JPH03173661A - image forming device - Google Patents

Abstract

PURPOSE:To enable correction of density through a simple circuit by varying the pulse width of a PWM image signal on the printer side. CONSTITUTION:Print conditions and the like are transmitted from a host computor 1 to a printer 2 through a command status signal lines, and a response is transmitted in the form of status from the printer 2 to the computor. A pulse width modulated VIDEO signal 4 is then transmitted to the printer 2 in synchronization with a VIDEO clock 5. The VIDEO signal is subjected to pulse width modulation through a density setting circuit 6 and inputted to a laser driver 8 thus driving a semiconductor laser 9 and performing printing operation. When a density switch 10 is turned ON, pulse width of the VIDEO signal 4 is widened through a density volume 7 to enhance the print density, whereas when the density switch 10 is turned OFF the pulse width is constricted to lighten the density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that inputs an image signal as a pulse width modulation signal and forms an image.

[Prior Art] Conventionally, in laser beam printers capable of intermediate density printing, image data with a pulse width corresponding to the density of the image data is input from a host computer, and the printer performs intermediate density printing using that image data. It is configured.

Here, the operation will be explained below with reference to FIGS. 9 and 10.

FIG. 9 is a schematic block diagram showing the configuration, and FIG. 10 is a timing diagram showing each signal between the host computer and the printer.

First, when a command such as printing conditions is sent as a command from the host computer 1 shown in FIG. 9 onto the command/status signal line 3, the printer 2 sends a reply or the like corresponding to the command as a status. Then, the host computer 1 determines the status, and if it is possible to print, sends the image data to the printer 2.
A DEO signal 4 and a VIDEO clock 5 which is an image clock are transmitted.

Next, in the printer 2, when the laser driver 8 is driven according to the VIDEO signal 4, the semiconductor laser 9 outputs laser light. The laser beam is irradiated onto the photoreceptor drum by a polygon mirror (not shown) to form an electrostatic latent image. Then, toner is attached to the electrostatic latent image, and the visualized toner image is transferred and fixed onto the transported printing paper to perform printing.

FIG. 10 is a diagram showing the timing of each signal 4 and 5 in the above operation. As described above (, host computer 1
A VIDEO signal 4 which is pulse width modulated and expresses the image density in pulse width is sent to the printer 2 in synchronization with the rising edge of the VIDEO clock 5. In the printer 2, the laser driver 8 is driven according to the pulse width of the VIDEO signal 4 (the irradiation time of the semiconductor laser 9 is controlled i1) to perform intermediate density printing.

That is, when the pulse width of the V I DEO signal is long, the concentration is high, and when it is short, the concentration is low.

[Problems to be Solved by the Invention] However, the above conventional example has the following drawbacks.

For example, in a printer of 300 DPI (print density of 300 dots per line), the VIDEO clock 5 is approximately 2 MH2. Also, when converted into a period, it is 500ns
becomes. When printing at an intermediate density of 16 gradations, it is necessary to have the ability to divide one dot into 16 parts.
The pulse signal of 500÷1631.25ns is V I D
Blink 2 from host computer 1 as EO signal 4
and sent via cable.

Therefore, when a pulse is transmitted using a thin cable, the pulse width of the VIDEO signal changes depending on the type and length of the cable, the influence of temperature and humidity around the printer, and variations in electronic components inside the printer. This has the disadvantage that the printing density is unstable.

The present invention was made to solve the above problems, and
An object of the present invention is to provide an image forming apparatus that enables density correction by making the pulse width of image information variable.

[Means for Solving the Problems] In order to achieve the above object, an image forming apparatus of the present invention has the following configuration. That is, in an image forming apparatus that manually inputs a pulse width modulated image signal and forms an image based on the image signal, there is an input means for inputting the image signal, and a pulse width correction of the image signal inputted by the human input means. and an image forming means that forms an image based on an image signal whose pulse width has been corrected by the pulse width correction means.

Preferably, the pulse width correction means includes a setting means for setting the pulse width to be thick or narrow, and the pulse width is corrected according to the setting means.

Furthermore, preferably, one aspect is that the setting means is set by an external command or by a switch installed in the printer.

Preferably, one aspect of the pulse width correction means is to correct the pulse width to be thicker or narrower depending on the surrounding environment of the image forming apparatus.

[For use] In the above configuration, a pulse width modulated image signal is input, the pulse width of the image signal is corrected, and an image is formed based on the pulse width corrected image signal. .

Further, the pulse width correction is performed according to the setting to make the pulse width thicker or narrower.

Further, the settings are made by an external command or by a switch installed in the printer.

Furthermore, the pulse width correction is performed to make the pulse width wider or narrower depending on the surrounding environment of the image forming apparatus.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First Embodiment> FIGS. 1 to 3 are diagrams showing a first embodiment according to the present invention. Figure 1 is a block diagram including the interface between the host computer and printer, and Figure 2 is a block diagram including the interface between the host computer and printer.
FIG. 2 is a diagram showing details of the density setting circuit shown in FIG. 1; FIG. 3 is a timing diagram of each signal.

Commands such as printing conditions are transmitted as commands from the host computer 1 in FIG. 1 to the printer 2 using command/status signal lines. The printer 2 then transmits the response and the like as a status to the host computer.

Thereafter, the pulse width modulated VIDEO signal 4 is sent to the printer 2 in synchronization with the VIDEO clock 5.

The VIDEO signal has its pulse width changed by a density setting circuit 6 and is input to a laser driver 8, which drives a semiconductor laser 9 to irradiate a photoreceptor drum (not shown) to print by electrophotography.

FIG. 2 shows a specific circuit example of the density setting circuit 6 shown in FIG. In the figure, 7 is a density adjustment volume, 10 is a density changeover switch, icl, ic2 is a buffer, ic3. ic4
．． ic5 is exclusive OR (EXCLUSIVE-OR)
, i ce is a logical sum (OR).

Further, as shown in FIG. 3, the VIDEO signal 4 is integrated according to a time constant determined by the density adjustment volume 7 and the capacitor C1. The integrated signal is ic2
, and outputs a signal delayed from VIDEO signal 4. Then, turn ON10 F F of the light/dark changeover switch 10.
Therefore, the pulse width is wide or narrow (output).

According to the first embodiment with the above circuit configuration, when the density changeover switch 10 is ON, the pulse width of the V I DEO signal 4 is widened by the density adjustment volume 7, and the print density can be increased.

Further, when the density changeover switch 10 is OFF, the pulse width of the VIDEO signal 4 becomes narrower by adjusting the density adjustment volume 7, and the print density can be reduced.

<Second Embodiment> Next, a second embodiment according to the present invention will be described below with reference to FIGS. 4 to 6.

In the second embodiment, a case will be described in which the print density is specified by a command from the host computer 1. Components with the same functions as those in the first embodiment are given the same reference numerals, and explanations thereof will be omitted.

FIG. 4 shows host computer 1. 2 is a block diagram including an interface between printers 2. FIG.

In the figure, 11 is a command discrimination circuit for discriminating commands from the host computer 1, and 12 is a density setting circuit IT in the second embodiment. When the host computer 1 sends a command specifying the print density to the command discrimination circuit 11 of the printer 2, the command discrimination circuit 11 outputs a 2-bit density specification signal, which will be described later, to the density setting circuit H12.

FIG. 5 is a diagram showing a specific circuit example of the density setting circuit II 12. In the figure, the above-mentioned 2-bit density designation signal is the input DB, D of the D/A converter 13 in FIG.
2b it is input. The relationship between input signal 1 and output voltage is shown in the following table.

Table Human output relationship of D/A converter In the second embodiment, the VIDEO signal 4 blunted by C2°R1 and the output of the D/A converter 13 are input to the comparator 14, and the VIDEO
The print density is changed by changing the pulse width of the signal (6th
(see figure).

That is, when a command specifying the darkest printing is sent from the host computer 1, the command discrimination circuit 11 shown in FIG. 4 outputs a 2-bit signal "OOB". This signal is then input to the D/A converter 13 shown in FIG. 5, and its output voltage becomes 0.9375 [V]. This state is the comparator output 4 shown in FIG.

In this way, according to the second embodiment, the density of the printout image can be adjusted using commands from the host computer.

In addition, in the above-mentioned embodiment, the process of widening the pulse width of the VIDEO signal was explained, but the process of narrowing the pulse width also applies.
Of course it's good.

Third Embodiment> Next, FIG. 7 is a schematic block diagram showing a third embodiment according to the present invention.

In this embodiment, the temperature sensor 17 and humidity sensor 1 shown in the figure are
8, the temperature and humidity sensors inside the printer 2 convert it into an electrical signal, input the electrical signal to the processing circuit 15, and send a 2-bit control signal to the density setting circuit I1116 to set the density.

Therefore, according to this embodiment, it is possible to correct changes in print density due to temperature and humidity inside the printer.

<Fourth Embodiment> FIG. 8 is a diagram showing an example of output from a binary printer that prints out characters. As shown in the figure, a case is shown in which smoothing is performed on a hatched portion 80, and the smoothing is indicated by a dot 81 which is a fraction of an l dot. And the signal of this smoothing dot 81 is also
Similar to the first to third embodiments described above, it is also possible to input a pulse width modulated VIDEO signal from the host computer.

Furthermore, in the above embodiment, the host computer performs pulse width modulation and transmits it to the printer. However, a pulse width modulation unit is provided between the host computer and the printer, and the pulse width modulation unit It may also be configured to pulse width modulate the multivalued image signal from the computer and send it to the printer.

[Effects of the Invention] As explained above, according to the present invention, density correction can be performed with a simple circuit by changing the pulse width of a pulse width modulated image signal on the printer side. be.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic block diagram in the first embodiment, FIG. 2 is a diagram showing details of the concentration setting circuit in the first embodiment, and FIG. 3 is a diagram showing the details of the concentration setting circuit in the first embodiment. Timing chart, FIG. 4 is a diagram showing a schematic block diagram in the second embodiment, FIG. 5 is a diagram showing details of the concentration setting circuit II in the second embodiment, and FIG. 6 is a diagram showing the details of the concentration setting circuit II in the second embodiment. Timing chart of each signal, Fig. 7 is a diagram showing a schematic block diagram in the third embodiment, Fig. 8 is a diagram showing an output example in the fourth embodiment, and Fig. 9 is a schematic block diagram in the conventional example. , FIG. 10 is a timing chart of each signal in the conventional example. In the figure, l... post computer, 2... printer, 3...
... 6 Command/status signal line, 4... VIDEO signal, 5... VIDEO clock, 6... Concentration setting circuit, 7... Concentration adjustment volume, 8... Laser driver, 9... It is a semiconductor laser. 7 8

Claims (1)

[Scope of Claims] (1) An image forming apparatus that inputs a pulse width modulated image signal and forms an image based on the image signal, comprising: an input means for inputting the image signal; and an input means for inputting the image signal. An image forming apparatus comprising: a pulse width correction means for correcting the pulse width of an image signal; and an image forming means for forming an image based on the image signal subjected to the pulse width correction by the pulse width correction means. (2) The image forming apparatus according to claim 1, wherein the pulse width correction means includes a setting means for setting the pulse width to be thick or narrow, and the correction is performed according to the setting means. (3) The image forming apparatus according to claim 2, wherein the setting means is set by an external command or a switch of the image forming apparatus. (4) The image forming apparatus according to claim 1, wherein the pulse width correction means corrects the pulse width to be thicker or narrower depending on the surrounding environment of the image forming apparatus.