JPH03184013A - Optical scanner - Google Patents

Abstract

PURPOSE:To uniform a scanning start position regardless of the end surface accuracy of a polygon mirror by storing the deviation of each end surface as time data for each reflecting surface of the polygon mirror and correcting the timing of the scanning start position, i.e. the start of scanning according to the storage contents. CONSTITUTION:A memory 1c is stored previously with scanning time from the end surface of each reflecting surface of the polygon mirror 9 to a specific scanning position. Then the output of a timing generating circuit 16 which generates a signal for starting printing operation a constant time after the detection timing of light reflected by an end surface of the polygon mirror 9 is corrected for each end surface according to the storage contents of the memory 1c. In this case, the printing operation can be started at timing corresponding to the deviation of each end surface, so optical scanning start positions in image formation are all constant on all scanning lines. Thus, the scanning start position of each scanning line can be made constant regardless of the end surface accuracy of the polygon mirror 9.

Description

Detailed Description of the Invention [Summary] The present invention relates to an optical scanning device having a polygon mirror equipped with a plurality of reflective surfaces that reflect laser light from a laser light source and scan a scanning line. The purpose is to provide an optical scanning device in which the scanning start position is aligned regardless of the edge area.The laser beam emitted from the laser light source is emitted according to image information by the rotation of a polygon mirror having multiple reflective surfaces. However, in an optical scanning device equipped with a control unit that controls exposure scanning on the surface of the photoreceptor, a memory is provided that stores in advance the difference in scanning time from the end face to a predetermined scanning position for each reflective surface of the polygon mirror. In addition to providing
The output of a tie generation circuit that generates a signal to start a printing operation after a certain period of time from the detection timing of the light reflected by the end face of the polygon mirror is corrected for each end face according to the stored contents of the memory. do.

[Industrial application field]

The present invention relates to an optical scanning device having a polygon mirror with a plurality of reflective surfaces that reflect laser light from a laser light source and scan a scanning line, and particularly relates to an optical scanning device employed in a laser printer or the like.

[Conventional technology]

Figure 5 shows the optical system in a conventional laser printer.
FIG. 6 is a waveform diagram showing the on/off state of the BD double signal image signal. This will be explained below with reference to the drawings.

In FIG. 5, the controller 1 includes a CPU 2, a laser diode drive circuit 3. A motor drive circuit 4 and a beam detector signal generation circuit (hereinafter referred to as BD signal generation circuit) 5 are connected, a semiconductor laser light source 6 is connected to the laser diode drive circuit 3, and a motor 7 is connected to the motor drive circuit 4. has been done. Further, a collimator lens 8. Polygon mirror 9 pivotally attached to motor 7. f-theta lens 10
, photosensitive drums 11 are arranged in this order. Furthermore, f-
A reflecting mirror 12 is arranged between the θ lens 10 and the photosensitive drum 11, and a photodiode 13 is provided in the direction of reflection of this reflecting mirror 12.

Note that the laser diode drive circuit 3 is connected to the controller 1.
Accordingly, the semiconductor laser light source 6 is controlled to turn on/off the emitted laser beam, and the motor drive circuit 4 controls the rotation of the polygon mirror 9 by controlling the motor 7. Further, the reflecting mirror 12 is placed on a part of the scanning line of the laser beam, and when the laser beam reflected at the side edge of the polygon mirror 9 is further reflected by the reflecting mirror 12 and the photodiode 13 receives the reflected light,
The BD signal generation circuit 5 generates a beam detector signal (hereinafter referred to as B
A signal (referred to as a D-times signal) is output to the controller 1.

In the optical system device configured as described above, when image information is input from the CPU 2 to the controller 1, as shown in FIG. The laser beam modulated by the zero image information that starts driving the semiconductor laser light source 6 by the laser diode drive circuit 3 becomes parallel light by the collimator lens 8, is reflected by the polygon mirror 9, and is reflected by the f-theta lens 10 onto the photosensitive drum 11. An electrostatic latent image is formed on the photosensitive drum 11 by the zero or more images formed thereon. Thereafter, toner is attracted to the electrostatic latent image, and the attracted toner is finally transferred and fixed onto a recording medium such as paper.

[Problem to be solved by the invention]

FIG. 7 is a diagram showing the shape of the polygon mirror, and FIG. 8 is a diagram showing the state of printing on recording paper. Hereinafter, problems with the prior art will be explained with reference to the drawings.

As described in [Prior Art], the printing start position (scanning start position) on a recording medium (paper, etc.) is determined by the photodiode detecting the light reflected from the end face of the polygon 5, and after a certain period of time (t) from the detection. s) Determined by the subsequently irradiated laser light. Therefore, in order to align the printing start positions for each line, the polygon mirror is required to have high end face accuracy.

However, due to the manufacturing method of polygon mirrors, it is difficult to obtain high end surface accuracy, and in reality, polygon mirrors with poor end surface accuracy are used as shown in FIG. For this reason, as shown in FIG. 8, undulations occur in the printed state.

In addition, even if a polygon mirror with high end face precision is adopted to eliminate even the slightest deviation in the printing start position (waving in the printing state), not only will the printing start position be slightly deviation, but the precision Currently, polygon mirrors are very expensive.

In view of the above problems, it is an object of the present invention to provide an optical scanning device in which scanning start positions are aligned regardless of the end face accuracy of a polygon mirror.

[Means for Solving the Problems] The present invention provides an optical scanning device that starts a printing operation after a certain period of time after detecting light reflected at the end face of a polygon mirror. The basic idea is to store the deviation of each end face as time data, and correct the scan start position, that is, the scan start timing, according to the stored contents. That is, as shown in FIG. 1, the laser light from the laser light source 6 emitted according to image information is directed to the photoreceptor 11 by the rotation of the polygon mirror 9 having a plurality of reflective surfaces.
In an optical scanning device equipped with a control unit l that controls the surface to be exposed and scanned, a memory IC is provided that stores in advance the difference in scanning time from the end face to a predetermined scanning position for each reflective surface of the polygon mirror 9. At the same time, the output of a timing generation circuit 16 that generates a signal to start the printing operation after a certain period of time from the detection timing of the light reflected on the end face of the polygon mirror 9 is transmitted to each end face according to the contents stored in the memory 1c. Configure to correct.

[For production]

According to the present invention, since the printing operation can be started with a timing corresponding to the deviation on each end face, the optical scanning start position during image formation is constant for all scanning lines, and high quality printing can be achieved. can.

〔Example〕

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2(a), (
b) is a diagram explaining the principle of collecting surface accuracy data, Fig. 3 is a time chart of BD signals ■, ■, ■, Fig. 4 is a BD signal ■,
3 is a waveform diagram showing the on/off state of the image signal; and FIG.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, 1a is a pattern generation circuit, and CP
A tone pattern is created according to the image information from U2. Reference numeral 1b denotes a timing generation circuit, which is used to determine the timing from when the controller l inputs the BD signal ■ until the laser diode drive circuit 3 is driven.

Reference numeral 1c denotes a correction ROM for storing correction data, which will be described later, for each end face of the polygon mirror 9. 14
1 is a photodiode, 15 is a BD signal generation circuit, and 16 is a reflecting mirror. In addition, the same reference numerals as those mentioned above represent equivalent items.

However, the polygon mirror 9 differs from the above-mentioned mirrors in that it has a reference surface. The laser light reflected at a specific point (not shown) on the reference surface (a protrusion provided on the reflective surface at a position that does not interfere with light scanning onto the photosensitive drum II) passes through the reflective diode 14 to the photosensitive drum. It is designed to be detected by the diode 14, and after detection, the BD signal generation circuit 15 outputs the BD signal ■ as a home position signal to the controller 1 for a certain period of time.

When the system is activated and the semiconductor laser light source 6 starts emitting light and the polygon mirror 9 starts rotating, the controller 1 recognizes the reference plane of the polygon mirror 9 by the BD signal . After recognizing the reference plane, the controller 1 sequentially receives the BD signal ■ corresponding to the reflection at each end face of the polygon mirror 9 (e.g., eight end faces when the polygon mirror 9 has eight reflecting faces). The surface irradiated with the semiconductor laser is sequentially recognized. That is, after the controller 1 recognizes the reference surface, it recognizes a specific reflective surface when receiving the first BD signal ■, recognizes the next reflective surface when receiving the next BD signal ■, and so on. It has become. Further, from the second rotation onward, the controller 1 recognizes each reflective surface by the BD signal ■, not by the BD signal ■.

In the conventional optical scanning device, driving of the semiconductor laser light source 6 was started after a certain period of time (ts) after receiving the BD signal (2). However, because the edge area of the polygon mirror was poor, waviness occurred in the printed characters. In order to avoid waviness in printing (printing start positions are aligned on all lines), the controller 1 must wait until the controller 1 receives the BD signal ■ and outputs the image signal (drives the semiconductor laser light source 6). The fixed time (ts) must be corrected for each end face. This correction data is stored in the correction R○M1c.

The principle of collecting the above-mentioned correction data is shown in Figure 2 (a).
, (b). When collecting correction data, as shown in the figure, a semiconductor laser light source 6, polygon mirror 9, f
A -θ lens 10, a reflecting mirror 12° 16, a photodiode 13, 14, etc. are arranged, and a reflecting mirror 21 is located at the scanning start position of the laser beam or on its leading axis.
, a photodiode 22 that detects the laser beam reflected by the reflecting mirror 12, a BDD signal generation circuit 23 that outputs a BD signal ■ according to the detection signal from the photodiode 22, and a BDD signal generation circuit 23 that inputs the BD signals ■, ■, ■, and processes them as described below. A measuring device equipped with a counter circuit 18 is used.

Specifically, as shown in FIG. 2(a), after the system is started, the laser beam 17 emitted from the semiconductor laser light source 6 is reflected at a specific point on the reference plane, and is detected by the photodiode 14. Ru.

Then, the BDD raw circuit 15 converts the BD signal ■ to the counter circuit 1.
Output to 8.

Next, as shown in FIG. 2(b), due to the rotation of the polygon mirror 9, the laser beam 17 is reflected at the end face, and the reflected light 1
9 and is detected by the photodiode 13. Then B
The DD signal generation circuit 5 outputs the signal to the BD signal section counter circuit 18.

Further, as the polygon mirror 9 continues to rotate, the laser beam 17 is reflected by the reflecting mirror 21 located at the location where electrostatic latent image formation would normally start on the photosensitive drum, and is detected by the photodiode 22. Then, the BDD signal generation circuit 23 outputs the BD signal ■ to the counter circuit 18.
Output to.

When the polygon mirror has N reflective surfaces, BD
The signal signal sections (2) are sequentially output from each of the N sets of BD signal generation circuits.

As shown in FIG. 3, in the counter circuit 18, after receiving the BD signal ■, the BD signal ■ is generated by detecting the light reflected on the first end surface.
The time t1 until reception of (PL' in the figure) is measured. Similarly, t2. t3..., tN are sequentially measured.

In this way, with respect to the N reflective surfaces, from the BD signal signal reception, a latent image is originally formed on the reflecting mirror 21 at the position where the latent image starts to be formed.
The time until the BD signal (2) is received by the reflected light is measured. In addition, the reflecting mirror 21. The photodiode 22.8D signal generation circuit 23 is used only for collecting correction data, and is not installed in the actual device.

Then, the certain time (t s) and the measured time (t
The difference ΔtN (-tN-ts) from the end face is calculated for each end face and stored in the correction ROM 1c.

To summarize the above, an electrostatic latent image is generally formed as follows.

1) After the system is started, the controller 1 recognizes the reference plane of the rotating polygon mirror 9 using the BD signal ■.

With this recognition, each end face of the subsequent polygon mirror 9 is sequentially set to P! I can understand.

2) Due to the light reflected from the end face of the polygon mirror 9, the BD
The signal is output to the signal section timing generation circuit 1b.

3) The timing generation circuit 1b reads the unique correction data ΔtN corresponding to the applicable end face from the correction ROMIC, and performs the correction of ΔL (ts
+Δt).

4) After a time period of ts+Δt (=tN), the pattern generation circuit 1a drives the laser diode drive circuit 3 according to the image information from the CPU 2.

If the above steps (1) to 4) are illustrated, the result will be as shown in FIG.

5) The semiconductor laser light source 6 is driven by the laser diode drive circuit 3, and the collimator lens 8. Polygon mirror9. An electrostatic latent image is formed on the photosensitive drum 11 via the f-θ lens 10 .

Thereafter, toner is attracted to the electrostatic latent image, and the attracted toner is finally transferred and fixed onto a recording medium such as paper.

Here, in this embodiment, in order for the controller 1 to recognize the end face of the polygon mirror 9, the controller 1 detects the reflected light from a protrusion provided at a specific location on one reflective surface of the polygon mirror 9. The reference surface may be detected by optical means, or a means for detecting the reference surface may be provided electrically and a detection signal may be output to the controller l.

〔Effect of the invention〕

According to the present invention, the scan start position for each scan line is constant regardless of the end face accuracy of the polygon mirror. Therefore, not only the scanning start position but also all the scanning lines are uniformly aligned, making it possible to form an image faithfully to the image information. Further, since it is not necessary to require end face precision as high as in the past, an inexpensive polygon mirror can be used, and the cost of the entire device can be reduced.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 (a) and (b) are diagrams explaining the principle of collecting surface accuracy data, Fig. 3 is a time chart of BD double signal, ■, ■, Fig. 4 is a waveform diagram showing the on/off state of the BD signal ■, FIG. 7 is a diagram showing the shape of a polygon mirror, and FIG. 8 is a diagram showing the state of printing on recording paper. In FIG. 1, the reference numerals are as follows. 1 -1---...-1--... la -----1---- lb ------1-- C 2--1・・−・−・・ 3 −・−−−1−・・ 4 −−−−−−・−−−−・・ 5.15 ・・・−−1−・−−−1−・6 ・−・
・・・−−１−・・・−・７ −・−・−・・・− ８−−−１・−−−−・−−−−・ Controller pattern generation circuit timing generation circuit correction ROM PU Laser diode Drive circuit Motor drive circuit BD signal generation circuit Semiconductor laser light source Motor Collimator Lens 0 1 12, 16 13.14 Polygon mirror f-theta lens Photosensitive drum Reflector Photodiode

Claims (1)

[Claims] A laser light source (6) is emitted according to image information by rotating a polygon mirror (9) having a plurality of reflective surfaces.
) in an optical scanning device comprising a control unit (1) that controls the laser beam from a photoreceptor (11) to scan the surface of the photoreceptor (11), the laser beam being emitted from a predetermined distance from an end face of each reflective surface of the polygon mirror (9). A memory (1c) is provided in which the difference in scanning time to the scanning position is stored in advance, and a timing is generated to generate a signal to start the printing operation after a certain period of time from the detection timing of the light reflected on the end face of the polygon mirror (9). An optical scanning device characterized in that the output of the circuit (16) is corrected for each end face according to the content stored in the memory (1c).