JPS62219755A - Optical scanning device - Google Patents

Abstract

PURPOSE:To prevent adverse influence on an image due to a synchronizing signal generating optical beam, by making scan an area except the latent image forming area of a photosensitive body, accompanied by the rotation of a rotary polygon mirror. CONSTITUTION:The laser beam printer is constituted so that a synchronizing signal generating laser beam B' is made incident on the reflecting plane 3a of a polygon mirror 3 diagonally from the upper side against a flat plane on which an image forming laser beam B is scanned, and after that, it is reflected diagonally to the lower side, and is made advance toward a synchronization control light receiving part 8. In other words, it is constituted so that, even when the synchronizing signal generating laser beam B' is scanned accompanied by the rotation of the polygon mirror 3, the synchronizing signal generating laser beam B' is prevented from arriving at the latent image forming area S of a photosensitive drum 4. In this way, no latent image which becomes the noise for a bit of picture information, is formed on the photosensitive drum 4, and deterioration in the image can be evaded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides an image forming light beam that forms a latent image on a photoreceptor and a synchronization signal generation light beam that are connected to the same reflective surface of a rotating polygon mirror. The present invention relates to an optical scanning device that reflects light.

[Conventional technology]

In laser beam printers, etc. that use a rotating polygon mirror for scanning a laser beam as a light beam, there are slight manufacturing errors in the angle division accuracy of the reflecting surface of the rotating polygon mirror, and there may be uneven rotation or rotation of the rotating polygon mirror. Because of vibrations associated with this, the scanning area of the light beam is not necessarily aligned in the sub-scanning direction. Therefore, for example, a light receiving section that detects the light beam is provided on the upper scanning side of the photoconductor, and after a predetermined time from when the light receiving section detects the light beam, modulation of the light beam based on the image signal is started. By synchronizing the timing of the start of modulation, the latent images formed by scanning the light beam multiple times on the photoreceptor moving in the sub-scanning direction can be aligned in the sub-scanning direction. What is done is done.

However, the light-receiving section for detecting the aforementioned light beam and controlling the synchronization of modulation needs to be installed at a position separated from the latent image forming area on the photoreceptor. In the configuration used for both the above-described synchronization signal generation for synchronizing the modulation start timing, it takes some time for the light beam to reach the latent image forming area after being detected by the light receiving section.

That is, in order to generate the synchronization signal, the light beam must be scanned extra, which becomes a factor that impedes an increase in the image forming speed.

Therefore, a known method uses different light beams for image formation and synchronization signal generation to eliminate the above-mentioned redundant scanning and increase the image formation speed. Conventionally, in this type of optical scanning device, the synchronizing signal generating light beam also scans the latent image forming area of the photoreceptor as the rotating polygon mirror rotates (for example, Japanese Patent Laid-Open No. 53-3833
(see publication).

[Problem that the invention seeks to solve]

However, in the case of the above-mentioned conventional configuration, the photoreceptor is exposed in the same way by the synchronization signal generation light beam,
Since this becomes noise to the image information, there is a possibility that it may cause image deterioration.

In view of the above circumstances, an object of the present invention is to prevent a light beam for generating a synchronization signal from adversely affecting an image.

[Means for solving problems]

The characteristic configuration of the optical scanning device according to the present invention is that, as the rotating polygon mirror rotates, the synchronizing signal generating light beam is directed to an area other than the latent image forming area of the photoreceptor where the latent image is formed by the image forming light beam. The reason is that it allows scanning.

[For production]

In other words, for example, for an image forming light beam that is incident on the reflective surface of a rotating polygon mirror from the horizontal direction, a synchronization signal generation light beam is incident on the reflective surface from diagonally above and then reflected diagonally downward. Or, even when scanning within the same plane, by making both light beams incident on the reflecting surface of the rotating polygon mirror with an appropriate angle difference, the light beams can be reflected by the reflecting surface of the rotating polygon mirror. The synchronizing signal generating light beam after the synchronization signal generation can be deflected in a direction different from the photoreceptor. This prevents the photoreceptor from being exposed to light and prevents the formation of latent images that would cause noise to the image information.

〔Example〕

The present invention will be described in detail below based on the drawings.

FIG. 1 shows a schematic configuration of a scanning device for a laser beam printer, which is an example of the optical scanning device of the present invention. (1)
is an image forming semiconductor laser that oscillates an image forming laser beam (B) which is an example of an image forming light beam, and is modulated based on input image information and oscillated from this image forming semiconductor laser (1). Image forming laser beam (B
) is made into parallel light by the collimator lens (2),
Reflective surface (3a) with a polygon mirror (3) rotating at high speed
) is reflected. By rotating this polygon mirror (3), which is an example of a rotating polygon mirror, an image forming laser beam (B) is generated.
The inclination of the reflecting surface changes with respect to the surface, and accordingly, the reflected image-forming laser beam (B) is scanned in the longitudinal direction of the photoconductor drum (4), which is an example of a photoconductor ( This direction is the main scanning direction).

This image forming laser beam (B) is transmitted through an fθ lens (5
), the image is focused onto the uniformly charged photoreceptor drum (4) to reduce the charging potential at that location.

By repeating this scanning as the photosensitive drum (4) rotates at a constant speed, an electrostatic latent image is formed on the photosensitive drum (4).

Thereafter, although not shown, toner, which is a colored pigment, is selectively attached to this electrostatic latent image area and developed, and output paper is adhered to the toner image surface to transfer the toner image onto the paper surface. The heat melts the toner and fixes it on the paper, creating an output image.

In addition to the image forming semiconductor laser (1), a synchronizing signal generating semiconductor laser (6) is provided.

The synchronizing signal generating laser beam (B") oscillated from the synchronizing signal generating half-body laser (6) is collimated by a collimator lens (7) different from that for the image forming laser beam (B). The image forming laser beam (B) is reflected at the same time by the reflecting surface (3a).

And the laser beam for synchronization signal generation after reflection (B゛)
is configured to scan an area including the synchronous control light receiving section (8) as the polygon mirror (3) rotates. This synchronous control light receiving section (8) is connected to the photoreceptor drum (
This is to align the latent image formation start position for each scan with respect to the rotation direction (4) (this direction is the sub-scanning direction).

In other words, there is a slight manufacturing error in the angle division accuracy of each reflective surface of the polygon mirror (3), and
Because of rotational unevenness and vibration accompanying the rotation, the scanning area of the image forming laser beam (B) is not necessarily aligned in the sub-scanning direction. Therefore, the polygon mirror (3) has a reflective surface (3a) on which the image forming laser beam (B) is reflected.
) is simultaneously reflected by the synchronization signal generating laser beam (B') is received by the synchronization control light receiving section (8), and the photosensitive drum (4) is scanned to form an image. This is to control the modulation of the laser beam (B).

Furthermore, as the polygon mirror (3) rotates, the laser beam for synchronizing signal generation (B') is scanned in the same direction as the laser beam for image formation (B), but the laser beam for image formation (B') is scanned in the same direction as the laser beam for image formation (B). ) reaches the starting end of the latent image forming area on the photoreceptor drum (4) during scanning, this synchronizing signal generating laser beam (B'), which is also scanned, is transmitted to the synchronizing control light receiving section. (8), the synchronizing signal generating semiconductor laser (6) is positioned relative to the image forming semiconductor laser (1).

The output from this synchronous control light receiving section (8) is manually input to a modulation control device (9). Then, the modulation control device (9) controls the image forming semiconductor laser when the modulation control light receiving section (8) receives the synchronization signal generation laser beam (B') and its output exceeds the set value. A synchronizing signal (2) is output to the laser drive unit (10) for (1). The laser driving section (10) receives this signal (Y), takes in data based on the input image signal from the memory (11), and starts direct modulation of the image forming semiconductor laser (1). As a result, formation of an electrostatic latent image using the image forming laser beam (B) that is modulated and output is started.

With the above configuration, the electrostatic latent images formed on the photoreceptor drum (4) by repeating scanning a plurality of times are aligned in the sub-scanning direction. Moreover, since the synchronization signal (Y) is generated using a synchronization signal generation laser beam (B'') that is different from the image formation laser beam (B), the image formation laser beam (B) is different from the image formation laser beam (B). It is sufficient to scan the minimum necessary range for image formation, and the image formation speed can be increased compared to a configuration in which the image forming laser beam (B) is scanned even to the synchronous control light receiving section (8). It is.

In this laser beam printer, as shown in FIG. Reflective surface (3) of mirror (3)
After the light is incident on the light beam a), the light is reflected diagonally downward and directed toward the synchronization control light receiving section (8). In other words, even if the synchronizing signal generating laser beam (B) is scanned with the rotation of the polygon mirror (3), the latent image forming area (S) of the photoreceptor drum (4) is not covered by the synchronizing signal generating laser beam (B). This is to prevent the beam (B) from reaching the target.

Therefore, no latent image is formed on the photoreceptor drum (4) as a noise to the image information, and image deterioration can be avoided.

Image forming light beam (B) and synchronization signal generation light beam (
Even in a configuration in which B') is scanned in the same plane,
By appropriately setting the angle of incidence of these two light beams (B) and (B') on the reflecting surface (3a) of the polygon mirror (3), the light beam (B') for synchronizing signal generation can be applied to the photoreceptor. It is possible to prevent the latent image forming area (S) of the drum (4) from being scanned.

Next, an example thereof will be explained.

Figure 3 shows a case where the image forming light beam (B) and the synchronizing signal generation light beam (B") are incident from the same side with respect to the normal (N) of the reflecting surface (3a). At the center of the reflective surface (3a), the image forming light beam (It)
The incident angle of [θI] is the optical beam for synchronization signal generation (Bo)
When the incident angle of
The beam is deflected while maintaining the angle θ1].

As the polygon mirror (3) rotates, this reflective surface (3a) has an inclination of 2π/nun for either light beam (B or B'), which constitutes the polygon mirror (3). It changes by the number of reflective surfaces (3a). Therefore, both light beams (IS) and CB') after being reflected by the reflecting surface (3a) are deflected within a range of [±2π/n] from the illustrated position.

In other words, in order to prevent the synchronization signal generation light beam (Bo) from scanning the latent image forming area (S) of the photoreceptor drum (4), the synchronization signal generation light beam (Bo) must be The scanning area of the light beam (Bo) and the image forming light beam (
It is necessary to prevent the scanning area in B) from overlapping. That is, the condition is θ2-θ1≧4π/n.

FIG. 4 shows a case where the image forming light beam (B) and the synchronizing signal generating light beam (Bo) are incident from opposite sides to the normal (N) of the reflecting surface (3a). There is. In this case as well, if the same considerations as before are made, the condition θ2-θ1≧2π/n will be satisfied.

In the previous embodiment, the image forming laser beam (B) and the synchronizing signal generating laser beam (Bo) were obtained separately from the two semiconductor lasers (1) and (6), respectively. Alternatively, one or both may be obtained using a gas laser or a solid laser. Furthermore, the laser beam for synchronizing signal generation (Bo) may be obtained by separating the image forming laser beam (B) from the same gas laser or fixed laser using a suitable optical element.

Furthermore, instead of the various laser beams mentioned above, LED
A light beam from the above may be used for synchronization signal generation, and these are collectively referred to as a synchronization signal generation light beam (Bo).

In addition, in the previous embodiment, the image forming light beam (B) and the synchronization signal generation light beam (Bo) are connected to the polygon mirror (
The configuration in which the light beams are irradiated onto the same spot on the reflecting surface (3a) in 3) has been described. Instead, those two light beams (B), (B'') are connected to the same reflective surface (3
a) It may be configured so that different spots on the top are irradiated. However, if the surface precision of the reflective surface (3a) of the polygon mirror (3) is not very high, it is preferable to irradiate the same spot.

In addition to the laser beam printer described in the previous embodiment, the optical scanning device according to the present invention can also be used for a laser facsimile or a laser beam printer.
Can be used in 0M systems, etc.

For example, when performing high-density recording as in a laser C0M system, the image forming light beam (B) is configured to be narrowed down to a small diameter by a scanning lens such as an fθ lens (5) and a Kagawa lens. As a result, the synchronization signal generation light beam (Bo) is excessively narrowed down and the synchronization control light receiving section (8
), in order to prevent the detection from becoming difficult to detect due to the synchronization signal generation light beam (B
o) It is preferable to prevent the light from passing through a scanning lens such as the fθ lens (5). Note that in this case, fθ
Since the scanning lens such as the lens (5) needs to cover only the scanning range of the image forming light beam (r3), it can be made compact.

〔Effect of the invention〕

As described above, the optical scanning device according to the present invention is configured to scan an area other than the latent image forming area of the photoreceptor with a synchronizing signal generating light beam, and the synchronizing signal generating light beam This prevents the photoreceptor from being exposed to light and forming a latent image that becomes noise in image information.

Therefore, by using different light beams for image formation and synchronization signal generation, it is possible to increase the image formation speed and to prevent image deterioration.

[Brief explanation of drawings]

The drawings show an embodiment of the optical scanning device according to the present invention, with FIG. 1 being a schematic configuration diagram, FIG. 2 being a ray diagram, and FIGS. 3 and 4 being ray diagrams showing each side of the embodiment. (3)...Rotating polygon mirror, (3a)...
Reflective surface, (4)...Photoreceptor, (B)...
-Light beam for image formation, (B゛)...Light beam for synchronizing signal generation, (S)...Latent image forming area.

Claims (1)

[Claims] An optical scanning device configured to reflect an image forming light beam for forming a latent image on a photoreceptor and a synchronizing signal generating light beam on the same reflecting surface of a rotating polygon mirror, An optical scanning device that scans an area other than a latent image forming area of the photoreceptor with a synchronizing signal generating light beam as the photoreceptor rotates.