JPS63274263A - Multi-color laser beam printer - Google Patents

Abstract

PURPOSE:To detect two horizontal synchronizing signals by one horizontal synchronizing signal detector by providing a different signal time to 1st and 2nd horizontal synchronizing signals of a laser beam and applying optical coupling. CONSTITUTION:The signal time width of a horizontal synchronizing signal of the 1st beam and the signal time width of the horizontal synchronizing signal of the 2nd beam are made different. A horizontal synchronizing signal detection means (b) detects a mixed signal between the horizontal synchronizing signal BD1 of the 1st beam and the horizontal synchronizing signal BD2' of the 2nd beam by time width adjusting means a, a'. The horizontal synchronizing signal BD1 of the 1st beam and the horizontal synchronizing signal BD2 of the 2nd beam are outputted from the mixed signal BD detected in this way separately respectively. Thus, one horizontal synchronizing signal detector can detect two horizontal synchronizing signals and a small sized and inexpensive multi- color laser beam printer is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a multicolor laser beam printer, and particularly to a multicolor laser beam printer suitable for forming two-color images.

[Prior Art] A laser beam printer has been proposed that sequentially performs the steps of charging, first exposure, first development, second exposure, and second development using electrophotography to form two-color images.

FIG. 2 shows an example of a schematic configuration of such a laser beam printer. In this figure, reference numeral 1 denotes a photosensitive drum that rotates steadily in the direction of arrow A, and a first charger 2. A first developing device that performs development after the first exposure 4.
2nd; LiF electric device for charging after development; 5. A second developer for developing the second color after the second exposure 7. A transfer device 8 that transfers the developed toner image onto recording paper. A static eliminator 9 for removing static electricity after transfer, a cleaner lO for removing residual toner, and a static eliminating lamp 11 for removing residual electric charge after toner removal are provided. Moreover, 12 and 13 are a first semiconductor laser and a second semiconductor laser that output laser beams, respectively. A laser beam 3.6 emitted from the semiconductor lasers 12 and 13 and modulated by an image signal is scanned by a rotating polygon mirror 14 through an imaging lens 15 over the photosensitive drum l.

The laser beam 3 output from the first semiconductor laser 12 is incident on a first exposure position between the first F electric device 2 and the first developing device 40 . The first electrostatic replacement image formed by the exposure with the laser beam 3 is developed in red by a first developing device 4 that develops using red toner by a two-component magnetic brush method.
The photosensitive drum 1 that has been developed by the developing device 4 is recharged by the second charging device 5.

On the other hand, the laser beam 6 output from the second semiconductor laser 13 enters the second exposure position between the second charger 5 and the second developer 7. After the photosensitive drum 1 is developed by the first developing device 4, it is irradiated with a laser beam 6 that performs rask scanning to form a second electrostatic latent image. The second electrostatic latent image is 2
The image is developed in black by a second developer 7 which uses black toner by a component magnetic brush method. The two-color toner image formed on the photosensitive drum 1 is transferred onto a recording paper S by a transfer device 8, and fixed by a not-shown rear-stage fixing device.

Residual charge on the photosensitive drum 1 after transfer is removed by a first static eliminator 9, and residual toner on the photosensitive drum 1 is removed by a cleaner l.
Photosensitive drum 1 after toner is removed by O and further removed.
The residual charge is removed by the static elimination lamp 11, and the first charger 2 uniformly charges the image again, and the next image formation is performed.

FIGS. 3(8) to 3(F) show changes in the potential on the photosensitive drum 1 in each process of the two-color laser beam printer configured as described above in FIG. First, the first charger 2 uniformly charges the electric potential to vS [
See FIG. 3(A)]. Next, exposure is performed with the first laser beam 3, and the potential of the exposed portion decreases to nearly zero volts [see FIG. 3 CB)]. Red toner R is attached by the first developing device 4 to the area where this potential drop has occurred, and the potential of this area rises to VT+ [Figure 3 (C)
reference]. In FIG. 3(C), VB+ indicates a bias potential applied to the first developing device 4 in order to facilitate the adhesion of the red toner R.

In a two-color recording device, in order to avoid destroying the toner image formed by the first developer 4, a single-component toner is used in the second developer 7, and the toner image is transferred onto a recording paper using plain paper. In order to facilitate this, a high-resistance toner is used as one component toner, but since such high-resistance toner has poor developability, it is recharged by the second charger 5 to compensate for this. to raise the potential of the photosensitive drum 1 to VS2 [see FIG. 3 ([1])]. At this time, the potential of the portion R developed by the first developing device 4 also rises from vT□ to V'a.

Subsequently, exposure is performed with the second laser beam 6,
The potential of the exposed portion drops to nearly volts [see FIG. 3(E)]. The second developing device 7 applies black B to the portion where the potential has decreased, and the potential of that portion increases to VT2 [see FIG. 3(F)]. Figure 3 (F
) (7) V112 represents the bias potential applied to the second developing device 7 to facilitate the attachment of the black toner B.

FIG. 4 shows details of the exposure section of the two-color laser beam printer of FIG. In this figure, 51 is the first semiconductor laser 1
2, the first image signal (VDOL signal), 51'
is the second image signal (
VDO2). A first loser beam 53 that is modulated on and off by a single VDO in the first semiconductor laser 12 is raster-scanned by a rotating polygon mirror 14 as a scanning beam 3, and is focused onto a photosensitive drum l by an imaging lens 15. are tied together.

On the other hand, the second laser beam 53', which is modulated on and off by the VDO2 signal by the second semiconductor laser 13, is raster-scanned by the rotating polygon mirror 14 as a scanning beam 6, and focused onto the photosensitive drum 1 by the imaging lens 15. It will be done.

At this time, the first scanning beam 3 is once reflected by the folding reflection mirror 63 and then formed into an image on the photosensitive drum 1, while the second scanning beam 6 passes through the imaging lens 15 and is formed into an image as it is. Here, Ll indicates a raster scan image formed on the photosensitive drum 1 by the first scanning beam 3, and Ll indicates a raster scan image formed on the photosensitive drum 1 by the second scanning beam 6. Further, the rotating polygon mirror 14 is rotated at a constant speed by a motor 54.

Reference numeral 61 denotes a reflection mirror disposed near the scanning start end of the first scanning beam 3, and the scanning beam 3 reflected by this reflection mirror 61 is detected by the first beam detector BIII.
The beam detector BDI outputs a detection signal for providing the timing of the writing scan start point of the image signal in the raster scan Ll. Further, 60 is the second scanning beam 6
The scanning beam 6 reflected by the reflecting mirror 60 is detected by the second beam detector BD2, and is raster scanned from the beam detector BD2. A detection signal for providing the timing is output.

62 is a recording paper, and 64 indicates an image transferred onto the recording paper. Note that the beam detectors BDI and BD2 are arranged equivalently at the same distance with respect to the raster scanning direction on the photosensitive drum 1. This allows the first red image information (VDOI
The image signal transmission timing can be made the same for the second black image information (VDO2 information) and the second black image information (VDO2 information), and the process of image signal transmission can be simplified.

[Problems to be Solved by the Invention] However, in such a multicolor laser beam printer, the laser beam is modulated at the same time using different image signals VDOL and VDO2 for each of the raster scans Ll and Ll. Therefore, two semiconductor lasers 12 and 13 are required, and along with this, two laser drivers (laser drive circuits) and two horizontal synchronization signal detectors are also required.

In general, semiconductor lasers, laser drivers, etc. are expensive, which causes an increase in manufacturing costs, and has the drawback of causing the device to become more compact.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks, reduce the required number of semiconductor lasers, etc., and provide a small and inexpensive multicolor laser beam printer.

Means for Solving Problem E] In order to achieve this object, the present invention creates a first latent image on a recording medium by alternately scanning the first beam and scanning the second beam. forming a second latent image;
In a multicolor laser beam printer that records a multicolor image by developing a latent image in different colors and then transferring it to a recording material, the signal time width of the horizontal synchronizing signal of the first beam and the second beam are signal time width adjustment means for making the signal time widths of the horizontal synchronization signals of the beams different from each other; and horizontal synchronization of the horizontal synchronization signals of the first beam and the second beam, the signal time widths of which are adjusted by the signal time width adjustment means. horizontal synchronization signal detection means for detecting a mixed signal of signals; and signal separation means for separating the horizontal synchronization signal of the first beam and the horizontal synchronization signal of the second beam from the mixed signal detected by the horizontal synchronization signal detection means. It is characterized by the following.

[Function] In the present invention, since the first and second horizontal synchronizing signals of the laser beam are optically coupled with different signal times, the mixed signal of both signals can be separated with a simple circuit configuration. Two horizontal synchronization signals can be detected with one horizontal synchronization signal detector, and as a result, a small and inexpensive multicolor laser beam printer can be obtained. In addition, since scanning is performed using a rotating polyhedron that performs polarized light scanning, only one semiconductor laser light source system is required compared to the conventional two systems, and the number of image signals is also reduced to one system. The required number of lasers and signal processing circuits is reduced, making it possible to reduce the size and manufacturing cost.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the basic configuration of an embodiment of the present invention. In this figure, a and a' are signal time width adjustment means, which create a first latent image and a second latent image on the recording medium by alternately scanning the first beam and scanning the second beam. form the first and second
In a multicolor laser beam printer that records a multicolor image by developing a latent image in different colors and then transferring it to a recording material, the signal time width of the horizontal synchronization signal of the first beam described above and The signal time width of the horizontal synchronization signal of the second beam is made different. b is a horizontal synchronizing signal detection means, and time width adjusting means a and a' combine the horizontal synchronizing signal BDI of the first beam and the horizontal synchronizing signal BD2 of the second beam, the signal time width of which is adjusted. Detect the signal. C is a signal dividing means, which separates and outputs horizontal synchronization signal No. 43 BDI of the first beam and horizontal synchronization signal BD2 of the second beam from the mixed signal BO detected by the horizontal synchronization signal detection means. .

FIG. 5 shows an example of the configuration of an exposure section of a laser beam printer to which the present invention is applied. In this figure, 65 and 66 are a pair of optical fibers whose tip receiving surfaces are arranged near the scanning start end of the scanning beam 3.6, and 67 is a pair of optical fibers Ii
Horizontal synchronizing signal detectors (beam detectors) provided at the coupling ends (rear ends) of optical fibers 65 and 66, 68 and 69 are slits attached to the front end light receiving surfaces of these optical fibers 65 and 66.

141 is a rotating polygon mirror rotated at a constant speed by a motor 54. In particular, as shown in FIG. It is formed into a polygonal mirror with different shapes. Therefore, as shown in FIG. 7, the laser beam 53 emitted from the semiconductor laser 12 is polarized and scanned with respect to the reflective surface group M1 in the direction of the first rask scan Ll, and with respect to the reflective surface group M2, the laser beam 53 is polarized and scanned with respect to the reflective surface group M2. Raster scanning is performed and polarization scanning is performed in direction 2, and as a result, raster scanning Ll and Ll are performed alternately by the rotating polygon mirror 1111.

FIG. 8 shows the relationship between the position of the rotating polygon mirror 141 and the output timing of the horizontal synchronization signal and image signal.

As shown in this figure, raster scanning by the rotating polygon mirror 141 is performed alternately in Ll and Ll, whereas in raster scanning 1, a horizontal synchronizing signal BDI is output, and the horizontal synchronizing signal BDI is synchronized with this signal BDI. Image signal VDO for first exposure
I is output to the semiconductor laser 12. Next, in raster scanning 2, a horizontal synchronizing signal BD2 is output, and an image signal v002 for second exposure is output to the semiconductor laser 12 in synchronization with this signal BD2.

At this time, the beams of the horizontal synchronization signals BDI and BD2 are picked up from the tip cross section of a pair of optical fibers 65 and 66, and since the optical fibers 65 and 66 are optically coupled before the horizontal synchronization signal detector 67, the horizontal synchronization The signal detector 67 receives the mixed signal (2) of BDI and DD2.

In addition, since slits 68 and 69 are provided in the cross section of the fiber serving as the signal receiving section to adjust the signal time width, the horizontal synchronizing signal detected by the horizontal synchronizing signal detector 67 is Synchronous signal mixed signal BD to 2
The horizontal synchronization signals BDI and 802 can be separated, respectively, as shown in FIG. 1O. The above-mentioned signal processing circuit 70 is connected to the horizontal synchronizing signal detector 67 or not shown (g
installed in the code processing section. Therefore, only one detector is required for two horizontal synchronizing signals 801.8D2.

Furthermore, since the rotating polygon mirror 141 that can perform polarization scanning is used, only one semiconductor laser is required.

In FIG. 9, F/F 1 is a flip-flop circuit in the previous stage, and a rising edge (rising r) is detected by a mixed signal BD of horizontal synchronizing signals inputted to the input terminal of CL, R
A pulse signal Q (F/Fl) that is reset and falls at a time t2 corresponding to the time constant of the C circuit is output from the Q output terminal. The moon is a negative circuit connected to the reset terminal of the flip-flop circuit F/F1.

F/F2 is a flip-flop circuit in the latter stage, and the output signal Q (F/Fl) of the flip-flop circuit (F/Fl) is input to CL when the mixed signal BO input to the D input terminal is at H level. The output signal Q (F/
A pulse signal (F/F2) that falls at the falling edge of F2) is output from the Q output terminal. 72 and 7
3 is an AND circuit (logical product circuit), and the output Q (F/F
l) and Q (F/F2) are ANDed by an AND circuit 72, and a horizontal synchronizing signal BDI is output. Further, the outputs Q (F/river and Q (F/F2)) are ANDed by an AND circuit 73, and a horizontal synchronizing signal BD2 is output.

Note that the time width (pulse width) of the signal BD is set to 1. ．． 13, the time width (pulse width) h of the output (F/Fl) is
The relationship is set so that t r < tz < h.

FIG. 1O shows the timing of the output signal of the signal separation circuit 70.

In this embodiment, the first. By picking up the horizontal synchronizing signal of the second beam at the cross section of the optical fiber and providing a means (slit) for changing the pulse width of the signal on the cross section, the two horizontal synchronizing signals BD are obtained from the optically coupled composite signal BD.
I and BO2 are separated, but it is not limited to this.
For example, by picking up horizontal signals with a reflective mirror,
By making the horizontal widths of these reflecting mirrors different, it is possible to change the pulse width of the horizontal synchronizing signal reflected by the reflecting mirrors, and it is possible to separate the horizontal synchronizing signal from the composite signal.

[Effects of the Invention] As explained above, according to the present invention, since the first and second horizontal synchronizing signals of the laser beam are optically coupled with different signal times, a mixed signal of both signals can be easily generated. With this circuit configuration, two horizontal synchronizing signals can be detected by separating the grains, so one horizontal synchronizing signal detector can detect them, and as a result, a compact and inexpensive multicolor laser beam printer can be obtained.

In addition, since scanning is performed using a rotating polyhedron that performs polarized light scanning, only one semiconductor laser light source system is required compared to the conventional two systems, and the number of image signals is also reduced to one system. The required number of lasers and signal processing circuits is reduced, making it possible to reduce the size and manufacturing cost.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, Fig. 2 is a schematic diagram showing the arrangement of a laser beam printer, and Figs. 3 (A) to (F) show changes in the potential on the photosensitive drum. 4 is a perspective view showing the structure of the exposure section, FIG. 5 is a perspective view showing the structure of the exposure section of the embodiment of the present invention, and FIG. 6 is the structure of the rotating polygon mirror shown in FIG. 5. FIG. 7 is an optical path diagram showing the operation of the rotating polygon mirror shown in FIG. 6, FIG. 8 is a timing chart showing the operation of the embodiment of the present invention shown in FIG. FIG. 10 is a circuit diagram showing a configuration example of a signal separation circuit that separates a composite signal in a horizontal synchronization signal detector. FIG. 10 is a timing chart showing signal timing of the circuit of FIG. 9. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 3.6... Scanning beam, 12... Semiconductor laser, 15... Imaging lens, 54... Motor, 63... Mirror, 65, 66... Light Fiber, 67...Horizontal synchronization No. 8 detector, 68.69...Slit, 70...Signal separation circuit, 141...Rotating polygon mirror. (A) (B) (C) (D)
(E) (F)! <Seven drums! /) Chair no Shoro that does not change the electric power Gen 3 Main residence T 3 Months of Kafang Basuguri's Kaiku No. face bell A Hariki district Picture 6 Kaiku Zhen face thing Indicating the use of Yu Liu Yue Figure 7 (2) Blowjob JTJ 1〒 IτJTI

Claims (1)

[Scope of Claims] 1) a) forming a first latent image and a second latent image on a recording medium by alternately scanning the first beam and scanning the second beam; In a multicolor laser beam printer that records a multicolor image by developing the first and second latent images in different colors and then transferring them to a recording material, b) a horizontal synchronization signal of the first beam; c) signal time width adjusting means for making the signal time width of the horizontal synchronizing signal of the second beam different from the signal time width of the horizontal synchronizing signal of the second beam; horizontal synchronization signal detection means for detecting a mixed signal of a horizontal synchronization signal and a horizontal synchronization signal of the second beam; d) horizontal synchronization of the first beam from the mixed signal detected by the horizontal synchronization signal detection means; A multicolor laser beam printer, comprising signal separation means for separating the signal and the horizontal synchronization signal of the second beam, respectively. 2) The apparatus according to claim 1, further comprising a rotating polygon mirror that separates the first beam and the second beam from a single incident beam and scans them in separate directions. Multicolor laser beam printer.