JP2502300B2 - Optical beam scanning device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device in which an image forming light beam and a synchronizing signal light beam are reflected by the same reflecting surface of a polygon mirror. It is used for a laser printer that forms a latent image on a photoconductor by a laser beam.

(Prior Art) With this type of light beam scanning device, the scanning area of the image forming light beam is affected by the accuracy of angular division of the reflecting surface of the polygon mirror, uneven rotation, vibration, etc., when scanning with the image forming light beam. It may not always be aligned in the sub-scanning direction, which is the moving direction of the photoconductor.

Therefore, in order to eliminate such a situation, the light signal for synchronizing signal for detecting that the light beam for image forming has reached the predetermined position on the scanning side is used to generate the image signal of the light beam for image forming at the time of the detection. It is common practice to initiate a based modulation.

Conventionally, as a typical example of the utilization form of the light beam for the synchronizing signal, the type shown in FIG. 9 (conventional example 1) and the type known in FIG. 2 of JP-A-53-3833 (conventional type) Example 2) and the type known from Japanese Patent Publication No. 60-10283 (conventional example 3).

In the conventional example 1, as shown in FIG. 9, a laser beam b from a laser oscillator a is applied to a polygon mirror d via a collimator lens c to be deflected, and the deflected laser beam b
In a light beam scanning device for forming a scanning line f on a photoconductor drum or film through a scanning lens e, a part of the laser beam b passing through the scanning lens e on the scanning upper side is reflected by a mirror g and is used as a synchronizing signal. Detector i as light beam h
It is designed to receive light.

In the conventional examples 2 and 3, the image forming light beam passes through the scanning lens, while the synchronizing signal light beam is received by the detector with the scanning lens removed.

(Problems to be Solved by the Invention) In the conventional example 1, a part of the laser beam b passing through the image forming scanning band e ′ of the scanning lens e on the scanning side is used as the synchronizing signal light beam g. Therefore, the laser beam b is used as the light beam h for the synchronizing signal while passing through the image forming scanning band e ′ of the scanning lens, and due to vignetting by the mirror f arranged for the use, The range shown in FIG. 9j cannot be used for image formation. However, the passing portion e ″ of the light beam b which is not used for image formation of the scanning lens e is also finished with high precision as a part of the entire scanning lens e, so that the finished portion is wasted and high precision. Finished scanning lens e
It is uneconomical because the scanning range for image formation is narrow relative to the aperture size of 1 or the scanning lens e with a large aperture is required for the scanning range.

In the conventional examples 2 and 3, the detection means for receiving the synchronizing signal light beam must be arranged in a portion of the scanning lens which is not on the light beam transmitting side. However, the light beam source, the polygon mirror, and the scanning lens have space for installation in a reader printer, etc., but due to problems such as guarantee of image forming accuracy, they are formed in a small unit that specifies their mutual positional relationship. There is. Therefore, if the above-mentioned detecting means is arranged in such a unit, there is no choice but to provide it between the polygon mirror and the scanning lens, but there is no such a space, and the polygon mirror and the scanning are arranged so that they can be arranged. If the distance between the lenses is increased, or if the distance between the lenses is increased from the position between the polygon mirror and the scanning lens, the unit becomes large.

(Means for Solving Problems) In order to solve the above problems, the present invention is designed to reflect an image forming light beam and a synchronizing signal light beam on the same reflecting surface of a polygon mirror. The optical beam scanning device according to claim 1, wherein the synchronizing signal light beam reflected from the polygon mirror passes through the portion other than the portion through which the image forming light beam reflected from the polygon mirror of the scanning lens passes, and passes through the scanning lens. The detector is configured to receive the synchronizing signal light beam.

(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 is directed into the imaging scan band of the scan lens and can be scanned through that band portion.

On the other hand, the synchronizing signal light beam is directed to a portion different from the image forming scanning band through which the image forming light beam of the scanning lens passes, and is positioned on the side where the image forming light beam of the scanning lens passes through the different portion. It can enter the detector and is received as a synchronization signal.

(Embodiment) Explaining a first embodiment of the present invention shown in FIG. 1, a laser beam 2 oscillated from a laser oscillator 1 is directed to a polygon mirror 4 via a collimator lens 3, but a half mirror 5 is used. The laser beam 2 is divided into an image forming light beam 2a and a synchronizing signal light beam 2b by means of.

The image forming light beam 2a remains 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, and the image forming light beam 2a is reflected by the polygon mirror 4 so that the image forming light beam 2a is a scanning lens. 7 is deflected toward the image forming scanning band 7a set on the diameter line of 7, and the synchronizing signal light beam 2b is emitted from the scanning lens 7 in the image forming scanning band 7a.
So that it is deflected toward the band 7b set in other parts,
The incident angles of the image forming light beam 2a and the synchronizing signal light beam 2b on the polygon mirror 4 are set.

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

The synchronizing signal light beam 2b passing through the scanning lens 7 is scanned by the scanning line 8
A timing signal is provided when the image forming light beam 2a is received by the detector 9 arranged in the vicinity of and reaches the scanning start position on the scanning line 8. When this timing signal is obtained and the image forming light beam 2a is modulated with respect to the image signal, the scanning regions of the image forming light beam 2a are aligned in the sub-scanning direction.

The detector 9 is a synchronizing signal light beam that has passed through a portion of the scanning lens 7 on the side through which the image forming light beam 2a is transmitted, and also has a portion other than the image forming scanning band 7a of the scanning lens 7. It may be provided at a portion outside the scanning area by the image forming light beam 2a by receiving the light 2b. Therefore, the synchronization signal light beam 2b is detected and used in the conventional space without narrowing the maximum scanning range commensurate with the aperture of the scanning lens.

The image forming light beam 2a and the synchronizing signal light beam
2b is obtained by dividing the laser beam 2, but individual light sources can be used for each.

In the second embodiment of the present invention shown in FIG. 2, the image forming light beam 2a is obtained by the laser oscillator 1 and the synchronizing signal light beam 2b is obtained by the dedicated light source 11.

The image forming light beam 2a is made incident on the polygon mirror 4 through the collimator lens 3 and is deflected from the polygon mirror 4 toward the image forming scanning band 7a set on the diameter line of the scanning lens 7 as in the first embodiment. Is done.

The synchronizing signal light beam 2b is generated from a light source 11 provided near the lower part of the scanning line 8 and an image is formed on the polygon mirror 4 through a portion 7c slightly below the image forming scanning band 7a of the scanning lens 7. The incident light beam 2a is made incident on the same reflecting surface, and is reflected from the polygon mirror 4 and is in the vicinity of the upper part of the scanning line 8 through the portion 7b of the scanning lens 7 which is located above the image forming scanning area 7a and deviates upward. The light is received by the detector 9 provided at.

Thus, both the light source 11 and the detector 9 for the synchronizing signal light beam 2b are provided on the side of the scanning lens 7 through which the image forming light beam 2a is transmitted, and in the vicinity of the scanning line 8.
While having a dedicated light source for the synchronization signal light beam 2b, the maximum scanning range within the conventional space and corresponding to the aperture of the scanning lens 7 is not narrowed.

The third embodiment of the present invention shown in FIGS. 3 to 5 is similar to the second embodiment in that the light source 11 for the light beam 2b for the synchronizing signal is used.
Both the detector 9 and the detector 9 are arranged on the side of the scanning lens 7 through which the image forming light beam 2a is transmitted, but they are different in that they are arranged inside the lens barrel 21 of the scanning lens 7.

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

The cylindrical lenses 29 to 31 are light beams 2a for image formation.
A narrow strip having a length that covers the entire scanning range may be used. This makes the cylindrical lens 30
Is located between the rearmost point-symmetrical lens 25 of the scanning lens 7 and the point-symmetrical lens 26 immediately after it, and the lens barrel 21 is located above and below itself.
Pocket spaces 32 and 33 are formed inside.

A light source 11 and a mirror 34 for directing 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 are reflected by the detector 9 and the polygon mirror 4 in the other pocket space 33. A mirror 35 for arranging the synchronizing signal light beam 2b that has passed through the scanning lens 7 toward the detector 9 is arranged.

In this embodiment, both the light source 11 and the detector 9 for the synchronizing signal light beam 2b are provided for the image forming light beam 2a for the scanning lens 7.
Should be provided on the side where the light passes through, using both the light source 11 side optical system and the detector 9 side optical system, using the pocket spaces 32 and 33 normally formed in the lens barrel 21, as usual or close to it. This can be achieved by installing it inside, and no special space or fixture for arranging the light beam 2b for synchronization signal is required.

The position D of the mirrors 34 and 35 from the optical axis is determined by the installation angle of the polygon mirror 4, and the position d of the light source 11 and the detector 9 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 replaced with each other.

The fourth embodiment of the present invention shown in FIGS. 6 to 8 is one in which the light source 11 and the detector 9 are arranged in a lens barrel 21 having a lens having a configuration different from that of the third embodiment. Is.

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 those in the third embodiment, but a cylindrical lens 29 for correcting various aberrations and tilt angles is used. Only the arrangement of ~ 31 is different.

A cylindrical lens 29 is located between the rearmost lens 25 of the scanning lens 7 and the point symmetrical lens 26, and pocket spaces 32 and 33 similar to those in the above-mentioned embodiment are formed above and below the cylindrical lens 29, and an upper pocket thereof. Light source 11 and mirror 34 in space 32
However, the detector 9 and the mirror 35 are arranged in the lower pocket space 33, respectively.

Also in the case of this embodiment, it is possible to exhibit the same operational effect as that of the third embodiment.

(Effects of the Invention) Since the present invention has the above-described configuration and operation,
Arrangement of a detector that detects the light beam for synchronization signals On the side where the image forming light beam of the scanning lens, which has a high degree of freedom, is transmitted, the maximum scanning range of the image forming light beam that matches the aperture of the scanning lens is not narrowed. In addition, it can be easily installed in a conventional space.

[Brief description of drawings]

1 is a perspective view showing a first embodiment of the present invention, FIG. 2 is a perspective view showing a second embodiment of the present invention, and FIG. 3 is a plan view showing a third embodiment of the present invention. FIG. 4 is the same side view, FIG. 5 is the front view, FIG. 6 is a plan view showing a fourth embodiment of the present invention, FIG. 7 is the same side view, and FIG. 8 is the same front view. FIG. 9 is a perspective view of a conventional example. 2a ...... Image forming light beam 2b ...... Sync signal light beam 7a ...... Image forming scanning band 7b ...... Part outside the image forming scanning band 9 ...... Detector

Claims (1)

(57) [Claims] 1. A light beam scanning device in which an image forming light beam and a synchronizing signal light beam are reflected by the same reflecting surface of a polygon mirror, wherein the image forming is reflected from a polygon mirror of a scanning lens. It is characterized in that the synchronizing signal light beam reflected from the polygon mirror passes through a portion other than the portion through which the working light beam passes, and the synchronizing signal light beam passing through the scanning lens is received by the detector. Light beam scanning device.