JPH05323733A - Ion current control system multilevel image recorder - Google Patents

Abstract

PURPOSE:To facilitate high tone control, to increase a printing speed and to execute tone reproduction with excellent quality even when high-speed driving is executed by providing a recording head and a waveform transformation circuit. CONSTITUTION:Independent pulses are respectively formed as a driving pulse for controlling the tone of one dot by an amplitude modulation part and a pulse width modulation part 11, and the pulse width of the modulation part 11 is changed by changing the pulse width of the amplitude modulation part stepwise as unit pulse width. Then, the N tone control is executed by the amplitude modulation part and the M tone control is executed by the modulation part 11 so as to obtain the NXM tone. Thus, in the case that the identical tone is realized, the driving speed can be made M-fold when N>M is attained and the driving speed can be made N-fold when N<M is attained. Then, the high-speed driving and the high tone reproduction are realized. Therefore, the printing speed is also increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation image recording apparatus for recording gradation images by controlling a charge flow of ions or the like.

[0002]

2. Description of the Related Art Conventionally, a corotron discharge type slit control system in which ions generated by corotron discharge are introduced into a slit portion and an electric field in the slit wall is changed to control an ion flow to form a charge pattern on a recording medium. The image recording device, the ion generated by the corotron, controls the electric field between the two control electrodes having the opening to control the ON / OFF of the ion flow toward the recording medium through the opening.
A corotron discharge type aperture control type image recording device that forms a charge pattern on a recording medium, a high frequency voltage is applied between electrodes arranged via an insulator to generate a discharge, and the ions generated by the discharge are controlled by an electric field. There is proposed an image recording apparatus of a solid-state discharge type aperture control system, which selectively draws out and forms a charge pattern on a recording medium.

In an image recording apparatus using such an ion flow, when the magnitude of the electric field between the electrodes for controlling the ion flow is small, the dot diameter formed by narrowing the ion flow becomes small, and the ion flow is also reduced. When the electric field between the electrodes for controlling is large, the diameter of the ion flow is large and the dot diameter is large, and a gradation image can be formed by controlling the electric field between the electrodes.

When the magnitude of the electric field between the electrodes for controlling the ion current is kept constant and the time during which the electric field is applied is changed, the amount of charge formed on the recording medium changes, and this charge causes Since the degree to which the electric field is distorted changes, as a result, a gradation image can be formed by utilizing the fact that the dot diameter increases as the latent image potential formed increases. Therefore, an image recording apparatus has been proposed in which the voltage applied to the control electrode is kept constant and the voltage application time is controlled by using the pulse width modulation technique (Japanese Patent Laid-Open No. Sho 60).
-175062, JP-A-61-228771).

[0005]

The conventional formation of a gradation image in an ion flow control type image recording apparatus is performed by voltage amplitude modulation, pulse width modulation or sawtooth wave modulation. In order to achieve high gradation, it becomes a problem how many gradations are carved in a certain fixed time.
That is, when the driving speed is determined, the required time τ for printing one dot is determined, and for example, in order to reproduce 256 gradations, gradation control must be performed in τ / 256 time. In this respect, there is no problem in low-speed driving, but at present, high-gradation expression is extremely difficult in high-speed driving. An object of the present invention is to solve the above problems, and an object thereof is to provide a gradation image recording apparatus capable of achieving high-speed driving and high gradation expression in an ion flow control type image recording apparatus.

[0006]

A gradation image recording apparatus according to the present invention comprises a recording head for forming a charge pattern on a recording medium by a charge flow, and a pulse voltage applied to the recording head according to the density level of an image to be recorded. And a waveform conversion circuit that modulates the amplitude and width of the pulse width modulation circuit. The waveform conversion circuit outputs a pulse including an amplitude modulation section and a pulse width modulation section that are independent of each other.

Further, according to the present invention, the change of the pulse width of the pulse width modulation section is changed stepwise with the pulse width of the amplitude modulation section as a unit pulse width. It is characterized in that it corresponds to an integral multiple of one cycle.

[0008]

According to the present invention, the amplitude modulation section and the pulse width modulation section each form an independent pulse as a drive pulse for gradation control of one dot, and the pulse width change of the pulse width modulation section is the pulse of the amplitude modulation section. The width is changed in a stepwise manner with a unit pulse width, and the amplitude modulation section performs N gradation control and the pulse width modulation section performs M gradation control to obtain N × M gradations. As a result, when realizing the same gradation, the driving speed can be increased by M times when N> M, and the driving speed can be increased by N times when N <M, and high speed driving and high gradation reproduction can be realized. It will be possible.

[0009]

The present invention can be applied to any type of ion flow control type image recording apparatus, but as an example, a solid-state discharge type aperture control type image recording apparatus will be described with reference to FIG. The recording head 1 includes a line electrode 1 on an insulator 1a.
b, the insulator 1c are sequentially laminated, and the finger electrode 1d, the insulator 1e, and the screen electrode 1f are formed so that an opening is formed in the central portion, and the high-frequency power source 5 is provided between the line electrode 1b and the finger electrode 1d. Connected and finger electrode 1
The signal source 6 is connected between d and the screen electrode 1f to apply a signal voltage. An insulating recording body 2 having an electrode 3 formed opposite to the recording head 1 is formed, and a DC power source E is connected between the recording head 1 and the recording body to accelerate an ion flow.

Next, the operation will be described. Ions are generated by applying a high frequency high voltage of several KV and several MHz between the line electrode 1b and the finger electrode 1d to generate discharge inside the head. .. The flow of the ions generated by the discharge is controlled according to the signal voltage between the finger electrode 1d and the screen electrode 1f. As this signal voltage, a pulse width / amplitude modulation signal as described below is used to form an electrostatic latent image having gradation on the recording medium.

FIG. 1 is a diagram showing an embodiment of a pulse width / amplitude modulated signal. As shown in FIG. 1A, the amplitude of a pulse having a unit time width t ₀ according to the input signal voltage is
The amplitude is changed to V at the unit amplitude step v. Further, when the input signal voltage is large, FIG.
As shown, the time width t _0, is changed in amplitude V of the unit time for the pulse width t ₀ corresponding phase-shifted is not a pulse in the same manner as unit amplitude step v of the unit time width t ₀ until the amplitude V.
Similarly, when the input signal voltage is higher,
As shown in (c), the unit time width t is changed by shifting the pulse having the time width 2t ₀ and the amplitude V by the unit time width t _0.
Similarly, the ₀ pulse is changed to the amplitude V at the unit amplitude step v. Furthermore, in similarly unit amplitude step v to only a unit time width t ₀ corresponding to pulses of the phase shifted by a unit time width t ₀ Similarly, if the signal voltage is large varied until the amplitude V. Thus, the amplitude modulation is performed in step v with a pulse having a unit time width t ₀ , the pulse width modulation is performed in units of the time width t ₀ , and the amplitude modulation and the pulse width modulation are performed independently.

If the amplitude modulation is N gradation control and the pulse width modulation is M gradation control, the total gradation is N × M gradation. In this case, the drive speed is defined by the larger of N and M. If N> M, the drive speed can be increased by M times. For example, in 256 gradation expression, N = 64, M = 4
Then, even with 256 gradations, the driving speed can be set to 64 gradations, and the driving speed can be increased four times. If N = M = 16, then 256
Even in gradation expression, the driving speed can be set to 16 gradations, and the driving speed can be increased 16 times.

In FIG. 1, the phase of the amplitude modulation section of the drive pulse waveform is sequentially shifted by t _{0 according to} FIGS. 1A, 1B, and 1C, but the phase of the amplitude modulation section is The actual control is easier if it is fixed. Therefore, it is desirable to perform the waveform control as shown in FIG. That is, as shown in FIG. 2A, the amplitude of the pulse having the unit time width t ₀ is changed to the amplitude V in the unit amplitude step v according to the input signal voltage. Further, when the input signal voltage is large, as shown in FIG. 2 (b), the time width t _0, a pulse of the unit time width t ₀ and phase shifted by the pulse time width t ₀ corresponding amplitude V in the same phase Similarly, the amplitude is changed to V at the unit amplitude step v. Similarly, when the input signal voltage is higher, as shown in FIG.
Duration 2t _0, changing the amplitude V of the width pulse time t ₀ corresponding phase-shifted is not a pulse of the unit time width t ₀ in the same phase as well unit amplitude step v until the amplitude V. Further, when the signal voltage is high, the pulse width and amplitude are similarly modulated. With such a pulse waveform, the phase of the amplitude modulation section is fixed, which facilitates amplitude modulation control.

FIG. 3 is a diagram for explaining the waveform conversion circuit for generating the pulse waveform shown in FIG. 2, and FIG. 4 is a diagram for explaining the operation of the waveform conversion circuit. In the figure, 10 is a voltage setting unit,
Reference numeral 11 is a pulse width setting unit, 12 is an output terminal, and S1 to S3 are switches.

As described with reference to FIGS. 1 and 2, the voltage setting section 10 outputs a plurality of different voltages corresponding to the number of gradations in a predetermined unit step. The pulse width setting unit outputs a plurality of types of pulses having different widths in steps of a predetermined unit time width. First, when the switch S1 is turned on, the output terminal 1
2 becomes the power supply voltage + B level. When the switch S1 is turned off and the switch S2 is turned on, the output terminal 12 becomes the output voltage level of the voltage setting section 10, and when the switch S3 is turned on, the output terminal 12 becomes the 0 level. Therefore, the switch S
By controlling the opening and closing of 2 with a unit time width and the switch S3 with a unit time width or an integral multiple thereof, the modulated pulse described in FIG. 2 can be generated and applied to the ion head from the output terminal 12. Thus, high-speed driving and high gradation expression can be realized.

When a sine wave as shown in FIG. 6A is used as the high frequency voltage in the gradation image recording apparatus shown in FIG. 5, the ion flow at that time is as shown in FIG. 6B. It is detected only at the peak of the high-frequency voltage, is generated discretely in a fixed cycle, and the amount of generated ions has unevenness.
Therefore, if the unit time width t ₀ described with reference to FIGS. 1 and 2 is set to one cycle of ion generation or an integral multiple thereof, an ion flow can be generated corresponding to a change in pulse width. It should be noted that although the AC drive system has been described in the above embodiment, it goes without saying that the present invention is also applicable to the DC ion generation system.

[0017]

As described above, according to the present invention, it becomes easy to control a high gradation even when driven at a high speed, so that it is possible to increase the printing speed and reproduce a high-quality gradation. Become.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a pulse width / amplitude modulation signal.

FIG. 2 is a diagram showing another embodiment of a pulse width / amplitude modulation signal.

FIG. 3 is a diagram showing an embodiment of a drive circuit.

FIG. 4 is an operation explanatory diagram of a drive circuit.

FIG. 5 is a diagram illustrating an example of an image recording apparatus to which the present invention is applied.

FIG. 6 is a diagram illustrating ion generation.

[Explanation of symbols]

10 ... Voltage setting unit, 11 ... Pulse width setting unit, 12 ... Output terminals, S1 to S3 ... Switches.

Claims (3)

[Claims] 1. A recording head which forms a charge pattern by a charge flow on a recording medium, and a waveform conversion circuit which modulates the amplitude and width of a pulse voltage applied to the recording head according to the density level of a recording image, An ion flow control type gradation image recording apparatus, wherein the waveform conversion circuit outputs a pulse composed of an amplitude modulation section and a pulse width modulation section which are independent of each other. 2. The recording apparatus according to claim 1, wherein the pulse width change of the pulse width modulation unit is changed stepwise with the pulse width of the amplitude modulation unit as a unit pulse width. Toned image recording device. 3. The recording apparatus according to claim 2, wherein the unit pulse width is equivalent to an integral multiple of one cycle of ion generation.