JPS61177860A - Laser beam printer - Google Patents

Abstract

PURPOSE:To equal the interval of a laser beam locus in the subscan direction in a photosensitive drum by adjusting the traveling path of a laser beam while the light emitting state of a light emitting body array is visibly checked. CONSTITUTION:When the locus 12a is emitted from a laser beam generator 12, a volume 42 is adjusted while the emitted light of the LED array is visibly checked. Accordingly, an photoacoustic effect deflector 41 can freely adjust the direction of the laser beam outputted from the laser beam generator 12 in accordance with the magnitude of a voltage impressed on said deflector 41, whereby the interval of the locus available on the photosensitive drum 14 can be set to the desired magnitude.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a laser beam printer,
In particular, the present invention relates to a laser beam printer using a plurality of laser beams, in which the line spacing in the sub-scanning direction is made uniform.

(Prior art) A conventional laser printer is, for example, disclosed in Japanese Patent Application Laid-open No. 58-1.
As described in Japanese Patent No. 8652, a method of printing using one laser beam was common. By the way, recently there has been a demand for laser beam printers that can record at high speeds, but in order to operate a laser beam printer at high speeds, it is necessary to rotate a rotating polygon mirror at an extremely high speed. Become.

However, since the rotating polygon mirror uses a bearing such as a ball bearing, there is a limit to its high speed rotation, and there is a problem in that the laser beam printer cannot operate at a sufficiently high speed.

Therefore, it was considered to use an air bearing as the rotating polygon mirror, but using an air bearing would require a device to generate compressed air, a means to guide the compressed air, etc., and the configuration would be complicated and large. At the same time, there was a problem of high cost.

In response to this, the present inventor has proposed a laser beam printer that uses two laser beams to alternately trace lines one line at a time on a photosensitive drum rotating at a constant speed.

The outline thereof will be explained using FIGS. 6 and 7. Here, FIG. 6 shows a plan view, and FIG. 7 shows a side view.

In this laser beam printer, the two laser beam generators 11 and 12 are arranged at an angle α in a plane perpendicular to the rotation axis of the rotating polygon M13 and at an angle β in a plane perpendicular to the plane. It is set up.

Moreover, this laser beam generator 11.12. A rotating polygon mirror 13 and a photosensitive drum 14 are arranged in the illustrated positional relationship. Further, laser beam generators 11 and 12,
Collimator lenses 15 and 16 are provided between the rotary polygon mirror 13 and the rotating polygon mirror 13, respectively. Further, an f/θ lens 17 is arranged between the rotating polygon mirror 13 and the photosensitive drum 14. Furthermore, near both ends of the photosensitive drum 14,
A scan start sensor 18 and a scan end sensor 19 are provided.

In a laser beam printer having such a configuration, laser beam generators 11 and 12 output laser beams 11a and 12a modulated by print information. In this case, if the laser beam 11a is modulated by the print information of the n-th line, for example, the laser beam 12a is modulated by the print information of the next line (n+1).
) is modulated by the print information. In this way, the laser beam generators 11 and 12 output laser beams modulated by print information for each line.

This laser beam is reflected by the rotating polygon 1t13 and irradiated onto the photosensitive drum 14. At this time, preferably, the laser beams 11a and 12a are
It is designed to hit the center part 13a of the. The rotating polygon mirror 13 and the photosensitive drum 14 are each rotating at a uniform speed, and the laser beam generators 11 and 12 are arranged at an angle α in the plane as described above, so that the laser beam 11a first enters the scan start sensor 18, then traces the generatrix of the photosensitive drum 14, and finally enters the scan end sensor 19, completing recording of one line on the photosensitive drum 14.

On the other hand, the laser beam 12a enters the scan start sensor 18 with a delay from the laser beam 11a by a time corresponding to the angle α, traces the generatrix of the photosensitive drum 14 parallel to the line, and then enters the scan end sensor 19. Then, recording of one line on the photosensitive drum 14 is completed.

Further, since the laser beam generators 11 and 12 are arranged at an angle β as described above, the photosensitive drum 1
As is clear from FIG. 7, the distance between the two lines on 4 is a value determined by the angle β, the rotational speed of the photosensitive drum 14, the distance between the rotating polygon mirror 13 and the photosensitive drum 14, etc. It becomes 1.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

Problems with the above device will be explained using FIG. This figure shows an example of the locus of a line formed on the photosensitive drum 14.

According to the above device, a trajectory 11a' written on the photosensitive drum 14 by the laser beam 11a emitted from the laser beam generator 11 and a trajectory 128' written by the laser beam 12a emitted from the laser beam generator 12. The spacing in the sub-scanning direction is as described above! l, but the trajectory 1
The distance between 28' and the locus 118'! It is difficult to rank it as 1, in general! 2 (~!1), and it is difficult to make the intervals in the sub-scanning direction uniform.

The present invention has been made to solve the above-mentioned problems.

(Means and operations for solving the problems) In order to solve the above problems, the present invention provides a plurality of laser beam generating means for generating a laser beam modulated by an input signal, and a scanning method for scanning the laser beams. In a laser beam printer having a rotating polygon mirror and a photoreceptor that is irradiated with a laser beam scanned by the rotating polygon mirror, the photoreceptor is downstream of the laser beam irradiation position of the photosensitive drum and is close to and opposite to the surface of the photosensitive drum. a surface potential sensor arranged as a surface potential sensor; a means for binarizing information read from the image sensor; first and second means for detecting an interval between the binarized signals; a light emitter array provided corresponding to each of the second means and in which a light emitter at a position corresponding to the magnitude of the signal outputted from the second means emits light; The present invention is characterized in that the interval in the sub-scanning direction of the laser beam locus on the photoreceptor is adjusted while visually observing the light emission state.

Another feature of the present invention is that the laser beam irradiation position of the photosensitive drum is located downstream of the laser beam irradiation position and close to the surface of the photosensitive drum;
surface potential sensors disposed facing each other, means for binarizing information read out from the image sensor, first and second means for detecting an interval between the binarized signals, and the first and means for outputting a difference signal of the second means, and an acousto-optic effect deflector for changing the deflection angle of the laser beam according to the difference signal, and an interval in the sub-scanning direction of the laser beam trajectory on the photoreceptor. The point is that it can be automatically adjusted so that it is uniform.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic block diagram of one embodiment of the present invention. Further, FIG. 2 shows a time chart of the main signals of FIG. 1. In Fig. 1, the same symbols as in Fig. 7 are the same.
FIG. 2 shows waveforms of signals in portions with the same reference numerals in FIG. 1.

In FIG. 1, the surface potential sensor 21 is connected to the photosensitive drum 14.
The photosensitive drum 14 is a surface potential sensor that detects the potential on the surface of the photosensitive drum 14, and is disposed opposite to and close to a part of the surface of the photosensitive drum 14. As this surface potential sensor, a well-known sensor commercially available from, for example, Monroe Co., Ltd. can be used. In this embodiment, when the laser beam 11a and the laser beam 12a scanned by the rotating polygon mirror 13 form mutually parallel laser beam trajectories on the photosensitive drum 14, the laser beam trajectories on the photosensitive drum 14 are The potential in response to decreases. On the other hand, the potential corresponding to the portion not hit by the laser beam remains high.

The surface potential sensor 21 detects this and outputs an output signal a having a waveform as shown in FIG. .

This output signal a is input to the comparator 22 and compared with the reference voltage Vo. As a result, if the output signal a from the comparator 22 is equal to or higher than the reference voltage V0, it is at H level and the reference voltage V.

If it is below, an L level signal is output. This signal is input to the flip-flop 23.

Flip-flop 23 is triggered by the falling edge of the input signal. Therefore, the output signal C at the Q terminal of the flip-flop 23 has a waveform as shown in FIG.
has the waveform shown in (d) of the same figure. That is, the H-level pulse width of the signal C represents the interval between the 2nth trajectory, the (2n+1)th trajectory, and the (2n+2)th trajectory.

The output signals C and d of the flip-flop 23 are then input to an AND gate, where each is logically ANDed with the clock output from the clock generator 24. Therefore, the counter 25a counts the number of clocks corresponding to the width of the H level of the output signal C;
The counter 25b counts the number of clocks corresponding to the H level width of the output signal d.

The output signal d of the flip-flop 23 is also input to a fall detector 26, and the fall of the signal d is detected. The waveform of the output signal e of the fall detector 26 is as shown in FIG.
> as shown.

This signal e is input to latch circuits 27a and 27b, and latches the outputs of counters 25a and 25b. Further, the signal e is input to a 1-bit delay circuit 28, and its output resets the counters 25a and 25b.

Therefore, the outputs of the counters 25a and 25b corresponding to the interval between the trajectories are latched in the latch circuits 27a and 27b.

Next, the output signals of the latch circuits 27a and 27b are decoded by decoders 28a and 28b, and the decoders 28a and 28b output a signal for selecting one of the LED arrays 29a and 29tl. As a result, the selected LED emits light.

Here, as the count values of counters 25a and 25b increase from small to large, LED arrays 29a and 29
If the lit LEDs in b move from the right end to the left end, the lit LEDs in the LED arrays 29a and 29b
If the positions of 29a1 and 29b1 are the same, it can be seen that the intervals between the trajectories, that is, the intervals in the sub-scanning direction are kept uniform. On the other hand, the lighting LEDs 29a1 and 2
It can be seen that if the positions of 9b5 are different, the spacing in the sub-scanning direction is non-uniform.

In this embodiment, the timing at which the counter 25a is reset is delayed by one pit, and the count is 1 less than the count of the counter 25b, so it is necessary to correct this.

This may be corrected, for example, by the decoder 28a.

In this embodiment, the traveling path of the laser beam is adjusted while visually observing the illuminated LEDs 29a 1 and 29b1, so that the intervals of the laser beam trajectory on the photosensitive drum 14 in the sub-scanning direction are made equal.

Next, means for adjusting the angle of the laser beam generator 12 will be explained with reference to FIG. FIG. 3 shows a side view of the means.

As shown, a support 32 of a semiconductor laser 31
are held between angle adjustment screws 34a and 34b that thread through the bracket 33, and fixing springs 35a and 35b whose ends are locked to the bracket 33. Therefore, if the trajectory 12a is now being emitted from the semiconductor laser 31 in the direction shown in the figure, either turn the ζ angle adjustment screw 34a to move it to the right, or turn the angle adjustment screw 34b in the opposite direction to move it to the left. By adjusting the advance, the direction of the beam emitted from the semiconductor laser 31 can be corrected by the angle Δβ and changed to the direction of the laser beam 12a1.

As a result, the distance between the trajectory 128' on the photosensitive drum 14 shown in FIG. 1 and the trajectory 11a' can be adjusted while keeping the trajectory 128' parallel to the trajectory 11a'.

The angle adjusting screw 34a or the angle adjusting screw 34b is adjusted while visually observing the light emitted from the LED arrays 29a and 29b.
l and 29b! When the light emitting positions of are at the same position,
The adjustment by the angle adjusting screw 34a or the angle adjusting screw 34b is completed.

A second means for adjusting the angle of the laser beam generator 12 is shown in FIG. In the figure, 41 is a well-known acousto-optic deflector, 42 is a volume, 43 is a constant voltage source, and other symbols are the same as or equivalent to those in FIG. 6.

In this example, the mechanical laser beam 12 described in FIG.
Instead of changing the direction of the laser beam 12a, the direction of the laser beam 12a can be electrically adjusted. That is, the above-mentioned ED29a.

The volume 42 is adjusted while visually observing the light emitting state of the light 29b. Then, the acousto-optic effect deflector 41 can freely adjust the direction of the laser beam output from the laser beam generator 12 in accordance with the magnitude of the voltage applied thereto, and the direction of the laser beam outputted from the laser beam generator 12 can be freely adjusted, and the direction of the laser beam can be obtained on the photosensitive drum 14. The interval between the trajectories in the sub-scanning direction can be set to a desired size.

Although the above embodiment is an example in which a laser beam printer is operated at high speed using two laser beam generators, the present invention is not limited to this, and the present invention is not limited to this. Of course, it can also be applied to beam printers. Further, the laser beam generator is not limited to a semiconductor laser, and may be another laser beam generator such as a gas laser. Furthermore, the shift register connected to the output end of the binarization circuit is not limited to this, and any storage device such as a line buffer that maintains the order of input signals may be used.

FIG. 5 shows another embodiment of the invention. In the figure, the same reference numerals as in FIG. 1 indicate the same or equivalent parts, and the explanation of their operation will be omitted.

In this embodiment, the values of the counters 25a and 25b corresponding to the width between the trajectories on the photosensitive drum 14 are determined by the falling edge detector 2.
Using the output signal from 6 as a trigger, the D/A converter 51a
and converted into an analog signal by 51b. D
The outputs of the /A converters 51a and 51b are then input to a differential amplifier 53, and the difference therebetween is detected. The output of the differential amplifier 53 is input to an acousto-optic deflector 54.

The acousto-optic deflector 54 is the same as the acousto-optic deflector 41 shown in FIG. 4, and is provided in the path of the laser beam. Further, a fixed bias voltage (1) is applied to the acousto-optic effect deflector 54 in advance, and this bias voltage (1) is applied to the first and second trajectories when the output of the differential amplifier 53 is zero. The spacing between 118' and 128' in the sub-scanning direction is selected to be uniform.

Therefore, according to this embodiment, the trajectories 118' and 1
2a' increases, the output from the D/A converter 51a becomes larger than the output from the D/A converter 51b, and the output of the differential amplifier 53 increases in the negative direction. Then, a voltage obtained by adding this negative voltage to the bias voltage (1) will be applied to the acousto-optic effect deflector 54, and the acousto-optic effect deflector 54 will be applied to the laser beam generator 1.
The laser beam 12a outputted from the laser beam 12a is deflected in a direction in which the distance is narrowed.

On the contrary, when the interval between the trajectories 118' and 12a' becomes smaller, the output of the D/A converter 51a becomes smaller than the output of the D/A converter 51b, and the output of the differential amplifier 53 becomes positive. becomes larger in the direction of

Therefore, the acousto-optic effect deflector 54 has a bias voltage V
A voltage obtained by adding the positive voltage to r is applied, and the acousto-optic effect deflector 54 deflects the laser beam 12a output from the laser beam generator 12 in a direction in which the interval becomes wider.

Therefore, according to this embodiment, the trajectories 118' and 1
The spacing between 2a' can be made constant automatically.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) The interval in the sub-scanning direction between the trajectories created by the two laser beams can be visually detected.

(a) Since the interval in the sub-scanning direction between the trajectories created by the two laser beams can be adjusted to a desired size while visually observing, the interval in the sub-scanning direction can be easily made uniform.

(The intervals in the sub-scanning direction of the trajectories created by the 32 laser beams can be automatically made uniform.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the first embodiment of the present invention, FIG. 2 is a waveform diagram of the main signals in FIG. 1, and FIGS. 3 and 4 are:
5 is a block diagram of the second embodiment of the present invention, and FIG. 6 is a side view of the first and second means for adjusting the angle of the laser beam generator, respectively, FIG. 6 is a block diagram of the second embodiment of the present invention, and FIG. FIG. 7 is a plan view of the printer, FIG. 7 is a side view thereof, and FIG. 8 is an explanatory view showing an example of the locus of the laser beam on the photosensitive drum of the apparatus shown in FIGS. 6 and 7. 11.12... Laser beam generator, 13... Rotating polygon mirror, 14... Photosensitive drum, 21;... Surface potential sensor, 22... Comparator, 23... Flip-flop, 24... ...Clock generator, 25a, 25b...
Counter, 27a, 27b--Latch circuit, 28a. 28 b...decoder, 29a, 29b LE
D array, 51a, 51b-D/A converter, 53-.
・Differential amplifier, 54...Patent attorney for acousto-optic effect deflector Michito Hiraki, one of the most prestigious d O O 〉 OuU OΦ \, y ζ-ノ -11
＼、ノFig. 5 7L Fig. 3 Fig. 4

Claims (2)

[Claims] (1) A plurality of laser beam generating means that generate a laser beam modulated by an input signal, a rotating polygon mirror that scans the laser beam, and a photoreceptor that is irradiated with the laser beam scanned by the rotating polygon mirror. a surface potential sensor disposed downstream of the laser beam irradiation position of the photosensitive drum and close to and facing the surface of the photosensitive drum; and a surface potential sensor that converts information read from the surface potential sensor into a binary value. means for detecting the interval between the binarized signals; first and second means for detecting the interval between the binarized signals; a light emitter array in which the light emitters at positions corresponding to the size of the light emitters emit light, and the interval in the sub-scanning direction of the laser beam trajectory on the photoreceptor is adjusted while visually observing the light emitting state of the light emitter array. A laser beam printer characterized by: (2) A plurality of laser beam generating means that generate a laser beam modulated by an input signal, a rotating polygon mirror that scans the laser beam, and a photoreceptor that is irradiated with the laser beam scanned by the rotating polygon mirror. a surface potential sensor disposed downstream of the laser beam irradiation position of the photosensitive drum and close to and facing the surface of the photosensitive drum; and a surface potential sensor that binarizes information read from the image sensor. means for detecting the interval between the binarized signals; means for outputting a difference signal between the first and second means; and means for determining the deflection angle of the laser beam by the difference signal. 1. A laser beam printer, comprising: an acousto-optic deflector that changes the distance between the laser beam trajectories on the photoreceptor in the sub-scanning direction;