JPH0258972A - Electrostatic recorder - Google Patents

Abstract

PURPOSE:To improve density nonuniformity in recording and the deterioration of picture quality by changing a recording pulse width according to the distributed state of black dots in a picture signal. CONSTITUTION:A recording pulse width deciding circuit 9 determines a recording voltage pulse width when the picture signal stored in a shift register 6 is to be recorded based on the data of the number of the black dots M from a counter 7 and the data of the number of changing points N from a counter 8 and gives the pulse width to a switching control circuit 4 as a command value. The control circuit 4 drives a recording electrode driver 2 according to the command value. Thus, a phenomenon, in which a fine line becomes extremely thin, or extreme density nonuniformity occurs because of the density difference in the black dots, can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrostatic recording device used for recording facsimile reception and the like, and particularly relates to a technology for improving image quality.

Conventional TechniquesRecently representative techniques related to electrostatic recording devices are described, for example, by National Technical Re.
port Vol.

24 No. 44 (Published August 1978) No. 674
It is explained in detail on pages 680 to 680.

Modern devices of this type use electronically scanned multi-stator stylus electrostatic recording heads. A large number of needle-shaped recording electrodes that correspond one-to-one to pixels (dots) for one line of scanning are arranged in a line, and each electrode is electronically switched and scanned, but in order to simplify the scanning circuit. It has a matrix structure. The recording electrodes are divided into a plurality of blocks and are wired in a matrix, and a plurality of long control electrodes are arranged close to the rows of recording electrodes.

Control electrodes are used to select the location to be recorded.

After applying a specified control voltage to one or a plurality of adjacent control electrodes, a specified recording voltage is applied to the recording electrode group according to the image signal. A black dot is recorded in the area where both the control voltage and the recording voltage are applied. There is no recording effect with only one voltage.

One recording electrode with a problem to be solved by the invention is called an electrode of interest B, and the recording electrodes on both sides thereof are called adjacent electrodes A and C. These electrodes A, B,
It is assumed that C belongs to a group in which recording is performed at the same timing.

Adjacent electrodes A and C when recording a black dot with electrode B of interest
As shown in FIG. 3, there are cases where both adjacent electrodes A and C record black dots (pattern 1), cases where only one of adjacent electrodes A and C records black dots (pattern 2). ) and a case in which neither adjacent electrodes A and C record a black dot (pattern 3).

The problem with the conventional method is that the recording density of the black dots formed by the target electrode B changes considerably depending on the pattern 1.2.3. Pattern 1 has the darkest black, pattern 2,
It becomes thinner in the pattern 3 term.

As a result, fine lines extending in the sub-scanning direction in the recorded image become very thin, and there is also extreme density unevenness between areas with low and high black dot density.

The above problem arises for the following reasons.・Cittern 1
In this case, the recording voltage is applied to the electrode B of interest and the adjacent electrodes A and C at the same time, so each electrode A, B, and C has the same potential. On the other hand, in pattern 3, the adjacent electrodes A and C are kept at the ground potential even during the period when the recording voltage is applied to the electrode of interest B.

Therefore, in the case of pattern 3, the electrode of interest B and the adjacent electrode A
The interelectrode capacitance between B and C becomes effective, and the time constant between the target electrode B and the ground becomes larger than in the case of pattern j. When a recording voltage pulse is applied to electrode B from the drive circuit, electrode B
The effective voltage acting on the recording paper in contact with the recording paper rises in an exponential curve according to the time constant. Therefore, if the time constant is large, the rate of rise of the effective voltage will be slow, and a sufficient voltage will not be reached within a specified recording pulse width.

This will reduce the recording density.

It is an object of the present invention to improve unevenness in recording density and deterioration in image quality caused by such a causal relationship.

Means for Solving the Problems The present invention provides an image signal inspection means for checking the number of black dots and the number of black and white change points in a series of image signals to be recorded at the same timing, and the image signal inspection means for checking the number of black dots and the number of black and white change points in a series of image signals to be recorded at the same timing. means for determining an appropriate recording pulse width based on the number of black dots and the number of change points; and a control means for driving the recording head with the recording pulse width obtained by the determining means at the timing of recording the image signal. and was added.

Effect: If there is a continuous portion of black dots (solid black portion) in the series of image signals, the number of black dots is large, but the number of black and white change points is small. In an image signal that includes many parts where black and white appear alternately, the number of change points becomes very thick compared to the number of black dots. When there is only one isolated black dot in the image signal, the number of black dots is one and the number of change points is two.

By checking the number of black dots and the number of change points, the third
It is possible to distinguish whether the image signal mainly consists of pattern 1 or the image signal mainly consists of pattern 3 shown in the figure. pattern 3
In the case of an image signal mainly consisting of , the recording pulse width is set appropriately long by the determining means, and this is executed by the controlling means.

In other words, by increasing the recording pulse width, the recording density of pattern 3 is prevented from decreasing.

Embodiment FIG. 1 shows a schematic configuration of an electrostatic recording apparatus according to an embodiment of the present invention. The recording head 1 is an electronic scanning multi-stylus type electrostatic recording head having the above-mentioned configuration, and a recording voltage pulse is applied from the driver 2 to its recording electrode, and a control voltage pulse is applied from the driver 3 to the control electrode. applied. ON-OFF of driver 2 and driver 3
Control and drive electrode selection control are performed by the switching control circuit 4.

The image signal to be recorded is serially supplied to the input terminal 5 one dot at a time, stored in a certain amount in the shift register 6, converted into parallel signals, and inputted in parallel to the recording electrode driver 2 at a predetermined recording timing.

A recording voltage pulse is applied by the driver 2 to the recording electrode corresponding to the l1'' signal stored in the shift register 6, and a black dot is recorded.The recording electrode has a larger load than the control electrode, so the recording The timing of application of the electrode is earlier than the timing of application of the control electrode.Therefore, the voltage application width of the control electrode may be fixed, but the recording voltage pulse width changes as follows.This recording voltage pulse width is the aforementioned recording pulse width. It is.

The image signal input to the shift register 6 is also input to a black dot counter 7 and a change point counter 8. The black dot counter 7 counts the black door F (the number of +1177 signals) in the series of image signals stored in the shift register 6. The change point counter 8 counts the number of changes between black and white (111LL and 0'') in a series of image signals.

The recording pulse width determining circuit 9 determines the recording voltage and ζ run when recording the image signal stored in the shift register 6 based on the data of the number of black dots M from the counter 7 and the number of change points N from the counter 8. The pulse width is determined and the pulse width is given to the switching control circuit 4 as a command value. The control circuit 4 drives the recording electrode driver 2 according to the command value.

I will explain in detail. In the image signal consisting of 24 dots shown in FIG. 2(1), the front half is black and the rear half is white.

In this case, the number M of black dots is 12, the number N of changing points is 2, and N7M is 0.16. In addition, in the case of an image signal in which black and white dots appear alternately one dot at a time, as in (2), the number of black dots M is 12, the number of change points N is 24. N7M becomes 2. In the case of the image signal (3), the number of black dots M is 3, the number of change points N is 4, and N7M is 1.33.

The decision circuit 9 selects one of three preset recording pulse widths: large, medium, and small. For example, the N/M
If the value of is smaller than 1, select pulse width "Small" and set N
If 7M is 1 or more and less than 1.5, select the pulse width "Medium", and if N7M is 15 or more, select the pulse width "Dog".

As a result, the image signal mainly consisting of pattern 1 in Fig. 3 ((1) in Fig. 2) is recorded with a "small" pulse width, and the image signal mainly consisting of pattern 3 and pattern 2 ((1) in Fig. 2) is recorded with a small pulse width. (2)
and (3)) are recorded with a "medium" or "large" pulse width.

Effects of the Invention As explained in detail above, according to the electrostatic recording device according to the present invention, the recording pulse width changes depending on the distribution state of black dots in the image signal, so that static electricity between adjacent recording electrodes is reduced. Fluctuations in recording density caused by the magnitude of capacitance are reduced, and phenomena such as thin lines becoming extremely thin and extreme density unevenness caused by differences in the density of black dots can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an electrostatic recording device according to an embodiment of the present invention, FIG. 2 is a conceptual diagram of an image signal that does not provide a detailed explanation of the present invention, and FIG. 3 is a diagram explaining conventional problems. FIG. 7... Black dot counter, 8... Change point counter,
9... Recording pulse width determining circuit. Name of agent: Patent attorney Shigetaka Awano and 1 other person

Claims (1)

[Claims] an image signal inspection means for checking the number of black dots and the number of black and white changing points in a series of image signals to be recorded at the same timing; 1. An electrostatic recording apparatus comprising: means for determining a recording pulse width; and a control means for driving a recording head according to the recording pulse width obtained by the determining means at the timing of recording the image signal.