JPH02109069A - Scanning optical system for electrophotographic device - Google Patents

Abstract

PURPOSE:To eliminate the misalignment for a printing start by calibrating a signal transfer time difference between each signal line caused by a propagation delay by a delaying circuit provided on each printing signal line and adjusting the transfer time, in a laser beam printer using plural light sources. CONSTITUTION:When a beam detector 7 is scanned by a laser light, a reference signal from the detector 7 is received by a control device 1, and a printing signal A and a printing signal B are sent out simultaneously to a signal line 9 and 10, respectively. In this case, the signal A and B generate a time difference (t) by a propagation delay of the respective signal lines, but allowed to reach as they are a delaying circuit 2 and 3, respectively. In this case, when the delaying circuit is set in advance so that the quicker signal is delayed by the time difference (t), the time difference between each signal is negated by passing through the delaying circuit, and the signals are sent out simultaneously to signal lines C, D again. Accordingly, laser devices 4, 5 are driven simultaneously, and laser beams 13, 14 are also emitted simultaneously. In such a way, the misalignment for a printing start on the surface of a drum 8 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a scanning optical system for a laser beam printer using a plurality of light sources.

[Background of the invention]

A laser beam printer that scans a plurality of beams has the advantage of significantly increasing printing speed compared to a laser beam printer that scans a single beam.

However, as the number of beams increases, variations occur in the printing start positions among the beams, and in order to ensure sufficient printing quality, it is necessary to control the positions between the beams.

FIG. 3 shows a conventional position control method for a single-beam scanning laser beam printer. A laser beam emitted from a laser device A4 is scanned over the surface of a drum 8 by a scanning device 6. At this time, the laser scans the beam detector 7 installed at a predetermined position from the printing position of the drum 8, and the beam detector 7 detects base 1! I can get a signal. The control device 1 receives this reference signal and sends a print signal to the printer after a certain period of time. The print signal is sent to the laser device a! in the printer. By immediately moving the A4 paper and printing with the laser emitted from there, the printing position for each of the five scans can be kept constant.

However, in the case of a laser beam printer that scans multiple beams, a controller receives the reference signal and sends multiple print signals to the printer after a certain period of time. In this case, it is extremely difficult to make the transmission time to the printer exactly the same, and a slight time lag occurs.

Furthermore, a time lag occurs between the plurality of printing signals when they reach the laser device. As a result, there is a problem in that the printing positions by the laser beams emitted from each laser device are shifted by this time shift.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to adjust the printing position between each beam in a laser beam printer using a plurality of light sources by adding a delay circuit.

[Summary of the invention]

The present invention focuses on the fact that a signal transmission time difference occurs between a plurality of signal lines due to propagation delay, and uses a delay circuit provided in each signal line to correct this time difference and align the printing start position between each beam. be.

[Embodiments of the invention]

The present invention will be explained in detail below using the embodiments shown in FIGS. 1 and 2.

FIG.
FIG. 2 is a schematic configuration diagram of a scanning optical system of a beam laser printer, and is a diagram showing print signal propagation in FIG. 1.

When the laser beam scans the beam detector 7, the control device 1 receives the reference signal from the beam detector 7, and the print signal A and print 4W No. B are sent to the equal line 9 and the signal line 1, respectively.
0 at the same time.

(Print signal A and print signal B sent simultaneously to No. 8 m9 and signal line jO are delayed, with a time difference between them as shown in Figure 2 due to the propagation delay of each signal line. Circuit 2 and delay circuit arrive at 3. Here, the delay circuit is set in advance so that the faster signal is delayed by the time difference, so the time difference between each print signal is equal to the delay of each print signal. After passing through the circuit, each print signal is sent out simultaneously to the signal line C and the signal line again.Therefore, each print signal immediately activates the laser device 4 and the laser device 5 at the same time, so that the laser beam from each laser device is transmitted simultaneously. Light 13 and laser light 14 are also emitted at the same time.

In this way, it is possible to obtain a printed image on the surface of the drum 8 without any deviation in the printing start position.

〔Effect of the invention〕

According to the present invention, in a laser beam printer using a plurality of light sources, the delay circuit provided in each print signal line can calibrate the signal transmission time difference between each print signal line due to propagation delay and match the transmission time. Therefore, it is possible to obtain a printed image without any deviation in the printing start position.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of the scanning optical system of a two-beam laser printer that is an embodiment of the present invention, Fig. 2 is a diagram showing the propagation of the printing signal in Fig. 1, and Fig. 3 is a diagram of a conventional one-beam laser printer. 1 is a schematic configuration diagram of a scanning optical system of a printer. In the figure, 1 is a control device, 2 is a delay circuit A, and 3
is a delay circuit B, 4 is a laser device FIA, 5 is a laser device 8, 6 is a scanning device, 7 is a laser detector 8 is a photosensitive drum,
9 is signal line A, 10 is signal line B, 11 is (line 8 C11
2 is Route 48, 13 is laser beam A, 14 is laser beam B
, 15 is the reference signal line) Figure 1 [P enable signal A tPjllJ inertia B a1#gfail 19 signal! t
u-mouth-→'']-r* し家1'f@'441412■! shi→”wang) Figure 3

Claims (1)

[Claims] A plurality of light sources, a plurality of switching means for controlling emission/non-emission of light from the plurality of light sources, a scanning means for scanning light from the light sources, and a detection means for detecting a starting position of scanning of the light by the scanning means. , in a raster scan type electrophotographic apparatus having a control means for driving and controlling the plurality of switching means using a scanning start signal from the scanning means as a time reference, a delay means is added to each of the plurality of control means individually. A scanning optical system for an electrophotographic device, characterized by: