JPH0359616A - Laser scanner unit for laser printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser scanner unit used in a laser printer.

[Prior Art] Conventionally, as a laser scanner unit used in a laser printer, the one shown in FIG. 5 is known. This includes a laser diode 1 that is a laser emitting element, a laser diode control circuit 2 that drives the laser diode 1, a start sensor 3 that includes a PIN diode that detects the start position of the laser beam, and a polygon motor that rotationally drives a polygon mirror 4. 5, a polygon motor drive circuit 6 for driving and controlling the polygon motor 5, and a PLL control circuit 7 for controlling the rotational speed of the motor 5 by the drive circuit 6.

Then, the polygon mirror 4 is rotationally driven by the polygon motor 5, and when the laser diode 1 irradiates the polygon mirror 4 with a laser beam, the laser beam is deflected by the inclination of the mirror surface of the polygon mirror 4 and is scanned over a certain width. ing.

During this scanning, when the laser beam is scanned to the start position that determines the preset printing start position, the start sensor 3 receives the laser beam via a separate mirror, and the sensor 3 outputs a print start signal to the printer's controller. It is now possible to do so. The controller determines the print start position on the paper by manually inputting a print start signal.

[Problems to be Solved by the Invention] However, in this conventional device, when the output of the laser light from the laser diode 1 is changed, the threshold level for light reception detection set in the start sensor 3 is changed. There is a problem in that the position of the laser beam point that exceeds the level shifts, resulting in a shift in the printing start position. In addition, if the output of the laser beam is extremely reduced, even if printing is possible with the laser beam at that time, if the level of the laser beam received by the start sensor 3 falls below the threshold level, the printing start signal will not be output. As a result, there was a problem that the printing operation could not be performed.

Therefore, the present invention provides a laser scanner unit for a laser printer that can always output a print start signal at the timing when the laser beam reaches the start position that determines the set print start position regardless of changes in the laser light output from the laser light emitting element. This is what we are trying to provide.

[Means for Solving the Problem] The invention corresponding to claim (1) scans a laser beam by irradiating a polygon mirror that is rotationally driven with a laser beam from a laser emitting element, and then scans a photoreceptor based on printed information. In the laser scanner unit of a laser printer that exposes images, a light emitting element irradiates light output to a position different from the laser beam irradiation position on the polygon mirror, and a laser beam scans to a start position that determines a preset printing start position. A light receiving element is provided to receive reflected light obtained by reflecting the light output of the light emitting element on a polygon mirror at the timing when the light emitting element is reflected, and the printing start position is detected from the output of the light receiving element.

The invention according to claim (2) further provides a sensor that detects the laser beam when the laser beam is scanned to the start position, and detects the laser power based on the output of the sensor.

[Operation] In the invention corresponding to claim (1), the polygon mirror is irradiated with laser light from the laser light emitting element, and the laser beam is scanned. When the laser beam reaches the start position, the light output from the light emitting element is reflected by the polygon mirror and the reflected light is received by the light receiving element, and the printing start position is detected from the output of the light receiving element. In this way, the printing start position can be detected using a light emitting element and a light receiving element that are separate from the laser light emitting element.

Further, in the invention corresponding to claim (2), the laser power is detected by a sensor detecting the laser beam being scanned when the laser beam reaches the start position.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows the overall structure of a laser printer, in which a photosensitive drum 12 whose surface is formed of a photosensitive material is provided in the center of a housing 11 that can be separated vertically. The photosensitive drum 12 is driven to rotate in one direction, and around the photosensitive drum 12 there is a charger 13 constituting a charging section according to the electrophotographic process.
A laser scanner unit 14 is a main part that irradiates a charged photoreceptor with a laser beam to record image information by exposure, a developing device 15 that attaches toner as a developer to the exposed photoreceptor, and a transfer section. A transfer charger 16 for removing toner from the photosensitive drum 12, a cleaning device 17 for removing toner from the photosensitive drum 12, and a discharging lamp 18 for discharging the photosensitive drum 12 are provided in this order.

A paper feed section 1 is located near the entrance in front of the transfer charger 16.
A pickup roller 20 is provided to convey the paper stored in the transfer charger 9 toward the transfer charger 16 at a predetermined timing.

Further, behind the transfer charger 16, there is a thermal fixing device 21 for thermally fixing the transferred paper, and a paper ejection roller 2.
2 is provided.

Further, inside the housing 11, a transport motor 23 and a fan 24 are provided.
, an interlock switch 25 for detecting opening of the upper half of the housing 11, and a DC power supply 26 are provided, respectively.

FIG. 3 is a block diagram showing the circuit configuration of the laser printer, and 31 is a CPU (central processing bag vI) that constitutes the main body of the control unit.
t), 32 is a ROM in which program data and various tables for controlling each part of this cpυ31 are provided.
(read-only memory), 33 is a RAM (random access memory) that stores image information and various processing data sent from an external host computer;
4 is an I10 boat. These are connected by a pass line 35.

The I10 boat 34 includes a motor drive circuit 36 for driving and controlling the transport motor 23, a high voltage power supply circuit 37 for supplying high voltage to the laser scanner unit 14, the charger 13 and the transfer charger 16, and A toner sensor circuit 4 that controls the provided toner empty sensor 38 and toner full sensor 39.
0. An operation unit 41, a vapor sensor 42 that detects paper jam, the fan 24, a deep switch 43, and an interface 4 that receives image information from the host computer.
4 are connected to each other.

The interlock switch 25 is inserted into a 24V supply line connected from the DC power supply 26 to the motor drive circuit 36, laser scanner 14, high voltage power supply circuit 37, and fan 24, and is connected to the 24V supply line when the housing 11 is opened. It is designed to detect this and shut off this supply line.

The CPU 31, ROM 32, RAM 33, and I10 board 34 are supplied with 15V from the DC power supply 26.

As shown in FIG. 1, the laser scanner unit 14 includes a laser diode 141 that is a laser light emitting element that outputs laser light, a laser diode control circuit 142 that drives the laser diode 141, and a laser diode control circuit 142 that drives the laser diode 141. A polygon mirror 143 that deflects and scans a predetermined range as a laser beam, a polygon motor 144 that rotates this polygon mirror 143, a polygon motor drive circuit 145 that drives and controls this polygon motor 144, and a drive circuit 145 that controls the polygon motor 144. PLL control circuit 1 that controls the drive rotation speed
46, a light emitting element 14 that irradiates a light output to a position different from the irradiation position of the laser beam on the polygon mirror 144;
7. At the timing when the laser beam scanned by the polygon mirror 144 reaches a start position that determines a preset printing start position, the light output of the light emitting element 147 is reflected by the polygon mirror 144, and the reflected light is obtained. It is composed of a light receiving element 148 that receives light. Note that the light emitting element 147 and the light receiving element 148 are integrated as one sensor.

The output when the light receiving element 148 receives the reflected light is supplied to the laser diode control circuit 142. When the laser diode control circuit 142 inputs the output from the light receiving element 148, the I10 port 3
4, a print start signal is output.

In this embodiment having such a configuration, when a printing operation is started, the photosensitive drum 12 rotates and the photosensitive member is charged by the charging charger 13.

On the other hand, in the laser scanner unit 14, a polygon motor 145 is driven by a polygon motor drive circuit 143.
is driven to control the rotation of the polygon mirror 144, and at the same time, the laser diode 141 is driven by the laser diode control circuit 142, and laser light is output from the laser diode 141. This laser light is deflected by a polygon mirror 144 and scanned over a predetermined range as a laser beam. Further, the light output from the light emitting element 147 is reflected by the polygon mirror 144, and the reflected light is transmitted to the light receiving element 14.
8 detects the printing start position. By detecting this print start position, a print start signal is output to the I10 boat 34, and thereby the CPU 31 supplies print information to the laser diode control circuit 142 via the I10 boat 34.

In this way, a laser beam carrying print information is scanned from the laser scanner unit 14 onto the charged photoreceptor, and the information is written as an electrostatic latent image on the photoreceptor. Then, toner supplied from the developing device 15 is attached to the electrostatic latent image formed on the photoreceptor, the image is visualized, and the image is further moved to a transfer section.

On the other hand, the paper stored in one paper feed section is sent to a conveyance path by a pickup roller 20 at a predetermined timing. When this paper is conveyed to the transfer charger 16, visualized information is transferred onto the photoreceptor strips of the photoreceptor drum 12. Then, the paper is further thermally fixed by the thermal fixing device 21, and is discharged by the paper discharge roller 22, thereby completing printing.

By the way, if the laser light output level of the laser diode 141 is changed, the intensity of the scanned laser beam changes. However, since the light emitting element 147 remains constant regardless of changes in the output level of the laser beam, the light receiving element 148
always detects the print start position by reliably receiving the reflected light at the timing when the laser beam reaches the start position that determines the set print start position. Therefore, even if the output level of the laser beam is changed, there is no risk of a shift in the timing at which the print start signal is generated. Further, even if the output level of the laser beam is extremely reduced, it has no effect on the optical output from the light emitting element 147, so there is no possibility that the printing start position cannot be detected.

Next, other embodiments of the present invention will be described with reference to the drawings. Note that the same parts as in the above embodiment are given the same reference numerals and detailed explanations will be omitted.

As shown in FIG. 4, the laser scanner unit 14 is further provided with a sensor 149 that detects the laser beam when it is scanned to the start position that determines the printing start position, and the output of the sensor 149 is sent to the laser diode. The control circuit 142 is supplied with the signal. The laser diode control circuit 149 detects the laser power based on the output level from the sensor 149.

By detecting the laser beam with the sensor 149 in this manner, the laser power can be detected.

This sensor 149 can also detect whether the laser beam is correctly irradiating the scanning line.

[Effects of the Invention] As described in detail above, according to the present invention, by detecting the printing start position using a separately provided light emitting element and light receiving element, the printing start position is always detected regardless of changes in the laser light output from the laser light emitting element. It is possible to provide a laser scanner unit for a laser printer that can output a print start signal at the timing when a laser beam reaches a start position that determines a set print start position.

[Brief explanation of drawings]

1 to 3 show embodiments of the present invention.
2 is a diagram showing the configuration of the laser scanner unit, FIG. 2 is a configuration diagram of the entire laser printer, FIG. 3 is a block diagram showing the circuit configuration, and FIG. 4 is a diagram of the laser scanner unit showing another embodiment of the present invention. FIG. 5 is a diagram showing the structure of a conventional laser scanner unit. 12... Photosensitive drum, 41... Laser diode (laser light emitting element) 144
... Polygon mirror 145 ... Polygon motor, 147 ... Light emitting element, 148 ... Light receiving element.

Claims (2)

[Claims] (1) In a laser scanner unit of a laser printer that scans the laser beam by irradiating a rotationally driven polygon mirror with laser light from a laser emitting element and exposes a photoreceptor based on printed information, the laser beam in the polygon mirror is a light emitting element that emits light output to a position different from the light irradiation position, and a light output of the light emitting element that emits the light output of the polygon mirror at a timing when the laser beam is scanned to a start position that determines a preset printing start position. 1. A laser scanner unit for a laser printer, characterized in that a light-receiving element is provided to receive reflected light obtained by reflection by a laser beam, and a printing start position is detected based on the output of the light-receiving element. (2) In a laser scanner unit of a laser printer that scans the laser beam by irradiating a rotationally driven polygon mirror with laser light from a laser emitting element and exposes a photoreceptor based on printed information, the laser beam on the polygon mirror a light emitting element that emits light output to a position different from the light irradiation position, and a light output of the light emitting element that emits the light output of the polygon mirror at a timing when the laser beam is scanned to a start position that determines a preset printing start position. a light-receiving element that receives the reflected light obtained by reflecting the light;
A laser printer characterized in that a sensor is provided to detect the laser beam when the laser beam is scanned to the start position, and the printing start position is detected by the output of the light receiving element, and the laser power is detected by the output of the sensor. laser scanner unit.