JPS63205634A - Optical scanning type image forming device - Google Patents

Abstract

PURPOSE:To prevent fluctuation in the timing for starting outputting of a synchronizing signal by adjusting the posture in the projection direction of a light beam in a light receiving part for modulation control to control the timing for starting the modulation to the light beam. CONSTITUTION:An operating means HM for adjusting the posture in the projection direction of the light beam B of the light receiving part 8 for modulation control provided to control the timing for starting the modulation of the light beam B by detecting the light beam B on the outside of an image forming region on a photosensitive body 7 is provided. The posture of the light receiving part 8 for modulation control can, therefore, be changed in the projection direction of the light beam and the side part on the front side in scanning of the light receiving part 8 for modulation control can be adjusted so as to intersect nearly orthogonal with the scanning direction of the light beam B. The timing for starting outputting the synchronizing signal from the light receiving part 8 for modulation control is, therefore, adjusted to nearly the same timing even if the passage route for the light beam B to be scanned fluctuates in the direction orthogonal with the scanning direction of the light beam B. The fluctuation in the timing for starting outputting the synchronizing signal for controlling the timing for starting the modulation is thereby decreased.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to, for example, laser beam printers and laser 00M
The optical scanning image forming apparatus, such as a system, is provided with a rotating polygon mirror that scans a light beam on a photoreceptor, detects the light beam outside the image forming area on the photoreceptor, and detects the light beam. The present invention relates to an optical scanning image forming apparatus provided with a modulation control light receiving section for controlling the start timing of modulation.

[Conventional technology]

A photodiode is generally used as a light receiving section for modulation control in this type of optical scanning image forming apparatus. and,
This modulation control light receiving section outputs a photocurrent as a synchronization signal to the modulation means for the light beam each time it is irradiated with the scanned light beam. The modulating means is configured to start modulating the light beam based on the image information in response to this synchronization signal.

A conventional optical scanning image forming apparatus is one in which the modulation control light receiving section is attached in a fixed posture (no literature can be cited).

[Problem that the invention seeks to solve]

However, in the case of the above-mentioned conventional configuration, the mounting orientation of the modulation control light receiving section tends to vary due to variations in the position and size of the hole when mounting the modulation control light receiving section, and as a result, the following problems occur. there were.

For example, as shown in FIG.
) is installed at an angle with respect to the horizontal direction in the figure, which is the scanning direction of the light beam.

The light beam is repeatedly scanned by being reflected by each reflecting surface of the rotating polygon mirror, but the angle that each reflecting surface of the rotating polygon mirror makes with the rotation reference plane (virtual plane perpendicular to the rotation axis) is subject to manufacturing errors. The passage paths of the multiple light beams to the modulation control light receiving section (8") are shown by the straight line [al] and the straight line [b] in the figure. It may be something that can be done.

However, since the modulation control light receiving section (8') is installed at an angle, and its upper scanning side (8a') is not perpendicular to the scanning direction of the light beam, the path of the light beam is different from that shown in the figure. Due to the variation in the upper and lower directions, variations occur in the timing at which the synchronization signal output from the modulation control light receiving section (8'') starts.

This situation is shown in Figure 5. □ [a゛] in Figure 4 indicates the waveform of the synchronization signal when the light beam is scanned along the path [al] in Figure 4. [b'] is for the light beam scanned along the path [b] in FIG.

If variations occur in the output start timing of the synchronization signal in this way, the modulation means will start modulating the light beam based on it, and the resulting image will not be straight in the sub-scanning direction, resulting in jitter. This will occur.

Recently, as recording speeds and densities have been increased more and more, even slight variations in the output start timing of synchronizing signals have a very large negative effect on recording.

In view of the above-mentioned circumstances, an object of the present invention is to change the start time of modulation to t.
The aim is to reduce the variation in the output start timing of synchronization signals for wm.

[Means for solving problems]

A characteristic configuration of the optical scanning image forming apparatus according to the present invention is that the light receiving section for modulation control is provided to detect a light beam outside the image forming area on the photoreceptor and control the start timing of modulation for the light beam. The present invention is provided with an operating means for adjusting the posture in the direction of irradiation of the light beam.

[For production]

In other words, since the posture of the modulation control light receiving section can be changed in the light beam irradiation direction by the operating means, the upper side of the scanning side of the modulation control light receiving section can be moved almost perpendicular to the scanning direction of the light beam. Can be adjusted. Therefore, even if the path of the scanned light beam varies in the direction perpendicular to the scanning direction of the light beam,
The output start timings of the synchronization signals from the modulation control light receiving sections can be made almost the same.

〔Example〕

Hereinafter, the present invention will be described in detail based on the drawings.

21st! I shows a schematic configuration of a laser beam printer which is an example of an optical scanning image forming apparatus according to the present invention.

The image information to be recorded is sent to the image control circuit (1
) is read out from the image memory (1a) and input to the laser driving device (2). The laser driving device (2) outputs excitation and electromotive current to the semiconductor laser (3) based on this image information. The semiconductor laser (3) oscillates a laser beam (B) that is directly modulated by this excitation current.

This laser beam (B) is made into parallel light by a collimator lens (4), and a polygon mirror (5) rotates at high speed.
) is reflected by the reflective surface (5a).

The reflected laser beam (B) is focused by an fθ lens (6), and is then focused on a photoreceptor drum (7) whose surface is uniformly charged.
), and the charged potential at the imaged position is attenuated according to its intensity.

By rotating the polygon mirror (5), which is a rotating polygon mirror, the inclination of each reflecting surface (5a) with respect to the laser beam CB) which enters as parallel light changes. As a result, the reflected laser beam CB) is directed to the photoreceptor drum (7), which is a photoreceptor.
is scanned in the longitudinal direction (this direction is the main scanning direction).

On the other hand, the photoreceptor drum (7) is configured to rotate at a constant speed in synchronization with the rotation of the polygon mirror (5) (this direction of rotation is the sub-scanning direction).

Then, as the photoreceptor drum (7) rotates, the scanning of the laser beam (B) described above is repeated, thereby forming an electrostatic latent image on the photoreceptor drum (7) according to the image information. It is.

Thereafter, although not shown, toner, which is a colored pigment, is selectively attached to this electrostatic latent image and developed. Then, the output paper is brought into close contact with the toner adhesion surface to transfer the toner onto the paper surface. Furthermore, this toner is melted and fixed on the output paper by heating to obtain an output image.

Further, a photosensor (8) is provided on the upper scanning side than the photosensitive drum (7). This photosensor (8) outputs a photocurrent when scanned by the laser beam (B) after being reflected by the polygon mirror (5). This photocurrent is shaped by a waveform shaping circuit (9), and after a certain period of time, that is, the scanned laser beam (B) reaches the recording start position of the photoreceptor drum (7) from the position of the photosensor (8). After a time corresponding to the synchronization signal (S
03) to the image control circuit (1).

In response to this synchronization signal (SOS), the image control circuit (1) controls the built-in image memory (
Reading of image information for one line from 1a) is started. And the laser drive circuit (2) has an image memory (
It receives the image information read out from 1a) and starts outputting an excitation current to the semiconductor laser (3a) based on the image information.

This synchronization signal (SOS) is used to align the starting position of the electrostatic latent image formed by repeated scanning of the laser beam (B) with respect to the rotational direction of the photoreceptor drum (7), that is, the sub-scanning direction. belongs to.

In other words, there is some manufacturing error in the angle division accuracy of each reflective surface (5a) of the polygon mirror (5). Furthermore, there are uneven rotations of the polygon mirror (5) and vibrations associated with the rotation. Therefore, the scanning area of the laser beam (B) may not always be aligned in the sub-scanning direction, which causes jitter in recording.

Therefore, the laser beam CB is
) is received as a reference, and by controlling the start of modulation of the laser beam (B) scanned on the photosensitive drum (7), occurrence of recording jitter is avoided.

The above-mentioned photosensor (8), which is a light receiving section for modulation control, is fixed on the substrate (10), as shown in FIG. This board (10) is screwed to an adjustment plate (11), and the adjustment plate (11) is further attached to a plywood (12) that is a member on the main body side.

The adjustment plate (11) is fixed to the plywood (12) with two upper and lower screws (13a) and (13b) that are screwed into the plywood (12).

The through hole (lla) of the adjusting plate (11) for the upper screw (13a) is formed to have an inner diameter approximately equal to the outer diameter of this screw (13a). On the other hand, the through hole (llb) of the adjustment plate (11) for the lower screw (13b) is formed in an arc shape centered on the upper screw (13a).

That is, the adjustment plate (11) has upper and lower screws (13a),
(13b) can be freely rotated around the center (X) of the upper screw (13a) with it temporarily fixed, and along with the rotation,
The photo sensor (8) is configured to be able to change its posture in the irradiation direction of the laser beam (B). Then, after that, install the upper and lower screws (13a), (
13b), the adjusting plate (11) can be fixed while maintaining the posture of the photosensor (8).

By adjusting the above-mentioned posture change and fixing, the side portion (8a) on the upper side of the scanning side of the photosensor (8) is adjusted to be almost orthogonal to the scanning direction of the laser beam (B), so that the laser beam (B) passes through the photo sensor (8). Even if the path varies in the sub-scanning direction, the output start timing of the synchronization signal (SOS) can be made almost the same, so it is possible to reduce the occurrence of recording jitter while increasing recording speed and density. .

That is, an adjustment plate (11) and two screws (13a) for fixing the adjustment plate (11) to the plywood (12).

(13b) etc., the food sensor (8), which is a light receiving part for modulation control, is connected to a laser beam (13b), which is an example of a light beam.
B) constitutes an operating means (HM) for adjusting the posture in the irradiation direction.

The range of posture adjustment of the photosensor (8) by the operating means (IIM) is determined according to the required resolution and the allowable amount of jitter.A specific example thereof will be explained below.

When resolution [Z (dpi)] is required, the allowable jitter amount is set to half a dot, and the scanned laser beam (B)
The adjustment range [θ] is calculated when the variation in the sub-scanning direction due to vibrations and various errors is [500 μm].

Dot diameter [dl] when resolution is [Z (dpi)]
is usually d=24000/Z(0m).

In order for the jitter to be within the allowable range when the photosensor (8) is at a certain angle with respect to the main scanning direction, the maximum value [φ] of this angle is tanφ=500/(d
/2) = 1000/ d=Z/24, so φ=jan-'(Z/24).

Therefore, the adjustment range [θ (deg)] is θ-90"-tan-' (Z /24) □
■It is.

For example, if the resolution is [240 (dpi)], θ=
The angle is 5.71°. Therefore, it is only necessary to make it adjustable within the range of [upper 5°7] using the operating means (HM).

Also, if the resolution is [480 (dpi)], θ-2,
86＠, therefore, by the operating means (HM) [upper 2°8
It is advisable to make it adjustable within a range of [°].

■The relationship between the equations is shown in the graph of Figure 3.

In the above embodiment, as the optical scanning image forming apparatus according to the present invention, an electrostatic latent image is once formed by scanning the photoreceptor drum (7) with the laser beam (B), and then this electrostatic latent image is developed. The explanation has been given using an example of an indirect laser beam printer that transfers images onto recording paper. In addition, the optical scanning image forming device invented by Zero also uses a laser beam (B
) may be a direct type laser beam printer that records directly on photosensitive paper by image formation scanning. It may be a laser 00M system that imprints a micro image on a silver halide film, a laser imager that imprints a C7 image on a silver halide film, or the like.

〔Effect of the invention〕

As described above, the optical scanning image forming apparatus according to the present invention is capable of adjusting the attitude of the light receiving section for modulation control in the irradiation direction of the light beam. Regardless of the tilt, the output start timing of the synchronization signal from the light receiving section for modulation control can be made almost the same, so the image formation in the form of an electrostatic latent image on the photoreceptor can be made at almost the same position. This makes it possible to reduce jitter in recording while increasing recording speed and density.

[Brief explanation of the drawing]

The drawings show an embodiment of the optical scanning image forming apparatus according to the present invention, in which Fig. 1 is an enlarged perspective view of the mounting portion of the photosensor, Fig. 2 is a schematic configuration diagram of the laser beam printer, and Fig. 3 is an illustration of the resolution and resolution. A graph showing the relationship between the adjustment range by the operating means,
FIG. 4 is a front view of the photosensor, and FIG. 5 is a time chart of synchronization signals. . (5)...Rotating polygon mirror, (7)...Photoreceptor, (8)...Modulation control light receiving section, (B)...
...Light beam, (HM) ...Operation means.

Claims (1)

[Claims] A rotating polygon mirror for scanning a light beam on a photoconductor is provided, and a modulation control light receiving section is provided for detecting the light beam outside an image forming area on the photoconductor and controlling a start timing of modulation for the light beam. The optical scanning image forming apparatus is provided with an operating means for adjusting the attitude of the modulation control light receiving section in the irradiation direction of the light beam.