JP3320231B2 - Laser beam printer and control method therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a laser beam printer for forming an image by scanning a laser beam printer, and a control method thereof.

[0002]

2. Description of the Related Art FIG. 8 shows a configuration of a laser beam printer to which the present invention is applied. The image forming operation of the laser beam printer will be described with reference to FIG.

An image signal (VDO signal) 101 is input to a laser unit 102. Reference numeral 103 denotes a laser beam on / off-modulated by the laser unit 102. Reference numeral 104 denotes a scanner motor for rotating a rotating polygon mirror (polygon mirror) 105 in a steady state. An imaging lens 106 focuses a laser beam 107 deflected by a polygon mirror on a photosensitive drum 108 which is a surface to be scanned.

Accordingly, the laser beam 107 modulated by the image signal 101 is horizontally scanned on the photosensitive drum 108 (scanning in the main scanning direction). A beam detection port 109 receives a laser beam from a slit-shaped entrance port. The laser beam entering through this entrance passes through the optical fiber 110 and is guided to the photoelectric conversion element 111. The laser beam converted into an electric signal by the photoelectric conversion element 111 becomes a horizontal synchronization signal (hereinafter, referred to as a BD signal) after being amplified by an amplifier circuit (not shown). 112 is
The latent image formed on the transfer drum and formed on the photosensitive drum 108 is
The toner image is visualized by a developing device (not shown), and is transferred to a transfer paper 112 by a transfer device (not shown).
Is transferred to

Next, control signals for forming an image will be described with reference to FIG.

Reference numeral 121 denotes a transfer sheet for forming an image.
The toner image is formed on the transfer paper 121, and the toner image formed by the shift or the like of the transfer paper 121 is transferred to the transfer paper 121.
From 21, a region (image forming region) 122 that can be exposed by laser so as not to protrude is provided. Also,
The image signal 126 is output by an image controller (not shown), which is often a controller separate from the control unit that handles control signals such as BD signals, or an external computer. In the case of such a configuration, even if the image controller turns on the image signal in the non-image area, the image forming area 12 is formed so as not to expose the photoconductor.
2 is provided. Therefore, each of the image forming areas 122 has a different size according to the size of the transfer paper 121.

Next, an image forming signal for forming an image corresponding to one main scan 123 on the transfer paper 121 will be described. The BD signal 124 is the synchronization signal in the main scanning direction described above, and generates other signals in synchronization with the BD signal.

The mask signal 125 is a signal that is turned on and off in accordance with the mask area 122 on the transfer paper 121, thereby prohibiting the image signal 126 having image information and prohibiting exposure outside the image forming area 122. .

The BD allowable range signal 127 is a signal for permitting the input of a BD signal. This signal masks the BD signal 124 so as not to receive the BD signal for a predetermined period from the previous BD signal. This prevents horizontal synchronization from being shifted due to noise.

The unblanking signal 128 is a timing signal for turning on and off the laser beam when the laser beam scans the detection port 109 of the BD signal.

This signal is also a signal generated after a predetermined time from the BD signal, like the previous signal.

Next, a circuit for generating these control signals in the main scanning direction will be described with reference to FIG. Reference numeral 16 denotes a CPU for controlling the sequence of the laser beam printer, which controls not only the main scanning direction but also the sub-scanning direction and others. In the present invention, circuits for control other than the main scanning are omitted. Reference numeral 1 denotes an address bus from the CPU 16 for selecting each register by the address decoder 15. Reference numeral 9 denotes a data bus for writing data from the CPU 16 to each register and for transferring data from each register to the CPU.
16 is a transfer route used when data is read into the memory 16. Reference numeral 2 denotes the various registers, which store the count values at the time of generation and termination of the mask signal, the BD permission signal, and the unblanking signal described above.

The count value stored in the register 2 is compared with a main scanning counter 13 which starts counting by a BD signal 14, and generates various signals. The comparator 3 for performing this comparison compares the value of the various registers 2 with the value of the main scanning counter 13. 18 is
It is a J / K flip-flop which combines various start timing signals and end timing signals to generate a mask signal 4, an unblanking signal 5, and a BD allowance signal 10 and send them to the image control signal generator 17. The image control signal generator generates a laser emission permission signal 6 based on these signals.
Is sent to the laser unit.

In this manner, control of image formation in each main scan is performed.

A scanner motor for scanning a laser beam controls a speed feedback (speed discrimination) and a phase feedback (PLL control) in order to control an FG signal generated in proportion to the number of revolutions so as to be synchronized with a reference clock. ). A signal for detecting the rotation is generally an FG signal, but a BD signal can be used for the purpose of improving rotation accuracy.

[0016]

However, in the case where the laser beam is detected before the scanner motor is rotated at a constant speed, for example, in which the rotation of the scanner motor is controlled based on the BD signal, the following disadvantages arise. Occurs.

In the state where the scanner motor has reached the steady rotation speed, control can be performed by using the BD signal instead of the FG signal as in the related art, but some problems occur until the scanner motor starts up. .

Further, since it is necessary to turn on the laser before rotating the scanner motor, a beam having a low scanning speed is irradiated on the photosensitive drum. The photosensitive drum receives a larger amount of energy than the energy applied to form a normal image, and has a disadvantage of being partially deteriorated.

When the scanner motor is controlled by the BD signal, it is necessary to continuously light the laser beam while the scanner motor starts up. The time required for the scanner motor to rise is usually several seconds, but considering intermittent printing, the accumulated time is sufficient to shorten the life of the laser chip.

Therefore, when controlling the scanner motor with the BD signal, it is necessary to generate the BD signal with the minimum required laser lighting time without irradiating the photosensitive drum with a beam when the scanner motor is started. .

An object of the present invention is to prevent a laser beam printer that scans a laser beam from damaging a photosensitive member during a start-up period before a laser beam scanning period becomes a steady rotation. An object of the present invention is to prevent the life of a laser from being shortened.

[0022]

A laser beam printer according to the present invention comprises a scanning means for scanning a laser beam on a scanning path including an image area and a non-image area, and a laser beam scanned by the scanning means. Detecting means for detecting a laser beam in a region, emission control means for forcibly emitting a laser so that the laser beam is detected by the detecting means, and measurement for measuring a scanning cycle of the laser beam scanned by the scanning means. Means, during a start-up period before the scanning cycle of the scanning means is in a steady state, so that the laser emission control means forcibly emits light, so that a laser beam is emitted immediately before the detection means. It is characterized by having timing control means for controlling based on the measurement result of the measurement means. Further, a control method of a laser beam printer of the present invention is a control method of a laser beam printer that scans a laser beam on a scanning path including an image area and a non-image area, wherein the scanning cycle of the laser beam is in a steady state. During the previous start-up period, a light emission control step of forcibly emitting a laser, a detection step of detecting a laser beam emitted by the light emission control step by a detector provided in the non-image area, and scanning. A measuring step of measuring a scanning cycle of the laser beam to be performed, and during the rising period, the forced emission timing by the emission control step is set such that the laser beam is started to be emitted immediately before the detector. It has a changing step of changing based on the measurement result of the measuring step.

[0023]

【Example】

(Embodiment 1) A first embodiment will be described with reference to FIG. The same parts as those in the function of FIG. 10 described above are denoted by the same reference numerals, and the details thereof are the same, and thus description thereof will be omitted. A description will be given of a newly added portion for implementing the present invention. The capture register 12 is a register for storing the count value of the main scanning counter 13 at that time in response to the BD signal 14, and has a configuration in which the BD signal 14 is used as a write signal of the register to capture the count value of the main scanning counter 13. . The contents of this register can be read by a read signal from the CPU 16 or by a BD cycle transfer circuit 30 described later. The OR gate 22 is for enabling reading by both of these read signals. Further, the register 20 for storing the timing of generating the unblanking signal can write data from the CPU 16 or write data using a write signal 32 from the BD periodic transfer circuit 30.

Now, the BD cycle transfer circuit 30 will be described in detail.

FIG. 2 is a diagram for explaining the BD periodic transfer circuit 30. The circuit comprises AND gates 36 and 39 and D flip-flops 37 and 38. The operation of these circuits is described in the timing chart of FIG. 34 is
These are clocks serving as references for operating these circuits, and the reset signal 35 is omitted from FIG. 1 which is a block diagram. When the CPU 16 turns on the signal 31, the data of the previous capture register 12 is output onto the bus line 9. The data on this bus line 9 is
6 is written to a register 20 for storing an unblanking signal generation timing. This operation will be described with reference to the timing chart of FIG. 3 and the circuit diagram of FIG. First, when the CPU 16 turns on the bus release signal 31, the transfer mode is entered.
In this mode, a clock 34 for operating the BD cycle transfer circuit 30 is input. This is performed by the AND gate 36. This clock 3
4 when the BD signal 14 is input, the flip-flop 37 causes the capture register 12
33, which is a readout signal of, is output. Based on this signal, data of the capture register 12 appears on the bus line 9. Next, flip-flop 38 and AND gate 39
As a result, a write signal 32 to the register 20 storing the unblanking start timing is generated. When this signal 32 is generated, the data on the bus line 9 is taken into the register 20 storing the unblanking start timing.

Since the value of the capture register 12 (BD cycle data of one line before) is output onto the bus line 9, this data is stored in the register 20 for storing the unblanking start timing. become. With the above operation, the start of the next blanking is determined based on the BD cycle one line before. As a result, the (n + 1) th B cycle from the nth BD cycle
When the D period is longer, in the (n + 1) th scan, the laser can be turned on immediately before the laser scans the BD detection port.

Therefore, the control by the BD signal can be realized without adversely affecting the photosensitive drum and without shortening the life of the laser chip.

(Embodiment 2) In the above embodiment, an example in which the present invention is realized in hardware has been described. In the next embodiment, an example of realizing the software will be described. By controlling the software, it is possible to control with flexibility. An example will be described with reference to FIG. B to CPU16
The D signal 14 is connected as the external interrupt signal 8. CP
The U 16 selects the contents of the capture register 12 by the address decoder 15 when the interruption by the BD signal occurs, and reads the data via the data bus 9. The contents are written to the register 20 for storing the unblanking start timing by performing an operation such as subtracting a predetermined value, as it is, or the like. Writing to the register 20 for storing the unblanking start timing is similarly selected by the address decoder 15 and written via the data bus 9. According to this method, not only the value of the capture register but also the value of the register 20 for processing by the CPU 16 to store the unblanking start timing is used. It is possible to do.

(Embodiment 3) In the above embodiment, the BD signal 1
Every time 4 is generated, the CPU 16 is interrupted, and the CPU 16 performs the above-described processing. The period at which the BD signal 14 is generated is on the order of several hundreds of microseconds. When a CPU with a slow processing speed is used, or when there is another task that needs to be processed at a high speed, the processing time of the CPU is reduced. In some cases, it is necessary to reduce these burdens by hardware in order to do so.
In the following embodiment, an example will be described in which a part of the functions described above is performed by hardware to reduce the load on the CPU. FIG. 4 shows the configuration. Components having the same functions as those in FIG. 1 described in the previous embodiment are given the same numbers. The added part of these circuits for this embodiment is 41 BD signal divider circuits. The details of the BD signal dividing circuit will be described below. FIG. 5 shows the BD
5 is a configuration example of a frequency dividing circuit. FIG. 6 shows the waveform of each part of this circuit. The function of this circuit is that instead of sending a BD signal that is generated multiple times each time the polygon mirror makes one rotation to the CPU as it is, focuses on a certain surface, and interrupts the CPU only when a BD signal comes out from that surface. multiply. This reduces the load on the CPU.
In this embodiment, the case where the number of polygon faces is six is described. Therefore, each time six BD signals 14 are generated, one of them is sent to the interrupt signal of the CPU 16.

Next, the configuration of FIGS. 5 and 6 will be described. The BD signal dividing circuit 41 is roughly divided into a wave forming circuit 53 for synchronizing a clock with the BD signal and shaping a waveform, and a dividing circuit 54 for generating one BD signal from six BD signals. , And a flip-flop 55 for connecting them. After being initialized by the reset signal 42, these circuits operate in synchronization with the basic clock 43. When the BD signal 44 is input to the waveform shaping circuit 53, the BD signal
And a constant waveform synchronized with. (The interval between the BD signals shown in FIG. 6 is set short for the sake of space. In an actual laser beam printer, the low level time is much longer than this waveform. However, the operation of this circuit is as follows. Is the same as an actual laser beam printer.) The waveform-shaped BD signal 47 is
5 is input to the frequency divider 54. The frequency divider 54 uses a Johnson counter, the details of which are described in the waveforms 48 to 51. 52 is B after frequency division
D interrupt signal. By inputting this signal to the interrupt terminal 8 of the CPU 16, the load on the CPU 16 can be reduced. Thereafter, as described in the previous embodiment, the value of the capture register 12 is transferred to the register 20 that stores the unblanking start timing.

[0031]

As described above, according to the present invention,
During the start-up period before the laser beam scanning period becomes steady rotation, it is possible to prevent the photoconductor from being strongly damaged, and to shorten the laser emission time as much as possible so that its life is not shortened. It becomes possible to.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for explaining a first embodiment.

FIG. 2 is a circuit diagram for explaining a first embodiment.

FIG. 3 is a timing chart for explaining the first embodiment.

FIG. 4 is a circuit diagram for explaining a second embodiment.

FIG. 5 is a circuit diagram for explaining a third embodiment.

FIG. 6 is a circuit diagram for explaining a third embodiment.

FIG. 7 is a timing chart for explaining a third embodiment.

FIG. 8 is a diagram illustrating a configuration of a laser beam printer.

FIG. 9 is a diagram for explaining signals in the main scanning direction.

FIG. 10 is a circuit diagram for explaining signals in the main scanning direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Capture register 13 Main scanning counter 14 BD signal 102 Laser unit 104 Scanner motor 105 Rotating polygon mirror (polygon mirror) 108 Photosensitive drum 111 Photoelectric conversion element

Claims (8)

(57) [Claims] A scanning means for scanning a laser beam on a scanning path including an image area and a non-image area; a detecting means for detecting a laser beam scanned by the scanning means in the non-image area; Emission control means for forcibly emitting a laser beam as detected by the detection means; measuring means for measuring a scanning cycle of a laser beam scanned by the scanning means; and a scanning cycle of the scanning means in a steady state. Timing control for controlling the forced emission timing by the laser emission control means based on the measurement result of the measurement means so that the laser beam is started to be emitted immediately before the detection means during the start-up period before A laser beam printer comprising: 2. The light-emission timing control means includes storage means for storing a value representing the light-emission timing, and comparison means for comparing a stored value of the memory with a timer value. 2. The laser beam printer according to 1. 3. The laser beam printer according to claim 2, wherein a predetermined arithmetic processing is performed on the scanning cycle measured by said measuring means, and a value representing the light emission timing is obtained based on a result of the arithmetic processing. 4. The laser beam printer according to claim 3, wherein a value obtained by subtracting a predetermined value from a scanning cycle measured by said measuring means is used as a value representing said light emission timing. 5. The laser beam printer according to claim 2, wherein the value representing the light emission timing is a value shorter than a scanning cycle measured by the measuring means. 6. The laser beam according to claim 1, wherein the scanning unit includes a polygon mirror for deflecting the laser beam, and a motor for rotating the polygon mirror. Printer. 7. A laser beam printer according to claim 6, wherein a rotation speed of said motor is controlled based on a beam detection signal from said detection means. 8. A method for controlling a laser beam printer that scans a laser beam on a scanning path including an image area and a non-image area, wherein during a start-up period before a scanning cycle of the laser beam becomes a steady state, A light emission control step of forcibly emitting a laser, a detection step of detecting a laser beam emitted by the light emission control step by a detector provided in the non-image area, and a scanning cycle of the laser beam to be scanned And measuring the forced emission timing by the laser emission control step, based on the measurement result of the measurement step, so that the laser beam is started to be emitted immediately before the detector during the startup period. A control method for a laser beam printer, comprising a changing step of changing.