JPS63202713A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To reduce the size of a device by forming a part other than a part where a light beam for image formation reflected by a polygon mirror passes so that a light beam for a synchronizing signal reflected by the polygon mirror passes. CONSTITUTION:The light beam 2a for image formation and light beam 2b for the synchronizing signal are reflected and deflected by the same reflecting surface of the polygon mirror 4. Further, the light beam 2a for image formation which is deflected is directed to a scanning zone 7a for image formation of a scanning lens 7 and passes through the zone part to make a scan. The light beam 2b for the synchronizing signal, on the other hand, is directed to the part other than the scanning band 7a for image formation of the scanning lens 7 where the light beam 2a for the image formation passes, passed through the different part 7b, and is made incident on a detector 9 positioned on the side where the light beam 2a for image formation is transmitted, so that the signal is detected as the synchronizing signal. Consequently, the device can be installed in a specific space without narrowing down the maximum scanning range of the light beam for image formation matching with the diameter of the scanning lens.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a light beam scanning device in which an image forming light beam and a synchronization signal light beam are reflected by the same reflecting surface of a polygon mirror. It is used in laser printers that form a latent image on a photoreceptor using a laser beam.

(Prior art) In this type of light beam scanning device, the scanning area of the image forming light beam is limited due to the angle division accuracy of the reflecting surface of the polygon mirror, rotational unevenness, vibration, etc. They may not always be aligned in the sub-scanning direction, which is the direction in which the photoreceptor moves.

In order to solve this problem, a synchronizing signal light beam is used to detect when the image forming light beam reaches a predetermined position on the upper scanning side. It is common practice to start modulation based on

Conventionally, this synchronizing signal light beam has been used in a typical manner as shown in FIG. In conventional example 1, which includes example 2) and the type known from Japanese Patent Publication No. 60-10283 (conventional example 3), laser beam b from a laser oscillator a is passed through a collimator lens C to a polygon mirror as shown in FIG. In a light beam scanning device in which the deflected laser beam b passes through a scanning lens e and forms a scanning line f on a photoreceptor drum or film, the upper scanning side of the laser beam b that has passed through the scanning lens e is The beam is reflected by a mirror g and received by a detector i as a synchronizing signal light beam h.

In Conventional Examples 2 and 3, the image forming light beam passes through a scanning lens, whereas the synchronizing signal light beam is received by a detector after removing the scanning lens.

(Problems to be Solved by the Invention) In Conventional Example 1, the image forming scanning band e of the scanning lens e is
A part of the upper scanning side of the laser beam b that has passed through ゛ is used as the synchronizing signal light beam g, and the laser beam b passes through the image forming scanning band e゛ of the scanning lens. Due to the amount used as the beam h and the vignetting caused by the mirror f arranged for the use thereof, the range shown in FIG. 9j cannot be used for image formation. However, the portion e'' of the light beam b that is not used for image formation of the scanning lens e is also finished with high precision as part of the entire scanning lens e, so the finished portion is wasted, and the high precision The scanning range for image formation is narrow relative to the aperture of the finished scanning lens e, or the scanning lens e has a large diameter relative to the scanning range, which is the molecular economy.

In conventional examples 2 and 3, the detection means for receiving the synchronizing signal light beam must be placed in a portion of the scanning lens that is not on the light beam transmission side. However, although there is space to install the light beam source, polygon mirror, and scanning lens in a reader printer, etc., there are also issues such as guaranteeing image formation accuracy, so they are formed into a small unit with a specified mutual positional relationship. There is. For this reason, if we were to arrange the above-mentioned detection means in such a unit, we would have to install it between the polygon mirror and the scanning lens, but there is no such extra space, and it is necessary to place the detection means between the polygon mirror and the scanning lens so that it can be arranged. If the distance between the lenses is increased or the lens is placed at a position away from between the polygon mirror and the scanning lens, the unit will become larger.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a method in which an image forming light beam and a synchronization signal light beam are reflected by the same reflecting surface of a polygon mirror. The optical beam scanning device is configured such that the synchronizing signal light beam reflected from the polygon mirror passes through a part other than the part through which the image forming light beam reflected from the polygon mirror of the scanning lens passes, and passes through the scanning lens. The present invention is characterized in that the synchronizing signal light beam is received by a detector.

(Operation) The image forming light beam and the synchronizing signal light beam are reflected and deflected by the same reflecting surface of the polygon mirror.

The deflected imaging light beam may be directed to and scanned through portions of the imaging scan zone of the scan lens.

On the other hand, the synchronizing signal light beam is directed to a part different from the image forming scan band through which the image forming light beam of the scanning lens passes, and is located on the side through which the image forming light beam of the scanning lens passes through the different part. The light can enter the detector and be received as a synchronization signal.

(Embodiment) To explain the first embodiment of the present invention shown in FIG. The laser beam 2 is divided into an image forming light beam 2a and a synchronizing signal light beam 2b.

The image forming light beam 2a is incident as it is, and the synchronizing signal light beam 2b is incident on the same reflecting surface of the polygon mirror 4 via the mirror 6. Also, upon reflection by the polygon mirror 4, the image forming light beam 2a is incident on the scanning lens. The direction of the synchronizing signal light beam 2b is deflected to a band 7b set on a portion of the scanning lens 7 other than the image forming scanning band 7a. The angle of incidence of the image forming light beam 2a and the synchronizing signal light beam 2b onto the polygon mirror 4 is set so that the image forming light beam 2a and the synchronizing signal light beam 2b are incident on the polygon mirror 4.

The image forming light beam 2a that has passed through the scanning lens 7 scans a photoconductor such as a photoconductor drum or film on a scanning line 8, forming a latent image, and forms a latent image on the photoconductor by sub-scanning the photoconductor side. I will do it.

The synchronizing signal light beam 2b passing through the scanning lens 7 is connected to the scanning line 8.
The image forming light beam 2a is received by a detector 9 disposed near the scanning line 8 and provides a timing signal when the image forming light beam 2a reaches a scanning start position on the scanning line 8. When this timing signal is obtained and the image signal of the image forming light beam 2a is modulated, the scanning area of the image forming light beam 2a is aligned in the sub-scanning direction.

The detector 9 is a portion with sufficient space on the side through which the image-forming light beam 2a of the scanning lens 7 passes, and the synchronous signal light beam that has passed through a portion other than the image-forming scanning band 7a of the scanning lens 7. It is only necessary to provide the light beam 2b in a portion outside the scanning area of the image forming light beam 2a. Therefore, the synchronizing signal light beam 2b can be detected and used within the conventional space without narrowing the maximum scanning range commensurate with the aperture of the scanning lens.

Although the image forming light beam 2a and the synchronizing signal light beam 2b are obtained by dividing the laser beam 2, separate light sources may be used for each.

In a second embodiment of the present invention shown in FIG. 2, an image sensing light beam 2a is obtained separately by a laser oscillator 1, and a synchronizing signal light beam 2b is obtained by a light source 11 exclusively for the same.

The image forming light beam 2a is incident on a polygon mirror 4 through a collimator lens 3, and is deflected from the polygon mirror 4 to an image forming scanning zone 7a set on the diameter line of the scanning lens 7, as in the first embodiment. That's what I do.

The synchronizing signal light beam 2b is generated from a light source 11 provided near the bottom of the scanning line 8, and forms an image on the polygon mirror 4 through a portion 7c slightly below the image forming scanning band 7a of the scanning lens 7. The optical beam 2a is incident on the same reflecting surface as the optical beam 2a, and is reflected from the polygon mirror 4, and passes through the portion 7b of the scanning lens 7 upwardly outside the image forming scanning zone 7a, near the upper part of the scanning line 8.・The light is received by the detector 9 installed at the

In this way, the light source 11 and the detector 9 for the synchronizing signal light beam 2b are both provided on the side of the scanning lens 7 through which the image forming light beam 2a passes, and in the vicinity of the scanning line 8. Although having a dedicated light source for the beam 2b, the maximum scanning range commensurate with the aperture of the scanning lens 7 is not narrowed within the conventional space.

A third embodiment of the invention, shown in FIGS.
As in the embodiment, the light source 1 of the synchronizing signal light beam 2b
Both the detector 1 and the detector 9 are arranged on the side of the scanning lens 7 through which the image forming light beam 2a passes, but the difference is that they are arranged inside the lens barrel 21 of the scanning lens 7.

The lens barrel 21 holds seven point-symmetrical lenses 22-28 and three cylindrical lenses 29-31. The scanning lens 7 is constituted by the fourth point-symmetrical lenses 22 to 25 from the reflective surface 4a side of the polygon mirror 4, and the latter three
Various aberrations are corrected by the point-symmetrical lenses 26 to 28, and the aperture diameter is increased and the inclination angle is corrected by the cylindrical lenses 29 to 31.

The cylindrical lenses 29 to 31 may be narrow rectangular lenses with a length that covers the entire scanning range of the image forming light beam 2a. As a result, the cylindrical lens 30 is located between the last point-symmetric lens 25 of the scanning lens 7 and the point-symmetric lens 26 immediately following it, and forms pocket spaces 32 and 33 in the lens barrel 21 above and below itself. ing.

A light source 11 and a mirror 34 that directs the synchronizing signal light beam 2b from the light source 11 to the polygon mirror 4 through the scanning lens 7 are arranged in one pocket space 32, and reflected by the detector 9 and the polygon mirror 4 in the other pocket space 33. The synchronizing signal light beam 2b that has passed through the scanning lens 7 is detected by a detector 9.
A mirror 35 is arranged to face.

In this embodiment, it is preferable to provide both the light source 11 of the synchronizing signal light beam 2b and the detector 9 on the side of the scanning lens 7 through which the image forming light beam 2a is transmitted. This can be achieved by installing both of the side optical systems in a normal or close to normal lens barrel by using pocket spaces 32 and 33 normally formed in the lens barrel 21,
A special space and mounting equipment for arranging the synchronization signal light beam 2b are not required.

The position of the mirrors 34 and 35 from the optical axis is determined by the installation angle of the polygon mirror 4, and the position of the mirrors 34 and 35 from the optical axis is determined by the installation angle of the polygon mirror 4.
The position d from the mirrors 34 and 35 is determined by the focal length of the scanning lens 7. The light source 11 and the detector 9 may be arranged interchangeably.

A fourth embodiment of the present invention shown in FIGS.
In this embodiment, a light source 11 and a detector 9 are arranged within a lens barrel 21 having a lens having a different configuration from that of the embodiment.

The point symmetric lenses 22 to 25 of the scanning lens 7 and the point symmetric lenses 26 to 28 for increasing the aperture diameter are the same as in the third embodiment, but a cylindrical lens 29 corrects various aberrations and tilt angles. The only difference is the arrangement of ~31.

A cylindrical lens 29 is located between the last lens 25 of the scanning lens 7 and the subsequent point-symmetric lens 26,
Pocket spaces 32 and 33 similar to the above embodiment above and below.
The light source 11 is located in the upper terminal space 32.
A detector 9 and a mirror 35 are respectively arranged in the lower pocket space 33.

This embodiment can also exhibit the same effects as the third embodiment.

(Effects of the Invention) Since the present invention has the above-described configuration and operation, the detector for detecting the synchronizing signal light beam can be placed on the side of the scanning lens through which the image forming light beam passes, which has a high degree of freedom. It can be easily installed within a conventional space without narrowing the maximum scanning range of the image forming light beam commensurate with the aperture of the lens.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a first embodiment of the invention, Fig. 2 is a perspective view showing a second embodiment of the invention, and Fig. 3 is a plan view showing a third embodiment of the invention. , FIG. 4 is a side view of the same, FIG. 5 is a front view, FIG. 6 is a plan view showing the fourth embodiment of the present invention, FIG. 7 is a side view of the same, FIG. 8 is a front view of the same, and FIG. FIG. 9 is a perspective view of a conventional example.

Claims (1)

[Claims] (1) An image forming light beam and a synchronization signal light beam,
A light beam scanning device in which a light beam is reflected by the same reflective surface of a polygon mirror, and the synchronization signal light is reflected from the polygon mirror in a part other than the part through which the image forming light beam reflected from the polygon mirror of the scanning lens passes. A light beam scanning device characterized in that the beam passes through the scanning lens, and the synchronization signal light beam that has passed through the scanning lens is received by a detector.