JPH03274016A - Scanning optical device - Google Patents

Abstract

PURPOSE:To decrease the number of components, to secure the position accuracy among plural lenses, and to improve the assemblability by uniting the lenses. CONSTITUTION:An lens 21 on an arc which is molded integrally out of transpar ent synthetic resin is fitted in the center of the housing 20 of the scanning optical device wile facing an opening part, and a rotary polygon mirror 4 as a deflector is positioned inside the lens 21 and driven by a scanner motor to rotate. A collimator lens part 21a is formed at one end part of the lens 21, and the center part of the lens 21 is formed as a collimator lens part 21a, whose center part is an ftheta lens part 21b. The other end part of the lens 21 is formed as a condenser lens part 21c. This constitution nearly determines the position accuracy among the lenses at the time of the lens molding, so when the lens 21 is incorporated in the housing 20, only the position and direction of the lens 21 are to be considered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning optical device used in laser printers and the like.

[Prior Art] Fig. 6 shows a scanning optical device of a conventional laser printer, in which a collimator lens 3 and a rotating polygon mirror 4 are arranged on the optical axis of a laser diode 2 that emits light according to commands from a control circuit 1. The polygon mirror 4 is rotated by a scanner motor 5 at a constant speed in the direction of the arrow. An fθ lens 6 is arranged on the reflection side of the rotating polygon mirror 40, and a photoreceptor drum 7, which is an imaging surface, is located in the transmission direction thereof, and a fixed mirror 8 is arranged near the end of the photoreceptor drum 7. In addition, a condenser lens 9 and a slit 1 are provided on the reflection side of the fixed mirror 8.
0, the light receiving elements 11 are arranged in sequence, and the light receiving elements 1
The output of 1 is connected to the control circuit 1.

The emitted light from the laser diode 2 is made into parallel light by the collimator lens 3, reflected by the rotating polygon mirror 4, and then fθ
The scanning speed on the photoreceptor drum 7 is kept constant by the lens 6,
When the scanning light formed on the photoreceptor drum 7 is reflected by the fixed mirror 8 near the end of the photoreceptor drum 7, it is focused by the condenser lens 9 and passes through the slit 10 to the light receiving element 11.
The output thereof is input to the control circuit 1 as a horizontal synchronizing signal, and control is performed so that the image information to be recorded on the photosensitive drum 7 is output to the laser diode 2 after a certain period of time of this signal.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, at least three lenses, the collimator lens 3, the fθθ lens, and the condensing lens 9, are required, and when adjusting these lenses, highly accurate relative measurement is required. Positioning must be done.

An object of the present invention is to provide a scanning optical device that has a simple configuration and can easily ensure positional accuracy between lenses.

[Means for Solving the Problem] In order to achieve the above-mentioned object, in the scanning optical device according to the present invention, a laser beam emitted from a laser oscillator is focused by a first lens, and is further focused by a deflector. The light is scanned and focused onto the scanned medium by a second lens, a part of the light transmitted through the second lens is deflected by a fixed mirror, and focused on a light receiving element by a third lens, and the light is received by a third lens. In a scanning optical system configured to use the output of an element as a trigger for a horizontal synchronization signal,
The present invention is characterized in that at least two of the first lens, the second lens, and the third lens are integrally formed.

[Operation] The scanning optical device having the above-described configuration improves the positional accuracy between the lenses by reducing the number of lenses.

[Example] The present invention will be described in detail based on the example illustrated in FIGS. 1 to 5. Note that the same reference numerals as in FIG. 6 indicate the same or the same members.

FIG. 1 shows a plan view of the first embodiment, and FIG. 2 shows a perspective view. A housing 20 molded from synthetic resin has an opening on the side of the photosensitive drum 7, which is the scanned medium. An arc-shaped lens 21 integrally molded with a transparent synthetic resin such as acrylic or polycarbonate is attached to the center of the housing 20 facing toward the opening.
A rotating polygon mirror 4, which is a deflector, is located inside the lens 21, and is driven to rotate in the direction of the arrow by a scanner motor. A collimator lens part 21a is formed at one end of the lens 21, and the center part of the lens 21 has an angle of fθθ.
A lens 21b is formed, and the other end of the lens 21 is formed as a condenser lens portion 21c. A laser diode 2 is arranged outside the collimator lens part 21a, a fixed mirror 8 is arranged outside the condensing lens part 21c, and a slit 10 and a light receiving element 11 are sequentially provided inside the condensing lens 21c. There is.

The laser light emitted from the laser diode 2 passes through the collimator lens section 21a, is condensed into parallel light, and enters the rotating polygon mirror 4, and the reflected light passes through the fθθ lens 21b.
The light is focused and scans the photoreceptor drum 7 at a constant scanning speed.

When the scanning light that has passed through the fθ lens section 1 at the beginning or end of one scan is reflected by the fixed mirror 8, the condenser lens section 2
1c, passes through the slit 10, and enters the light receiving element 11, from which a horizontal synchronizing signal is sent to a control circuit (not shown).

In this embodiment, since the positional accuracy between the lenses is almost determined at the time of lens molding, only the position and direction of the lens 21 need be taken into consideration when assembling the lens 21 into the housing 20.

FIG. 3 shows a plan view of the second embodiment, in which an integrally molded lens 22 has optical axes in two perpendicular directions and combines the functions of a collimator lens 3 and a condensing lens 6. It has become. FIG. 4 is a perspective view of the lens 22, with the surface 22
a and 22b, surfaces 22c and 22d face each other, and 2
The two surfaces C and 22d act as the collimator lens 3, and the surfaces 22a and 22b act as the condensing lens 6. The laser diode 2 is placed in front of the surface 22d on the optical axis of the collimator lens 3, the rotating polygon mirror 4 is placed in front of the surface 22c, and the fθθ lens is placed in the substantially perpendicular reflection direction.
A photoreceptor drum 7 is provided ahead of it. A fixed mirror 8 is provided between the photoreceptor drum 7 and the lens 22 on the optical axis of the condensing lens, so that the reflected light from the fθ lens 6 through the fixed mirror 8 is perpendicularly incident on the surface 22a of the lens 22. ing. A slit 10 and a light receiving element 11 are sequentially arranged on the surface 22b side.

The laser light emitted from the laser diode 2 passes through the surfaces 22d and 22c of the lens 22, becomes parallel light, and enters the rotating polygon mirror 4, and the reflected light passes through the fθ lens 6 and hits the photoreceptor drum 7. An image is formed and scanned, but a part of the scanning light is reflected by the fixed mirror 8 and is reflected by the surfaces 22a and 2 of the lens 22.
2b, is condensed and passes through the slit 10 to the light receiving element 1.
1 to generate a synchronization signal.

FIG. 5 shows a plan view of the third embodiment, in which the shape of the lens 22 of the second embodiment is changed to form an integrally molded lens 23. The lens 23 has a shape in which the collimator lens 3 and the condensing lens 6 are combined at the end, and the surface 23
a and 23b are the condensing lenses 6, surfaces 23c and 23d are the collimator lenses 3, and the other functions and configurations are the same as the second lens.
This is exactly the same as the embodiment.

These second and third embodiments use lenses with simpler shapes than the first embodiment, and furthermore, it is easier to ensure positional accuracy between the lenses than in the prior art.

In all of the embodiments described above, an optical fiber may be placed in place of the light receiving element 11 to guide the laser beam to another position, and the light receiving element 11 may be placed there. Furthermore, the rotating polygon mirror 4 can be implemented with any number of surfaces, and each surface of the lens can be adjusted according to the desired optical performance.
It may be either spherical or aspherical.

[Effects of the Invention] As explained above, the scanning optical device according to the present invention reduces the number of parts by integrating a plurality of lenses, reduces the degree of freedom in positioning the lenses, and improves the positioning of the lenses. Positional accuracy can be easily ensured, ease of assembly can be improved, and costs can be reduced.

[Brief explanation of drawings]

Drawings 1 to 5 show embodiments of the scanning optical device according to the present invention, in which FIG. 1 is a plan view of the first embodiment, FIG. 2 is a perspective view, and FIG. 3 is a second embodiment. A plan view of the example, FIG. 4 is a perspective view of the compound lens, and FIG. 5 is a plan view of the third embodiment.
FIG. 6 is a plan view of a conventional example. 1 is a laser diode, 4 is a rotating polygonal path, and 6 is f
θ lens, 8 is a fixed mirror, 20 is a housing, 2■,
22 and 23 are integrally molded lenses. Figure 3

Claims (1)

[Claims] 1. A laser beam emitted from a laser oscillator is focused by a first lens, further scanned by a deflector, and focused onto a scanned medium by a second lens; A scanning optical system configured to deflect part of the light transmitted through the lens by a fixed mirror and focus it on a light receiving element by a third lens, and to use the output of the light receiving element as a trigger for a horizontal synchronization signal, A scanning optical device characterized in that at least two of the first lens, the second lens, and the third lens are integrally formed. 2. The scanning optical device according to claim 1, wherein the integrated lens is molded using a synthetic resin mold.