JPH04146160A - Optical printer - Google Patents

Abstract

PURPOSE:To improve print quality by a constitution wherein a D/A converting circuit converts a print data constituted of a plurality of bits per a single print dot into analog signals having different levels and printing is performed with different dot diameter by varying the amount of light emitted from a micro light emitting element. CONSTITUTION:An optical printer, in which an optical dot generating means comprising micro light emitting element arrays performs optical writing into a photosensitive body, comprises means for inputting data comprising a plurality of bits including gradation data for a single dot print data, means for holding the data fed from the input means based on a latch signal, and means for controlling the amount of light to be emitted from the micro light emitting means based on an output comprising a plurality of bits from the data holding means. According to the constitution, step is eliminated from an oblique line print resulting in an optical printer having excellent print quality.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to light emitting
The present invention relates to an optical printing device in which minute light emitting elements such as diodes are arranged in an array, and optical writing is performed on a photoreceptor by light emission from the minute light emitting elements.

[Conventional technology]

2. Description of the Related Art An LED printer is a typical example of an optical printing device in which minute light emitting elements are arranged in an array and optical writing is performed on a photoreceptor using light emitted from the minute light emitting elements. This LED printer is a device that selectively causes each LED element to emit light based on print data, performs optical writing on a photoreceptor for each line, and prints on paper using a known electrophotographic process.

FIG. 5 shows an example of an LED element drive circuit that constitutes a part of the optical printing device in the above-mentioned LED printer. The drive circuit shown in the figure is composed of a shift register 1, a latch section 2, a data selector 3, and a driver 4, and the above-mentioned LED elements are connected to outputs DOI to DO64 of the driver 4. The print data D is input to the shift register l by the clock signal (
CLK) and is sequentially shifted serially within the shift register 1. For example, when print data D of 64 bits or more is input, the print data D that has already been input to the shift register 1 is transferred to the shift register in the adjacent drive circuit. Output. The above-mentioned print data D is inputted via the buffer las or the cascade buffer 1b, and the clock signal is supplied via the inverter IC.

When all of the print data D for one line is input to the shift register 1, the print data D held in the shift register 1 is transferred to the latch section 2 in synchronization with the latch signal (LA) supplied via the buffer 2'. is latched to. Furthermore, the print data D latched by the latch unit 2 is output to the driver 4 according to the output of the strobe signal (STR) that determines the light emission time, and when the print data D output to the driver 4 is a high signal, the driver 4 is driven. The corresponding LE
The D element emits light. Further, when the print data D output to the driver 4 is a low signal, the LED element is controlled not to emit light.

In addition, the light emitting/non-emitting control of the LED element as described above is performed using the PL.
The same method is used in optical printing devices using other microscopic light emitting elements such as ZT (image storage display element).

[Problems with conventional technology]

However, using the driving circuit as described above, the LED
When controlling the light emission of a small light emitting element such as a light emitting device, basically the light emission/non-light emission control of the small light emitting element is performed. In other words, the light amount when emitting light is "'1'', and the light amount when not emitting light is "0".
However, there is no intermediate light amount. The size of the printed dots formed on the phosphor varies depending on the amount of light, but in the case of the above-mentioned "1" and "°0" control, the sizes of the printed dots formed are all the same. For this reason, for example, when printing the diagonal line 5 shown in FIG. 6, dot rows 5a, 5b, 5C1, etc. having a predetermined interval are optically written, and each dot row 5a, 5b, 5b, 5c, etc. There will be a step difference of one dot at most between them. For example, when printing at a printing density of 240 DPI, this level difference is 0.
．． It is 1058mm. Therefore, the conventional optical printing apparatus has a drawback that when printing characters or the like that include many diagonal lines, the resulting image is of poor overall print quality.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide an optical printing device with excellent print quality by reducing steps in diagonal line printing.

[Key points of the invention]

In order to achieve the above object, the present invention provides an optical printing device that performs optical writing on a photoreceptor using a light dot generating means in which minute light emitting elements are arranged in an array. input means for inputting multiple bits of data including data; data holding means for holding the data input to the input means based on a latch signal; It is characterized by having a light emission amount control means for controlling the light emission amount of the micro light emitting element.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

This embodiment describes an example of an LED printer using the optical printing device of the present invention. FIG. 1 shows a driving circuit for an LED element used in an LED printer. Furthermore, LED
The mechanical configuration of the printer is compatible with the known electrophotographic process, and includes, for example, a charger and an LE near the photoreceptor drum.
A D head, a developing device, a transfer device, etc. are installed, and optical writing is performed on the circumferential surface of the photoreceptor drum, which is uniformly charged by a charger, from an LED element whose light emission is controlled by a drive circuit, which will be described later. An electrostatic latent image is formed, a developing device converts the electrostatic latent image into a toner image, and then a transfer device transfers the toner image onto paper. In addition, the LED elements, a drive circuit described later, and an imaging lens array are provided in the LED head, and the LED elements are arranged in an array on the same chip on which the drive circuit is formed, and their arrangement direction is so-called main scanning. It is the direction. And L
The structure is such that the light emitted from the ED element is optically written onto the photosensitive drum via an imaging lens array.

On the other hand, the drive circuit 6 shown in FIG. In addition, the output Dot of each driver 11
~Don is connected to an LED element and ~L1, respectively.

Specifically, the shift register 7 is constructed by serially connecting 2n so-called delayed type flip-flops (hereinafter simply referred to as DF and F). However, in this embodiment, two DFs and two Fs correspond to one dot of print data.

In other words, the DF composed of the two DFs and F shown in the same figure
, F sections 7-1 to 7-n each hold 2-bit print data D for controlling the light emission of the LED elements. Also,
DF, F7-1 constituting each DF, F section 7-1 to 7-n
A and 7-1b, 7-2a and 7-2b, . . . are configured to be supplied with a clock signal via an inverter 15.

Furthermore, the latch circuit 8 also has a structure that corresponds to the structure of the shift register 7 described above and can latch 2 bits of data for one dot of print data. That is, each latch portion 8-
1 to 8-n are 2-bit latches 8-1a, 8-1b, 8
-2a and 8-2b.

..., each latch 8-1a, 8-1b.

A latch signal is outputted to 8-2a, 8-2b, . . . via a buffer 13, and the print data D in the shift register 7 described above is latched by the latch section 8 in synchronization with this latch signal. It is.

The data selector 9 also corresponds to the configurations of the shift register 7 and latch circuit 8 described above, and has two outputs per dot of print data.
AND gate (hereinafter referred to as AND gate) 9-1a
and 9-1b, 9-2a and 92b, . . . This data selector 9 is a circuit that outputs the print data D from the latch circuit 8, which is supplied to the AND gate, to the D/AIO in synchronization with the strobe signal. This strobe signal consumes an excessive amount of current when the LED elements -1 to Ln are turned on, and the LED elements L+ and 'Ln
Since the amount of emitted light is relatively large, a short period of light emission is sufficient for optical writing on the photoreceptor drum, so this is a signal for time-divisionally driving the LED elements Ll-Ln. For example, when time-divisionally driving LED elements -1 to Ln, strobe signal 1
~4 (STRI~5TR4) is output to the AND gate one by one, and one write cycle (LED element -1~Ln However, the drive circuit 6 shown in FIG. 1 is normally a cascade buffer 13
Since the LED elements of all the connected drive circuits 6 are connected via a plurality of lines, this output is repeated for each line (-Ln). Note that this strobe signal is not always used (for example, it is not used when a large amount of light is required, such as in a high-speed printer).

D/AIO is AND gate 9-1a, 9-1b, 9-2
This is a circuit that converts the 2-bit configuration print data D output from a and 9-2b, .
-1 to 10-n. The internal configuration of each D/A 10 includes, for example, a decoder that decodes 2-bit data, a voltage selector circuit that selects an output voltage based on the data decoded by the decoder, etc. An analog signal with a voltage value corresponding to the voltage value is output to the driver 11.

The driver 11 is a power MOS) transistor Q, ~Q
, which amplifies the analog signal supplied to (G). In addition, the output (source (S)) of the MOS) transistors Q1 to Qfi, the power supply (Vcc), and the ground (GN
D) The diodes Ila and llb connected between MO
S) Transistors QI to Q, (7) Output at a predetermined level (
This is for circuit protection to maintain the level between GND level and Vcc). Although the amplification factor of the signal level in this driver 11 is constant, the analog signal output from the D/AIO to the driver 11 has multiple levels (four levels in this embodiment as described later). The amplified signal (voltage) at any output level is transmitted to the LED element,
~ Output to L7. The LED elements L and -L output an amount of light according to the supplied voltage level, and perform optical writing on the photoreceptor drum via the imaging lens array.

In the drive circuit 6 having the above configuration, the configuration of the print data D supplied to the shift register 7 will be described below. This print data D is obtained by converting a character code supplied from a host device such as a host computer into dot pattern data using an interface controller (not shown), and performing predetermined processing on each dot of the converted dot pattern data. This is the data. This process is a process for causing the LED elements -1 to Lfi to emit light of different levels of emitted light amounts. That is, one piece of print data supplied to control the light emission of one LED element is processed into 2-bit data ``00'', ``ol''010'', and ``11'', and the above-mentioned D/A 10 circuit is processed. LED based on operation
It supplies signals at voltage levels of elements -1 to L7.

Here, FIG. 2(a) shows the characteristics of the amount of light emitted from the LED elements-1 to L when the supplied voltage levels are different. Characteristics a, b, and c shown in the figure are such that the supplied voltage level is a <
This is an example where b < (), and it can be seen that when the supplied voltage level changes, the amount of emitted light also changes proportionally. Also, dl, dz, d:+ shown in the same figure (a) are LEDs.
The maximum value (peak point) of the output light amount of the element, ~Lfi is 1
When the light intensity is 00%, the diameter of the dot from which 13.5% (1/e2) of the light intensity is emitted is shown. And this one
A light amount of 3.5% is the light that can print dots on the photoreceptor drum (effective spot light). Therefore, the above-mentioned a
The output of the voltage level with the output light amount characteristics of ~C is
By supplying the dots to the elements-1 to L, it becomes possible to print dots on the photosensitive drum with the diameter shown in FIG.

Therefore, for example, when printing diagonal lines 12 shown in FIG. 4, the interface controller processes as follows. However, to make the explanation easier to understand, it is assumed that the same data as in FIG. 6 explained in the conventional example is supplied from the host device. Therefore, in this case, first, as the print data D, the print data of the dot row 5a shown in FIG.
"°0" ... is input [however, data pad 1" is luminous dot data, "0" is non-luminous dot data,
Luminescent dots are shown as solid lines, non-luminous dots are shown as dashed lines). The interface controller calculates this data including the data before and after in the sub-scanning direction, and calculates the data as shown in Fig. 4.
Processed as "1", 1""1'°"1"O"..."
Three printed dots are treated as four-dot data. next,
The size of each printed dot is set based on the characteristics shown in FIGS. 2(a) and 2(c) above.

That is, along the length of the dot row 12a, the dot 12a-1 is a dot that is desired to be printed with a small diameter, and is processed into 2-bit data of 01'', for example.The dot 12a-2 is a dot that is desired to be printed with a medium diameter, for example, The dot 12a-3 is processed into 2-bit data of "10". Also, the dot 12a-3 is a dot that is desired to be printed with a large diameter, and is processed into 2-bit data of "11", for example.Furthermore, in the same way, the dot 12a-4 is This is the dot you want to print in diameter, and it is processed into 2-bit data of "1o". Also, non-print data "0" is processed into 2-bit data of "OO".
The relationship between the data, the amount of emitted light, and the dot diameter is shown in FIG.

The print data D of the dot row 12a processed as described above is..."00""01" II 1011
"11", "10", "00", etc. Also,
Similar processing is performed on other dot rows 12b, 12c, etc.

The print data D created as described above is outputted to the shift register 7 of the drive circuit 6 described above via the amplifier 14, and is supplied in synchronization with the output of the clock signal as described above. Further, the print data D before the above-mentioned processing is composed of n pieces, and the print data D after the processing is composed of 2n pieces, but as mentioned above, the shift register 7 is composed of 2 bits of D.
Since it consists of F and F, when 2n pieces of print data D are outputted in synchronization with 2n pieces of clock signals, the print data D is input to all shift registers 7. And each DF, F department? -1 to 7-n, the corresponding LED element Lt=L- is controlled to have a large diameter, a medium diameter, a small diameter, or no printing 2
This means that the focus data has been input. Therefore, the 2-bit print data D held in each DF and F section 71 to 7-n is then sequentially sent to the latch circuit 8 and data selector 9 in synchronization with the latch signal and strobe signal output at a predetermined timing. The signal is outputted to the corresponding D/A 10 via the D/A 10. For example, when one line of print data D including the dot row 12a is output to the D/A 10, as described above... "01""10"11"'"10""
Data 00'... is supplied to the D/AIO. For example, the D/AIO to which the print data “01” is supplied
Then, as described above, the decoder and voltage select circuit in the D/AIO output an analog signal (voltage VGSI) at a voltage level corresponding to the input data "01".Then, this analog signal is output to the driver 11; Amplify the corresponding voltage level with the corresponding LED.
Element L+ emits light Ln. At this time, LED elements L1 to L
The amount of light emitted from n is a light amount characteristic a as shown in FIG. 3, and dots with a small diameter d1 are printed on the photosensitive drum. Furthermore, when the print data D is "10", it is converted into an analog signal (VGS2) of the corresponding voltage level by the D/AIO, and after a predetermined amplification process is performed by the driver 11, the LED element LI-Ln emits light. The light emitted at this time has a light quantity characteristic, and dots with a medium diameter d2 are printed on the photoreceptor drum. Similarly, when the print data is '11'', it is converted to an analog signal (VGS3) of the corresponding voltage level by the D/AIO, and the LED element emits ~Ln through the driver 11, and the photoreceptor drum Dot printing with a large diameter d3 is performed.

On the other hand, in the case of print data D"oo", no analog signal is output from the D/AIO (the output signal is OV), so no current flows through the corresponding LED element ~Ln, and the LED element is controlled not to emit light.

By controlling the light emission of the LED elements 1 to 1 as described above, for example, in the case of the above-mentioned dot row 12a, it is possible to print with the corresponding dot diameter as shown in FIG. Similarly, large diameter, medium diameter, and small diameter printing can be performed based on preset processing data.
The diagonal line 12 can be printed in a much more natural straight line than in the past, that is, the stepped portion can be filled with small-diameter dots.

In the seventh embodiment, 2-bit processed data was created as the print data D supplied to the LED elements -1 to L1, but the shift register 7, latch circuit 8, and data selector 9 were constructed using 3 bits, 4 bits, etc. By using a configuration in which data with other bit numbers such as ・ etc. can be shifted, latched, and selected, processed data with other bit configurations can be used. It is possible to print with fine dot diameters, further improving the printing quality of diagonal lines.

Further, in this embodiment, the D/AIO is configured to output signals with different voltage levels, but it may be configured to convert into analog signals with different current values.

For example, the D/AIO may be configured to include a decoder and a current selection circuit, and the current value output to the driver 11 may be set at multiple levels.

Furthermore, although an LED element is used as a microscopic light emitting element in this embodiment, an optical printing device using a fluorescent display tube, PLZT, or the like can also be used.

〔Effect of the invention〕

As explained in detail above, according to the present invention, print data consisting of a plurality of bits per print dot is converted into analog signals with different levels by a D/A conversion circuit and output, and the amount of light emitted from a minute light emitting element is Since it is possible to perform printing with different dot diameters by changing the dot diameter, printing accuracy of diagonal lines can be improved and images with excellent print quality can be created.

[Brief explanation of drawings]

Figure 1 is a drive circuit diagram in an LED printer of one embodiment, Figure 2 (a) is a characteristic diagram of the signal level supplied to the LED element and the amount of emitted light, and Figure 2 (b) is a diagram of the same figure (a). ) Figure 3 is a diagram explaining the relationship between the print data D and the output light volume and dot diameter, Figure 4 is a diagram explaining the printing of diagonal lines according to this embodiment. 5 is a diagram of a drive circuit in a conventional LED printer, and FIG. 6 is a diagram illustrating printing of diagonal lines according to the conventional example. 6... Drive circuit, 7... Shift register, 8... Latch circuit, 9... Data selector, 10... D/A, 11... Driver 12... Diagonal line, 12a~ 12c... Dot row. Patent applicant Casio Electronics Industries Co., Ltd. Same as above
Casio Computer Co., Ltd.<a> Figure Figure 111-I゛1''1''゛1''"o"--■ Figure Q Figure Procedure Amendment February 7, 1991 2゜Heisei 2 years Patent Application No. 270208 Name of the invention 3゜4゜5゜6゜Relationship with the optical printing device amendment case Patent applicant name Casio Electronic Industries Co., Ltd. Representative Kazu Kashio Name (144) Casio Computer Co., Ltd. Representative Kashi
Kazuo Yuyo Masato Zip code 102 Address Kojimachi Kyoei Building, 6-1-18 Kojimachi, Chiyoda-ku, Tokyo Telephone (03) 32.38-0031 Name (74)
09) Date of amendment order issued by Patent Attorney Yoshiyuki Osuga Drawing subject to voluntary amendment 8″ I 7 Contents of amendment 1) In the first line of page 12 of the specification, the statement “shows.
" is corrected to "show. Here, the vertical axis shows the amount of light, and the horizontal axis shows the spread of light. In the same figure...". 2) On page 12, lines 4 to 10 of the specification, there is a statement that ``the amount of spot light is shown in (a) in the same figure)''. The dot diameter is L
When the maximum value (peak point) of the output light amount of the ED element -L is taken as 100% light amount, the area is determined by the area to which 13.5% (1/e2) of the light amount is irradiated. dl shown in FIG. 5A is the dot diameter at the maximum light amount C, and similarly, dz and dz are the dot diameters at the light amount b and light amount a, respectively. ” he corrected. 3) Correct the drawings in Figures 2(a) and 2(b) as shown in the attached sheet. (b) Figure 2

Claims (3)

[Claims] (1) In an optical printing device that performs optical writing on a photoreceptor using optical dot generation means in which minute light emitting elements are arranged in an array, multiple bits of data including gradation data are generated for one dot of print data to be printed. An input means for inputting data, a data holding means for holding data inputted to the input means based on a latch signal, and controlling the amount of light emitted by the micro light emitting element based on a plurality of bits output from the data holding means. 1. An optical printing device comprising: a light emission amount control means. (2) The optical printing device according to claim 1, wherein the light emission amount control means controls the light emission amount by varying the output voltage value to the micro light emitting element. (3) The optical printing device according to claim 1, wherein the light emission amount control means controls the light emission amount by varying the output current value to the micro light emitting element.