JPH02185456A - Recording device - Google Patents

Abstract

PURPOSE:To perform the conversion process of printing density without impairing the sharpness of an original image and density deterioration by distinguishing an edge section from any other section in an original image based on a difference from the density of reference dots, and interpolating the edge section and the other section using different systems. CONSTITUTION:A selector 29 selects and outputs A-B from among two input data, if a carry output from an adder 25 is 1, that is, A>B. On the contrary, if the carry output is 0, the selector 29 selects and outputs data B-A. This output data becomes a absolute value IA-BI which is a difference between A and B. If the difference between input data A and B is larger than a specified value C, an edge detection signal DIF is output. The edge detection signal DIF is entered as a selection signal SEL from the selector 23 through an OR circuit 22. If edge detection signal DIF is 1, the average value of data A and B is not used for interpolation but the same data as the preceding pixel, that is, data A is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording device such as a laser beam printer.

[Prior Art] In recent years, laser beam printers have become widely used as output devices for computers and the like. In particular, low densities (e.g. 3
00 dpi) laser beam printers are rapidly becoming popular due to their low cost and compact size.

For example, in a laser beam printer that prints at a printing density of 300 dpi, as shown in FIG. receives the code data sent from the external host computer 54, generates page information consisting of dot data based on this code data, and sends the printer driver 5
1, and a printer controller 52 that sequentially transmits dot data to the printers 1 and 1.

The host computer 54 is loaded with a program by a floppy disk 55 having application software, starts the application software,
For example, it functions as a word processor.

Many types of application software have been created and used, and users create and store a large amount of data using these application software.

On the other hand, the printer drive unit 51 has a higher printing density and higher gradation for the purpose of performing higher quality printing, and has a printing density of 600 dpi or more and one that handles multi-value data. Proposed.

The printer controller 52 connected to these high-density printer drive units 51 has conventionally had data memory of an amount corresponding to each print density and gradation value. For example, when the print density is 600 dpi, the memory is four times that of 300 dpi.

Furthermore, application software is created exclusively for high-density printers, and many of the application software mentioned above cannot be used as is for high-density printers.

For example, if a 300 dpi image is printed as is in a dot configuration at a print density of 600 dpi, the size of the image will be reduced to one-half in both the vertical and horizontal directions.

Therefore, one data interpolation method is to simply double the dot configuration in both the vertical and horizontal directions and obtain a 300 dpi
There is a method of applying this dot configuration to 600 dpi.

Here, FIG. 9 is a schematic diagram showing the relationship between the printing position on the l line and the gradation at a printing density of 300 dpi. Further, FIG. 10 is a schematic diagram showing the relationship between the printing position on the l line and the gradation at a printing density of 600 dpi by simply converting the dot configuration of the image shown in FIG. 9.

However, if the dot configuration is simply converted as described above, the image size does not become smaller; however,
As can be seen by comparing Figure 9 and Figure 1θ, there is no difference in the smoothness of the gradation between printing at 300 dpi and printing at 600 dpi. I can't get an image.

Therefore, instead of simply doubling the dot configuration, the applicant interpolated between the 300 dpi image data using the previous and subsequent average value data, as shown in FIG.
We have proposed a data interpolation method that produces smooth gradation.

[Problem to be solved by the invention WUI However, in such a data interpolation method,
For example, as shown in Figure 12, when interpolating an image that includes an edge part a that changes from "white" to "black" or an edge part that changes from "black" to "white," a black border that is originally three dots wide will be interpolated. As shown in FIG. 13, in the edge portion a, interpolated dots of intermediate density are formed on the outside of the edge portion a, and conversely, as shown in FIG.
There is a problem that the quality of one image deteriorates because it is expressed with an intermediate density.

The present invention can perform printing density conversion processing without impairing the sharpness of the edges of the original image and without impairing the gradation, and can obtain high-quality images using conventional application software. The purpose of this invention is to provide a recording device that can perform the following functions.

[Means for Solving the Problems] The present invention receives multivalued dot information of a first print density and generates interpolated dots of this received dot information.
A recording device that generates multivalued dot information of a second printing density includes a plurality of types of interpolation dot generation means that generates multivalued interpolation dots by referring to predetermined dots of the received dot information; The present invention is characterized by comprising a density difference detecting means for detecting a density difference between reference dots during generation, and a switching means for selectively switching the interpolation dot generating means based on the detection result of the density difference detecting means.

[Operation] In the present invention, the density difference between the reference dots is detected, and based on this detection result, edge portions existing in the original image and other portions are identified, and interpolation of the edge portions and portions other than the edge portions are performed. By performing the interpolation using a different method, it is possible to perform printing density conversion processing without impairing the sharpness of the edges of the original image and without impairing the gradation. You can obtain high-quality images.

[Embodiment] FIG. 1 is a block diagram showing the configuration of a data conversion circuit of a laser beam printer according to a first embodiment of the present invention.

In this embodiment, a 300 dpi (dots/inch) image signal sent from the printer controller 52 is
Convert to 600 dpi data by interpolation, and convert this to 600 dpi data.
A case where printing is performed by the printer drive unit 51 of 00 dpi will be described.

The data conversion circuit is provided in the printer drive section 51. Here, the printer driving section 51 includes a laser driver that modulates a laser beam based on an image signal (dot information), a scanner for scanning the laser beam, a photosensitive drum, and the like. Note that the data conversion circuit may be provided on the printer controller 52 side.

The printer controller 52 includes the horizontal synchronization signal generation circuit 4
3 according to the horizontal synchronization signal H5YNC output by
Image signal VDO and image clock VCLK for 00dpi
and is sent to the printer drive section. Note that the horizontal synchronization signal generation circuit 4 sends out a horizontal synchronization signal based on the BD double signal, which is a synchronization signal in the main scanning direction.

The printer drive unit 51 uses a data conversion circuit to
Image signal VDO and image clock v for 16 gradations of dpi
From CLK, 600 dpi, 16 gradation image signal VD
O' is generated and printing is performed at 600 dpi and 16 gradations.

Next, this data conversion circuit will be explained in detail.

The frequency multiplication circuit 1 multiplies the frequency of one image clock VCLK to obtain a clock VCLK' whose frequency is doubled.

The oscillation circuit 5 generates a clock LCLK having a frequency four times that of the image clock VCLK.

The switching circuits 11-13 each select the above-mentioned clock VCLK° or LCLK and supply it as a write clock or a read clock to the line memories 6-8, respectively.

The first interpolation circuit 17 inserts interpolation data between the 300 dpi data, thereby providing 300 dpi data in the main scanning direction.
0 dpi.

The demultiplexer 2 selectively supplies the signals interpolated by the first interpolation circuit 17 to the line memories 6 to 8.

The horizontal synchronization signal generation circuit 4 generates one horizontal synchronization signal H every time two BD double signals are input.
Outputs 3YNC.

The first to third line memories 6 to 8 each have a memory capacity twice that of data in the main scanning direction at 300 dpi, that is, 60 dpi.
It has a data memory capacity of 0 dPi in the main scanning direction. The image signals read out from these line memories 6 to 8 are designated as D1 to D3, respectively.

The data selectors 14 and 15 select two of the read signals D1 to D3 of the line memories 6 to 8 during a read operation. For example, when the line memory 6 is in a write operation and the line memory 7.8 is in a read operation, the data selector 14 selects the read data D2 of the line memory 7, outputs the first data selector signal (DSL signal), and also outputs the first data selector signal (DSL signal). 15 selects the read data D3 of the line memory 8 and outputs the second data selector signal (D
S2 signal) is output.

The second interpolation circuit IO performs interpolation in the sub-scanning line direction, receives the DSI signal and DS2 signal, averages each data, and outputs an output signal Q according to the result.

The fourth line memory 9 stores the output signal Q, and has the same memory capacity as each of the line memories 6 to 8. Note that the above-mentioned LCLK is used as a clock for writing and reading data into the line memory 9. Further, the image signal read out from this line memory 9 is assumed to be D4.

The device control circuit 3 executes control of write/read operations of the line memories 6 to 9 and selection control of the data selectors 14 and 15, and determines when to write the BD double signal and the image in the sub-scanning direction. Vertical synchronization signal VS
Control is performed for each line based on YNC and image clock VCLK.

The data selector 16 selects one of the signals D1 to D3 read from the line memories 6 to 8 and the signal D4 read from the line memory 9 and outputs the selected signal as the image signal VDO'.

FIG. 2 is a block diagram showing a specific configuration of the first interpolation circuit 17.

A 4-bit 16-gradation input image signal VDO is input to the shift register 18, and shift outputs B and A are sequentially outputted in response to an image clock signal VCLK. The shift outputs B and A are image data adjacent to each other in the main scanning direction.

The adder 20 calculates and outputs the average value of data B and data A resulting from the shift output. That is, specifically,
By taking the upper 4 bits from the 5-bit data that is the addition result including the carry output of 4-bit data B and A, the average value (A+B)/2 of the two data B and A is obtained.

The average value data (A+B)/2 and the shift output data A are input to the selector 23, and the selection signal S
When EL is rlJ, data A is output, and on the other hand, when selection signal SEL is "0", the average value data (A
+B)/2 is output.

The control circuit 21 alternately switches between original image data and interpolated data by outputting a selection signal SEL'' every cycle of the double image clock signal vCLK''.

On the other hand, the difference calculation circuit 19 calculates the difference between the adjacent image data B and A, and when this value is larger than a predetermined value, it is regarded as an edge portion of one image and outputs an edge detection signal DIF.

FIG. 3 is a block diagram showing the configuration of the difference calculation circuit 19.

In the figure, inversion circuits 26 and 28 have the function of inverting the logic of each bit of input 4-bit data. The adder circuit 27 adds 1 to the input data and outputs the lower 4 bits of data.

The 4-bit data A is input to one data input terminal of the adder 25. Moreover, the above 4-bit data B is
After each bit is inverted by the inverting circuit 26, the adder 2
5 is input to the other input terminal. Adder 25 adds two input data, and when A>B, carry output C
Outputs O. This carry output Co is the selector 29
Used as a selection signal.

The addition circuit 27 adds "1", that is, 4-bit data roooleJ, to the 4-bit data obtained by omitting the carry output of the addition result. This addition circuit 2
The output value of 7 is the difference A-B between A and B when the value of the input data is A>B, and this data A-B is input to one input terminal of the selector 29.

Further, when the value of the input data is A≦B, the value obtained by inverting each bit of the added output value in the adder 25 by the inverting circuit 28 becomes the difference B-A between B and A, and this value B -A is input to the other input terminal of the selector 29.

The selector 29 selects when the carry output of the adder 25 is rlJ among the two input data, that is, A>
When it is B, data A-B is selected and output, and on the other hand, when the carry output is "0", that is, when A≦B, data B-A is selected and output. This output data.

The absolute value of the difference between A and B is IA-87. This data IA
-Bl is set to 5 in the comparison circuit 31 by the predetermined value setting circuit 32.
When the difference between input data A and B is larger than the predetermined value C, the edge detection signal D
IF is output. Note that the predetermined value setting circuit 30 is
For example, it consists of a ROM or the like. Further, the set value may be made variable by a depth sweeper or the like.

At the time when the edge detection signal DIF is output, the data A
and B can be considered to be the data of pixels forming the z+7 edge of the image, the edge detection signal DIF is inputted as the selection signal SEL of the selector 23 via the OR circuit 22 in FIG. . When the edge detection signal DIF is "1", interpolation is performed using the same data as the previous pixel, that is, data A, without interpolating the average value of data A and B.

The data that has been interpolated in the main scanning direction as described above is synchronized with the double image rsync signal VCLK' by the 4-bit flip-flop 24, and sent to the demultiplexer 2 in FIG. is input.

FIG. 4 shows a second interpolation circuit lO that performs interpolation in the sub-scanning direction.
FIG. 2 is a block diagram showing the configuration of FIG.

Output data DSI from the above data selector 14.15
and DS2 to create interpolated data for l lives in the main scanning direction. The interpolation algorithm is the first one described above.
This is the same as that in the Kikuma circuit 17. That is, the difference calculation circuit 19° calculates the difference between the input data DSL and DS2, and outputs the edge detection signal DIF when this difference is larger than a predetermined value. In this second interpolation circuit lo, all output data is interpolated data, so the signal DIF becomes the selection signal for the selector 23°, and this selector 23° detects when the edge detection signal DIF is "0". Time average value (DS1+DS2)/2
When the edge detection signal DIF is "1", interpolated data is created by outputting data Ds1.

This interpolated data is synchronized with the flip-flop 24 degree flip-flop signal LCLK, and the fourth line memory 9
is input.

FIG. 5 is a timing chart showing the operation of the above configuration.

In the figure, "W" indicates a memory write operation, and r
l(J indicates a memory read operation.

By recording based on the interpolated data VDO° created by the method explained above, the 300 dp
The halftone image of i has a smooth gradation expression as shown in FIG. 11 through interpolation, and has edge portions a and b as shown in FIG.
Then, as shown in FIG. 6, sharp edges can be expressed.

Moreover, FIG. 7 is a block diagram showing another example of the above-mentioned difference calculation circuit.

In this difference calculation circuit 19'', 4-bit input data A and B are compared in value by 1. comparator circuit 32, and only when the result is A<B, outputs signals A and B, which are sent to the selector. 33 and selector 34 as a selection signal.

The selector 33 selects the smaller one of the two input data A and B based on the selection signal and outputs it as an m1n (A, B) signal. Further, the selector 34 selects the input data A
, H is selected and output as the max (A, B) signal.

The adder circuit 37 adds a predetermined value C to the value of the win(A,B) signal to obtain an addition signal win(A,B).

B) Output +C. Konomin (A, B)
+C and the above max (A, B) No. 8 are the comparison circuit 3.
8, and (win(A,B)+c)<ma
The edge detection signal DIF is output only in the case of x(A, B). This edge detection signal DIF is the same as that in the first embodiment.

In the above explanation, an example is shown in which the printer controller 52 with a print density of 300 dpi and the printer drive unit 51 with a print density of 600 dpi are combined;
It may be a combination of an i printer controller and an 800 dpi printer driver. Also, although the number of interpolated dots has been explained as one dot, interpolation of multiple dots or 256
It is also effective when handling data with high gradations such as gradations. Furthermore, the printer driving section is not limited to a laser beam printer, but may also be an LED printer or an inkjet printer.

[Effect of the Invention J] According to the present invention, edge portions existing in the original image and other portions are identified from the density difference of reference dots for creating interpolated dots, and interpolation of the edge portions and edge portions are performed. The edges of the original image are interpolated using a different method. Print density conversion processing can be performed without impairing sharpness or gradation, and high-quality images can be obtained using conventional application software.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a data conversion circuit of a laser beam printer according to a first embodiment of the present invention. FIG. 2 is a block diagram showing a specific configuration of the first interpolation circuit provided in the data conversion circuit. FIG. 3 is a block diagram showing a specific configuration of a difference calculation circuit provided in the first interpolation circuit. FIG. 4 is a block diagram showing a specific configuration of the second interpolation circuit provided in the data conversion circuit. FIG. 5 is a flowchart showing the operation of the data conversion circuit. FIG. 6 shows the laser beam printer of the same embodiment.
FIG. 2 is a schematic diagram showing the relationship between printing position and gradation on an output image l line, illustrating a state in which edge portions of an original image are sharply expressed. FIG. 7 is a block diagram showing another example of the difference calculation circuit. FIG. 8 is a block diagram showing an example of a system configuration in a general laser beam printer. FIG. 9 is a schematic diagram showing the relationship between the printing position on the l line and the gradation at a printing density of 300 dpi. FIG. 10 is a schematic diagram showing the relationship between the printing position on the l line and the gradation at a printing density of 600 dpi by simply converting the dot configuration of the image shown in FIG. 9. FIG. 11 is a schematic diagram showing the relationship between the printing position on one line and the gradation when the image shown in FIG. 9 is converted to a printing density of 600 dpi using average value interpolation data. FIG. 12 is an image with edge portions. FIG. 2 is a schematic diagram showing the relationship between the printing position on the l line and the # tone at a printing density of 300 dpi. FIG. 13 is a schematic diagram showing the relationship between the printing position on one line and the gradation when the image shown in FIG. 12 is converted to a printing density of 600 dpi using average value interpolation data. DESCRIPTION OF SYMBOLS 1... Multiplier circuit, 2... Demultiplexer, 3... Device control circuit, 4... Horizontal synchronization signal generation circuit, 5... Oscillation circuit. 6-9...Line memory. 10.17...Interpolation circuit, 11-13...Switching circuit. 14-16...Data selector. 19.19°, 19″'...Difference calculation circuit, 51...
- Printer drive unit, 52... printer controller. Patent Applicant: Canon Co., Ltd. Agent Arata Yokubo Figure 1 Figure 3 Figure 1.9: & Intermediate Calendar Figure 4 Figure 6 Touge Manabu I'L L Figure 7 Figure 8 1'P Science Ii Figure 9: Printing in vertical position Figure 12: Figure 13: Closed in the palm of your hand! r:P zero i, 1

Claims (2)

[Claims] (1) By receiving multilevel dot information of the first printing density and generating interpolated dots of this received dot information, the second
In a recording device that generates multivalued dot information of print density, a plurality of types of interpolation dot generation means generate multivalued interpolation dots by referring to predetermined dots of the received dot information; A recording device comprising: density difference detection means for detecting a density difference between reference dots; and switching means for selectively switching the interpolation dot generation means based on the detection result of the density difference detection means. . (2) In claim (1), an edge portion existing in the image is detected based on the detection result of the density difference detection means, and in the interpolation of this edge portion, the first printing density information in this edge portion is detected. A printing apparatus characterized in that interpolation dots with a density equal to the density are generated, and in interpolation other than the edge portion, interpolation dots are generated with an average value of the density of the reference dots.