JPH02118612A - Lazer light scanner - Google Patents

Abstract

PURPOSE:To omit respective circuit components to be exclusively used and wiring parts such as a connector and a lead wire to be connected therebetween by directly fitting a lazer light output element and a photodetector to the circuit substrate arranged at one edge side of a device main body. CONSTITUTION:A circuit substrate 32 is arranged on one edge wall 21a outer surface of a device 21 main body, and to the circuit substrate 32, a lazer diode 33 as a lazer light output element and a photodiode 34 as a photodetector are directly fitted. When an optical path indicated by an arrow in a full line is formed, one part of the lazer light is light-received by the photodiode 34, and the write starting position of printing is detected. Thereafter, by the lazer light (indicated by a two-point chain line) to be reflected on the same surface of a polygon mirror 24, the scanning of the lazer light to a photosensitive drum corresponding to the printing for one line is executed from the prescribed write starting position. Thus, the circuit substrate exclusive-use for the lazer diode 33 and photodiode 34 and the wiring parts such as the connector and lead wire to execute the connection between respective circuit substrates can be omitted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser beam scanning device for a laser beam printer.

[Conventional technology]

FIG. 5 shows a conventional laser beam scanning device, in which a motor 3 for rotating a polygon mirror 2 is installed in the main body 1 of the device, and an input unit 4 is also installed. The input unit 4 includes a laser diode 4a and a collimator lens 4b, and emits a laser beam toward a first mirror 5 attached to the main body 1f of the apparatus. The laser beam reflected by the first mirror 5 passes through the lens 6.7, and then is reflected by the second mirror 8 and is reflected by the polygon mirror 2.
The laser light incident on the mirror 2 is reflected by a second mirror 9 attached to the apparatus main body 1, and is then reflected by a third mirror 10 attached within the apparatus main body 1 toward the photosensitive drum (not shown). It is designed to be reflected towards.

A circuit board 4C to which the laser diode 4a is mounted is also attached to the incidence unit 4, and a circuit board 14 is connected to this board 4C via wiring connectors 11, 12 and lead wires 13. This circuit board 14 is disposed outside the main body 1 of the apparatus, and other control circuit parts (not shown) for adjusting the gain of the laser diode are attached to this circuit board 14.

Further, a detection hole 15 is provided in the peripheral wall of the device main body 1 on the side opposite to the input unit 4 with the motor 3 in between, and a detection hole 15 is provided in the peripheral wall of the device main body 1 on the side opposite to the incident unit 4. Diode 16# is arranged. The photodiode 16 detects a signal for aligning the start position of each line when scanning the photosensitive drum with a laser beam.

The diode 16 is mounted on a circuit board 17, which is connected to the circuit board 14 via a wiring connector 18.degree. and a cable 20. An optical fiber or a shielded wire is used for the cable 20, thereby preventing the detection signal of the photodiode 16 from being affected by external noise, and thereby preventing the S/N ratio from decreasing.

In such a conventional scanning device, when the optical path indicated by the solid line arrow in FIG. The laser beam reflected from the same surface (see the optical path indicated by the dotted chain line in Figure 5) scans the photosensitive drum corresponding to one line of printing from a predetermined writing start position. be done. Below, Polygon Mira 2
As the mirror rotates, the same laser beam scanning as described above is repeated for each reflective surface.

[Problem to be solved by the invention]

In the conventional device as described above, although the photodiode 16 is arranged far away from the laser diode 4a of the incidence unit 4, the diode 1
Noise is likely to be superimposed on the detection signal No. 6 due to external influences. Therefore, as a noise countermeasure, a high-cost cable such as an optical fiber or a shielded wire must be used as a wiring member that connects the circuit board 17 on which the photodiode 16 is attached and the control circuit board 14. .

Moreover, the circuit boards 4c are arranged apart from each other.

14.17 To connect each other, connectors 11゜1.
2, 18, 19, lead wires 13, and cables 20, as well as a large number of circuit boards, the conventional laser beam scanning device has a complex structure and is difficult to assemble. There is a problem.

An object of the present invention is to provide an S/N ratio of a detection signal that specifies the starting position of printing without using a cable for noise suppression.
It is an object of the present invention to provide a laser beam scanning device that can prevent a reduction in ratio and is simple in structure and assembly.

[Means to solve the problem]

In order to achieve the above object, the laser beam scanning device of the present invention includes a circuit board on one end side of the device body to which the motor for rotating the polygon mirror that reflects the laser beam emitted from the laser beam output element is attached. A photodetector element for detecting the starting position of printing by receiving the laser beam reflected by the polygon mirror is directly attached to this board together with the laser light output element and its peripheral circuit components. be.

[Effect]

In the present invention, since the laser light output element and the photodetection element are each directly attached to the circuit board placed at one end of the device main body, a dedicated circuit board for the laser light output element and the photodetection element 4 can be omitted. At the same time, wiring components such as connectors and lead wires for connecting each circuit board, which were conventionally necessary, can be omitted. Since the detection signal of the photodetector element is directly inputted via the circuit board to the control circuit formed by the peripheral circuit components attached to the circuit board, noise affecting the detection signal from the outside is superimposed on the detection signal. Therefore, cables for noise countermeasures can also be omitted.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

In the figure, reference numeral 21 denotes a main body of the apparatus whose top opening is closed by a lid 22 (see FIG. 3). Inside this main body 1 is a motor 23.
is attached, and a hexagonal polygon mirror 24, for example, is attached to this.

A second mirror 40 is attached to the inner surface of one side of the apparatus main body 21, and a third mirror 25 is attached to the other side of the apparatus main body 21, facing this mirror 40.

A first mirror 26 is installed within the apparatus main body 21, located between the polygon mirror 24 and the second mirror 40. This mirror 26 is provided at an angle of approximately 45 degrees with respect to the laser beam that is incident on the mirror 26 in order to cause the laser beam to be incident on the polygon mirror 24 . A cylindrical lens 27 and a lens 28 having one flat surface and a convex surface are attached to the first mirror 26 on the laser beam incident side. Furthermore, as shown in FIG. 1, a collimator lens 29 is attached to one end wall 21a of the apparatus main body 21 by penetrating it, and this lens 29 faces the cylindrical lens 27. Furthermore, a correcting fθ lens 30 is installed below the third mirror 25 in the main body 21, through which the laser beam reflected by the mirror 25 passes. Note that 31 in FIGS. 2 and 3 is a photosensitive drum disposed below the laser beam scanning device of the present invention, into which the laser beam that has passed through the fθ lens 30 is incident. .

A circuit board 32 is arranged on the outer surface of one end wall 21a of the device main body 21. A laser diode 33 as a laser light output element is directly attached to this circuit board 32, and a photodiode 34 as a light detection element is also directly attached. The laser diode 33 is attached to the circuit board 32 facing the two collimator lenses.

Note that 35 in FIG. 1 is connected to the circuit board 3 via a spacer 36.
The heat dissipation box screwed to 2, this is the laser diode 3
3 and is connected to the laser diode 33 via a heat transfer plate 37. This suppresses the temperature rise of the laser diode 33 and reduces changes in its output characteristics. Furthermore, the circuit board 3
Attached to 2 are peripheral circuit components of the laser diode 33, that is, circuit components for gain adjustment of the laser diode 33 and other control circuit components (not shown).

The photodiode 34 uses the polygon mirror 2 to determine the starting position of printing when scanning the laser beam onto the photosensitive drum 31.
It is used to receive and detect a part of the laser beam reflected by the laser beam. This diode 34 is connected to the main body 2 of the device.
1 is fitted into a groove 38 (see FIG. 4) and is supported by the one end wall 21a, with its light-receiving surface facing into the device main body 21.

Inside the device body 21, a detection mirror 3 is placed on the opposite side of the photodiode 34 with a polygon mirror 24 placed between them.
9 is installed. This mirror 39 has an optical path between the second mirror 40 and the photodiode, that is, an optical path of incidence to the photodiode 34, which is connected to the laser diode 3.
It is provided so as to be parallel to the output optical path of No. 3.

When using the laser beam scanning device with the above configuration, the laser beam is modulated based on the printed information and the laser diode 33
It is emitted from. This laser beam is applied to each lens 27.28
The motor 2 is reflected by the first mirror 26.
The light enters the polygon mirror 22 which is being rotated by the angle 3. Then, the laser beam reflected by the polygon mirror 24 is reflected by the second mirror 40, but a part of the reflected laser beam enters the three detection mirrors, so at that point,
Laser light reflected by the detection mirror 39 parallel to the output optical axis of the laser diode 33 enters the photodiode 34 facing the mirror 39 . That is, the unprinted writing start position indicated by the solid line in FIGS. 1 and 2 is detected.

The detection signal detected by the photodiode 34 as described above is directly inputted via the circuit board 32 to a control circuit formed by peripheral circuit components attached to this board 32. Therefore, the laser beam reflected from the same surface of the polygon mirror 24 (see the optical path indicated by the dashed line in FIGS. 1 and 2) is then directed onto the photosensitive drum 31 corresponding to one line of printing. Laser light scanning is performed from a predetermined writing start position. Thereafter, as the polygon mirror 24 rotates, the same laser beam scanning as described above is repeated for each of its reflecting surfaces, so that printing is performed with the top positions of each line aligned.

According to the laser beam scanning device having the above configuration, since the laser diode 33 and the photodiode 34 are each directly attached to the circuit board 32 disposed on one end side of the device main body 21, the laser diode 33 and the photodiode 34
It is possible to omit a dedicated circuit board for each circuit board, and accordingly, wiring components such as connectors and lead wires for connecting each circuit board, which were conventionally necessary, can be omitted. therefore,
Since the number of parts is considerably reduced, the overall structure can be simplified, and the number of man-hours required for assembly is also reduced, making assembly easier. Of course, costs can be reduced.

In addition, as already mentioned, the detection signal obtained by the photodiode 34 is directly inputted via the circuit board 32 to the control circuit formed by the peripheral circuit components attached to this board 32. It is possible to almost eliminate noise superimposition due to the influence of Therefore, it is possible to omit cables such as optical fibers, which were conventionally required for noise countermeasures, and therefore costs can be reduced in this respect as well.

[Effects of the Invention] According to the present invention configured as described above, a circuit board is disposed at one end of the apparatus main body to which a motor for rotating a polygon mirror is attached, and a laser beam is applied to the mirror onto this board. By installing a photodetector element that detects the starting position of printing by receiving the laser beam reflected by the mirror, as well as the incident laser light output element and its peripheral circuit components, connectors etc. are easier to use than conventional devices. By eliminating the wiring parts and reducing the number of circuit boards, the structure is simple, easy to assemble, and can be obtained at low cost, and the optical fibers or shielded wires conventionally used for the photodetector element are omitted. Nevertheless, it is possible to prevent the S/N ratio of the output signal of the photodetecting element from becoming low.

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention, FIG. 1 is a schematic plan view of the entire device with the lid removed, FIG. 2 is a diagram showing the optical path of the emitted laser beam, and FIG. Figure 3 shows ■-■ in Figure 1.
FIG. 4 is a sectional view taken along the line, and a perspective view showing the photodetecting element and its mounting portion. FIG. 5 is a schematic plan view showing the entire conventional device with the lid removed. 21... Device main body, 21a... One end wall, 22...
Polygon mirror 23...Motor, 31...Photosensitive drum, 32...Circuit board, 33...Laser diode (laser light output element) Prayer diode (light detection element). Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] When the laser beam emitted from the laser beam output element is reflected by a polygon mirror and scanned onto the photosensitive drum, the starting position of the print is determined by one point of the laser beam reflected by the polygon mirror. A circuit board is placed at one end of the device main body to which the motor for rotating the polygon mirror is attached, and the laser beam output element and its peripheral circuits are mounted on this circuit board. A laser beam scanning device characterized in that the above-mentioned photodetecting elements are directly attached to each of the components.