JP2920914B2 - Drive circuit for solid-state scanning device - Google Patents

Description

The present invention relates to a driving circuit for driving a solid-state scanning element such as a light-emitting diode (LED), a liquid crystal, a PLZT, etc. The present invention relates to a driving circuit for a solid-state scanning element capable of outputting a halftone image without lowering the resolution when gradation is expressed by using such a solid-state scanning element for a print head or the like.

[Conventional technology and its problems] In recent years, laser beams and light emitting diodes (LE
D), solid-state scanning devices such as liquid crystals have come to be used in the field of image output devices and the like. For example, as an optical printer using an electrophotographic process, a laser printer, an LED, etc.
Printers, liquid crystal printers, and the like have come into practical use.

On the other hand, recently, with the diversification of image information and the digitization of copiers, the above-described image output apparatus is required to have an image output function having high resolution and high gradation expression. It has become

Therefore, in each of the image output devices as described above, various methods have been studied in order to enhance the gradation expression power and skillfully output a halftone image.

For example, in the case of a laser printer, as a method for expressing a halftone image, a continuous recording is generally represented by a binary recording method as represented by a dither method, a density pattern method, or the like. A pseudo-halftone expression method of changing the area ratio of black by changing the number of black dots per fixed area has been used.

However, such a pseudo-halftone expression method has a problem that the image quality is remarkably changed depending on how to obtain the number of black dots, the resolution is reduced, and noise is generated. However, they did not provide sufficient images.

Further, a method of modulating the intensity of the laser beam to several levels to perform multi-level recording to express a halftone has been studied, but there are still many unsolved problems.

On the other hand, various gradation expression methods have been studied for an optical printer using a solid-state scanning element such as an LED or a liquid crystal for a print head.

However, even in a print head using the solid-state scanning element as described above, the driving method is conventionally based on binary image data. There is no other choice but to use the objective gradation expression, and it has the same problem as the laser printer.

For example, in a conventional LED printer, when the print head is driven, the drive circuit includes a shift register (1), a latch circuit (2), and a driver (3) as shown in FIG. From the image signal input to the shift register (1)
The electric signal that reaches (4) is all processed as a digital binary signal, and the signal input to the LED (4) outputs an intermediate value, either ON or OFF. I couldn't.

That is, in the conventional LED print head, since the shift register (1) is configured by a flip-flop, it naturally has only a digital signal transfer function, and the image signal input to the shift register (1) The data signal latched from the shift register (1) to the latch circuit (2) and the electric signal input to the LED (4) by the driver (3) by the driver (3) are all digitally processed. It was.

Therefore, even in a solid-state scanning printer using a solid-state scanning element such as an LED or a liquid crystal, in the case of performing halftone expression, as in the case of a laser printer, it is absolutely necessary to rely on pseudo gradation expression. However, there is a problem that the resolution is deteriorated and the image quality is deteriorated due to generation of noise or the like.

[Problems to be Solved by the Invention] The present invention solves the above-described problems in performing gradation expression using a solid-state scanning element such as a light emitting diode (LED), liquid crystal, or PLZT in a print head or the like. That is the task.

That is, according to the present invention, when a solid-state scanning element such as an LED, a liquid crystal, and a PLZT is used in a print head or the like to perform gradation expression, each solid-state scanning element can provide an intermediate output and reduce the resolution. It is another object of the present invention to provide a driving circuit for a solid-state scanning element that can easily and independently modulate the intensity of dots in each solid-state scanning element.

[Means for Solving the Problems] In a drive circuit for a solid-state scanning element according to the present invention, in order to solve the above-mentioned problems, an input multi-bit digital electric signal is converted into an analog electric signal. A digital-analog converter that serially outputs the analog electric signal, and an analog shift register that sequentially transfers the signal charges injected from the input unit based on the analog electric signal serially input from the digital-analog converter. An analog latch for temporarily storing the signal charge transferred to the analog shift register, a shift gate for controlling transfer of the signal charge from the analog shift register to the analog latch, and a signal charge stored in the analog latch. Providing a driver unit for providing an electric signal based on the amount to the solid-state scanning device It was.

[Operation] In the driving circuit for a solid-state scanning element according to the present invention configured as described above, a digital electric signal composed of multiple bits is input to a digital-analog converter, and the digital-analog converter is operated. The above-mentioned digital electric signal is converted into an analog electric signal, and this analog electric signal is serially input to an input section of an analog shift register, and a signal charge based on the analog electric signal is serially injected from the input section into the analog shift register. Then, the injected signal charges are sequentially transferred in the analog shift register.

Then, when a predetermined number of data is input to the analog shift register, each signal charge input to the analog shift register is latched by the analog latch by the action of the shift gate.

Then, based on the amount of signal charges stored in the analog latch, each driver of the driver section supplies an electric signal corresponding to each signal charge amount to each solid-state scanning element.

Here, as described above, a digital electric signal composed of multiple bits is input to a digital-to-analog converter, and the digital-to-analog converter converts the digital electric signal to an analog electric signal. When the signal is input serially to the input portion of the register, the deterioration and fluctuation of the electric signal during transmission are reduced as compared with the case where the signal is transmitted in the form of an analog signal and the analog signal is input to the analog shift register.

When an electric signal based on the signal charge amount stored in the analog latch is given to each solid-state scanning element as described above, each solid-state scanning element is driven in accordance with the signal charge amount, and the signal charge amount is reduced. An appropriate gradation expression is performed.

Embodiment An embodiment of the present invention will be specifically described below with reference to the accompanying drawings.

(Embodiment 1) In this embodiment, a driving circuit will be described in the case where a light emitting diode (LED) is used as a solid-state scanning element and this is used for a print head of an optical printer.

In the drive circuit of the print head according to this embodiment, as shown in FIG. 2, an input section (11) for serially injecting a signal charge into an analog shift register (10) based on an analog electric signal, and the input section (11). An analog shift register (10) for sequentially transferring the signal charges input from the section (11), and an analog electric signal based on the signal charges transferred through the analog shift register (10) and passed to the next analog shift register (10). An output section (12) for outputting to the 10) side, a shift gate (30) for transferring each signal charge inputted to the analog shift register (10) to an analog latch (20), and an analog shift register (10). An analog latch (20) for temporarily storing the transferred signal charges, and an electric signal based on the amount of signal charges stored in the analog latch (20) for each light emitting device. Driver applied to the diode (50) (40) and is configured as a unit (A).

In this embodiment, the analog shift register (1
0) can transfer analog signal charge as C
A CD shift register (10) is used. As the CCD shift register (10), one having a capacity for 40 image data is used. Because we need image data,
As shown in FIG. 3, a plurality of the above-mentioned one unit (A) including the CCD shift register (10) are connected and used.

As shown in FIG. 2, the driver section (40) includes a preamplifier (41) for exchanging the signal charge amount stored in the analog latch (20) into an electric signal for driving the light emitting diode (50) easily. ) And an individual amplifier (42) for individually supplying the electric signal converted by the preamplifier (41) to each light emitting diode (50).

Next, a case where a print head is driven using such a drive circuit will be described.

First, a digital-to-analog converted analog image signal is input to the input unit (11), and a signal charge based on the analog image signal is converted through the input diode and the channel gate of the input unit (11) into the signal charge. Charge is injected under the transfer electrode of the CCD shift register (10).

The signal charges thus injected are sequentially transferred in the CCD shift register (10), and the signal charges passing through the CCD shift register (10) are sequentially output as analog signals from the output section (12). And the next CCD
It is led to the shift register (10).

When a predetermined number of data is input to the CCD shift register (10) in each unit (A) in this manner, the shift gate (30) operates to operate each signal input to each CCD shift register (10). The electric charges are latched in the corresponding analog latches (20).

An electric signal which is easy to drive the light emitting diode (50) by the preamplifier (41) of the driver section (40) according to the amount of each signal charge latched by the analog latch (20). The electric signals thus converted are individually supplied to the corresponding light emitting diodes (50) via the individual amplifiers (42).

Accordingly, each light emitting diode (50) emits light corresponding to each electric signal converted according to the signal charge amount, and performs various gradation expressions depending on the difference in the charge amount.

(Embodiment 2) The drive circuit of this embodiment is almost the same as the drive circuit of Embodiment 1 described above. However, in the drive circuit of this embodiment, as shown in FIG. A digital-to-analog converter (13) is provided on the input side of the input unit (11) to convert the signal into a signal and input it to the input unit (11).
On the other hand, the analog electric signal output from the output unit (12) is converted into a digital electric signal to guide the next CCD shift register (10). A vessel (14) is provided.

In this embodiment, the digital image signal of 3 bits, that is, 8 gradations is converted into an analog electric signal by the digital-analog converter (13), and this analog electric signal is serially inputted to the input section (11). , And a signal charge based on the analog electric signal is sequentially injected from the input section (11) into the CCD shift register (10).

The analog electric signal output from the output unit (12) after passing through the CCD shift register (10) is converted into a digital electric signal by the analog-digital converter (14), and is converted into the next CCD shift register ( 10) sent to the side. Then, on the next CCD shift register (10) side as well, the digital-to-analog converter (13) converts the digital electric signal into an analog electric signal in the same manner as described above, and transmits the converted signal via the input unit (11). Signal charge in order
It is to be injected into the D shift register (10).

Thus each CCD shift register (10)
After a predetermined number of data is input to each of the light emitting diodes (50), each electric signal corresponding to the signal charge amount is individually supplied to each light emitting diode (50) in the same manner as in the first embodiment. ) Emits light based on each electric signal corresponding to the signal charge amount.

In this embodiment, a digital image signal of 3 bits, that is, 8 gradations is input, so that 8 gradations can be expressed. However, in order to further increase the number of gradations, a larger number of bits is required. It is also possible to input a digital image signal having the following.

Further, in each of the above embodiments, an example in which the light emitting diode (50) is used as the solid-state scanning element (50) has been described, but the solid-state scanning element (50) to be used is not limited to this. It is also possible to use elements such as liquid crystal, PLZT, and the like.

Further, in these embodiments, an example in which such a drive circuit is used for a print head of an optical printer has been described, but a print head such as an electrostatic printer, an ion flow printer, a thermal printer, or an ink jet printer using a multi-needle electrode is used. It is also possible to use as a drive circuit of

Further, such a drive circuit is not limited to a printer,
It can also be applied as a drive circuit for displays such as LED displays, fluorescent display displays, electroluminescent (EL) displays, liquid crystal (LC) displays, plasma displays, and electrochromic displays.

[Effects of the Invention] As described above in detail, in the solid-state scanning element and the driving circuit according to the present invention, a digital electric signal composed of multiple bits is input to a digital-analog converter, and the digital-analog converter performs the above-described operation. The digital electric signal is converted into an analog electric signal, and the analog electric signal is serially input to the input section of the analog shift register. Therefore, the analog electric signal is transmitted in an analog signal state and the analog electric signal is transmitted to the analog shift register. The deterioration and fluctuation of the electric signal during transmission are reduced as compared with the case of inputting.

Then, as described above, an analog electric signal is serially input to the input unit from the digital-analog converter, and a signal charge corresponding to the analog electric signal is sequentially injected from the input unit to the analog shift register. By causing the analog latch to latch by an action, an electric signal based on the amount of each signal charge accumulated in the analog latch is given from each driver of the driver section to each corresponding solid-state scanning element, so that each solid-state scanning element An output expression corresponding to each signal charge amount accumulated in the latch can be performed.

As a result, when the solid-state scanning element driving circuit according to the present invention is used, each of the solid-state scanning elements can independently perform various gradation expressions, and can perform the pseudo halftone expression as in the related art. Halftone expression can be easily performed regardless of the method, and the resolution and noise are not reduced due to the decrease in the number of dots unlike the conventional method. Powerful image output is now possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a conventional drive circuit for driving an LED print head, FIG. 2 is a block diagram showing one unit of a drive circuit of an LED print head according to Embodiment 1 of the present invention, and FIG. FIG. 4 is a block diagram showing a state in which a plurality of units shown in FIG. 2 are connected, and FIG. 4 is a block diagram showing one unit of a drive circuit of an LED print head according to a second embodiment of the present invention. [Description of Signs] (10) Analog shift register (CCD shift register), (11) Input section, (13) Digital-analog converter, (20) Analog latch, (30) … Shift gate, (40)… Driver section, (50)… Solid-state scanning element (light emitting diode).

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kane Matsubara 2-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Camera Co., Ltd. (72) Koichi Aragaki 2-chome Azuchi-cho, Higashi-ku, Osaka, Osaka 30 Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Tomohiko Masuda 2-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-63-252764 (JP, A) JP-A-63-37969 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/45 B41J 2/35

Claims (1)

(57) [Claims] A digital-analog converter for converting an input multi-bit digital electric signal into an analog electric signal and outputting the analog electric signal in a serial manner;
An analog shift register for sequentially transferring signal charges injected from an input section based on an analog electric signal serially input from the digital-analog converter, and temporarily storing the signal charges transferred to the analog shift register An analog latch, a shift gate for controlling transfer of signal charges from the analog shift register to the analog latch, and a driver unit for supplying an electric signal based on the amount of signal charges accumulated in the analog latch to a solid-state scanning element. A driving circuit for a solid-state scanning element, comprising: