shocks.

In the present invention, among a plurality of optical lenses arranged in an optical path from a rotating polygon mirror to a photosensitive drum surface constituting an optical scanning device,
By adjusting the optical arrangement such as the inclination and eccentricity of at least one optical lens, for example, some optical lenses constituting the f-theta lens, the laser spot diameter on the photosensitive drum surface can be adjusted to a well-balanced spot diameter on the entire scanning surface. The object of the present invention is to provide an optical scanning device that enables good image formation by, for example, placing the depth of focus at a position corresponding to a drum at the center position.

(Means for Solving the Problems) The optical scanning device of the present invention reflects and deflects a luminous flux emitted from a light source by a rotating polygon mirror, and then guides the light onto a scanning surface via a plurality of optical lenses. In an optical scanning device that scans at a constant speed, at least one of the plurality of optical lenses is provided with decentering means, and the decentering means tilts and decenters the optical lens with respect to the scanning plane. The feature is that the spot diameter of the incident light beam is adjusted.

(Example) FIG. 1 is a schematic diagram of a main part of an optical scanning device according to the present invention.

The arrangement of each element of the optical scanning device in this embodiment is almost the same as that of the optical scanning device in FIG. 2, but the major difference is that some optical lenses constituting the f-θ lens are provided with decentering means
The point is that the optical lens can be eccentrically adjusted.

Next, each element of this embodiment will be explained in order.

8 is a laser unit, which emits a substantially parallel laser beam. A cylindrical lens 9 focuses the laser beam from the laser unit 8 in a one-dimensional direction and focuses it on one reflective surface 3a of the rotating polygon mirror 3. Reference numeral 14 denotes an f-theta lens, which is composed of a spherical lens 4 and a toric lens 5 having refractive power in the main scanning direction and whose eccentricity can be adjusted.

The f-theta lens 14 collects the laser beam reflected and deflected by the rotating polygon mirror 3 and directs it to the photosensitive drum 1 via the mirror 13.
Light is guided onto the 0 plane, and the photosensitive tram surface 10 is scanned at a constant speed with a predetermined laser spot diameter.

Reference numeral 11 denotes a lens holder on which the toric lens 5 of the f-θ lens 14 is placed. Also lens holder 11
+B is an elongated hole provided at the other end of the lens holder 11. +B is a long hole provided at the other end of the lens holder 11. 12 is a jig driver, and one end has two shafts 0. P is provided.

Of these, O is a fixed axis and P is a rotating axis. The fixed axis O is positioned and fixed to the housing 1. The rotation axis P is inserted into the elongated hole B of the lens holder 1, and the jig driver 1
2 rotates around the fixed axis 0. That is, by rotating the jig driver 12 about the fixed axis O, the lens holder 11 is rotated about the bin A by the rotation axis P. As a result, the toric lens 5 placed on the lens holder 11 is tilted and decentered.

C and D are SEMS screws provided at both ends of the lens holder 1, respectively, and are fixed to the housing 1 after the adjustment of the lens holder 11 is completed. The jig driver 12, the lens holder 11, etc. each constitute one element of the decentering means.

In this embodiment, a BD folding unit for obtaining the horizontal synchronization signal shown in Fig. 3 and an optical fiber for condensing the reflected light from the BD folding unit are naturally arranged, but these are omitted in the figure for simplicity. are doing.

Next, a method for adjusting each optical element in this example will be explained.

In this embodiment, first, a motor 2 for rotationally driving a rotating polygon mirror 3 is attached to a housing. A rotating polygon mirror 3 for deflecting a laser beam is fixed to the mirror 2 using a G ring, a wave washer, or the like. and f-theta lens】4
Of these, a spherical lens 4 and a laser unit 8 are attached to the housing 1.

The mW of the optical arrangement of the cylindrical lens 9 is determined as follows. First, N radiation is deflected by the one-rotation polygon mirror 3, and f-θ
Of the plurality of laser beams at each angle of view incident on the lens, the laser beam is transmitted near the positioning pin A, which is near the rotation center, which is an area not affected by the rotational adjustment of the Dolly lens 5. In order to improve the laser spot on the photosensitive drum 10, for example, move the cylindrical lens 9 in the optical axis direction and the rotational direction so as to make it the most convenient, and adjust the optical arrangement m! ! ! ! do.

After that, attach the cylindrical lens 9 to the housing l with adhesive or the like.
It is stuck to.

Next, the optical arrangement of the Dolly lens 5 is adjusted as follows.

Of the f-theta lenses 14, the toric lens 5 whose tilt and eccentricity are adjusted is fixed to the lens holder 11 with an adhesive or the like. Then, the lens holder with the toric lens 5 fixed thereto is first temporarily fixed to the housing 1 with a Sems screw or the like.

Of the laser beams that pass through the toric lens 5, the laser beam that passes near the elongated hole B of the toric lens 5, which is tilted and decentered by a slight displacement of the toric lens 5, that is, a slight rotation angle, is used. The jig driver 12 is rotated so that a good spot diameter is obtained at a position corresponding to the photosensitive drum 0, for example, so that the spot diameter is the smallest, and the rotating shaft P inserted into the elongated hole B is rotated about the fixed shaft 0. That is,
The toric lens 5 is rotated around point A to tilt and decenter it by a predetermined amount. Then, the laser beam has a good laser spot diameter at a corresponding position on the photosensitive drum 10, that is, on the photosensitive drum 1.
Adjustment is made so that the laser beam becomes the center of the depth of focus at a position corresponding to zero. Finally, I put adhesive into the Sems screws C and D, which had been temporarily tightened, and performed the actual comparison.

This fixes the lens holder 11 to the housing l.

In this way, in this embodiment, three
The laser beam is adjusted so that it is approximately at the center of the depth of focus.

In this embodiment, instead of configuring the lens holder 11 and the toric lens 5 independently, they may be integrally molded from a plastic material or the like.

This is preferable because it reduces the number of parts and simplifies the entire device.

In this example, the optical lens to be tilted and decentered is f
The spherical lens constituting the -θ lens may be tilted and decentered, or the entire f-θ lens may be tilted and decentered. In addition, when a cylindrical lens or the like is arranged near the photosensitive drum surface, the cylindrical lens may be tilted and decentered.

(Effects of the Invention) According to the present invention, at least one optical lens disposed in the optical path from the rotating polygon mirror to the photosensitive drum surface is tilted eccentrically with respect to the main scanning direction of the photosensitive drum surface. The laser spot can be easily adjusted to within the depth of focus, and the laser spot can be located in the center of the wharf cleanliness at a corresponding position on the photosensitive tram surface, making it resistant to vibration and impact. can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of essential parts of an embodiment of the present invention, and FIG. 2 is a schematic diagram of a conventional optical scanning device. In the figure, 1 is a housing, 2 is a motor, 3 is a rotating polygon mirror, 14 is an f-theta lens, 4 is a spherical lens, 5 is a toric lens, 8 is a laser unit, 9 is a cylindrical lens, I
O is a photosensitive drum, 11 is a lens holder, 12 is a jig driver, and 13 is a mirror.

Claims (3)

[Claims] (1) In an optical scanning device in which a light beam emitted from a light source is reflected and deflected by a rotating polygon mirror, the light is guided onto a scanning surface via a plurality of optical lenses, and the scanning surface is scanned at a constant speed. At least one of the optical lenses is provided with an eccentric means, and the eccentric means tilts and decenters the optical lens with respect to the scanning surface, thereby adjusting the spot diameter of the light beam incident on the scanning surface. optical scanning device. (2) The plurality of optical lenses include f-θ lenses, and some of the f-θ lenses are tilted and decentered by the decentering means. Optical scanning device. (3) The optical scanning device according to claim 2, wherein a part of the optical lens of the f-theta lens and a lens holder on which the part of the optical lens is placed are integrally molded.