JPS62219756A - Optical scanning device - Google Patents

Abstract

PURPOSE:To prevent an image from being affected adversely by a synchronizing signal generating optical beam, by setting the wavelength of the synchronizing signal generating optical beam as the one of an area of low spectral sensitivity in a photosensitive body. CONSTITUTION:Electrostatic latent images formed on a photosensitive drum 4 by the plural number of times of repeated scannings are the ones arranged in a subscan direction. Also, in the titled device, a synchronizing signal, the inverse of SOS, is generated by using a synchronizing signal generating laser beam B' separately from an image forming laser beam B. Consequently, it is enough for the image forming laser beam B to perform the minimum range of scanning required for an image forming, therefore, an image forming speed is made into a high speed compared with a constitution in which the image forming laser beam B is made scan on a synchronization control light receiving part B. And in the laser beam printer, the wavelength of the area having the lower spectral sensitivity in the photosensitive drum 4 is used as the synchronizing signal generating laser beam B'.

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 for detecting the light beam is provided on the upper side of the scanning side than the photoreceptor, and after a predetermined period of time from when the light receiving section detects the light beam, the light beam is modulated based on the image signal. By synchronizing the start timing of modulation so that the light beam starts moving in the sub-scanning direction, the latent image formed by scanning the light beam multiple times on the photoconductor moving in the sub-scanning direction can be aligned in the sub-scanning direction. will be carried out.

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. . However, in order to generate the synchronization signal, the light beam must be scanned extra, which becomes a factor that hinders the speedup of image formation.

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, a light beam for image formation and a light beam for generating a synchronization signal have the same wavelength (see, for example, Japanese Patent Laid-Open No. 53-3833).

[Problem that the invention seeks to solve]

However, in the case of the above-mentioned conventional configuration, this synchronizing signal generating light beam is also scanned on the photoreceptor as the rotating polygon mirror rotates.

Further, the light beam for image formation usually has a wavelength in a region where the spectral sensitivity of the photoreceptor is high.

Therefore, the photoreceptor is exposed in the same way by the synchronizing signal generation light beam having the same wavelength as the image forming light beam, and in the latent image forming area, this becomes noise to the image information, leading to image deterioration. There is a possibility that

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 optical scanning device according to the present invention is characterized in that the wavelength of the synchronizing signal generating light beam is in a region of low spectral sensitivity of the photoreceptor where a latent image is formed by the image forming light beam.

[For production]

In other words, even if the latent image forming area of the photoconductor is irradiated with the synchronization signal generation light beam, the photoconductor has a low spectral sensitivity to the wavelength of the synchronization signal generation light beam, so the photoconductor cannot produce an image. It is not significantly exposed to light as it would be when scanned by a forming light beam, and no latent images are formed that add 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. 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 (r3) is scanned in the longitudinal direction of the photoreceptor drum (4), which is an example of a photoreceptor. direction is the main scanning direction).

This image forming laser beam (n) is transmitted through an fθ lens (5
) and uniformly charged photoreceptor drum (
4) image above 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 this synchronizing signal generating half-body laser (6) is converted into parallel light by a collimator lens (7) different from that for the image forming laser beam CB). and the reflecting surface (3) of the polygon mirror (3) on which the image forming laser beam (B) is reflected.
They are simultaneously reflected at the same spot in a).

And the laser beam for synchronization signal generation after reflection (B゛)
is converged by the fθ lens (5), and is transmitted to the synchronous control light receiving section (8) provided on the upper scanning side than the photoreceptor drum (4)
) is configured to reach. This synchronous control light receiving section (8) is for aligning the latent image formation start position for each scan with respect to the rotation direction of the photoreceptor drum (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).

In addition, as the polygon mirror (3) rotates, the synchronizing signal generation laser beam (B'') is scanned in the same direction as the image forming laser beam (B), but the image forming laser beam ( B) is the photosensitive drum (4) as it scans.
The semiconductor for synchronizing signal generation is arranged so that when the laser beam for synchronizing signal generation (B") which is subsequently scanned reaches the starting end of the latent image forming area above, it reaches the light receiving part for synchronization control (8). The laser (6) is positioned relative to the image forming semiconductor laser (1).

The output from this synchronous control light receiving section (8) is input to a modulation control device (9). The modulation control bag W (9) receives the laser beam (Bo) for generating a synchronization signal when the modulation control light receiving section (8) receives the laser beam (Bo) for generating a synchronization signal, and when the output exceeds a set value, A synchronizing signal (Y) is output to the laser driving section (10) for (1). The laser driving section (10) receives this signal (2), 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. Furthermore, since the synchronization signal (average) 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 It is sufficient to scan the minimum necessary range for image formation, and compared to a configuration in which the image forming laser beam (B) is scanned as far as the synchronous control light receiving section (8), the image forming speed can be increased. It can be measured.

In this laser beam printer, a laser beam (Bo) for generating a synchronizing signal is used whose wavelength is in a region where the spectral sensitivity of the photoreceptor drum (4) is low. In other words, as the polygon mirror (3) rotates, the synchronization signal generation laser beam (Bo) also rotates on the photoreceptor drum (4).
) will be scanned. Therefore, suppose that the laser beam (B") for generating a synchronizing signal is connected to the photoreceptor drum (4).
Even when the photoreceptor drum (4) is scanned, its wavelength is shifted from the high-sensitivity region of the photoreceptor drum (4) in order to prevent the formation of a latent image that becomes noise to the image information.

For example, an image forming semiconductor laser (
1) as the photoreceptor drum (4) [700nn+
] to [900nm], the synchronization signal generation laser beam (Bo)
If the wavelength is [1300nm] or [1600nm]
It is sufficient to use a synchronizing signal generating semiconductor laser (6) made of InGaAs P which can obtain a laser diode of 100 nm.

In the previous embodiment, the image forming laser beam (B) and the synchronizing signal generating laser beam (B'') were obtained separately from the two semiconductor lasers (1) and (6). Alternatively, one or both may be obtained using a gas laser or a solid state laser.

For example, as before, Ga/V! An image forming semiconductor laser (1) made of As, and a Si-based photoreceptor drum (
For the combination of 4), the laser beam for synchronizing signal generation (
B'') may be obtained from a He-Cd laser with a wavelength of [442 nm.Alternatively, one of the two types of laser beams obtained from an Ar laser with a wavelength of [514,5 nm] may be used.
One is used as the image forming laser beam (B), and a CdS type photoreceptor drum (4) with a sensitivity peak near [520 nm] is used, and the other one [488 nm] is synchronized. It may also be used for signal generation.

In this case, it becomes possible to share a part of the optical system.

Furthermore, as the photoreceptor drum (4), a Se-based material having high sensitivity in [450 nm] to [650 r+m] is used,
When obtaining the image forming laser beam (13) from an Ar laser, a light beam from an LED with a wavelength of about [700 nm] may be used for synchronization signal generation, and this light beam or the already mentioned laser beam may be used. Together, they are referred to as a synchronization signal generation light beam (B').

Figure 2 shows the spectral sensitivity characteristics of various photoreceptor drums (4),
The oscillation wavelengths of various light beams are shown.

In carrying out the present invention, they may be used in appropriate combinations.

In the previous embodiment, the image forming light beam (B) and the synchronizing signal generating light beam (B') were configured to be irradiated onto the same spot on the reflective surface (3a) of the polygon mirror (3). explained things. Instead, these two light beams (B) and (B') are directed to the same reflective surface (3a).
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.

The optical scanning device according to the present invention can be used not only for the laser beam printer described in the previous embodiment but also for laser facsimiles and laser beam printers.
Applicable to 0M system etc.

For example, when performing high-density recording as in a laser 00M system, the image forming light beam (B) is configured to be narrowed down to an extremely small diameter by a scanning lens such as an fθ lens (5). Optical beam for synchronization signal generation (
The synchronization signal generation light beam (B) is connected to a scanning lens such as an f-theta lens (5) to prevent the light beam B for generating a synchronization signal from being narrowed down too much and becoming difficult to detect by the synchronization control light receiving unit (8). It is preferable not to allow it to pass through.

In this case, the scanning lens such as the fθ lens (5) needs to cover only the scanning range of the image forming light beam (B), so it can be made compact.

〔Effect of the invention〕

As described above, in the optical scanning device according to the present invention, the wavelength of the light beam for generating a synchronizing signal is set to a wavelength in a region where the spectral sensitivity of the photoreceptor is low. Even if the photoreceptor is irradiated with the photoreceptor, a latent image that becomes noise in the image information is not formed.

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, and FIG. 1 is a schematic configuration diagram, and FIG. 2 is a graph showing the spectral sensitivity characteristics of the photoreceptor and the oscillation wavelength of the light beam. (3)...Rotating polygon mirror, (3a)...
Reflective surface, (4)...Photoreceptor, (B)...
・Light beam for image formation, (B゛)...Light beam for synchronization signal generation.

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 synchronization signal generation light beam on the same reflecting surface of a rotating polygon mirror, An optical scanning device, wherein the wavelength of the light beam is in a region where the spectral sensitivity of the photoreceptor is low.