JPH05110806A - White mask controller for laser beam printer - Google Patents

Abstract

PURPOSE:To execute a white mask by outputting picture data only when a dot location during recording stays in a prescribed region corresponding to the print location of a picture and outputting white data in other cases. CONSTITUTION:A white mask control section 4 detects a position recorded by a laser beam printer recording section 1 and outputs a mask rear page synchronizing signal PSYNC-M when the position stays in an image forming range in the subscanning direction. Moreover, when the position stays in an image forming range in the main scanning direction. The control section 4 outputs a mask rear line synchronizing signal LSYNC-M. Then the mask rear page synchronizing signal PSYNC-M and the mask rear line synchronizing signal LSYNC-M are given to a memory control section 2 and picture data VDATA are read from a buffer memory 5 and in other cases, white data are outputted. Thus, white mask is applied to portions protruded from the picture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white mask control device for a laser beam printer in which image data is supplied to a recording section via a buffer memory.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of a conventional laser beam printer. In FIG. 7, 1 is a laser beam printer recording unit, 2 is a memory control unit, 3 is a page memory,
PSYNC is a page sync signal, LSYNC is a line sync signal, VCLK is a video clock, and VDATA is image data.

The page memory 3 stores one page of image data VDATA. The memory control unit 2 reads the image data VDATA from the page memory 3 according to the video clock VCLK, the line synchronization signal LSYNC, and the page synchronization signal PSYNC sent from the laser beam printer recording unit 1, and the laser beam printer recording unit 1
Send to. In the laser beam printer recording unit 1, the photosensitive drum is rotated at a constant speed, and the page memory 3 is placed on the drum.
After forming a latent image according to the print image of (1), developing it, and transferring it to paper to perform printing.

FIG. 8 shows a latent image forming section and a line synchronization signal LS.
It is a figure which shows the relationship with YNC and page synchronization signal PSYNC. Reference numerals correspond to those in FIG. 7, 17 is a latent image forming portion, and 18 is an arrow indicating a line forming direction. Figure 8
The arrow x direction is the main scanning direction, that is, the laser beam scanning direction, and the arrow y direction is the sub scanning direction, that is, the direction opposite to the rotation of the photosensitive drum.

When the page synchronization signal PSYNC is raised, the laser beam starts scanning on the rotating photosensitive drum. Next, when the line synchronization signal LSYNC is raised, the image data VD is generated according to the video clock VCLK.
ATA is sequentially output, the laser beam is modulated by the image data VDATA, and a latent image is formed on the photosensitive drum along the scanning line. Then, when the line synchronization signal LSYNC falls, the image data VDATA
Is stopped, and the formation of one line is completed at that point. The operation for each line is repeated in the y direction to form a predetermined number of lines, and then the page synchronization signal PSYNC is generated.
Then, the latent image formation for one page is completed. Therefore, the width of the latent image forming unit 17 in the x direction is determined by the line synchronization signal LSYNC, and the length of the latent image forming unit 17 in the y direction is determined by the page synchronization signal PSYNC.

An example of such a laser beam printer using a page memory is Japanese Patent Laid-Open No. 60-16026.
There is one as disclosed in Japanese Patent Publication No. 4 publication.

By the way, in such a printer,
When an image of a size smaller than the size of the paper is input to the page memory, the data (image) written last time remains as it is in the memory around the input image. Therefore, when the data of the page memory is output by the page synchronization signal PSYNC and line synchronization signal LSYNC corresponding to the paper size, the previous data remaining in the peripheral portion of the current image data is also printed. Since this is a problem, an operation is performed to clear the data in the peripheral portion memory so that nothing is recorded in the outer portion of the image. That is, the white mask is applied to the outer portion of the image.

FIG. 9 is a diagram showing an example in which a white mask is applied to the outer portion of an image and printed. In FIG. 9, 19 is a sheet and 20 is an image. FIG. 9A shows an example in which the image 20 is offset to the upper left end of the paper sheet 19 and the periphery thereof is masked, and FIG. 9B shows the image 20 in the center of the paper sheet 19. An example is shown in which the mask is arranged and a mask is applied to the entire circumference. For the purpose of the following description, the upper left point will be the origin O, and points A to G where the corners of the image are located and the corners of the paper that are diagonal to the origin O will be indicated by the coordinates as shown. And

In the laser beam printer using the page memory as shown in FIG. 7, the dot position on the recording paper and the bit position on the page memory have a one-to-one correspondence. Masking can be performed relatively easily by clearing the area outside the size and setting white data.

[0010]

(Problem) However, in a laser beam printer having a buffer memory having a smaller capacity than the page memory, the dot position on the recording paper and the bit position on the buffer memory are different from each other. 1 body 1
However, there is a problem in that the white mask technology used in the case of page memory cannot be applied. (Explanation of Problems) A RAM (Random Access Memory) having a capacity of one page is required to configure the page memory. However, since the RAM is expensive, instead of the page memory, it is better than the page memory. A technique using a buffer memory that requires a much smaller capacity has been proposed (Japanese Patent Application No. 3-177515). Since such a buffer memory can store only a part of the image data for one page, the dot position on the recording paper and the bit position on the buffer memory do not have a one-to-one correspondence.
Therefore, when a white mask is applied to the image input to the buffer memory, the white mask technique as in the case of the page memory cannot be used. An object of the present invention is to solve such a problem.

[0011]

In order to solve the above-mentioned problems, according to the present invention, in a white mask control device of a laser beam printer for supplying image data to a recording portion through a buffer memory, the main of dots currently being recorded is recorded. A means for detecting the position in the scanning direction and a means for detecting the position in the sub-scanning direction of the dot currently being recorded, and the position of the dot currently being recorded is the image in both the main scanning direction and the sub-scanning direction. Only when it is within the predetermined area corresponding to the print position of
Image data is output, and at other times, white data is output.

[0012]

[Operation] Image data is output only when the dot position currently being recorded is within a predetermined area corresponding to the print position of the image, and white data is output otherwise. Thus, the white mask can be applied even in the laser beam printer of the buffer memory system.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 2 is a block diagram of a laser beam printer to which the present invention is applied. Reference numerals correspond to those in FIG. 7, 4 is a white mask control unit, 5 is a buffer memory, and PSY.
NC-M is a post-masking page sync signal, LSYNC-M is a post-masking line sync signal, and VDATA-M is a post-masking image data.

In the present invention, the page sync signal PS from the laser beam printer recording unit 1 corresponding to the image of the paper size is used.
Even if YNC and the line synchronization signal LSYNC are output, the image data is not read from the buffer memory 5 in accordance therewith. Instead, a page sync signal and a line sync signal corresponding to the current image size and print position on the paper are generated, and the image data is read from the buffer memory 5 in accordance with them. The part that causes them is the white mask control unit 4. The generated sync signals are respectively masked to the page sync signal PSYN-M.
And the post-masking line synchronization signal LSYNC-M. The image data VDATA stored in the buffer memory 5 is output during the period in which the post-mask page synchronization signal PSYNC-M and the post-mask line synchronization signal LSYNC-M are output, but in the other periods, it is white. Output the data. The image data obtained in this way is
The image data after masking will be referred to as VDATA-M.

FIG. 1 is a diagram for explaining a masked page sync signal and a masked line sync signal in the present invention. Reference numerals correspond to those in FIGS. 2 and 8, and M _B indicates an area corresponding to the capacity of the buffer memory 5. The coordinates shown correspond to the coordinates shown in FIG. Since the image data of the entire latent image forming unit 17 cannot be stored in the buffer memory 5 at the same time, one page is finished by rewriting the read portions one after another. Regarding the coordinate in the y direction, a system that keeps increasing until the end of one page is adopted regardless of the storage location in the buffer memory 5.

As in the case of FIG. 9 (a), FIG. 1 (a) shows a case in which the image is arranged offset to the upper left end of the paper and a white mask is applied to the periphery thereof. In this case, in the image size, the coordinates (x ₁ , y ₁ ) of the point B at the corner located diagonally to the origin are set. And 0 to x ₁ which is the position in the x direction where the image is to be arranged
A line synchronization signal is generated in correspondence with the above, and this is used as a post-masking line synchronization signal LSYNC-M. Further, a page synchronization signal is generated in correspondence with the positions 0 to y ₁ in the y direction, and the page synchronization signal PSYNC-M after masking is generated.
And

As shown in FIG. 9B, FIG. 1B shows a case where an image is arranged near the center of a sheet and a white mask is applied to the entire periphery thereof. In this case, the coordinates (x ₂ , y ₂ ) and (x ₃ , y ₃ ) of a pair of points D and F in the diagonal direction of the image arrangement position are set. And
As in the case of FIG. 1A, the page synchronization signal and the line synchronization signal corresponding to the image position are the masked page synchronization signal PSYNC-M and the masked line synchronization signal LS.
YNC-M.

Next, the white mask control section 4 will be described. The white mask control unit 4 detects the position currently being recorded by the laser beam printer recording unit 1, and if the position is within the image forming range in the sub-scanning direction (y direction),
The post-masking page synchronization signal PSYNC-M is output, and if the position is within the image forming range in the main scanning direction (x direction), the post-masking line synchronization signal LSYNC- is output.
Output M. Then, the masked page synchronization signal PSY
The NC-M and the post-masking line synchronization signal LSYNC-M are given to the memory control unit 2 to read the image data VDATA from the buffer memory 5, and otherwise output white data.

(First embodiment ... In the case of one-point control) FIG.
It is a circuit diagram of a first embodiment of a white mask control unit. this is,
This is a circuit when a white mask is applied as shown in FIG.
In this case, as shown in FIG. 1A, by setting the coordinates (x ₁ , y ₁ ) of the point B in the diagonal direction with respect to the origin O, the area where the image is to be formed and the white mask should be formed. The area is determined and the white mask is controlled based on the area. For convenience, this is referred to as one-point control. Reference numerals correspond to those in FIG. 2, 6 is an x-direction (main scanning direction) counter, 7 is a y-direction (sub scanning direction) counter, 8 and 9 are comparators 10, 1
1, 12 are AND circuits, CLR is a clear signal input terminal,
x is the output value of the x-direction counter 6, x ₁ is the set value in the x-direction (x-coordinate value of the point B), y is the output value of the y-direction counter 7,
y ₁ is a set value in the y direction (y coordinate value of the point B).

The operation of this circuit is as follows. First, in the comparators 8 and 9, the values x ₁ and y ₁ for setting the image area are set.
give. The y-direction counter 7 has a page synchronization signal PSY.
Cleared by the rising edge of NC, x-direction counter 6
Is cleared by the rising edge of the line synchronization signal LSYNC. The x-direction counter 6 has a video clock VCL
It counts up each time K is input, and the count value x is sent to the comparator 8. This count value x indicates where on the line the dot position currently being recorded is.
On the other hand, the y-direction counter 7 displays the line synchronization signal LSYNC.
Each time is input, the count is incremented and the count value y is sent to the comparator 9. This count value y indicates which line is currently being recorded. Therefore, the position determined by the count value x and the count value y is the position currently being recorded by the laser beam printer recording unit 1.

The comparator 8 compares the set value x ₁ with the count value x, and outputs "1" when x ₁ ≥x. Further, the comparator 9 compares the set value y ₁ with the count value y to determine y ₁
When ≧ y, “1” is output. Therefore, the comparator 8,
When both outputs of 9 are "1", the position currently being recorded is in the shaded portion of FIG. If neither of the outputs of the comparators 8 and 9 is "1", the position currently being recorded is outside the shaded portion in FIG.

The AND circuit 10 outputs the line synchronization signal LSY.
When NC is output and the output of the comparator 8 is "1", the post-masking line synchronization signal LSYNC-M is output. The AND circuit 11 outputs the post-masking page synchronization signal PSYNC-M when the page synchronization signal PSYNC is output and the output of the comparator 9 is "1".

The AND circuit 12 receives the masked line synchronization signal LSYNC-M and the masked page synchronization signal PSYNC.
The image data VDATA read from the buffer memory is output only when -M is output together, that is, when the outputs of the AND circuits 10 and 11 are both "1".
In other cases, the output of the AND circuit is "0", which corresponds to outputting white data. As a result, the image data VDATA is output only when the position currently being recorded is within the range in which the image of this time is drawn, that is, in the shaded portion of FIG. 1A, and the white mask is applied to the other portions. To be done.

FIG. 4 is a time chart showing the relationship between the synchronizing signals in the first embodiment. The reference numerals correspond to those in FIG. Line sync signal LSYN of FIG. 4 (2)
C and the post-masking line synchronization signal LSYNC of FIG.
The numbers 0, 1, ... Attached to -M are numbers sequentially assigned to the lines of the page from the top. Also, FIG.
X ₁ attached to the line synchronization signal LSYNC of (2)
Shows the position of the set value in the x direction (x coordinate value of the point B) for each line synchronization signal LSYNC.

Since the counter value of the y-direction counter 7 which is cleared by the rise of the page sync signal PSYNC becomes "0" which is smaller than the set value y ₁ , the output of the comparator 9 becomes "1" and the AND circuit 11 outputs. The output, that is, the post-masking page synchronization signal PSYNC-M rises. Therefore, the page synchronization signal PSYNC and the post-masking page synchronization signal PSYNC-M rise at the same time. On the other hand, when the line synchronization signal LSYNC rises, similarly, the post-masking line synchronization signal LSYNC-M rises.

The count value x of the x-direction counter 6 is x ₁
When it becomes +1 and becomes larger than the set value x ₁ , the comparator 8
Output becomes "0", and the masked line synchronization signal LSY is output.
NC-M falls. When the count value of the y-direction counter 7 becomes y ₁ +1 and becomes larger than the set value y ₁ , the output of the comparator 9 becomes “0”, and the post-masking page synchronization signal PSYNC-M rises. Go down. Therefore, the dots after the x ₁ + 1st line in one line are not printed, and the lines after the y ₁ + _1st line in a page are not drawn.

(Second embodiment ... In case of two-point control) FIG.
It is a circuit diagram of a second embodiment of the white mask control unit. this is,
This is a circuit when a white mask is applied as shown in FIG.
In this case, an image should be formed by setting the coordinates (x ₂ , y ₂ ) and (x ₃ , y ₃ ) of two points D and F as shown in FIG. The area and the area to be white masked are determined, and the white mask control is performed based on that. This will be referred to as two-point control for convenience. Reference numerals correspond to those in FIG. 3, 13 and 14 are comparators, 15 and 16 are AND circuits, x ₂ is a first set value in the x direction (x coordinate value of point D),
y ₂ is the first set value in the y direction (y coordinate value of point D), x ₃
Is the second set value in the x direction (x coordinate value of the point F), y ₃ is y
It is a second set value of the direction (y coordinate value of the point F).

The operation of this circuit is as follows. First, the comparators 13, 14, 8, and 9 are provided with values x ₂ , y ₂ , x ₃ , and y ₃ for setting the image area. y-direction counter 7
Is cleared by the rising edge of the page sync signal PSYNC, and the x-direction counter 6 is cleared by the rising edge of the line sync signal LSYNC. The x-direction counter 6
It counts up each time the video clock VCLK is input, and the count value x is sent to the comparator 8 and the comparator 13. On the other hand, the y-direction counter 7 receives the line synchronization signal L
It counts up each time SYNC is input, and the count value y is sent to the comparator 9 and the comparator 14. As in the first embodiment, the position determined by the count value x and the count value y is the position currently being recorded by the laser beam printer recording unit 1.

The comparator 8 compares the set value x ₃ with the count value x, outputs "1" when x ₃ ≥x, and the comparator 13
Compares the set value x ₂ with the count value x, and outputs “1” when x ₂ ≦ x. Further, the comparator 9 sets the set value y ₃
And the count value y are compared, and when y ₃ ≧ y, “1” is output. The comparator 14 compares the set value y ₂ with the count value y. When y ₂ ≦ y, “1” is output. Output.

The AND circuit 15 outputs "1" when both the outputs of the comparators 8 and 13 are "1", and the AND circuit 16
Outputs "1" when the outputs of the comparators 9 and 14 are both "1". Therefore, when the outputs of the AND circuits 15 and 16 are both "1", that is, the comparators 8, 9 and 1
When the outputs of 3 and 14 are all "1", the position currently being recorded is in the shaded portion of FIG. Comparator 8,
If even one of the outputs of 9, 13, 14 is not "1", that is, if neither of the outputs of the AND circuits 15, 16 is "1", the position currently being recorded is as shown in FIG.
It is outside the shaded area in (b).

The operation by the AND circuits 10, 11 and 12 is similar to that in the case of FIG. 3, and as a result, the image data VDATA is output only in the shaded portion of FIG. 1B, and in the other portions, A white mask is applied.

FIG. 6 is a time chart showing the relationship between the synchronizing signals in the second embodiment. The reference numerals correspond to those in FIG. Line sync signal LSYN of FIG. 6 (2)
C and (5) post-masking line synchronization signal LSYNC-M
The numbers 0, ..., Y ₃ +1 given to the lines are numbers sequentially given to the respective lines of the page from the top. And FIG.
X ₂ and x ₃ attached to the line synchronization signal LSYNC of (2) indicate the position of the set value in the x direction (x coordinate value of the point D and the point F) for each line synchronization signal LSYNC. is there.

Since the counter value of the y-direction counter 7 which is cleared by the rise of the page sync signal PSYNC becomes "0" smaller than the set value y ₂ , the output of the comparator 14 becomes "0" and the AND circuit 16 outputs. The output remains "0". Therefore, the output of the AND circuit 11, that is, the post-mask page synchronization signal PSYNC-M does not rise at this point. It rises when the counter value of the y-direction counter 7 becomes y ₂ and the outputs of the comparators 9 and 14 both become “1”. Then, it falls when it becomes larger than y ₃ , that is, when it becomes y ₃ +1.

On the other hand, the counter value of the x-direction counter 6 which is cleared by the rising edge of the line synchronization signal LSYNC becomes "0" which is smaller than the set value x _2, so that the comparator 1
The output of 3 becomes "0", and the output of the AND circuit 15 remains "0". Therefore, at this point, AN
The output of the D circuit 10, that is, the post-masking line synchronization signal LSYNC-M does not rise. X stands up
The counter value of the direction counter 6 becomes x ₂ and the comparator 8,
This is the time when the outputs of 13 are both "1". And x
_It falls when it becomes larger than ₃ , that is, when it becomes x ₃ +1.

[0036]

As described above, in the present invention, the coordinate value of the position of the dot currently being recorded is compared with the preset coordinate value, and only when they are within a predetermined area, the image is displayed. Data is output, and in other cases, white data is output. Therefore, even in a laser beam printer in which the image data is developed on a buffer memory whose bits do not correspond to dots on the recording paper in a one-to-one correspondence, by monitoring the coordinate values, the image can be projected to the portion that does not protrude. A white mask can be applied.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a masked page synchronization signal and a masked line synchronization signal according to the present invention.

FIG. 2 is a block diagram of a laser beam printer to which the present invention is applied.

FIG. 3 is a circuit diagram of a first embodiment of a white mask control section.

FIG. 4 is a time chart showing the relationship between each synchronization signal in the first embodiment.

FIG. 5 is a circuit diagram of a second embodiment of a white mask control section.

FIG. 6 is a time chart showing the relationship between each synchronization signal in the second embodiment.

FIG. 7 is a block diagram of a conventional laser beam printer.

FIG. 8 is a diagram showing a relationship between a latent image forming unit and a line synchronization signal and a page synchronization signal.

FIG. 9 is a diagram showing an example in which a white mask is applied to an outer portion of an image and printed.

[Explanation of symbols]

1 ... Laser beam printer recording unit, 2 ... Memory control unit,
3 ... page memory, 4 ... white mask control section, 5 ... buffer memory, 6 ... x-direction counter, 7 ... y-direction counter,
8, 9 ... Comparator, 10, 11, 12 ... AND circuit, 1
3, 14 ... Comparator, 15, 16 ... AND circuit, 17 ... Latent image forming section, 18 ... Arrow indicating line forming direction, 19 ... Paper, 20 ... Image, 21 ... Latent image, PSYNC ... Page sync signal, PSYNC -M ... Page sync signal after masking, LS
YNC ... Line sync signal, LSYNC-M ... Post-mask line sync signal, VCLK ... Video clock, VDATA
... image data, VDATA-M ... masked image data,
CLR ... Clear signal input terminal

Claims (1)

[Claims] 1. A white mask control device for a laser beam printer, which supplies image data to a recording unit via a buffer memory, a means for detecting the position of a dot currently being recorded in the main scanning direction, and a dot currently being recorded. And a means for detecting the position in the sub-scanning direction of the image, only when the position of the dot currently being recorded is in a predetermined area corresponding to the image print position in both the main scanning direction and the sub-scanning direction. A white mask control device for a laser beam printer, which outputs data and outputs white data at other times.