JPS59127468A - Printer - Google Patents

Abstract

PURPOSE:To form a half-tone picture through simple circuit constitution by modulating the luminance of a light emitting element and giving respective picture elements gradations. CONSTITUTION:When a base line CS is activated by a decoder and a switching element S is switched, switching elements SA and SB on a data line side are turned on corresponding to 2-bit picture element data DMSB and DLSB. Then, the values of current limiting resistances RA and RB are predetermined so that the current IFA flowing through the resistance RA is smaller than the current IFB flowing through the resistance RB, imposing quad luminance modulation upon an LED. Therefore, the density of each dot on a photosensitive body is modulated by said brightness modulation. Then, the luminance modulation having 2<n> gradations is made possible by (n) switching elements and (n) current limiting resistances.

Description

Detailed Description of the Invention The present invention relates to a printer that prints a desired image by driving light emitting elements such as LEDs (light emitting diodes), and in particular to a printer that prints a desired image by driving light emitting elements such as LEDs (light emitting diodes). It is designed to form shading.

BACKGROUND OF THE INVENTION Recently, LED printers, which are suitable as facsimile receiving devices or computer output devices, have been attracting attention, and are capable of printing (image recording) by arranging a large number of light emitting elements such as LEDs. Usually, this kind of LED printer has 2
An image is formed on the photoreceptor by turning on (lighting up) or turning off (burning off) the EO in accordance with the digital image signals of the values. Therefore, when forming a halftone image such as a photograph using a conventional apparatus, a gradation expression method called a dithering method is generally used to express the gradation of the image. Therefore, not only does the circuit become complicated, but the dither method expresses shading by the number of dots in a predetermined area (region), which has the disadvantage of lowering the resolution.

In view of the above-mentioned points, the present invention modulates the brightness of a light-emitting element by using n switching elements and n current-limiting resistors for n-focus image signals forming an I@ element, and each It is an object of the present invention to provide a link that forms shading of pixels and thereby allows a halftone image to be obtained with a simple circuit configuration without using a conventional shading expression method such as a teaser method.

Example The present invention will be described in detail below with reference to one drawing.

FIG. 1 shows an example of the configuration of an LED printer to which the present invention is applied, where 1 is an LED printer head, and a large number of LEDs corresponding to donts constituting one scanning line of an image.
Normally, this large number of LEDs is divided into several blocks, a common line is connected to the LEDs at the same position in each block, and the LED array is illuminated by a dynamic driving method. For example, 4096 LEs
D Ll-1 to L84-84 are arranged in a line, each having 64 blocks Ll-1 to Ll-84.

L2-1 hoof 2-64. ...L64-1~(,84-
Divide into 84 parts. A switching element (transistor) Sl-5l14 is connected to the cand side of this LED for each block.
7 of the LEDs in tied positions in each block.
Connect each maid side with a common line.

Each LED in the same rank is connected to a current limiting resistor R
A (representative of RA1 to RA84) and switching element (transistor) 5A (representative of SAI-3A134)
and current limiting resistor Re (representative of RBI-ReO2)
and switching element (transistor) 5B (SBI
The switching element SA or SB is turned on (conducted) in response to the 2-focus digital image signal, which performs brightness modulation using the -8B84 (representative of 8B84). Pass current. At this time, only the LEDs of the blocks selected by the switching elements 51 to S64 are lit in accordance with the pixel data (digital image No. 44).

2 and 3 are input terminals to which serial continuous digital pixel data of 2 bits per pixel for one scanning line is input; pixel data DH5R is input from terminal 2, and pixel data DLSB is input from terminal 3. 4 is the input terminal of pixel data transfer lock CIJ, and 5 is! An interval signal VIDEO- representing a valid interval of serial pixel data of a scanning line
This is the ENABLE input terminal. 6 and 7 are 64-bit serial-in-parallel-out 64-clock shift registers that each operate as a buffer 7 memory, and of the 2-pit pixel data, the pixel data DLSB input from the human input terminal 3 is sequentially and alternately 64 bits at a time. -force is input to switching element SAI -! When pixel data DLSB is output to 3Ae4, the other inputs 64-bit pixel data DLSB. Similarly, 8 and 8 are 64-bit serial/parallel-out θ4 clock shift registers each operating as a buffer memory, and sequentially and alternately input pixel data DMSB and output them to switching elements SBI to 5iBft4. 10
is an output control section, which includes shift registers 6 and 7, and 8.
and 8 output control, and at the same time, LED Lll~
Control is also performed to sequentially switch common switching elements S1 to S84 from St to 884 for each block of Lf14-84.

Reference numeral 11 denotes a 64-decimal counter, which receives a count clock signal to-5- transmitted from the output control unit 10 every time l block of pixel data is output from the shift registers 8 to 8.
Count 1 from "o" to '[13]. 12 is 8
This is a 6-line manual 64-bit output decoder that decodes the binary count value of the quaternary counter 11.
1 to S84 are switched in order.

Next, an example of the operation of the LED printer shown in M1 is shown in FIG.
This will be explained in more detail with reference to the timing charts a) to (i). Note that the numbers in 0 appended to each number 48 in FIGS. 2(a) to (i) correspond to the input terminals in FIG. 1 and 4? ”r
Corresponds to the line number. First, at the first timing TA, the interval signal Q! input from the terminal 5! DEO-EN
In response to the rise of ABLE (see Figure 2 (a)), the edge A4
Block CLK input from (see Figure 2 (b) 116
), serial pixel data DMSB and DLSB from terminals 2 and 3 are supplied to shift registers 6 and 8 of the first group in 64-bit units.

That is, the pixel data transfer lock CLK is changed by the output control unit 1o as shown in FIG. 2(d), and is supplied to the shift registers 6 and 8 through the signal line 1o-1. , pixel data DMSB and D
The LSB is stored in shift registers 6 and 8 in synchronization with each falling edge of clock cLK-A.

At the next timing TH, the pixel data DLSB and DMSB are transferred to the shift register 7 of the second group.
and 9 are stored in 84 bits each. That is, at this timing TB, the shift registers to which the pixel data DAT^ are input are switched from B and 8 to 7 and 8. Also, during the period from timing TB to 10, the output control unit 1
An output enable signal 0ENABLE-A (see FIG. 2(f)) is supplied from 0 to the shift registers 6 and 8 through the signal line 10-3, whereby the 84-bit pixel data D stored in each shift register is
LSB and DMSB are connected to switching element '3Al-
5A64 and SBI-3B 114 to cause their respective switching elements to perform switching operations according to the pixel data DLSB and DMSB. On the other hand, between timing TB and 10, 64 bits of the next serial pixel data are stored in shift registers 7 and 8 as described above, but at this time, the pixel data transfer lock CLK is set by the output control unit IO. By changing the clock CLK-8 shown in FIG. 2(e), the shift register 7
and 9.

At that time, the 64-decimal counter 11 receives the count signal 10-5-1 from the output control unit 1o and the output enable signal 10-
8-1 is supplied. Count clock signal 10-5
-1 is the output enable signal 0E in Figure 2 (g)
This corresponds to NABLE-B, and the 84-decimal counter 18 counts at the rising edge of this signal. Output enable signal IQ-
8-l fx's 2 Figure (1) Output permission M No. VI
This corresponds to DEOEM-8D, and the decoder 12 does not output unless this signal is 1°' (H level). Since the signal 0ENABLE-B rises for the first time at timing TC, the content of the 64-decimal counter 11 is "0" from timing TB to TC, and the signal VIDEOE
Since N-8 rises to l'' at timing TB, the switching element Sl decoded by the decoder 12
Only then becomes a low (conducting) state. Therefore, from timing TB to TC, LEDs Ll-1 to Ll-1 of the first block correspond to the first 84 bits of pixel data.
1, 1-84 are lit.

From the next timing TG to TO, the next pixel data DATA (DMSB!'3 Yohi DLSB) (7
)129 hi' y h 192nd bit 6
Four bits are stored in shift registers 6 and 8 by image data transfer lock CLK-A. At the same time, the 64-pint pixel data stored in shift registers 7 and 8 is output to switching elements SAI -9Aθ4i and SBI ~5sea, and is output to LE of the second block.
D Turn on L2-1 to L2-84. At this time, output enable signal 0ENABLE-B is applied to shift registers 7 and 9 through signal line 10-5.
becomes l°゛, which indicates output permission. Further, the count value of the 84-decimal counter 11 becomes ゛1'' due to the rise of the count clock signal 10-5-1, and the decoder 12
The inching element S2 is selected and turned ON (conducting).

The above-described operations are sequentially repeated until timing TE, and 4086 bits of pixel data of one scanning line are sequentially output to switching elements SAI-SAθ4 and SBI-5B64 in units of 64 bits. Then timing TE
- At TF, the last 64 bits of pixel data stored in shift registers 7 and 8 are output, and printing of the scanning line is completed.

FIGS. 3(a) and 3(b) show the principle of brightness modulation for the LED array of the LED printer of the present invention shown in FIG.

Here, S is a switching element common to each block of the LED array, and the switching element 5t-
It corresponds to 364. It is now assumed that the base line C8 is activated by the decoder 12 shown in the first diagram, and the switching element S is switched. At this time,
Switching elements SA and SB on the data line side are turned on (conducted) in response to two hints of pixel data DMSB and DLSB. DMSB and D of pixel data
When the active state of LSB is cleared, the current value of the current IF flowing through the LED becomes as shown in Fig. 3(b),
If the currents IFA and IFB flowing through the current limiting resistors RA and Re are determined so that IFA <IFB, then 4
Brightness modulation of the value will be performed. Therefore, by such brightness modulation, the density of one dot on the photoreceptor can be modulated.

Note that in this example, a digital pixel signal of 2 bits per lli]Ii element was explained, but in the case of a digital pixel signal of 3 bits or more (iR), the digital pixel signal (
It is possible to perform H-degree modulation according to the 1'i signal.

That is, in the case of a digital signal with n pips, n
(With N switching capacitors and n current limiting resistors,
It is possible to perform brightness modulation of 2'' gradation.In addition to LEDs, an ELi element or the like may be used as the light emitting element.

As explained above, according to the present invention, each pixel modulates the brightness of a light emitting element using n switching elements and n current limiting resistors for an n-bit image signal forming one tooth. Since the bar 21 is formed in shading, a high-resolution bar 21 image can be obtained with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of an LED printer to which the present invention is applied, FIGS.
Figures (a) and (b) are circuit diagrams showing the principle of brightness modulation of the LED printer shown in the first figure, and surfaces of output characteristics. I... ED printer hand, 2... Input terminal for pixel data DMSB, 3... Input terminal for pixel data DLSB, 4... Input terminal for pixel data transfer long CLK. 5-[%,: between 4r No. VIDEO-ENABLE (7
) input terminal, 6.7... Shift register (Panza memory) that stores pixel data DLSB, 8.9... Shift register (Panza memory) that stores pixel data DMSB, 10... Output control 11...64-decimal counter. 12...Decoder. 11 to 84-1 (4... ED (light emitting diode), S, Sl to S64... switching element (transistor). SA, SAI to 5A84... switching element (transistor off, RA, RAI) ~RAθ4...Current limiting resistance, F!
B, R, B I~l'? BI34...Current limiting resistance, 1F, IFA, IFB...Current, TA-
TF...timing. CLK-A, C; LK-8...Cronk, VIDE
OEN'-A, VIDEOEN-8...Output enable signal, 0ENABLE-A, 0ENABLE-8...Output I enable signal. 10-1 to 10-6...I word line, IQ-5-1...Count clock other things, to-e-
t...Output enable signal. Patent applicant: Canon Co., Ltd. - Friend procedural amendment (Hogen Showa SR, April 28, 1999, Director General of the Patent Office, Kazuo Wakasugi, 1, Indication of the case, Patent Application No. 3T-2293, 2, Name of the invention, Printer 3) , Relationship with the case of the person making the amendment Patent applicant (100) Canon Co., Ltd. l) "Figure 2 (a) to (1)
)" should be corrected to "Figure 1." 2) Correct "[Figure 2 (a) to (i)]" in line 6 of page 6 of the same page to "(a] to (1) in Figure 2)". 3) Page 6 of the same page, line 1O Correct "Figure 2 (March)" in the line "Figure 2 (March)" to "(a) in Figure 2".
(b) in Figure 2. ri) "(d) in Figure 1" on page 6, line 76 of the same page is corrected to "(d) in Figure 1." 6) Correct "(f) in Figure 1" on the 7th line of page 7 to "(f) in Figure 2". 7) Correct ``Figure 2 (e)'' on page 7, line 20 to ``(e) in Figure 2''. g) Correct "(g) in Figure 1" in line 6 of the same letter to "(g) in Figure 1." D) In line 9 of the same letter, correct ``θ month in Figure 2'' to ``(1) in Figure 2.'' 10) "Figure 1 (a) ~" in the same page 1/page 1g~/9th line
(1) are respectively corrected to "P" and "Figure 1 to J.

Claims (1)

[Claims] In a printer where each pixel is formed by a light emitting element,
Each pixel is formed by an n-bit digital signal, and H
- A printer characterized in that the brightness of each of the light emitting elements forming a pixel is modulated by n switching elements and n current limiting resistors to form shading of each pixel.