JPS5926005A - Detection of beam position in multibeam scanner - Google Patents

Abstract

PURPOSE:To detect exactly the positions of respective beams by disposing photodetection parts for detecting the positions of respective beams with deviations in the main scanning direction on the scanning lines of the beams and lighting, detecting and putting out the beams in order of the beams detected from the side where the scanning is started. CONSTITUTION:Plural photodetectors E1-E5 are disposed for plural overlapping beams B1-B5 with deviations from each other in the main scanning direction on the scanning lines of the respective beams. A detector M consisting of such photodetectors is disposed on the lateral side of a photosensitive drum 6 which is the plane to be scanned. The intervals between the respective photodetection parts in the main scanning direction are required to give no influence on the photodetection parts for the beams before the beams are lighted. When the first beams B1 is first lighted and B1 is detected in the photodetector E1, B1 is put out, then the beam B2 is lighted at the prescribed timing and when the beam B2 is detected in the photodetector E2, the beam B2 is put out. Thereafter, the similar operations are continued. As a result, the positions of the respective beams are exactly detected even if the beams overlap on the plane to be scanned.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multi-beam scanning device that simultaneously scans an area to be scanned by deflecting a plurality of beams capable of modulating 8J' using a scanning device such as a polygon mirror. Specifically, the present invention relates to a beam position detection method that detects a signal (hereinafter referred to as SUS signal) for determining a printing start position on a scanned surface.

The multi-beam scanning device mentioned above has great advantages in terms of durability and vibration dots because it can reduce the number of rotations of the polygon mirror compared to the shingle beam scanning device. However, S
Detection of the O5 signal becomes extremely difficult due to the relationship between each beam.

One method is to accurately position the beam generators relative to each other so that only one beam position of each beam is detected, and the positions of the other beams are corrected to the SO5 signal. I can think of a way to do this.

For example, as shown in FIG. 1, a semiconductor laser (1) having light emitting parts spaced apart by 1()oIIl1 is installed at an angle of θ with respect to the main scanning direction, and a focal point II′IJ+JI shown in FIG.
l', a 5 mm collimator lens (2), a polygon mirror (3), and an fθ lens (4) with a focal length of 500 mm.
) on the scanned surface, 100μ
! Even if an error of 10'309 μm is allowed in scanning improvement for a beam spacing of If it is not even step-like, ±0; 3
Even the precision of μin must be met. It is extremely difficult to arrange or mount a semiconductor laser with such surface precision.

As a modification of the above method, as shown in FIG. 3, a mirror (5
1+51 +5), i+, ``ll 'l can be considered.

That is, each mirror (5) (51 (51) is rotated around an axis that is central to the main scanning direction to adjust the beam interval, and at the same time, the beam interval is adjusted by rotating around an axis parallel to the sub-scanning direction. The position in the main scanning direction is adjusted.

However, this method also adds a new IM adjustment element of adjusting the mirror f51 +5+ +5), and the adjustment is always delicate, and is actually a difficult method.

Therefore, it is possible to detect the beam position for each beam separately, but in normal laser beam printers, the beams are set to overlap on the scanned surface in order to prevent gaps between scanning lines. (Funeral figure 4). For example, if the peak interval is +00μ, the beam diameter defined as 1/e2 of the center intensity is set so that the scanned surface is 2 fl FI μm Jhj degrees. However, such an oval wrap causes the detection device provided for each beam to detect other beams as well, contributing to erroneous operation.

The present invention has been made in view of the above points, and it is possible to overlap the beam position 1 of the multi-beam running RJ device with one beam and one beam at each beam f position. It is an object of the present invention to provide a beam position detection method that can detect the beam position well.

1. In order to detect the position of each beam, a plurality of light-receiving parts for detecting the position of each beam are arranged at a fixed distribution m of each beam, and are shifted in seven scanning directions. This is achieved by detecting the beam and extinguishing the beam in the order of the detected beam from the start side. In other words, the beam is turned on when the beam approaches the light receiving part, and when this beam is detected, this beam is turned off and the next beam is turned on at a predetermined timing. It lights up, detects, and extinguishes the beam.

By controlling the position of each beam in a positive manner (
11f.

Embodiments of the present invention will now be described with reference to the drawings.

The embodiment of FIG. 5 has multiple overlapping beams B+
, j3z, B3. Multiple light receiving elements for B4,13s? :+.

E2. Es, E4. Let Es be the scanning line 1. of each beam. hand! 1
．． It was placed in the direction of the main runner. For convenience, the detection device N1 comprising such a light-receiving element is arranged on the side of the photosensitive drum (6), which is the surface to be scanned, as shown in FIG.

The spacing in the main scanning direction between each light receiving section must be determined from the size of the light receiving section in the main scanning direction, the size of the beam, positional error in the scanning direction, etc., so that when the beam is applied, it does not affect the light receiving section for the previous beam. It is custom made.

In addition, the size of the light receiving part is preferably large enough to cover the beam depth in order to take as many incident light meters as possible for the sub-scanning direction, and for the main scanning direction + ri
(As shown in the figure, it is best to use a beam or a Causs beam and set the threshold 1'h in the middle of the peak to be least affected by errors.) It is necessary to have at least half the size of the J-th beam.

・In the example of Figure 5, the number of 1 erased by each beam is 1371
This is done as shown in step 1. That is, the first beam B
] This beam B1 is transmitted to the light receiving elements 1', 1.
When detected, beam B+ is extinguished, and then beam 13 is detected.
Two places are lit at a specified timing, and this beam I%
2 is detected by the light-receiving elements 1 and 2, the beam 132 is turned off, and the beam 132 continues to be transmitted sequentially to the beam Bs.

As a result, each light receiving element E1 to E5 receives a detection signal Sl.
, S2. S3. S4. S5 is output corresponding to each beam position. Then, beam 1 is delayed by a certain period of time for each beam, such as time 11 after detection signal S1, beam 132 after time J2 from detection signal S2, and printing is performed by aligning the printing start positions if.

- The embodiment shown in Figure 8 on the right uses one light-receiving element Eo, and the light-receiving element EO is oriented in the main direction of 111A+.

A2. A3. z\4, A5, and A6 are covered with an open screen SP. In this case as well, the control is 1
, as shown in Figure 7. However, the detection signal 81~
S6 is output from one light receiving element Eo. In the present invention, the beams B+ to 136 are connected to the main beam 7 as shown in FIG.
:L May be slightly shifted in the blue direction.

As can be seen from the overlapping state of the beams in Figure 5, adjacent beams overlap or distant beams do not overlap.

Therefore, it may be possible to arrange the light receiving elements in multiple stages to group the beams.

9th P: A is an example based on the consideration of L, in which light receiving elements El, l, 2 . E
3 and light receiving element E4 for beam IS4, 135136
, 1"B5.E6, and arranged in two stages in the sub-scanning direction.

In Fig. 10, this is further advanced, and one light-receiving element EA is used for beams B+, B2°IS3, and beams B4,
Another light-receiving element EB is provided in line with ISs and IS6, tilted with respect to the main scanning direction H, and these light-absorbing elements EA
, G, and B are printed on a screen S1' having openings LIA+ to A6 for each beam. At this time, the screen SP may be provided on each base element.

The embodiment shown in FIG. 11 uses one light-receiving element IZ(), and apertures 11AI and A are arranged in two stages on the screen sp that covers it.
2゜A3. A4, As, A6, A7, and A8 are provided. In this case, the openings 1 in each stage are arranged so that they do not overlap each other from the sub-scanning direction, and the light-receiving elements that have good +, p, and : responses are used.

As described above, the present invention provides a multi-beam scanning device that simultaneously scans an object to be scanned with a plurality of variable beams, in which a plurality of light receiving sections for detecting the position of each beam are scanned by each beam. This is because the beams are shifted by H times (on the line), and the beam is focused, the beam is detected by the corresponding light receiving part, and the beam is extinguished in the direction of the beam, which is unknown from the scanning start rule. Even though the beams overlap on the scanned surface, the position of each beam can be accurately detected.

Further, the number of light receiving elements can be reduced by covering a common light receiving element with a screen provided with an opening 1-1 along the scanning line of each beam in the main scanning direction.

Furthermore, if each beam is divided into groups and the light receiving section for each group is arranged in multiple stages in the sub-scanning direction, the detection device can be constructed compactly even when many beams are used.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a semiconductor racer with multiple light emitting parts.
Figure 2.3 is a diagram explaining a method proposed and considered by the present inventor as an example of beam position detection in a multi-beam scanning device, and Figure 4 shows mutual interaction between the light emitting parts of multiple beams and the scanned surface. Diagram explaining the relationship, tlGs,s, 9.1
Figures o and 11 are diagrams explaining the relationship between the beam and the light-receiving section in each embodiment of the present invention, Figure 6 is a diagram explaining the relationship between the beam and the output of the light-receiving element f, and Figure 7 is the beam position of the present invention. FIG. 3 is a diagram illustrating the limitations of a detection method. 1... Semiconductor laser IS... Beam 2...
Collimator lens 1",...-￥ Light 4 J'3
・・・Polygon mirror A・Open 18'' 4...fθ
Lens N1...Detection device 5...Mirror
5. Detection +, j bow. 6 ・Photosensitive drum S ll Screen output:
i1! 1 person Minolta Camera Co., Ltd. Noah\sha Figure 1 Figure 2 Figure 4 Erosion and eclipse support A L-IP Figure 5 E no whistle Figure 8 Figure 7 Figure 6

Claims (1)

[Claims] 1. In a multi-beam scanning device that simultaneously scans the scanned rli with multiple modulated beams, multiple light receiving units for detecting the position of each beam are arranged on the scanning line of each beam in the main scanning direction. A beam position detection method characterized in that the beam is turned on, the beam is detected by a corresponding light receiving section, and the beam is turned off in the order of the beams detected from the scan start side.