JPS62236254A - Laser beam printer - Google Patents

Abstract

PURPOSE:To classify a printed place corresponding to a designated color in a printing way by making variable the size of the printing dot even when the developer or the developing unit of a color designated by color designating information inputted from an external device does not exist. CONSTITUTION:A printer controller 10, based upon a coded image signal sent to an image processor 12 from a host computer 13, has a function to generate a laser modulating signal to drive a semiconductor laser in a laser unit 9 and controls the whole of a printer. Further, in the printer controller 10, a pulse modulating circuit 10a is held, when the developer designated by a color designating command does not exist or a developing device itself is not set, the pulse modulating means pulse-width-modulates the exposing time of a laser beam 11 and makes variable the dot size of a place corresponding to the designated color.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention irradiates a laser beam onto a photoreceptor to form a latent image, and develops the formed latent image with a developing device of a predetermined color to produce a color image. The present invention relates to a laser beam printer that forms images.

[Conventional technology]

Conventionally, in a laser beam printer using an electrophotographic process, a laser beam modulated by an image signal is transmitted through a rotating prism or reversing mirror (scanner).
An image is formed by being reflected by and scanning an electrophotographic photoreceptor. In this case, a drum-shaped photoreceptor is mainly used. When applying this method to a color printer, it is necessary to superimpose a plurality of images of different colors on recording paper. The following systems have been proposed as main configurations for achieving this superposition technology.

That is, a first color image signal is scanned onto a photosensitive drum to form a latent image, a developer is attached to it for visualization, this is transferred to recording paper, the photosensitive drum is then cleaned, and a second color image is formed again. A signal is scanned onto the same photosensitive drum, a latent image is created, and the same process as the first process is performed. However, the second color developer is used. In addition, the third color, the fourth color,
The same process is repeated for the image signal of the nth color. In this way, one image is recorded by superimposing the development multiple times on the same recording paper.

In a multicolor laser beam printer configured as described above, the color to be printed is normally specified by a host computer or controller that is directly connected online. For example, set the text font to black,
Rules and underlines should be specified in red.

[Problem that the invention seeks to solve]

However, if the developer of the color specified by the host does not exist, an error status such as "specified color does not exist" is returned to the host, making printing impossible. Alternatively, the color specification from the host side is ignored and the default color, for example black, is used for printing instead of the specified color.

For this reason, as mentioned above, in a multicolor laser beam printer, if the specified color does not exist, the printing operation will stop or, for example, the specified color will become the same color as the default color. As a result, it becomes impossible to clearly distinguish between the font and the specified color, leading to problems such as the inability to print as intended.

This invention was made in order to solve the above problems, and even if there is no developer or developing unit of the specified color, the size of the printed dots can be varied to print the specified color. It is an object of the present invention to provide a laser beam printer that can distinguish printing locations corresponding to the following.

[Means for solving problems]

The laser beam printer according to the present invention changes the dot size at a location corresponding to the color specified by the color specification information when there is no developer or developing means corresponding to the color specification information input from an external device. A printing control means for printing is provided.

[Effect]

In this invention, if there is no developer or developing means corresponding to color designation information input from an external device, the print control means changes the dot size at the location corresponding to the designated color.

〔Example〕

FIG. 1 is a cross-sectional view illustrating the configuration of a multicolor laser beam printer showing an embodiment of the present invention. Reference numeral 1 denotes a photosensitive drum. 3. Pre-transfer charger4. Cleaner 5. A transfer charger 6 is provided, and the developing devices 2 and 3 are connected to the photosensitive drum 1.
The electrostatic latent image formed is developed into black or red, for example. Reference numeral 7 denotes a conveyance path through which recording paper fed from the paper feed cassette 14 is conveyed in the direction of the arrow. A fixing device 8 fixes the toner image transferred to the recording paper using heat and pressure.

A laser unit 9 includes a semiconductor laser (not shown), a scanner, and a laser optical system, and generates a modulated laser beam 11 sent out from a printer control device 10 (also serving as a print control means of the present invention). An image processing device 12 performs predetermined image processing on image information sent from a host computer 13 (external device), and then outputs an image signal to the printer control device 10. The printer control device 10 has a function of generating a laser modulation signal to drive the semiconductor laser in the laser unit 9 based on a coded image signal sent from the host computer 13 to the image processing device 12, and has a function of generating a laser modulation signal to drive the semiconductor laser in the laser unit 9. control the whole thing.

Reference numeral 15 denotes a flapper for selecting the conveyance path of the recording paper. 16
The recording paper on which 11 images have been formed is stored in the paper discharge tray. The image processing device 12 has a page memory that stores one page of image information for the developing device 2.3 in a bitmap image. Further, while the developing device 2 is performing development, the developing device 3 moves away from the photosensitive drum 1.
When performing development using the developing device 3, the developing device 2 is configured to move away from the photosensitive drum 1, and the developing device 3 approaches the photosensitive drum 1. 17 is an interface for communicating between the host computer 13 and the image processing device 12;

18 is a video interface through which the image processing device 12 communicates dot data to the printer control device 1o using a rask scanning method. A transport roller 19 transports the recording paper fed from the paper feed cassette 14 toward the photosensitive drum 1, and transports the printed recording paper that has been circulated in the printer by the flapper 15 toward the photosensitive drum 1 again. Note that the printer control device 10 includes a pulse modulation circuit 10a, which will be described later, and when there is no developer specified by the color designation command, or when the developer itself is not set, this pulse modulation circuit is activated. changes the amount of laser light for the specified print information.

Next, while referring to Figures 2, 3 (a) and (b),
The printing operation of the multicolor laser beam printer shown in the figure will be explained.

FIG. 2 is a block diagram illustrating an interface between the printer control device 10 and the image processing device 12 shown in FIG. 1, and the same components as in FIG. 1 are given the same reference numerals.

In this figure, PRINT is a print signal that is sent from the image processing device 12 to the printer control device]O to prompt the printer to feed paper. VIDEO is image data, and horizontal synchronization signal H3YN is sent from the image processing device 12.
C and the vertical synchronization signal VSYNC to the printer control device 10. VCLK is an image clock and is used as a clock for conveying image data VIDEO. ST is a serial communication line that communicates the internal status of the printer, control commands from the image processing device 12, etc. to the printer control device 10. Note that after the horizontal synchronization signal H3YNC rises, the image data VI
By varying the sending timing of DEO, it is possible to adjust the margin formed at the left end of the conveyed recording paper, and the image data VI D is started after the vertical synchronization signal VSYNC rises.
By varying the EO sending timing, the amount of blank space formed at the leading edge of the conveyed recording paper can be adjusted.

FIGS. 3(a) and 3(b) are timing charts illustrating the sending timing of each signal shown in FIG. 2. In addition,
Figure (a) shows the image sending timing of the vertical scanning system,
FIG. 5B shows the image sending timing of the horizontal scanning system.

The image processing device 12 selects one page of code data.
First, the code data corresponding to the first specified color or default color is expanded into bitmap data.
Before the image processing device 12 sends out the developed data, the printer control device 1o
A “color specification command (for example, black)” is sent to the device. Then, the image processing device 12 outputs the print signal PRINT to T.
Set R1JE (HIGH) to start printing. The image processing device 12 receives a vertical synchronization signal VSYNC and a horizontal synchronization signal HSYN sent from the printer control device 1°.
Image data VIDEO is sent to the printer control device 10 in synchronization with C. On the other hand, in accordance with the "color designation command" sent from the image processing device 12, the printer control device 10 brings the developer 2 of the designated color (for example, containing black developer) close to the photosensitive drum 1, and removes the undesignated developer. agent (red)
The developing device 3 having the following characteristics is moved away from the photosensitive drum 1 by a driving means such as a solenoid (not shown). In this way, only the designated color is developed. Then, the photosensitive drum 1 is rotated in accordance with the print signal PRINT received from the image processing device 12, and a high voltage is applied to the pre-transfer charger 4 to charge the photosensitive drum 1 to a uniform potential. Furthermore, recording paper is fed from the paper feed cassette 14. The printer control device 10 modulates the image data VIDEO obtained from the image processing device 12 into an ON10FF signal of the laser beam 11. Then, the laser beam 11 is scanned by the scanner of the laser unit 9 and written on the photosensitive drum 1. The latent image thus formed on the photosensitive drum 1 is developed black in the developing device 2, and is transferred and charged. The developer (toner image) is transferred onto the recording paper conveyed by the device 6. The recording paper onto which this image has been transferred is conveyed to a fixing device 8, where heat and pressure are applied to fix the toner image on the recording paper. At this time, the flapper 15 is instructed by the printer control device 211o to circulate the recording paper on which the fixing has been completed through the conveyance path 7, convey it to a position where the conveyance roller 19 is disposed, and then stop it. Next, the image processing device 12 develops the code corresponding to the second designated color out of the code data for one page into a bitmap. Then, the controller 10 sends an r-color designation command (for example, red) corresponding to the second color to the printer control device 1o again, and starts the printing operation again. At this time, the image processing device 12 notifies the printer control device 1o via the serial communication line ST that there is no more data than this page to be printed on the recording paper.

Then, similarly to the first printing operation, the latent image formed on the photosensitive drum 1 is developed with a developer of the same designated color, and the developer is transferred and fixed onto the recording paper that is conveyed again. At this time, the orientation of the flapper 15 is set so that the recording paper being conveyed passes through the paper output tray 16.1, and the recording paper that has been fused is directly conveyed to the paper output tray 16 and placed there. do.

However, when printing of the first color is completed, if the developer corresponding to the color designation command sent to the printer control device 1o is not stored in the developer 2 or 3, or if there is no developer itself, Printing control is performed as shown in FIGS. 4 and 5.

FIG. 4 is a block diagram illustrating the pulse modulation circuit 10a in the printer control device 10 shown in FIG. 1, and the same components as in FIG. 1 are given the same reference numerals.

In this figure, reference numeral 21 denotes a triangular wave generation circuit which converts the image clock VCLK inputted from the image processing device 12 into a triangular wave signal A and sends it to the analog adder 22. The analog adder 22 generates a triangular wave signal B by adding the triangular wave signal A and the level signal SIG, and outputs it to the comparator 23 .

A reference potential generator 24 outputs a reference potential TH to the comparator 23. The comparator 23 compares the reference potential TH and the triangular wave signal B, and outputs an output pulse C to the digital AND gate 25 when the triangular wave signal B exceeds the reference potential TH.

The digital AND gate 25 ANDs the output pulse C and the image data VIDEO, and outputs the modulated image data MVIDEO to the laser unit 9. That is, the modulated image data MVIDEO is the level signal SIG
The pulse width will be modulated by the voltage level of . Therefore, when the level signal SIG becomes higher than the reference potential TH.

The modulated image data MVIDEO and the image data VIDEO completely match and are no longer pulse width modulated.

FIG. 5 is a timing chart explaining the timing of each signal shown in FIG. 4.

Normally, the level signal SIG is set to a value larger than the reference potential TH. In this case, since the pulse width of the image data VIDEO does not change, the modulated image data MVIDEO
The amount of light of the laser beam 11 driven by VIDEO becomes equal to that when driven directly by image data VIDEO.

If the developer or development unit of the color designated by the image processing device 12 does not exist, the printer control device 10 sets the level signal SIG below the reference potential TH and pulse-width modulates one image data VDIO. At this time, since the exposure amount of the laser beam 11 changes dot by dot,
The print density will change. Therefore, even if there is no developer of the specified color, or even if the developer itself is not set, this pulse width modulation exposure allows printing with the existing default color developer (for example, black) to ensure normal printing. It becomes possible to replace the change in color at time with a change in the concentration of a monochrome developer.

For example, the developing device 2 shown in FIG. 1 is a fixed black developing unit that cannot be replaced, the developing device 3 is a removable second developing unit, and by replacing the developing device 3, red,
If the configuration is configured so that various developers such as blue and green 2 can be used, if a developing unit of the color specified by the image processing device 12 is installed, pulse width modulation will not be performed and the specified color will be normally processed. If the developer of the color specified by the color specification command is not available, or if the development unit itself is not installed, the black developer stored in developer unit 2 will print the color specified by the color specification command. Furthermore, print information such as ruled lines and underlines is printed with a density difference by pulse width modulating the exposure time of the laser beam 11.

In the above embodiment, a multicolor laser beam printer is used as an example in which print information is printed using two developers, a black developer and a red developer contained in the developer 2.3. It doesn't matter if it's just one piece. In particular, in laser beam printers that have only a single color developer, color separation is not possible, so the pulse width of the laser beam 11 is always modulated to vary the printing density between normal characters and the area where color specification is desired. This makes it possible to identify them.

Further, in the above embodiment, a case has been described in which a means for performing pulse width modulation is provided in the printer control device 1o, but it goes without saying that similar effects can be expected even if the means is provided in one image processing device 12.

〔Effect of the invention〕

As explained above, the present invention changes the dot size of the portion corresponding to the color specified by the color specification information when there is no developer or developing means corresponding to the color specification information input from an external device. Since we have provided a printing control means for printing, for example, even when there is no developer for a specified color during multi-color printing, the printing information that requires color specification can be printed in a way that is distinguishable from the printing information for other colors. The printing expressions of color printers can be greatly expanded. Further, even in a monochromatic laser beam printer, the present invention has excellent advantages such as being able to distinguish and print printing colors and printing information that requires emphasized printing.

[Brief explanation of drawings]

FIG. 1 is a sectional view illustrating the configuration of a multicolor laser beam printer showing an embodiment of the present invention, and FIG. 2 is a block diagram illustrating the interface between the printer control device and the image processing device shown in FIG. 1. Figure 3 (a) and (b) are the second
FIG. 4 is a block diagram explaining the modulation circuit in the printer control device shown in FIG. 1, and FIG. 5 is a timing chart illustrating signal timing. In the figure, 1 is a photosensitive drum, 2.3 is a developer, 4 is a pre-transfer charger, 5 is a cleaner, 6 is a charger, 7 is a transport path, 8 is a fixing device, 9 is a laser unit, and 1° is a a printer control device; 12 an image processing device; 13 a host computer;
21 is a triangular wave generation circuit, 22 is an analog adder, 23 is a comparator, 24 is a reference potential generator, and 25 is a digital AND gate. Figure 2 Figure 3 (a) 5YNC (b)

Claims (2)

[Claims] (1) Modulate the laser beam based on printing information input from an external device to form a latent image on the photoreceptor,
In a laser beam printer having a developing means for developing the latent image in a single color or multiple colors, when the developer or the developing means corresponding to the color designation information input from the external device does not exist, the color designation is performed. 1. A laser beam printer characterized by comprising a printing control means for printing a portion corresponding to a color specified by information by changing a dot size. (2) The printing control means is configured to perform one printing based on the pulse width modulation signal.
Claim 1 (1) characterized in that the dot size is controlled by making the laser beam exposure time per dot variable.
) Laser beam printer described in section 2.