JP2001105670A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance image quality while suppressing cost increase by taking account of the type of image, e.g. character, line, photograph and graphics. SOLUTION: A PDL interpreting section 32 command interprets PDL(page describing language) delivered from a PC. A writing section 33 writes into bit map (binary data) at a resolution higher than engine resolution and generates an object tag Tag indicative of a photographic image/graphics or a character/ line for each pixel. A rendering section 35 binary expands the bit map and object and performs doubling (conversion into low resolution multivalued data) of each object in accordance with the engine resolution with reference to the object tag Tag. A pulse modulator 36 generates a drive signal for turning a laser beam on/off according to data subjected to doubling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a digital color printer and a color multifunction machine of an electrophotographic system.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a color printer, PostScript is used in a decomposer.
After interpreting the page description language (PDL) and rendering (compression), the printer engine controller expands the rendering data according to the resolution of the printer engine and turns on / off the laser beam according to the rendering data. A drive signal for turning off is generated. Then, a latent image is formed on the photoconductor by the laser beam by a printer engine (not shown). Hereinafter, configurations and operations of three typical image forming apparatuses of the related art will be described.

First, in the image forming apparatus shown in FIG. 4, in a decomposer 1, a PDL interpretation unit 2 sends a Pos signal transmitted from a terminal (a personal computer or the like) TA.
A page description language (PD such as tScript)
L) is interpreted, and the drawing unit 3 generates bitmap data of the engine resolution and performs binary compression. Next, the printer engine controller 4 expands the binary-compressed data in the rendering unit 5 and generates a drive signal for turning on / off the laser beam in accordance with the data in the pulse modulator 6. A latent image is formed on the photoconductor by the laser beam.

In the image forming apparatus shown in FIG. 5, first, in the decomposer 11, a page description language (PDL) typified by PostScript or the like transmitted from a terminal (personal computer or the like) TA by the PDL interpreter 12 Is interpreted, and the drawing unit 13 performs multi-valued intermediate code generation for the portions other than the image portion and multi-valued compression for the image portion in consideration of the image type (character / line drawing, graphic / photo) (tag generation: tag Image type). Next, in the printer engine control unit 14, the rendering unit 15 converts the data into multi-value raster data.
After screening is performed by the screen generator 16 in accordance with the tag, a drive signal for turning on / off the laser beam is generated by the pulse modulator 17 in accordance with the data, and a latent image is formed on the photoconductor by the laser beam by a printer engine (not shown). Form an image.

In the image forming apparatus shown in FIG. 6, first, in the decomposer 21, a page description language (PDL) typified by PostScript or the like transmitted from a terminal (personal computer or the like) TA by a PDL interpreting unit 22. Is interpreted, and the drawing unit 23 generates a bitmap at a resolution N times the engine resolution (for example, 1200 dpi). Next, in the printer engine control unit 24, the rendering unit 25 sets the engine resolution (for example,
At 600 dpi), multi-value rasterization (doubling processing) is performed, and a drive signal for turning on / off the laser beam is generated in accordance with the data rasterized by the pulse modulator 26. Form a latent image.

[0006]

However, the image forming apparatus shown in FIG. 4 has a disadvantage that the image quality is poor because it is processed with binary data, although the cost is low. In particular, binary screening causes image quality degradation. Further, the image forming apparatus shown in FIG. 5 has high image quality because of processing with multi-valued data, but has a problem of high cost since multi-valued data must be handled by all processing systems. This results in an increase in cost due to the use of a multi-level compression method for compression and an increase in required memory capacity. Further, in the image forming apparatus shown in FIG. 6, since the rasterization is performed from binary to multi-value, cost increase can be prevented. Therefore, characters
There is a trade-off between graphics quality and photographic image quality.

The present invention has been made in view of the above circumstances, and provides an image forming apparatus capable of improving image quality in consideration of image types such as characters, line drawings, photographs, and graphics while suppressing costs. It is intended to be.

[0008]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, a high-resolution binary image is developed, a low-resolution multi-level image is pulse-width modulated, and the pulse-width modulated image is modulated. In an image forming apparatus for forming an image based on a pulse signal, a developing means for developing an image file described in a page description language into binary data, and an object tag indicating an image type in a pixel unit with respect to the image file. A tag generating means for generating, and a multi-value generating means for converting the binary data expanded by the expanding means to a multi-value by a different method according to the object tag generated by the tag generating means. Features.

According to the present invention, when the image file described in the page description language is expanded into binary data by the expansion unit, the tag generation unit generates an object tag indicating the image type in pixel units. The multi-value conversion means multi-values the binary data expanded by the expansion means by a different method according to the object tag generated by the tag generation means. Therefore, it is possible to improve image quality in consideration of image types such as characters and line drawings and photographs and graphics while suppressing costs.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. A. Configuration of Embodiment FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. In the figure, decomposer 3
1 includes a PDL interpretation unit 32 and a drawing unit 33. PD
The L interpreting unit 32 interprets a PDL (Page Description Language) sent from the PC as a command. The drawing unit 33 draws a bitmap (binary data) at N times (for example, twice as high as 1200 dpi) the engine resolution. The screening parameter at the time of drawing is not particularly limited, but in the case of the present embodiment, since the desired number of lines is 200 lines,
Screening is performed at 200 dpi and 200 lines using the dither pattern (screen pattern) shown in FIG. The screen has a trade-off between gradation and the number of lines. In the case of a color electrophotographic printer, registration misregistration, moiré and rosette occur. Desirably, there are 256 levels. In addition, the drawing unit 33 generates an object tag Tag indicating whether the image is a photograph image / graphic or a character / line drawing for each pixel in accordance with the command. In the case of the present embodiment, “0” is assigned to the photo image / graphic and “1” is assigned to the character / line drawing as the object tag Tag. The drawing unit 33 binary-compresses the bitmap data and the object tag data Tag, and supplies them to the printer engine control unit 34.

Next, the printer engine control unit 34 includes a rendering unit 35 and a pulse modulator 36. The rendering unit 35 expands the bitmap and the object tag Tag in a binary manner, and then performs the object tag Tag
, A doubling process (conversion of high-resolution binary data to low-resolution multi-value data) is performed for each object according to the engine resolution. In the doubling process, it does not matter which pixel is referred to and how to perform multi-value processing. However, for a photographic image, a method for smoothing is adopted. Adopt a method that does not fall. In addition, when the doubling process is performed, the rendering unit 35 determines the printing start position by looking at the left and right weights in pixel units.

The pulse modulator 36 generates a drive signal for turning on / off the laser beam in accordance with the data subjected to the doubling process, and forms a latent image on the photoconductor by the laser beam by a printer engine (not shown).

B. Next, an operation of the above-described embodiment will be described. First, the PDL (page description language) sent from the PC is interpreted as a command by the PDL interpreting unit 32 and supplied to the drawing unit 33. In the drawing unit 33, 1 times twice the engine resolution
It is drawn on a bitmap (binary data) at 200 dpi. At this time, what is drawn on one pixel line is
Since image quality defects occur when lines are interrupted or disappear, the image is drawn with two pixel lines. Then 120
The screen is screened at 0 dpi and 200 lines using the dither pattern shown in FIG. Further, in the drawing unit 33, according to the command interpretation, for each pixel, if it is a photographic image / graphic, the object tag Tag = "0";
If it is a character / line drawing, the object tag Tag = "1"
Is generated. The bitmap data and the object tag Tag are binary-compressed and transmitted to the printer engine control unit 34.

In the printer engine control unit 34, after the bitmap and the object tag Tag are binary-expanded in the rendering unit 35, doubling processing is performed for each object according to the engine resolution as shown in FIG. Specifically, when the object tag Tag is “0”, that is, when the object tag is a photographic image / graphic, as shown in FIG.
L = p (1,1) + 2p (1,2) + 2p in consideration of surrounding pixels (4 × 4 pixels in total) including the target pixel with respect to 200 dpi binary data: 2 × 2 pixels (2,
1) + 4p (2,2) + 2p (3,1) + 4p (3
2) + p (4,1) + 2p (4,2), R = 2p (1,
3) + p (1,4) + 4p (2,3) + 2p (2,4)
+ 4p (3,3) + 2p (3,4) + 2p (4,3) +
p (4, 4) and Width = (L + R) / 36 are calculated. On the other hand, when the object tag Tag is “1”,
That is, in the case of a character / line drawing, as shown in FIG. 3B, the target pixel (1200 dpi, binary data: 2 ×
L = p (1,1) + p (2,1)
R = p (1,2) + 2p (2,2), Width = (L
+ R) / 4 is calculated.

Next, a printing start position is determined according to the calculated L, R, and Width. That is, if L> R, the print start position is to the left of the pixel, and if R <L,
The right side of the pixel is the print start position, and if L = R, the center is the print start position. In the case of the example shown in FIG. 3A, when doubling processing is performed on a photographic image, 36 gradations can be ensured per pixel, so that a 200-line screen can be used to secure 256 gradations. letter·
For the line drawing part, in the case of the example shown in FIG. 3B, 36 gradations cannot be secured, but the edges are not dull and good character reproduction is achieved.

In the pulse modulator, a pulse signal for turning on / off the laser beam is generated in accordance with the data subjected to the doubling process, and a latent image is formed on the photosensitive member by the printer engine.

[0017]

As described above, according to the present invention, when an image file described in a page description language is expanded into binary data by an expansion unit, an image type is determined in pixel units by a tag generation unit. Is generated, and the binary data expanded by the expansion means is converted to multi-values by a different method according to the object tag generated by the tag generation means. , While keeping costs down,
Multivalued data can be obtained in consideration of the type of image such as graphics, and the advantage that image quality can be improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a dither pattern (screen pattern) used in the present embodiment.

FIG. 3 is a conceptual diagram for explaining a doubling process according to the embodiment;

FIG. 4 is a block diagram illustrating a configuration example of an image forming apparatus according to the related art.

FIG. 5 is a block diagram illustrating a configuration example of an image forming apparatus according to a related art.

FIG. 6 is a block diagram illustrating a configuration example of an image forming apparatus according to a related art.

[Explanation of symbols]

 31 Decomposer 32 PDL Interpretation Unit 33 Drawing Unit (Expansion Unit, Tag Generation Unit) 34 Printer Engine Control Unit 35 Rendering Unit (Multi-Value Conversion Unit) 36 Pulse Modulator

Continued on front page F-term (reference) 2C087 AA11 AA15 AA16 AC08 BA02 BA03 BA04 BA05 BA07 BA12 BC05 BD01 BD05 BD40 5B057 AA11 CA06 CA12 CA16 CB08 CB12 CB16 CC01 CD06 CE11 CE13 9A001 EE02 HH24 HH34 JJ35 KK42

Claims (4)

[Claims] 1. An image forming apparatus which develops an image based on a high resolution binary value, performs a pulse width modulation based on a low resolution multivalued image, and forms an image based on the pulse width modulated pulse signal. Expanding means for expanding the image file into binary data; tag generating means for generating an object tag indicating an image type in pixel units with respect to the image file; and generating the tag data by developing the binary data expanded by the expanding means. An image forming apparatus comprising: a multi-level conversion unit that performs multi-level conversion by a different method according to an object tag generated by the unit. 2. The developing means expands the binary data into binary data at a resolution N times the resolution of the final output stage, and the multi-level converting means multiplies the binary data at a resolution of 1 / N. The image forming apparatus according to claim 1, wherein the image is formed into a value. 3. The tag generating means generates an object tag indicating whether the image is a photographic image / graphic or a character / line drawing for each pixel, and the multi-value converting means determines whether a target pixel to be multi-valued is an object. If the tag indicates that the image is a photographic image / graphic, it is multi-valued by taking into account the density values of the peripheral pixels of the pixel of interest, and the pixel of interest to be multi-valued is represented by a character / line drawing by the object tag. 3. The image forming apparatus according to claim 1, wherein when it is indicated that there is, the multi-value is set based on the density value of the pixel of interest. 4. The multi-level converting means separately calculates a first density value on the left side including the pixel of interest and a second density value on the right side including the pixel of interest. 4. The image forming apparatus according to claim 3, wherein a print start position of the multi-valued pixel is determined based on a magnitude relationship with the second density value.