JPS62162547A - Laser beam printer - Google Patents

Abstract

PURPOSE:To enable a dot density to be output to be changed easily by providing a laser beam scanning means for photosensitive surface, a reference clock signal generating means for printer output dot density variation and a reference clock frequency dividing means, and changing laser beam scanning speed through designation of divided frequency count corresponding to output dot density. CONSTITUTION:A 41MHz clock signal oscillated by a crystal oscillation circuit 71 is output to a counter 72 and then is counted down to (1/1,000). In addition, an output clock signal from a preset counter 73 which is counted down to '1/N' in accordance preset counter 73 which is counted down to '1/N' in accordance with data 'N' to be set by a latching circuit 74 is reference signal to a PLL circuit 75. Further any value of '1'-'256' to be sent by CPU 66 is set to the latching circuit 74, and the preset counter 73 selects a countdown value (1/N) according to a value to be set by the latching circuit. The PLL circuit 75 controls the rotation of a polyfacet mirror motor 53 so that a signal fc to be obtained from a rotary pulse signal generator 77 which generates pulses at a rate of one pulse/rotation following the rotation of the polyfacet mirror motor 53 may equal a reference frequency fo.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a laser beam printer that forms an output image by scanning a photosensitive surface with laser light using a scanning means.

[Prior Art] A widely known laser beam printer records an image by scanning a laser beam onto a rotating drum using a rotating polygon mirror or the like to form a latent image, and then transferring the image to paper after development. It is something.

FIG. 14 is a diagram showing an example configuration of a conventional laser beam printer, and a description will be added below with reference to the diagram.

In FIG. 14, numeral 1 denotes paper as a recording medium, and numeral 2 denotes a paper cassette that holds the paper 1. In FIG. 3 is paper cassette 2
A paper feed cam separates only the topmost sheet of paper 1 placed on top of the paper 1 and transports the leading edge of the separated paper to the paper feed rollers 4 and 4' position by a driving means (not shown). It rotates intermittently every time.

18 is a reflective photosensor; reflective photosensor 18
performs paper out detection by detecting reflected light from the paper 1 through a hole 19 provided at the bottom of the paper cassette 2.

When the paper 1 is conveyed to the gap by the paper feed cam 3, the paper feed rollers 4, 4' rotate while lightly pressing the paper 1, thereby conveying the paper 1. When the paper 1 is transported and the leading edge reaches the registration shutter 5 position, the transport of the paper 1 is stopped by the registration shutter 5, and the paper feed roller 4.4
' continues to rotate while generating conveyance torque while slipping against the paper 1. In this case, by driving the registration solenoid 6 and releasing the registration shutter 5 upward, the paper 1 is conveyed to the conveyance roller 7.7'. The registration shutter 5 is driven at a constant timing with the image formed by the laser beam 20 focusing on the photosensitive drum 11. Note that 21 is a photosensor, which detects whether or not there is paper at the location of the registration shutter 5.

Here, 52 is a rotating polygon mirror, and the rotating polygon mirror 52 is driven by a polygon motor 53, and the beam 20 from the semiconductor laser 51 is reflected onto the photosensitive drum 54.
1 to form a recorded image on the photosensitive drum 11. Furthermore, the beam detector 55 arranged at the scanning start position of the beam 20 outputs a BD signal which is the image writing timing in the main scanning direction by detecting the beam 20.

Thereafter, the paper 1 is fed to the photosensitive drum 11 with a conveyance torque obtained by a conveyance roller 7' instead of the paper feed rollers 4 and 4'. Here, the image exposed on the photosensitive drum 11 is transferred onto the paper 1 by the cooperation of a cleaner 12 , a charger 13 , a developer 14 , and a transfer charger 15 . The sheet 1 on which the image has been transferred is then subjected to a fixing process by a fixing roller 8.8', and is discharged onto a stacker 10 by a discharge roller 9.9'.

Note that in the figure, reference numeral A indicates a guide for regulating the conveyance direction of the paper 1.

Further, 16 is a paper feed tray, and paper cassette 2. This makes it possible to manually feed sheets one by one from the sheet feed table 16, as well as to feed sheets from the paper feed stand 16. The paper that is manually fed into the gap between the paper feed roller 17 on the paper feed table 16 is lightly pressed by the manual paper feed roller 17, and the leading edge of the paper is pushed in the same way as the paper feed roller 4.4'. is conveyed until it reaches the registration shutter 5, where it slips and rotates. The subsequent conveyance sequence is exactly the same as when feeding paper from a cassette.

Note that the fixing roller 8 houses a fixing heater 24.
The surface temperature of the fixing roller 8 is controlled to a predetermined temperature based on the temperature detected by the thermistor 23 that makes slip contact with the roller surface, and the recorded image on the paper 1 is thermally fixed. 2
A photo sensor 2 detects whether or not there is paper at the position of the fixing rollers 8, 8'.

Such printers are generally not used alone;
It is connected to the controller with an interface cable and receives print commands and image signals from the controller.
This is to perform a print sequence. The configuration of this interface cable and the signals transmitted and received through the interface cable will be briefly described below.

FIG. 15 is a diagram showing interface signals between a conventional general printer and a controller.

Each of the interface signals will be explained as follows.

PPRDY signal: This is a signal that informs the controller that the printer is powered on and ready for operation.

CPRDY signal: This is a signal that informs the printer that the controller is powered on.

RDY signal: This is a signal indicating that the printer is in a state where it can start or continue a printing operation whenever it receives a PIINT signal, which will be described later, from the controller.

For example, if the paper cassette 2 is out of paper and the printer operation is not possible, the flag becomes FALSE.

PRNT signal...The controller sends a message to the printer.
This is a signal that instructs to start a printing operation, or, if the printer is in a printing operation, a signal that instructs to continue the printing operation.

When the printer receives this signal, it starts printing.

The VSREQ signal, RDY signal and PRNT signal are all
This is a signal indicating that the printer is ready to receive a VSYNC signal, which will be described later, after receiving the RIIE signal.

VSYNC signal: A vertical (sub-scanning direction) synchronization signal for the printed image, which is output by the controller to the printer to synchronize the image on the drum with the paper.

BD signal: This is a horizontal (main scanning direction) synchronization signal for the printed image, and is a signal indicating that the laser beam is at the starting point of main scanning.

VDO signal: The image signal to be printed output by the controller.The printer outputs TRUE of this signal as the black of the output image.
Output FALSE as white.

SC signal: A bidirectional serial 8-bit signal that sends and receives OMMAND, which is a command signal from the controller to the printer, and 5TATUS, which is a status notification signal from Blink to the controller, which will be described later. The 5CLK signal, which will be described later, is used as a synchronization signal when transmitting and receiving signals. Also, since it is a bidirectional signal, the 5BSY signal and CBSY signal, which will be described later, are used to control human output.

Also, here OMMAND is a serial signal consisting of 8 bits, and for example, only the fixing heater of the printer is turned off.
and sends a paper feed command to enter the so-called paper feeding state to maintain an energy-saving state, and also cancels the paper feeding state and turns on the fixing heater.
It includes various control commands for the printer, such as a paper feed cancellation command to set the printer to N, a cassette paper feed command to feed paper from a paper cassette, and a manual paper feed command to feed paper manually.

On the other hand, 5TATtlS is a serial signal consisting of 8 bits. For example, if the printer is in a wait state where the fuser temperature has not yet reached the printable temperature, a jam has occurred, or the paper cassette is out of paper. This is to notify each status of the printer.

5CLK signal: This is a synchronizing pulse signal for the printer to capture COMMAND or for the controller to capture 5TATIIS.

5BSY signal: This is a signal for occupying the SC signal line and the SOL signal line before the printer transmits 5TATIIS.

CBSY signal: A signal used by the controller to occupy the SC signal line and the SCL signal line before transmitting (:OMMAND).

GNR5T signal: This is a reset signal by which the controller initializes the state of the printer.

Next, the mutual operation between the printer section and the controller section will be explained according to a system configuration diagram showing a connection configuration between the printer section and the controller section.

Suppose now that the power switch of the printer is turned on, and the power switch of the controller is also turned on. In this case, the printer initializes the internal state of the printer and then
Send a signal to the controller. On the other hand, after initializing the internal state of the controller, the controller
Send the RDY signal to the printer. After that, the printer energizes the fixing heater 24 housed inside the fixing roller 8.8', and when the temperature of the surface of the fixing roller 8.8' reaches a temperature that allows fixing, it sends an RDY signal to the controller. .

After receiving the RDY signal, the controller transmits a Pr1NT signal to the printer as required for printing. When the printer receives the PRNT signal, the printer prints the photosensitive drum 1.
1 to uniformly initialize the potential on the photosensitive drum surface, and at the same time, in the cassette paper feeding mode, the paper feeding cam 3 is driven to transport the leading edge of the paper to the registration shutter 5 position. In the manual paper feed mode, the manual paper feed roller 17 transports the paper manually fed from the paper feed tray 16 to the registration shutter 15 position. When the printer becomes ready to accept the VDO signal, it transmits the VSREQ signal to the controller.

After the controller receives the VSREQ signal, the VSYNC
Send a signal to the printer. The printer is VSY
When receiving the NC signal, the registration solenoid 6 is driven in synchronization with the NC signal to release the registration shutter 5. As a result, the paper is conveyed to the photosensitive drum 11. After issuing the VSYNC signal, the controller uses the signal as a BD double signal horizontal synchronization signal transmitted from the printer, and sequentially transmits the image signal VOO to be recorded to the printer in synchronization with this signal.

The printer blinks a laser beam in response to a VDO signal to form a latent image on the photosensitive drum 11, and develops it by applying toner to the developing device 14. Next, the transfer charger 1
The image developed by step 5 is transferred onto a sheet of paper, and fixed by fixing roller 8.
8' fixes the image and discharges the paper.

Next, when switching the paper feed mode of the printer to cassette i paper mode or manual paper feed mode, the controller sends the 8-bit serial code corresponding to each paper feed mode to the printer via the SC signal line in synchronization with the 5CLK pulse signal. Send. When the printer receives the cassette paper feeding mode code, the manual paper feeding roller 17 is not driven during printing, and the printer switches to a mode in which the paper feeding cam 3 is driven to feed paper from the cassette.

On the other hand, when the printer receives a manual paper feeding mode code, the paper feeding cam 3 is not driven during printing, but the manual feeding roller 17 is driven to switch to a mode in which manual paper feeding is possible.

Note that when the power of the printer is turned on for the first time, the printer sets the paper feeding mode to the "cassette paper feeding mode" as an initial mode.

GNR5T is used to initialize the printer by commands from the controller, and when the same signal is received from the controller, the printer resets all jobs midway through.
It is reset to the state immediately after power-on. For example, when a plurality of printers are connected to the controller, this signal is used to make all the connected printers have the same status.

In the configuration of the conventional example described above, the printer and the computer serving as the controller generally send and receive interface signals to and from each other via a connecting cable with a length of 1 m to several meters, as shown in Fig. 16. . The computers connected to the printer are not limited to one type, but are often of various types.

At this time, in conventional printers, the output dot density is fixed, and depending on the image processing speed of the computer to be connected and the required output dot density, for example, 20 dots with a dot density of 200 dots per inch are printed.
0dpi dedicated printer, similarly each 240dpi, 30
0dpi.

Like 400dpi, 480dpi dedicated printers, etc.
It was necessary to prepare a plurality of printers with a fixed number of output dots for each output dot density, and select a model from among these printers that met the requirements.

Other printers are equipped with an output dot density selector switch on the printer's operation panel, and the desired output dot density can be set manually by a service person or user according to the requirements of the connected computer, etc. I was getting it.

[Problems to be Solved by the Invention] If the output dot density of a printer is fixed, the types of printers will not only be diverse. Of these, AAA fif
It was not possible for users who purchased ffi to change the printing dot density.

On the other hand, in printers that change the dot density using a changeover switch, the dot density to be output is fixed in a bird-like manner by the changeover switch, and not only is it not easy to change it, but it also requires human intervention to adjust the dot density. I had to configure it.

Furthermore, it was not possible for the computer to know whether the set dot density was appropriate or not.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and as one means for solving the problems, for example, scanning a photosensitive surface with a laser beam. a scanning means for generating a reference clock for changing the output dot density of the printer; a frequency dividing means for dividing the reference clock generated by the clock generating means; The apparatus includes a designation means for designating the number of cycles, and a scan control means for controlling the laser beam scanning speed of the scanning means based on a clock frequency-divided by the frequency division number designated by the designation means.

[Operation] In such a configuration, the laser beam scanning speed can be changed by specifying the frequency division number in accordance with the output dot density to be printed.

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

[Configuration of Embodiment (FIGS. 1 to 6)] FIG. 1 is a block diagram of a laser beam printer according to an embodiment of the present invention, and the mechanism of this embodiment is approximately the same as FIG. 14. -, and the same components as in FIG. 14 are given the same numbers and their explanations will be omitted.

In the figure, 100 is a printer, and 200 is a computer that outputs output information to the printer 100 and controls the dot density etc. to be output by the printer 100, which will be described later.

Further, in the printer 100, 56 is a drum motor that rotates the photosensitive drum 11, 60 is a laser drive circuit that is controlled by a PCPU 66 via a data line 63, and drives the semiconductor laser 51 via a control line 57 in accordance with the control, and 61 is a drum motor that rotates the photosensitive drum 11. A polygonal mirror motor control circuit 62 controls the polygonal mirror motor 53 which is controlled by the PCPt 166 via the data line 64 and rotates the rotary polygonal mirror 52 via the control line 58;
The drum motor control circuit 62 also controls the PCPt1 via the data line 65.
66 and controls the rotation of the drum motor 56 via a control line 59.

Here, the drum motor 56 is also used as a drive source for paper conveyance via a gear (not shown).

Here, the image signal from the computer 200 is sent to the PCPU
66 from the data line 63 to the laser drive circuit 60
Instead of the configuration in which the laser beam is sent to the laser drive circuit 60 via the input/output interface 30, it is also possible to control the seed directly input to the laser drive circuit 60.

Further, 66 is a microprocessor (PCPU) that controls the entire printer 100, and pH:PU66 is a ROM memory 66a%f that stores a control program.
It has a built-in RAM memory 66b that stores control data for each ffi, and an I10 boat (not shown) that controls human output.

The PCPU 66 controls all the drive systems of the printer 200, such as the drive system for transporting and unloading the recording paper, the system for executing the electrophotographic process, etc., via the I10 boat. Only the drive system of the drive system and the connection and control of the sensor and optical system provided in the drive system are shown, and the others are omitted. However, it is of course possible to control other parts using known methods. be.

On the other hand, the computer 200 that controls the printer 100 includes an input/output interface 32 that performs serial communication and image communication with the printer 100. Note that 67 in the computer 200 is a C for executing various information processing.
It is PU.

The printer 100 and the computer 200 are connected via each other's input/output interfaces 30 and 32, a connection cable 38, and each other's I10 buses 34 and 36. The input/output signals via the connection cable 38 are similar to the configuration shown in FIG. 15 described above.

Reference numeral 69 denotes a switching means composed of a rotary switch or the like, and the PCPt 166 can read the set value of the switching means 69 via the data line 68 when necessary. In this embodiment, this switching means is used to switch the dot density to be output, and depending on the setting position of the switching means 69, the output dot density can be set to 240.
dpi.

It is determined as 300dpi, 480dpi, etc.

Further, 99 is a BD signal processing circuit that converts the photodetection signal from the beam detector 55 into a digital signal and outputs the digital signal.

Figure 2 shows details of the polygon mirror motor control circuit.

71 in FIG. 2 is a crystal oscillation circuit, and the crystal oscillation circuit 71
A 4 MHz clock oscillated by the counter 72 is output to the counter 72. 72 is the clock from the crystal oscillation circuit 71 (1/1
This is a counter that counts down to 000). Also 7
3 is a preset counter that counts down to 1/N according to the data "N" set by the latch circuit 74, and the output clock fO from the preset counter 73 serves as a reference signal for the PLL circuit 75.

That is, fo=4MIIZX (1/1000)
) There is a relationship between ゛.

Further, 74 is a latch circuit, and the latch circuit 74 has P
An arbitrary value (an arbitrary value from "°1" to "256") sent from the CPU 66 via the data line 78 is set. An 8-bit data line is output from the latch circuit 74 to the preset counter 73, and the preset counter 73 determines a countdown value (1/N) according to the set value of the latch circuit 74.

75 is a PLL circuit, and the PLL circuit 75 is a rotational pulse signal generator 7 that generates one pulse per rotation of the polygonal mirror motor 53 as the polygonal mirror motor 53 rotates.
The error signal is detected so that the signal fc obtained from 7 is equal to the reference frequency fo, and the rotation of the polygonal mirror motor 53 is controlled via the amplifier 76 based on the error signal.

In this case, the PLL circuit 75 is (7)-1 from the PCPU 66.
- It starts rotating upon receiving the overnight ON signal 79, and when the rotational speed of the polygon mirror motor 53 reaches the specified rotational speed and is rotating at a constant rate, a ready signal 80 is sent back to the PCPU 66.

Output dot density and each counter 72.7 in the above configuration
FIG. 3 shows the relationship between the number of output clocks and the number of rotations of the polygon mirror motor 53.

As shown in FIG. 3, the 4M) IZ oscillation frequency from the oscillation circuit 71 is divided in accordance with the output dot density, thereby changing the rotational speed of the polygon mirror motor 53 and rotating the polygon*.
By changing the scanning speed of the light beam 20 by 52, an arbitrary output dot density is obtained.

The PCPU 66 latches the data to the latch circuit 74 that latches the preset value to the preset counter 73.
via data line 78.

The PCP 066 reads the set value set in the switching means 69 via the data line 68, and latches a value corresponding to the set value in the latch circuit 74.

In addition to the control by the PCPU 66, the computer 2
00 to input/output interface 32, connection cable 3
When a specified dot density, for example 240 dpi, is specified directly to the latch circuit 74 in accordance with an output dot density specification command, which will be described later, and which is sent via 8, (
It is also possible to set a value such that N=100) in the latch circuit 74.

Note that the oscillation frequency by the crystal oscillator of the oscillation circuit 71 is
Polygon mirror motor 5 to obtain the required output dot density
Select by counting backwards from the rotation speed in 3. That is, the least common multiple of each fo value corresponding to the output dot density is selected.

Specifically, when each dot density shown in FIG. 3 is required, the required rotation speed of the polygon mirror motor 53 and the output frequency fO of the preset counter are also the values shown in FIG. f.

The least common multiple of is 13333.333 Hz.

In this embodiment, the oscillation frequency of the oscillation circuit 71 is set to an integral multiple (300 times) of this least common multiple, and 4M)Iz is selected.

In this manner, the scanning speed of the light beam 20 with respect to the surface of the photosensitive drum 11 can be arbitrarily selected according to a specified command from the computer 200 or according to the setting value of the switching means 69.

Furthermore, in the above embodiment, an example was explained in which an 8-bit counter was used as the preset counter 73 (for example, if the number of bits is increased, such as by using a 16-bit counter, the number of steps for switching the scanning speed becomes even more multi-stage). Needless to say, in 8 bits (2
B = 256 steps) was (218 = 65536 steps)
step switching becomes possible.

With this configuration, it is possible to meet all output dot density requirements.

Note that the content of the specification command sent from the computer 200 may be a specification of the dpi, or may be the data itself to be loaded into the preset counter.

Next, details of the drum motor control circuit 62 are shown in FIG.

In FIG. 4, 81 is an oscillation circuit, 82 is a counter, and 83
is a preset counter, 84 is a latch circuit, and 85 is a PL
The L circuit 86 is an amplifier, and since the configuration and role of each circuit are substantially the same as those of the polygon mirror motor control circuit 61 shown in FIG. 3, the explanation will be omitted.

Further, 87 is a rotational pulse generator that generates a pulse signal corresponding to the rotation of the drum motor 56.

89 is an ON signal for the drum motor 56, and 90 is a ready signal similar to the ready signal 80 in FIG.

Also in the drum motor control circuit 62, the computer 20
The feed speed of the drum motor 56 can be controlled to a predetermined speed in response to the output dot density designation command from 0 or the setting value of the switching means 69.

FIG. 5 is a diagram showing details of the BD signal processing circuit 99 shown in FIG. It is output as a signal and used for synchronization in the main scanning direction. Also, BD double signal BD
The signal is also input to an error detection circuit 92, and the BD error detection circuit 92 monitors whether or not the BD double signal is output at a regular timing. If the BD error signal is not output at the regular timing, a BD error signal is output to the PCPU 66.

Here, when the output dot density changes, the scanning speed of the light beam 20 also changes, and the BD double signal output timing also changes. Therefore, the PCPU 66 provides data corresponding to the output dot density described above to the BD error detection circuit 92. According to this data, the BD error detection circuit 92
For example, the output timing of the unblanking signal (UNBL) and the error detection auxiliary signal (ERDT) is switched as in the case of the preset counter shown in FIGS. 2 and 4 described above.

Here, the unblanking signal (UNBL) is a signal for causing the laser 51 to emit light at the timing when the light beam 20 reaches the beam detector 55 in order to reliably obtain a BD double signal.
The laser beam 51 is output to force the laser 51 to emit light at the timing of scanning immediately before the fifth section.

Further, the error detection auxiliary signal (ERDT) is a timing signal for determining whether or not the BD double signal detection timing is within a specified timing width range that varies depending on the output dot density.

That is, the unblanking signal (UNBL) is the previous B.
It is output a certain period of time after the D detection signal (a time slightly shorter than the BD signal generation cycle). In addition, the error detection auxiliary signal (ERDT) is detected after the previous BD multiplied signal and after the BD multiplied signal output period when the next BD multiplied signal is expected to arrive.
The time will be output. This Δ time may be a variable value corresponding to the output dot density, or may be a fixed value.

Unblanking signal (UNB) for output dot density
The output timings of the error detection auxiliary signal (ERDT) and the error detection auxiliary signal (ERDT) are shown in FIGS. 6(A) to 6(E).

Here, the dot density in FIG. 6(A) is 200 dpi, in FIG. 6(B) is 240 dpi, and in FIG. 6(C) is 300 dpi.
i, Figure 6 (D) is 400 dpi, Figure 6 (E) is 48
Each output timing in the case of 0 dpi is shown.

Here, if the BD signal is detected at the output timing of the error detection auxiliary signal (ERDT), it is determined that the BD signal output cycle is normal, and the BD signal is detected at a timing other than this error detection auxiliary signal (ERDT) output timing. When detected at the time of , or when not detected at all, a BD error signal is output to PCPl] 66 as a BD error.

In this manner, the BD error detection circuit 92 outputs an unblanking signal (UNBL) corresponding to the dot density to be output.
) and BD signal error detection timing is PCPt1
66, it is possible to select an (arbitrary) optimum value, and accurate scanning of the light beam can be performed even for an arbitrary output dot density, and scanning errors can be detected.

Further, details of the laser drive circuit 60 are shown in FIG.

In the figure, 94 is a latch circuit, 95a to 95e are NAND gates, 96a to 96e are driver transistors, and 97
A to 97e are resistors having different resistance values.

The laser drive circuit 60 turns on or clears the semiconductor laser 51 in response to an image signal sent from the computer 200.

In addition, in this embodiment, the drive current value for driving the semiconductor laser 51 is changed in accordance with the emission light amount designation data (laser emission light amount change command) of the semiconductor laser 51 sent from the PCPU 66 via the data line 63. Specifically, one of the latch circuits 94 is configured to
NAND connected to the set output
The gate is satisfied and an output corresponding to the image signal is performed.

Then, the selected driver transistor 96 for driving the laser is turned on/off according to the image signal, and the transistor 9
A current value corresponding to the resistance value of a resistor 97 connected to the collector side of the semiconductor laser 51 is supplied to the semiconductor laser 51. The semiconductor laser 51 emits light with an amount of light corresponding to the supplied current.

With the above configuration, when a command to change the amount of laser emitted light is received from the computer 200 via the I10 bus 34, the output of the latch circuit 94 corresponding to the corresponding transistor 96 is set, and the semiconductor laser 51 is activated at the specified amount of light. Emits light. In this way, since the computer 200 can arbitrarily change the amount of laser light, for example, in the graphic print output mode, the amount of laser light emitted is weakened,
Print output using thin dots can be selectively performed by increasing the amount of laser light emitted in the character print output mode, and printing output using thick dots can be selected.

[Operation of Embodiment] Next, the operation control of this embodiment, which is comprised of the above 41 components, will be explained below with reference to the flowcharts shown in FIGS. 8 to 13.

[First Operation (FIGS. 8 and 9)] The basic control procedure of this example will be described below with reference to the flowcharts of FIGS. 8 and 9.

When the laser beam printer of this embodiment is powered on, first, step SIO is executed to initialize the contents of the RAM 66b, and initialization processing such as rotating the rotating polygon mirror 52 is executed. Subsequently, in step S20, the computer 20
When the receiver receives a command, the receiver executes the command communication control routine that will be described later to execute communication processing of printer control commands with Processing corresponding to the taken command is executed, and the main routine of step S40 is executed. In the main routine, various known printer controls are executed.

Details of the command communication control routine shown in step 320 are shown in FIG.

First, in step S21, it is checked whether or not a printer control command has been sent from the computer 200. If it has not been received, the process returns without doing anything, and if it has been received, an output dot density notification request command is sent in step S22. Check whether it is received or not. If the output dot density notification request command is received, the process advances to step S23, and the output dot density currently set in the printer 100 is sent to the computer 2.
00, completes the processing for the received command, and returns. Note that the set output dot density is held in the RAM 66b.

On the other hand, if the output dot density notification request command is not received in step S22, the process proceeds to step S24, and it is checked whether an output dot density setting command for newly setting (resetting) the output dot density has been received. If the output dot density setting command is received here, step S2
Proceeding to step 5, the PCPII 68 first sets the latch circuit 74 of the polygon mirror motor control circuit 61 to a value corresponding to the designated output dot density included in the received setting command,
In the following step S26, a value corresponding to the similarly specified output dot density is set in the latch circuit 84 of the drum motor control circuit 62, and further, in step S27, a value corresponding to the output dot density is also set in the BD error detection circuit 92. do. As a result, the rotating polygon mirror 52, the photosensitive drum 11, and the BD signal processing circuit 99 perform operations that match the respective designated output dot densities, and the process ends and returns.

Further, if the printer control command received from the computer 200 in step S24 is not an output dot density setting command, the process advances to step S28, and it is checked whether or not a laser emission light amount change command has been received. Here, in the case of receiving a command to change the amount of laser emitted light, an output corresponding to the amount of emitted light is set in the latch circuit 94 of the laser drive circuit 60 in step S29. As a result, the semiconductor laser 51 will thereafter synchronize with the image signal and select the selected latch circuit 94.
Emit light with an amount of light corresponding to the output.

If it is determined in step S28 that a command for changing the amount of laser emitted light has not been received, the process proceeds to step S30, executes processing corresponding to the received command, and returns after completing the execution of the process.

[Second Operation (FIG. 10)] Next, another operation control of the above-described configuration of the present invention will be explained with reference to the flowchart of FIG. 10.

The same step numbers are assigned to the same controls as in FIG. 7. Therefore, the description of these steps will be omitted since they are the same.

After executing the command communication control routine in step S20,
In step S35, an output dot density setting command is already received from the computer 200, and it is checked whether the output dot density has been set according to the instruction from the computer 200. If it is not received here, step S20 is performed again.
The program returns to the command communication control routine and waits for the output dot density setting command to be received. If the output dot density setting command has already been received, the process advances to step S40, the main routine S40.

By controlling as described above, the printer 100 does not perform print processing or the like until the output dot density is specified by the computer 200. Therefore, it is possible to eliminate the problem of printing being executed while the dot density output by the printer 100 and the output dot density desired by the computer are different from each other.

[Third Operation (FIG. 11)] Next, still another operation control of the above-described configuration of the present invention will be explained with reference to the flowchart of FIG. 11.

The same step numbers are assigned to the same controls as in FIG. 10. Therefore, the description of these steps will be omitted since they are the same.

Here, after receiving the output dot density designation command in step S35, the PCPU 66 in step S36 outputs the rotary polygon signal 79 to the PLL circuit 75 of the polygon motor control circuit 61 in order to rotate the rotary polygon mirror 52. Set the mirror drive permission flag. As a result, a motor-on signal 29 is output, the polygon mirror motor 53 is rotated, and the rotary polygon mirror 52 is rotated.

In this operation, in the initialization process in step S10, control is not performed to output the polygonal mirror motor on signal 79 for driving the rotating polygonal mirror 52.

In this way, rather than having the rotating polygon mirror 52 constantly rotate from when the printer 100 is powered on to when it is powered off, the rotation of the polygon mirror 52 is controlled so that it does not start rotating until the output dot density is set, thereby controlling the rotation of the motor. Conventionally, when changing from one predetermined rotation speed to another predetermined rotation speed, especially if the difference in rotation speed is large, depending on the motor control circuit system, the motor may run out of control, for example, rotating at twice the rotation speed. However, according to this embodiment, such inconvenience can be eliminated.

[Fourth Operation (FIG. 12)] Next, another operation control of the above-described configuration of the present invention will be explained with reference to the flowchart of FIG. 12.

The same step numbers are assigned to the same controls as in FIG. 7. Therefore, the description of these steps will be omitted since they are the same.

Here, following the initialization processing routine in step S10, the output dot density of the printer 100 is set to a certain specific dot density (for example, 200 dpi, which is the lowest dot density that can be specified in this embodiment) in step 515, After this setting is completed, the process proceeds to step S20 and subsequent steps. This setting process is performed from step 325 to step S shown in FIG.
The same process as No. 29 is performed.

By controlling in this manner, the printer 100 is automatically set to a specific output dot density immediately after power is turned on, and operates at this specific output dot density until a new output dot density designation command is sent from the computer 200. When a new output dot density is designated by the computer 200, the output dot density is changed in accordance with the designation.

For this reason, in systems that do not require many changes to the output dot density and often print out using a specific output dot, it is not necessary to specify the output dot density each time by automatically setting this output dot density. It disappears.

[Fifth Operation (FIG. 13)] Next, another operation control of the above-described configuration of the present invention will be explained with reference to the flowchart of FIG. 13.

The same step numbers are assigned to the same controls as in FIG. 7. Therefore, the description of these steps will be omitted since they are the same.

Here, following the initialization routine of step SIO, the output dot density set in the switching means 69 is read in step Stt, and the latch circuits 74, 84 and
A value corresponding to the BD error detection circuit 92 is set. This process is performed from step 325 to step S shown in FIG.
The same process as No. 27 is performed. The process then proceeds to the command communication control routine of step S20.

By controlling in this way, the default value of the output dot density when the power of the printer 100 is turned on can be set to the setting value of the switching means 69, and an arbitrary output dot density can be selected, and the output dot density from the computer 200 can be changed to the default value set by the switching means 69. Only when the density is specified, the specified dot density can be set.

Therefore, it is possible to prevent unnecessary output dot density specification commands from being sent from the computer 200.

Further, the above explanation has been made only for an example in which the laser beam is scanned only in the horizontal direction on the photosensitive drum 11 by the rotating polygon mirror 52, but the invention is not limited to this, and the photosensitive section may be flat rather than drum-shaped. In some cases, a configuration may be adopted in which a galvanometer performs polarization scanning in the vertical direction, and the current supplied to the galvanometer may be controlled according to the output dot density using control corresponding to the scanning speed setting control similar to that described above.

Furthermore, the scanning of the laser beam is not limited to these methods. For example, when controlling the scanning of the laser beam using a hologram scanner, the rotation of the hologram disk can be controlled in the same way as described above to correspond to the output dot density. Just control it.

It is clear that these control methods are included in the present invention.

[Effects of the Invention] As explained above, according to the present invention, the dot density to be output can be easily changed.

Furthermore, it is possible to provide an easy-to-use laser beam printer in which the dot density can be arbitrarily selected using a computer connected to the printer.

[Brief explanation of drawings]

Fig. 1 is a block 93 diagram of one embodiment of the present invention, Fig. 2 is a detailed diagram of a polygonal mirror motor control circuit of this embodiment, and Fig. 3 is a polygonal mirror motor control diagram shown in Fig. 2. A diagram showing the relationship between the set value to the preset counter of the circuit, the rotation speed of the polygon mirror motor, and the output dot density, Figure 4 is a detailed configuration diagram of the drum motor control circuit of this embodiment, and Figure 5 is this embodiment FIG. 7 is a detailed block diagram and timing chart of the BD signal processing circuit of this embodiment; FIG. 7 is a detailed configuration diagram of the laser drive circuit of this embodiment; FIGS. Figure 15 is a diagram showing the mechanism of a conventional laser beam printer, Figure 15 is a diagram showing interface signals between a typical laser beam printer and a controller, and Figure 16 is a diagram showing a connection state between a typical printer and a computer. . In the figure, 1...paper, 2...paper feed cassette, 3...
Paper feed cam, 4... Paper feed roller, 5... Registration shutter, 6... Registration solenoid, 7... Conveyance roller, 8... Runner roller, 9... Paper discharge roller, 11.
...Photosensitive drum, 30.32...Interface,
51... Semiconductor laser, 52... Rotating polygon mirror, 53
... polygon mirror motor, 55 ... beam detector, 5
6... Drum motor, 60... Semiconductor laser drive circuit, 61... Polygon mirror motor control circuit, 62... Drum motor control circuit, 69... Switching means, 71.8
1...Oscillation circuit, 72.82...Counter, 73.
83...Preset counter, 74,84.94...
・Latch circuit, 75.85...PLL circuit, 92...
・BD error detection circuit, 95a to 95e...
N A N D gate, 98a to 96e: driver transistor, 99: BD signal processing circuit. Patent applicant Canon Co., Ltd. Figure 3 0α C) CL
()αo″o o″o
co-Of”)
Figure 11 Figure 12

Claims (5)

[Claims] (1) In a laser beam printer that forms an output image by scanning a laser beam onto a photosensitive surface using a scanning means, there is a clock generation means for generating a reference clock, and a frequency division of the reference clock generated by the clock generation means. a frequency dividing means, a specifying means for specifying a frequency division number of the frequency dividing means, and a laser beam scanning speed of the scanning means is controlled based on a clock frequency divided by the frequency dividing number specified by the specifying means. 1. A laser beam printer, comprising: a scanning control means, wherein the laser beam scanning speed can be changed by specifying the frequency division number in accordance with the output dot density to be printed. (2) Equipped with a communication means for data communication with an external device,
2. The laser beam printer according to claim 1, wherein the number of frequency divisions specified by the specifying means can be specified from an external device via the communication means. (3) The scanning means includes a rotating polygon mirror and a drive motor for the rotating polygon mirror, and the scanning control means controls the rotation of the drive motor. laser beam printer. (4) The oscillation frequency of the reference clock generated by the clock generation means should be an integral multiple of the least common multiple of the rotation drive timing frequencies of the drive motors that are rotated at a rotation speed corresponding to the output dot density that should be possible. A laser beam printer according to any one of claims 1 to 3, characterized in that: (5) The laser beam printer according to any one of claims 1 to 4, wherein the scanning means includes a galvanometer, and the scanning control means controls the current supplied to the galvanometer.