JPS62162550A - Laser beam printer - Google Patents

Abstract

PURPOSE:To enable a dot density to be output to be changed easily by providing an output dot density designation means, a printing means at designated dot density and a data communication means with an external device, and making it possible to designate a dot density to be output by the communication means from the external device. CONSTITUTION:One of latching circuits 94 is set in accordance with data for designation of quantity of light for light emission of a semiconductor laser (command for changing the quantity of emission of laser light) to be transmitted from PCPU 66 via a data line 63. Then NAND gate 95 connected to an output set is satisfied, making an output corresponding to an image signal. After this, a driver transistor 96 for laser drive selected is turned ON/OFF according to an image signal, and a current value corresponding to a resistor value 97 on the collector side is supplied to the semiconductor laser 51, emitting a quantity of light corresponding to a supplied current. Thus it is possible to perform printing by selecting a printing output depending on thin or thick dots corresponding to a command for variation of quantity of emission of laser light, if this command is received from a computer through I/O bus 34.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of 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 J A laser beam printer is widely known in which a latent image is formed by scanning a laser beam on a rotating tram using a rotating polygon mirror, and after development, the image is recorded by transferring it to paper. It is something.

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

In FIG. 14, 1 is a sheet of paper that is a recording medium, and 2 is a paper cassette that holds the sheet of paper 1. In FIG. 3 is paper cassette z
The paper is fed by a paper feed cam that separates only the topmost sheet of the paper l placed on top 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; 1 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 roller 4.4' rotates while lightly pressing the paper 1, thereby conveying the paper 1. When the paper l is transported and the leading edge reaches the registration shutter 5 position, the transport of the paper l is stopped by the registration shutter 5, and the paper feed rollers 4, 4
' continues to rotate while generating conveyance torque while slipping against the paper l. In this case, by driving the registration shutter 5 and releasing the registration shutter 5 upward, the paper l 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 being focused on the photosensitive drum ll. 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 times signal which is the image writing timing in the main scanning direction by detecting the beam 20.

Thereafter, the paper l is conveyed by the conveyance rollers 7, 7' instead of the paper feed rollers 4, 4', and is conveyed to the photosensitive drum 11 section. Here, the image exposed on the photosensitive drum 11 is transferred onto the paper 1 by the cooperation of the cleaner 12, the charger 13, the developer 14, and the transfer charger 15.The paper 1 on which the 0 image has been transferred is then transferred to the fixing roller. The sheet is fixed by rollers 8 and 8', and is discharged onto a stacker 10 by discharge rollers 9 and 9'.

In addition, in the figure, A is a guide for regulating the conveyance direction of the paper l.

Reference numeral 16 denotes a paper feed tray, which allows not only paper feeding from the paper cassette 2 but also manual feeding of sheets one by one from the paper feed tray 16. The paper fed into the gap between the upper manual paper feed roller 17 is lightly pressed by the manual paper feed roller 17, and the leading edge of the paper reaches the registration shutter 5 in the same way as the paper feed rollers 4 and 4'. It is transported to a point 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 nermistor 23 that makes slip contact with the roller surface, and the recorded image on the paper l 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 signal indicates that the power of the river control signal port controller is turned on and is 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 PRNT 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, when RUE is detected.

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 double 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 COMMAND, 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.This signal is sent and received by both the controller and printer. A 5CLK signal, which will be described later, is used as a synchronization signal when doing so. Further, since it is a bidirectional signal, a 5BSY signal and a CBSY signal, which will be described later, are used for input/output control.

Also, COMMAND here is a serial signal consisting of 8 bits, and for example, only the fixing heater of the printer is turned off.
A paper feed command to set the so-called paper feed state yE to maintain an energy-saving state, a paper feed release command to cancel the paper feed state and turn on the fixing heater, and a cassette to feed paper from the paper cassette. It includes various control commands for the printer, such as a paper feed command and a manual paper feed command for manually feeding paper.

5TATUS 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 GOMMAND or for the controller to capture 5TATUS.

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

CBSY signal: A signal for occupying the SC signal line and the 5CLK signal line before the controller transmits COMMAND.

GNR8T 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 its internal state and then transmits the PPRDY signal to the controller. On the other hand, after initializing the internal state of the controller, the controller
Send a Y signal to the printer. After that, the printer starts using the fuser heater 2 housed inside the fuser roller 8.8'.
When the temperature of the surface of the fixing rollers 8, 8' reaches a temperature that allows fixing, an RDY signal is sent to the controller.

After receiving the RDY signal, the controller transmits a PRNT signal to the printer as required for printing.

When the printer receives the PRNT signal, the photosensitive drum 11
is rotated to uniformly initialize the potential on the photosensitive drum surface, and at the same time, in the cassette paper feeding mode, the paper feed cam 3 is driven to transport the leading edge of the paper to the registration rough 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 vDO to be recorded to the printer in synchronization with this signal.

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

Next, when switching the printer's paper feeding mode to cassette paper feeding mode or manual paper feeding mode, the controller sends the 8-bit serial code corresponding to each paper feeding 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.

GNR3T is for initializing 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 conventional structure described above, the printer and the computer serving as the controller generally exchange interface signals with each other via a connecting cable with a length of 1 meter to several meters, as shown in FIG. And the computer connected to the printer is not limited to one type.
There are often many different types.

At this time, in conventional printers, the output dot density is fixed.2 Depending on the image processing speed of the computer to be connected and the required output dot density,1.
0dpi dedicated printer, similarly each 240dpi, 30
0dpi.

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

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. It was impossible for users who purchased a single model 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.

The following margin [Means for solving the problem] The present invention has been made in order to solve the above-mentioned problem, and as a means to solve this problem, for example, the output dot density can be changed. The apparatus includes a designating device for specifying switching, a printing device for printing at a density specified by the specifying device, and a communication device for performing data communication with an external device.

[Operation] In this configuration, the output dot density by the specifying means can be specified by an external device via the communication means.

[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 PCPU 66 via the data line 64 and rotates the rotary polygonal mirror 52 via the control line 58 in accordance with the control, and 62 is the drum motor 56.
The drum motor control circuit 62 is also connected to PC:PH1 via a data line 65.
6 and controls the rotation of the drum motor 56 via the control 2-in 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 signal is sent to the laser drive circuit 60 via the input/output interface 30, the control may be such that the signal is directly input to the laser drive circuit 60.

Further, 66 is a microprocessor (PCPU) that controls the overall control of the printer 100, and the PCPU 66 includes a ROM memory 66a that stores a control program, a RAM memory 66b that stores various control data, and an I10 board that controls input and output. (not shown) is built-in.

The pcpus s controls all drive systems of the printer 200, such as a drive system for transporting and unloading recording paper, a system for executing an electrophotographic process, etc., via the I10 port.

Here, only the recording paper drive system and the connection and control of the sensor and optical system provided in the drive system are illustrated, and the others are omitted. However, it goes without saying that other parts can also be controlled using known methods.

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 have mutual input/output interfaces 30, 32, and connection cables 38. They are connected via each other's I10 paths 34.36. 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, etc., and the PCPU 66 switches the switching means 6 when necessary.
A set value of 9 can be read in via data line 68. 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 is set to 240d.
pi.

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
The 4 MHz clock oscillated at 2 is output to the counter 72. 72 is the clock from the crystal oscillation circuit 71 (1/
1000). Further, 73 is a preset counter that counts down to 17 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=4MHzX (1/1000)X (1/N
).

Further, 74 is a latch circuit, and the latch circuit 74 has P
Any value sent from the CPU 66 via the data line 78 (any value from "1" to "256°")
is set. An 8-bit data line is output from the latch circuit 74 to the preset counter 73.
The preset counter 73 determines a countdown value (1/N) according to the setting 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, PLL circuit 754iPCPU66 colors (7)%
- upon receiving the polygon mirror ON signal 79, the polygon mirror motor 53 starts rotating, and when the number of rotations of the polygon mirror motor 53 reaches the specified number of rotations 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 oscillation frequency of 4 MHz from the oscillation circuit 71 is divided in accordance with the output dot density, thereby changing the rotation speed of the polygon mirror motor 53 and rotating the polygon mirror 5.
An arbitrary output dot density is obtained by changing the scanning speed of the light beam 20 according to No. 2.

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 PCPυ 66 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 input/output interface 32. According to the output dot density designation command, which will be described later, and which is sent via the connection cable 38, the dot density designated directly to the latch circuit 74, for example, when 240 dpi is designated, the value (N = l OO) is set. It can also be set 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 rotational 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 the case of the nut side tilt, the oscillation frequency of the oscillation circuit 71 is set to an integral multiple (300 times) of this least common multiple, and 4 MHz 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, but if the number of bits is increased, for example, by using a 16-bit counter, the number of steps for switching the scanning speed will increase accordingly. 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 error detection circuit 92 is also manually operated, 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 PC:PO 26 supplies data corresponding to the output dot density described above to the BD error detection circuit 92. The BD error detection circuit 92 adjusts the output timing of the unblanking signal (UNBL) and the error detection auxiliary signal (ERD T) according to this data, for example, like the preset counter shown in FIGS. 2 and 4 above. Switch.

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 the BD double signal. 5
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). Additionally, the error detection auxiliary signal (
ERDT) is output at a time interval of ±Δ with a BD double signal output period between which the previous BD double signal and the next BD double signal are expected to arrive. 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) ff30.
0dpi, flB6 figure CD) + f400dpi, ff
Each output timing in the case of 00dpi and 480dpi is shown.

Here, if the BD double 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 double signal is output as the error detection auxiliary signal (ERDT). When detected at a time other than the timing, or when not detected at all, a BD error signal is output to the PCPt 166 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 double signal error detection timing is PCPU6
6, 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 PCPυ66 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 the Embodiment] Next, the operation control of the embodiment configured as described above 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 on the actual side will be described below with reference to the flowcharts of FIGS. 8 and 9.

When the power of the laser beam printer of this embodiment is turned 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 described later that executes the communication processing of the printer control command between the receiver and the receiver. 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.

FIG. 9 shows details of the command communication control routine shown in step S20.

First, in step 321, 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. The set output dot density is RAM66b
It is held inside.

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
5, the PCPU 66 first sets a value corresponding to the specified output dot density included in the received setting command in the latch circuit 74 of the polygon mirror motor control circuit 61, and then in step 526 sets the latch circuit 74 of the polygon mirror motor control circuit 61 to a value corresponding to the specified output dot density included in the received setting command. A value corresponding to the similarly specified output dot density is set in the launch circuit 84, and a value corresponding to the output dot density is also set in the BD error detection circuit 92 in step S27. As a result, the rotating polygon mirror 52. The photosensitive drum 11 and the BD signal processing circuit 99 perform operations consistent with the respective designated output dot densities, and the process ends and returns.

Further, if the printer control command received from the computer 200 at step 324 is not an output dot density setting command, the process proceeds to step 328, where it is checked whether a command for changing the amount of laser emitted light 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 synchronizes with one image signal and selects the latch circuit 94.
Emit light with an amount of light corresponding to the output.

If it is determined in step 528 that a command to change 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 processing.

[Second Operation (10th UgJ)] 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 520,
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 main routine 540 in step S40.

By controlling as described above, the printer 100 does not perform print processing until the output dot density is specified by the computer 200, so that the dot density output by the printer 100 and the output desired by the computer are adjusted. It is possible to eliminate the problem of printing being executed with the dot density misaligned.

[Third Operation (FIG. 11)] Next, still another operation control of the above-described configuration of the present invention will be described 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, in step S36, the PCPυ66 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 510, 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 S15, After this setting is completed, the process proceeds to step 320 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 in step 310, the output dot density set in the switching means 69 is read in step Sll, 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 printer 100 is turned on can be set to the setting 1 of the switching means 69, and an arbitrary output dot density can be selected, and the output from the computer 200 can be set to 1. The specified dot density is set only when the dot density is specified.

Therefore, it is possible to prevent the computer 200 from transmitting unnecessary dot density designation commands.

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 may be controlled in the same manner as described above to correspond to the output dot density. It can be controlled by

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 density of dots 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 configuration diagram of an embodiment according to the present invention, Fig. 2 is a detailed configuration diagram of a polygon mirror motor control circuit of this embodiment, and Fig. 3 is a preset counter of the polygon mirror motor control circuit shown in the WIJz diagram. Figure 4 shows the detailed configuration of the drum motor control circuit of this embodiment, and Figure 5 shows the BD signal processing of this embodiment. Detailed circuit block diagram, timing chart, Figure 7 is a detailed configuration diagram of the laser drive circuit of this embodiment, Figures 8 to 13 are operation flow charts of each embodiment according to the present invention, Figure i14 is a diagram of the conventional laser A mechanical diagram of a beam printer. FIG. 15 is a diagram showing an interface signal between a general laser beam printer and a controller. FIG. ff116 is a diagram showing a connection state between a general printer and a computer. In the figure, ■...Paper, 2...Paper cassette, 3...
Paper feed cam, 4... Paper feed roller, 5... Registration shutter, 6... Registration solenoid, 7... Conveyance roller, 8... Fixing 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, 8200. counter, 73
．． 83...Preset counter, 74.84.94.
...Latch circuit, 75.85...PLL circuit, 92.
・・BD error detection circuit, 95 a ~ 95 e −・
-N A N D gate, 96a to 96e... dry/to transistor, 99... BD signal processing circuit. 0α 0α 0α0
℃ 0″0a)-O('Q
Arm 1111 Figure 12

Claims (5)

[Claims] (1) In a laser beam printer that scans a photosensitive drum with laser light in a raster pattern to form an output image,
The apparatus includes a specifying means for switching and specifying the dot density to be output, a printing means for printing at the specified density of the specifying means, and a communication means for performing data communication with an external device, and the output dot density by the specifying means is changed through the communication means. A laser beam printer is characterized in that it can be specified by an external device. (2) Claim 1 characterized in that the printing means is not activated until the output dot density is designated by the communication means.
Laser beam printer as described in section. (3) Starting of a polygonal mirror motor that rotates a rotating polygonal mirror for scanning a photosensitive drum surface with a laser beam is prohibited until the output dot density is designated by the communication means, as claimed in claim 1. Or the laser beam printer according to item 2. (4) The laser beam printer according to claim 1, wherein the laser beam printer prints out at a specific output dot density when the output dot density is not designated by the communication means. (5) A setting means for setting the output dot density is provided, and when the output dot density is not specified by the communication means, the output dot density set by the setting means is printed out as a specific output dot density. A laser beam printer according to claim 4.