JPS60194472A - Picture recorder - Google Patents

Abstract

PURPOSE:To obtain a recorded picture having superior resolution, brightness, half tone, smoothness or the like by switching the size of dots constituting the picture by a signal processor in accordance with the kind of the picture to be recorded. CONSTITUTION:A picture reader 12 reads out picture data I , outputs the read- out data to the signal processor 1 and also outputs discrimination signal D indicating whether data I discriminated by the reader 12 is a linear picture or a tone picture to a control device 13. The control device 13 outputs a control signal C1 to a processor 1, a control signal C2 to a laser writing device 2 and a control signal C3 to a bias power supply 11 respectively. The processor 1 converts the picture data I into a binary picture in accordance with the control signal C1 and outputs the binary picture to the laser writing device 2. The writing device 2 irradiates the diameter of a laser spot on the surface of a switching drum 3 in accordance with the kind of the picture. Thus, the recorded picture having superior resolution, brightness, half tone, smoothness, or the like can be always obtained in accordance with the kind of the picture to be recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention processes image information using a predetermined method to obtain an image signal, and forms a latent image on an image forming body based on the image signal. The present invention relates to an image recording device that forms a dot-structured image by attaching toner to the latent image under an electric field, and more particularly, relates to an image recording device that can reproduce and record under conditions suitable for the type of image to be recorded. .

[Prior art]

2. Description of the Related Art Conventionally, an electrophotographic recording apparatus using a laser as an exposure source as shown in FIG. 1 is known. This recording device uses a signal processing device 1 to process image data l obtained from a signal input from a document image sensor, other equipment, or data stored in a data storage unit, thereby generating binary data (i.e., An image signal (hereinafter referred to as a binary image) consisting of pixel data converted into black and white (black and white) is obtained, and the pixel data of this binary image is used to generate signals from a laser, an acousto-optic modulator, a lens device, a single-rotation polygon mirror, etc. Turn on the laser writing device 2 for each pixel.

OFF control, the surface of the photoreceptor drum 3 rotated in the direction of the arrow and uniformly charged by the charger 4 is subjected to image exposure using a laser spot, and the electrostatic latent image formed thereby is exposed in detail to the second image. The toner is deposited under an electric field by the developing device 5 as shown in the figure, and the resulting toner image is transferred to the recording paper P, which is fed into contact with the surface in synchronization with the rotation of the photosensitive drum 3, to the transfer device 6. The recording paper P with the toner image transferred thereto is separated from the surface of the photoreceptor drum 3 by a separator 7, and then the toner image is fixed by a roller fixing device 8, and the recording paper P is discharged outside the machine. After the surface of the photosensitive drum 30 on which the toner image has been transferred is neutralized by the static eliminator 9, residual toner is removed by the IJ +ning device 10, and the -th image recording process is completed.

Now, the developing device shown in FIG. 2 will be explained.

51 is a developing sleeve made of a non-magnetic material such as aluminum or stainless steel, and a bias power source 11 is connected to this developing sleeve.
By applying a bias voltage from , an electric field is generated in the developing area A between the photosensitive drum 3 whose base portion is grounded. Inside the developing sleeve 51, there are a plurality of N on the surface.
A magnet body 52 having an S magnetic pole is provided. and,
When the developing sleeve 51 stands still or rotates to the left and the magnet body 52 rotates to the right or stands still, the developer attracted from the developer reservoir 53 to the surface of the developing sleeve 51 by the magnetic force of the magnet body 52 is rotated in one direction or the other direction. Both rotations cause it to move counterclockwise. The developer conveyed in this manner develops the electrostatic latent image on the photoreceptor drum 3 with its conveyance amount being regulated by the thickness oven side blade 54 . The remaining developer layer that has passed to the developing area is removed from the surface of the developing sleeve 51 by the cleaning blade 55 and returned to the developer reservoir 53, and the developer in the developer reservoir 53 is stirred by the stirring blade 56. , toner hopper 57
The toner is uniformly mixed with the toner supplied from the toner supply roller 58.

The signal processing method in the signal processing device 1 of the conventional image recording device as described above converts the image data into 2 by comparing each pixel data of multi-valued or continuous tone image data This is called converting it into a value image. Such a processing method is a method in which the threshold value is set to the same K for all pixels (hereinafter referred to as the simple binarization method).
and a method of setting the value to VCM for each pixel (hereinafter referred to as a dither method). The simple binarization method is effective in reproducing images that basically require high resolution, such as lines and characters, but when images where gradation is important, such as photographs, are converted to binary images, false contours appear. , smoothness is lost. On the other hand, the dither method is effective in processing images such as photographs because it can pseudo-represent halftones by the density of the quantitative distribution of black dots (5), but the resolution generally deteriorates.

This point will be explained with reference to FIG.

FIG. 3 is a diagram showing the principle of binarization conversion of image data in the signal processing device 1, and shows a case where a systematic dither method is used as an example of the dither method. ■1 indicates the density level of the pixel to 16
Input image data expressed in stages, R1 is a predetermined threshold value matrix, and Sl is the pixel and threshold value matrix of input image data E1)
This is output image data that is compared with the corresponding threshold of IJxR1 and set to "0" or "1'° depending on whether the density level of the pixel is below or above the threshold. This "0" is white, and is "1'". If it is black, then "O" is obtained from this output image data 81.

Although the distribution of "1"s can represent gradations in a pseudo manner, it is clear that the resolution is lowered. Note that the dithering method is not limited to the systematic dithering method shown in Fig. 3; other suitable methods may be used, such as randomly setting a threshold value of "1 to 16" for each pixel, or using pixels around the pixel of interest. It is also possible to obtain a binary image with excellent gradation reproducibility by using the method (6) in which the settings are made using data. However, compared to these other methods, the systematic dither method is superior in that it has a faster calculation speed and better halftone reproducibility.

In contrast to the above dithering method, in the case of the simple binarization method, for example, if the threshold value is set to "9°" and the input image data E1 is similarly converted to "0'" or "1" from 1 to 2, the input The arrangement of 10'' in image data E1 becomes \"1" black pixel as it is, and with that distribution, the gradation cannot be expressed smoothly.On the other hand, the resolution of input image data E1 can be maintained.

On the other hand, if the input image data is a halftone photograph that has already been practically binarized and has halftones reproduced in a pseudo manner, it is more advantageous to use the dither method. Generally speaking, it cannot be said that this is the case. The reason for this is that moiré may occur due to the spatial frequency of the halftone dots and the spatial frequency of the dither pattern. Halftone photographs etc. are simple 2
There are cases where it is better to process by converting into values.

As explained above, if a binary image is formed using an appropriate signal processing method depending on the type of input image data, an excellent recorded image can be obtained. for example,
The simple binarization method is suitable for line drawings and halftone dot drawings, and the dither method is suitable for gradation surfaces.

However, conventional image recording devices convert image data into binary images using the same signal processing method regardless of the type of image.

Furthermore, the conventional image recording apparatus uses a laser writing device 2 to perform image sawing with a laser spot of the same diameter, regardless of the type of image to be recorded, unless the electrostatic latent image formed thereby is particularly changed. Developing was performed under an electric field using a bias voltage under the same conditions. As a result, the recorded image was always composed of dots of the same size.

This point will be further explained with reference to FIG.

Figure 4 is an enlarged view of the recorded image (a).

(b) and (c) schematically show cases in which the dot diameter increases with respect to the interval between dots (represented by circles) in that order. In general, line drawings representing characters, diagrams, etc. are required to have high resolution and sharpness, but for this, it is necessary to have high resolution and sharpness.
) It is necessary to make the unevenness of the lines less noticeable. In other words, in line drawings, dots are continuous,
Furthermore, it is required that the dots overlap to form an image as shown in FIG. 4(C). On the other hand, in the case of gradation surfaces such as photographs where halftone reproducibility and smoothness are important, it is necessary to reproduce the halftones in a pseudo manner with dots, and to do this, it is necessary to increase the spatial frequency. In other words, as explained earlier, it is necessary to arrange the dots so that they do not aggregate too much in one place. To do this, it is easier to reproduce the gradation of the original image by arranging the dots in a forest-like manner so that the dots do not overlap and the area to be colored is proportional to the number of dots. In other words, if the original image is a gradation surface composed of continuous gradation or halftone dots, the dots may be arranged as shown in Figure 4(b) where they do not overlap, or the dots may be arranged discontinuously as shown in Figure 4(b). (It is desirable to record in a way that you can see it quickly.

However, as mentioned above (9), conventional image recording devices record dots of a fixed size regardless of the type of image, making it difficult to obtain both excellent line drawings and gradation planes. It was extremely difficult.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances.The present invention has been made in view of the above-mentioned circumstances. The present invention provides a recording device.

[Structure of the invention]

The present invention processes image information using a predetermined method to obtain an image signal, forms a latent image on an image forming body based on the image signal, and attaches toner to the latent image under an electric field to form a dot. An image recording device for forming an image of a composition, characterized in that the size of dots constituting the image can be switched depending on the type of image to be recorded,
This configuration achieves the above object.

The present invention will be explained with reference to FIG.

FIG. 5 is a schematic diagram (10) showing an example of the image recording apparatus of the present invention, and the same reference numerals as in FIG. 1 indicate the same functional members.

In the recording device shown in FIG. 5, an image reading device 12 reads a document using a 00D image sensor and outputs image data to the signal processing device 1, and at the same time or prior to this, the operator's judgment or the image reading device 12 An identification signal indicating whether the identified image data is a line drawing or a gradation drawing is output to the control device 13, which is a control section of the recording apparatus. Thereby, the control device 13 transmits the control signal C1 to the signal processing device 1.
Then, the control signal C2 is outputted to the laser writing device 2, and the control signal C3 is outputted to the bias power supply 11. The signal processing device 1 converts the image data into a binary image using a method according to the image and outputs the binary image to the laser writing device 2 according to the control signal C1. Upon input of the control signal C2, the laser writing device 2 irradiates the photosensitive drum 3 while changing the diameter of the laser spot depending on the type of image. The bias power supply 11 applies a bias voltage according to the type of image to the developing sleeve 51 of the developing device 5 as shown in FIG. 2 in accordance with the control signal C3. A recording operation is performed.

The effect of switching the developing bias, which applies a bias voltage depending on the type of image to the developing sleeve 51, will now be explained with reference to FIGS. 6 and 7.

6 and 7 show a DC component and an AC component applied to the developing sleeve 51 by the bias power supply 11 when forming a toner image on the photosensitive drum 3 using the developing device shown in FIG. It shows changes in development characteristics with respect to the amplitude Vac and frequency f of the alternating current component of the bias voltage, that is, the reciprocal of the period. In these figures 6 and 7,
The surface potential of the photosensitive drum 3 is Vs%, and the DC component of the bias voltage is Vdc.

As is clear from FIGS. 6 and 7, the larger the amplitude Vac of the AC bias and the smaller the frequency f, that is, the closer the synchronization, the higher the image density can be obtained. Furthermore, under conditions where high image density is obtained, the dot diameter of the image tends to become large. That is, if one or both of the amplitude Vac and period of the alternating current component of the bias voltage is increased, the diameter of the recorded dot becomes larger, and vice versa, the diameter of the dot becomes smaller. By utilizing this fact and switching the bias voltage, it is possible to obtain line drawings with high resolution and sharpness, gradation drawings that reproduce halftones and smoothness, and the like. Note that the TE image density can also be changed by changing the DC component Vclc, but fogging tends to occur when trying to obtain a high image density, so it is preferable to change the AC component as described above.

The recorded images obtained by the image recording device shown in Fig. 5 are recorded by changing the recording conditions depending on the type of image as described above. It has the advantage of being easy to reproduce smoothness and smoothness.

The present invention is a signal processing method that obtains a binary image depending on the type of image to be recorded, as shown in the example shown in FIG.

It is not necessarily necessary that the spot diameter of the light beam and the bias voltage are all switched, and one or both of the signal processing method (13) and the bias voltage may not be switched.

〔Example〕

Next, the present invention will be further explained by specific examples.

Embodiment 1 In an image recording apparatus such as that shown in FIG. , thereby causing the control device 13 to output the control signals 01, 02, 0
3 to the signal processing device 1. Laser writing device 2.
Output to bias power supply 11.

The signal processing device 1 forms a binary image using a systematic dither method when the document is a gradation image, and by a simple binarization method when the document is a line image or a halftone image.

In the laser writing device 2, the diameter of the laser spot is 80 μm for line drawings and 95 μm for single gradation drawings and halftone drawings.
Expose to μm.

During development, toner adheres to areas that are not exposed to light (14), so the dots that make up the recorded image are large in line drawings and small in gradation images and halftone images. Further, according to the control signal C3, the bias power supply 11 applies the bias voltages shown in Table 1.

Table 1 (Note) The amplitude is 1/2 from peak to peak.

The photoreceptor drum 3 has a Se photoreceptor layer on its surface and has a diameter of 120111 m, and the rotation in the direction of the arrow is at the same speed of 120 tnm/sea% and the charger 4 has a rotation rate of +600 mm.
is charged with electricity.

The laser writing device 2 uses a He-Ne laser as a light source, and an acousto-optic modulator modulates the laser light according to a signal from the signal processing device 1, and changes the spot diameter as described above depending on the type of image (12 dots). The charged surface of the photoreceptor drum 3 is spot exposed at a density of /tnm.

In the developing device 5, the developing sleeve 51 has a diameter of 30 cm, the gap with the photosensitive drum 3 is set to Q, 7 tntn, and during development, the developing device 5 rotates counterclockwise at a circumferential speed of 120 ms/sec, and the magnet body 52 rotates at a speed of 800 rpm. The developing sleeve 51 is rotated clockwise to form a layer of a two-component developer containing a mixture of non-magnetic toner and magnetic carrier, which is negatively triboelectrically charged, with a layer thickness Q of 5 mm on the surface of the developing sleeve 51. The developing device 5 performs development in which toner is attached to the non-exposed portions of the photoreceptor drum 3.

When line drawings, gradation drawings, and halftone dot drawings were recorded using the image recording device under the above conditions, the recorded images obtained in both cases of II & 11 and 2 showed noticeable skipped dots and uneven lines in the line drawings. The images were sharp and clear, and the gradation and halftone images were smooth and had good midtone reproducibility.

Embodiment 2 Using the image recording apparatus shown in FIG. 5 The operator specifies the type of document (line drawing or gradation drawing), which becomes an identification signal and is input to the control device 13. outputs control signals 01, 02, and 03.

In accordance with the control signal C1, the signal processing device 1 forms a binary image using a simple binarization method if the original is a line drawing, or a systematic dithering method if the original is a gradation drawing. Although it is difficult to distinguish between dot and gradation images, if the threshold matrix of the systematic dithering method is set to a dot-distributed type, it is possible to minimize the occurrence of moiré even in halftone images.

The laser writing device 2 selects a lens according to the control signal 02, and performs exposure with a laser spot of 100 μm in diameter in the case of a line drawing, and with a laser spot of 70 μm in diameter in the case of a gradation image. , developing device 5
Using a developer in which the toner has a positive charge due to frictional charging, the toner is attached to the exposed portion of the photo drum 3 (17).
1 reversal development. Further, the developing sleeve 5 of the developing device 5
The gap between 1 and photoreceptor drum 3 is 0.51 uI.

The thickness of the developer layer is regulated to 0.611fi. During development, the bias voltage shown in Table 2 was applied to the developing sleeve 51 by the bias power supply 11 controlled by the control signal C3.

Table 2 (Note) Amplitude is peak-to-peak IA.

Other conditions are the same as those in Example 1.

When line drawings and gradation drawings were recorded using the image recording apparatus under the above conditions, in both cases 1 and 2, the line drawings and gradation drawings were as good as or better than those in Example 1. 0 [Effects of the Invention] According to the image recording device of the present invention, line drawings have high resolution and sharpness, and gradation drawings have smooth and good halftone reproducibility. A recorded image composed of excellent dots can be obtained.

The present invention is applicable not only to image recording devices that write on an electrophotographic photoreceptor with a laser, but also to image recording devices that use electrostatic recording or magnetic recording to form images made up of approximately dots. can do.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of a conventional laser writing electrophotographic recording device, and FIG. 2 is a partial diagram showing an example of a developing device.
Figure 3 is a diagram of the principle of binarization conversion of image data, Figure 4 (a)
, (b) and (c) are respectively plan views showing partially enlarged recorded images, FIG. 5 is a schematic configuration diagram showing an example of the image recording apparatus of the present invention, and FIGS. 7 is a graph showing how development characteristics change when the amplitude and the same wave number are changed. ■...Image data, 1...Signal processing device, 2...
- Laser writing device, 3... Photosensitive drum, 4... Charger, 5... Developing device, 11... Bias power supply, 51... Developing sleeve, 52... Magnet, 54... ...Layer thickness regulation blade, Technique 1...Input image data, R1...Threshold value matrix, Sl...Output image data, Vac...Amplitude,
f...frequency, Vs...photosensitive drum surface potential, Vda...DC component, 12...image reading device,
13...Control device, D...Identification signal, 01-C3
···Control signal. Patent Applicant: Konishiroku Photo Industry Co., Ltd. Bishang Tsuba/Ken Proceedings Amendment Paper April 7, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office 1, Indication of the Case 1981 Relationship with Patent Application No. 48245 Case Patent Applicant '5.1)'f, W 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name) (127) Konishiroku Photo Industry Co., Ltd. 6 Number of inventions increased by amendment 0 7, Subject of amendment In Column 8 of the Detailed Description of the Invention of the Specification, Contents of the Amendment, at the end of page 9 of the Specification, after ``However,'' ``The disadvantageous points were overlooked without being noticed'' should be inserted. (2)

Claims (5)

[Claims] (1) Signal processing the image information using a predetermined method to obtain an image signal, and forming a latent image on an image forming body based on the image signal,
An image recording device that forms an image composed of dots by attaching toner to the latent image under an electric field, characterized in that the size of the dots constituting the image can be switched depending on the type of image to be recorded. Image recording device. (2) The image forming body has a photoconductive layer, the means for forming the latent image is means for irradiating a light beam as a spot, and the spot diameter is switched depending on the type of image to be recorded. The image recording device according to item 1. (3) The image forming apparatus according to claim 1 or 2, wherein the signal processing method is switched depending on the type of image to be recorded. (4) A patent claim in which the signal processing method includes a simple binarization method in which each pixel of an image signal is binarized by setting the same threshold, and a dithering method in which a different threshold is set for each pixel and binarized. The image recording device according to item 3. (5) The image recording apparatus according to any one of claims 1 to 4, wherein the electric field is switched depending on the type of image to be recorded.