JPS64692B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light beam recording device that records images based on pixel signals.

In electrostatic recording, the electrode may or may not be placed close to the photoreceptor during development. In the case of the latter type of development, the charge distribution and electric field distribution on the photoreceptor are as shown in FIGS. 1a and 1b. however
BE is the supporting electrode, and SL is the electrostatic image protection surface. When it is desired to attach toner to areas where positive charges are distributed on the surface of the electrostatic image protective layer SL, the small area A will be developed in pure black, but the large area B will be developed in pure black only at the periphery. This development is well known as the edge effect. This type of development method is suitable for recording paintings, but is not suitable for recording large-area images. In such a case, if the large area is made into a set of points, the charge distribution and electric field distribution on the photoreceptor will become as shown in FIG. 2a and b, and the edge effect can be reduced.

Therefore, when recording such a large-area image with a light beam, it is possible to convert the large-area image into a set of points and record it, thereby reducing the influence of the edge effect.

FIG. 3 explains the recording method of a conventional laser beam printer using a laser beam as the light beam. First, a generating section 1 generates a pixel signal to be recorded, for example, a character pattern formed by a collection of dots. This is a read signal from the memory included in the generating section 1 and is a parallel signal. For example, one line has n pieces, one row has m pieces, a total of n
Assuming that one character is composed of ×m dots, n pixel signals on one line are connected to the signal line.
They are simultaneously derived in parallel on SLI.

This is stored in the shift register 2 and sent to the semiconductor laser 3 as a serial pixel signal, and the semiconductor laser 3 is driven according to the pixel signal to emit a laser beam modulated by the pixel signal. The beam from the laser 3 is deflected by a scanner 4 and then imaged by a lens 5 to expose a photosensitive drum 6.

In order to synchronize the laser beam scanning the drum 6 with the pixel signal, the beam detector 7 is activated as shown in FIG. 4A immediately before the laser beam starts scanning the drum 6.
The beam position is detected by the image clock synchronizing circuit 8, and its output is used as a trigger signal for the image clock synchronizing circuit 8 to synchronize the image transfer clock applied to the shift register 2.

Since the shift register 2 is moved by this image transfer clock, the image formed on the drum 6 is as shown in Fig. 4B.
As shown in the figure, synchronization is achieved.

In order to detect the beam with the beam detector 7, the laser 3 is activated before the beam starts scanning the beam detector 7.
must be controlled to emit the beam.

The unblanking signal generating circuit 9 controls the laser 3 to emit a beam in synchronization with the output of the beam detector 7, and generates the unblanking signal (see Fig. 4) after a certain period of time after the beam detection signal is derived. C), and when the beam detection signal is derived, this unblanking signal is caused to fall.

The unblanking signal and the pixel signal are added by an adder circuit 10, and the laser 3 is controlled by the added output.

In order to convert a large-area image into a set of dots using a laser beam printer, the serial pixel signal described above may be modulated to be appropriately intermittent.

In this case, a problem arises when line drawings and large-area images are mixed, and if the signal is interrupted for line drawings, the lines become jagged and unsightly. In the case of line drawings, it is better to actively use edge effects to obtain sharper line drawings.

Therefore, it is necessary to identify whether a small-area image is a large-area image and then intermittent the pixel signals.

Another problem is that even in large-area images, the edges are completely black, and if you make these areas into dots, the edges of the image will be jagged and unsightly. Since it is necessary to form dots only within a large-area image, it is necessary to identify whether the image is at the edge or not before continuing the pixel signal.

The present invention has been made in view of the above points, and an object of the present invention is to provide a light beam recording device capable of recording high-quality images without unsightly appearance.

That is, the present invention provides a light beam recording device that scans a photoreceptor with a light beam modulated by a pixel signal and develops an exposed portion of the scanned photoreceptor with toner, including an input means for inputting a pixel signal; means for storing the pixel signal inputted from the input means, the storage means being configured to be able to store the pixel signal to be processed and the surrounding pixel signals; a determining means for determining whether a surrounding pixel signal is an image to which toner is attached; a means for generating a beam position detection signal indicating a recording start position of the image; and a beam position detection signal generated from the generating means; masking means for performing masking processing on the pixel signal to be processed based on the pixel signal to be processed,
The masking means periodically intermittents the pixel signal of the part to which toner adheres, when the determination means determines that the pixel signal to be processed and the surrounding pixel signal are an image to which toner adheres. , and the phase of the period is switched for each scanning line.

In this embodiment, both the shape and area of the image are determined, and the pixel signals are modulated based on the results, thereby eliminating the above-mentioned drawbacks.

FIG. 5 shows an example of an image obtained according to the present invention. For example, if a square large-area image consisting of 6×6 pixels is to be reproduced with all adjacent pixels being black, one embodiment of the present invention is shown in FIG. If we follow the example, white pixels are provided in a staggered manner except for the edges, so that only the shaded areas in FIG. 5 are reproduced as black, and the other areas remain white.

During recording with a laser beam printer, pixels around the point must be checked to determine whether the point is a pixel in a large-area image and not an edge. For example, in order to determine point a in FIG. 5, it is necessary to check eight pixels that have all been written and pixels that will be written in the future. In order to make such a determination, three line memories are prepared, one for the line that has already been written, one for the line that is currently being written, and one for the line that will be written in the future. shall be.

If the pixel to be written to and the surrounding points of these three line memories are all black, it can be determined that the pixel to be written must be white. However, in order to arrange the points to be whitened in a staggered manner, it is necessary to use black points above, below, and to the left and right of the white point, and it is necessary to perform masking with a signal whose phase is reversed in the upper and lower rows, with 2 pixels as one period. .

One embodiment will be described below with reference to FIG. Note that the members denoted by the same numbers as in FIG. 3 are the same as those in FIG. 3.

An image signal (also referred to as a pixel signal) sent from the signal generator 1 enters from a terminal 20 and is stored in a line memory 21 that stores pixel signals corresponding to one scan of the beam. Storing in the line memory 21 is performed during t1 when the laser beam shown in FIG. 7B is not writing an image. As mentioned above, when scanning a photosensitive drum with a laser beam, a beam position detection signal (BD signal) is outputted as shown in FIG. 7a at the start of each scan, and in synchronization with this, an image writing signal is outputted as shown in FIG. 7b. Sent to Laser 3.

Of these image write signals, up to T1 are image signals, and after T1 there is only an unblanking signal, so as described above, there is a blank time t1 until the next BD signal. During this time, image signals are transmitted from the generating section 1 in parallel as shown in FIG. 7c and stored in the line memory 21.

When storing, the address of the line memory 21 is set by the address signal (FIG. 8a) from the line memory address counter 27, and the memory 21 selection signal FIG. 8b is output. At the same time as the line memory control circuit 28 sends a write signal as shown in FIG. 8C to the line memory 21, the line memory control circuit 28 sends an image signal sending pulse shown in FIG. 8D to the generator 1 from the terminal 29. . Then, a parallel signal as shown in FIG.
Stored at 1. When writing of one address is completed, a signal for incrementing the line memory address counter 27 by one is sent out from the line memory control circuit 28, and the above operation is repeated.
Since the storage to the line memory 21 is performed in parallel, the time to transmit the pixel signal C is shortened compared to the image signal section of the image write signal shown in FIG. 7b, which sends out the same amount of data serially. It will be about 1/8.

The pixel signal stored in the line memory 21 is loaded into the shift register 24 as an input means at the rising edge of the load pulse shown in FIG. Shifted according to figure a). Immediately after loading, the pixel signal loaded into the shift register 24 is stored in the line memory 22 via the signal line SL in synchronization with the memory write pulse in FIG. 9c. The address to store is presented by the line memory address counter 27. It has the same address as the line memory 21. line memory 2
The designation of addresses 1, 22, and 23 is performed as shown in FIG. 9e before loading the shift registers 24, 25, and 26 as input means. The pixel signals loaded into the shift register 25 from the line memory 22 are stored in the line memory 23 as before. The pixel signal loaded into the shift register 25 is shifted by the image transfer clock 9a to become a serial pixel signal 9d.

In other words, from terminal 20 to line memory 2
When one block is written to line memory 21 and one block is read from line memory 21 to shift register 24, one block read from line memory 21 is written to line memory 22, and at the same time, one block read from line memory 22 is written to line memory 22. 23.

Also, one block read from the line memories 22 and 23 is written into the shift registers 25 and 26.

Shift register 24, 2 as input means
The pixel signals loaded into the pixel signals 5 and 26 are transferred to flip-flops 32, 33, and 34 as storage means, respectively, in synchronization with the image transfer clock. These signals are further transferred to flip-flops 38, 39, and 40 via flip-flops 35, 36, and 37 as storage means, and in response to such transfer, new signals are sequentially transferred from shift registers 24 to 26 to the flip-flops. 32 to 34.

Flip-flop 3 as a storage means for these
2 to 40 each constitute a 3-bit shift register, and flip-flops 32, 35,
38 stores pixel signals of the next row to be printed;
Flip-flops 33, 36, and 39 store pixel signals for the row currently being printed, and flip-flops 34, 37, and 40 store pixel signals for the rows that have already been printed. The flip-flop 36 stores the signal of the point currently being printed (pixel signal to be processed), the flip-flop 39 stores the signal of the already printed point, and the flip-flop 33 stores the signal of the next point to be printed. In this way, since the pixel signal to be processed and the surrounding pixel signals are stored in the flip-flops 32 to 40,
AND circuit 4 as a means of determining whether all of these flip-flop outputs become high level.
By checking 2, it can be determined whether the pixel signal to be processed and all surrounding pixel signals are black. In other words, the AND circuit, which is the determination means, determines whether the pixel signal to be processed and the surrounding pixel signals are images with toner attached.By increasing the number of line memories and flip-flops, the image that can be checked can be increased. It is clear that it will increase. If all the points are black, the masking signal from the masking signal generation circuit 41 as a masking means passes through the NAND circuit 43, and the AND circuit 4
4, the serial pixel signal is intermittent.

Details of the masking signal generation circuit 41 are shown in FIG. 10, and its timing chart is shown in FIG. 11. Beam position detection signal (BD signal) Figure 11b
An image transfer clock (a) in FIG. This signal is frequency-divided by 1/2 by the flip-flop 51 and outputted from the Q and Q outputs as shown in Fig. 11e and f.
Output. The flip-flop 51 is cleared every time a BD signal is input. Since the BD signal is output at the start of a scanning line, the signals e and f in FIG. 11 always have a constant phase at the start of the line. The phases of these two signals are inverted from each other, and either e or f in FIG. 11 is output as a masking signal for each line. In other words, the masking signal from the masking signal generation circuit 41 serving as masking means periodically intermittents the pixel signal of the portion to which toner adheres, and switches the phase of the period for each scanning line. A flip-flop 52 selects a masking signal whose phase is inverted. This frequency divides the BD signal input to the terminal 53 by 1/2, and its Q and Q outputs (c and d in FIG. 11) are inverted for each line. The AND circuits 54 and 55 are connected to the first signal only when the signals c and d in FIG. 11 are at high level, respectively.
Pass through e and f in Figure 1.

The outputs are combined by an OR circuit 56, but since the signals c and d in FIG. 11 are mutually inverted, one of the signals e and f in FIG. 11 appears as the output of the OR circuit 56. This is the masking signal shown in FIG. 11g and is output from the terminal 57. This masking signal has one cycle equal to two image transfer clocks. In other words, two pixels constitute one period, and the phases are reversed in the upper and lower rows. For this reason, when printing is performed using serial pixel signals interrupted by masking signals, white dots are arranged in a staggered manner in a black image. This improves the edge effect that causes black images to appear white.

In addition, as shown in Figure 5, by determining the state of the currently written point and the surrounding points and performing masking only when all nine points become black, the edges and line drawings of large area images can be masked. It is possible to obtain images with smooth and sharp edges in line drawings and large-area images without having to do this.

As detailed above, in the electrostatic recording device according to this embodiment, both the shape and area of the image are determined,
Since it modulates the pixel signal to be recorded,
This can effectively eliminate edge effects and the like in electrostatic recording devices.

As explained above, according to the present invention, high-quality image recording can be performed.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the charge distribution of the photoreceptor, respectively. FIG. 3 is a block diagram showing a conventional recording device. FIG. 4 is a signal used to explain the operation of the recording device shown in FIG. 3. A waveform diagram, FIG. 5 is a front view showing a recording pattern according to the present invention, FIG. 6 is a main circuit block diagram of a recording apparatus according to the present invention, FIGS. 7 and 8,
9 is a signal waveform diagram for explaining the operation of the circuit block shown in FIG. 6, and FIG. 10 is a circuit diagram showing the block diagram shown in FIG. 9 in more detail, and
FIG. 1 is a signal waveform diagram of each part of the circuit diagram shown in FIG. 10. Here, 21, 22, 23 are line memories,
24-26 are shift registers, 32-40 are flip-flops, 41 is a mask signal generation circuit, 4
2 is and gate.

Claims (1)

[Scope of Claims] 1. In a light beam recording device that scans a photoreceptor with a light beam modulated by a pixel signal and develops the exposed portion of the scanned photoreceptor with toner, the input means inputs the pixel signal. and means for storing the pixel signal input from the input means, the storage means being configured to be able to store the pixel signal to be processed and the surrounding pixel signals, and further comprising the pixel signal to be processed. and determining means for determining whether or not the surrounding pixel signal is an image to which toner is attached; means for generating a beam position detection signal indicating a recording start position of the image; and beam position detection generated from the generating means. and a masking means for performing masking processing on the pixel signal to be processed based on the signal, and the masking means is configured to detect that the pixel signal to be processed and the surrounding pixel signals are detected by the discrimination means to prevent toner from adhering to the pixel signal to be processed. A light beam recording device characterized in that, when it is determined that the image is an image with toner attached, the pixel signal of the part to which toner is attached is periodically intermittent, and the phase of the period is switched for each scanning line.