JPS60194473A - Picture recorder - Google Patents

Abstract

PURPOSE:To always obtain a recorded picture having superior resolution, brightness, half tone, smoothness, or the like by switching an electric field in accordance with the kind of the picture to be recorded. CONSTITUTION:A picture reader 12 reads out an original, outputs picture data I to a signal processor 1 and also outputs a discrimination signal D indicating whether the picture 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 C to a bias power supply 11. A processor 1 converts the picture data I to a binary image and outputs the binary image to a laser writing device 2. The device 2 exposes an image on the surface of a photosensitive drum 3 as a laser spot in accordance with the picture data. The formed electrostatic latent image is developed under an electric field increasing at least one of the amplitude and period of an AC component by a developing device 5 in case of a linear picture, and also developed under an electric field reducing at least one of the amplitude and period of the AC component in case of a tone picture, so that a linear picture having high resolution and brightness and a tone picture having superior reproducing property of a half tone are obtained.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an image recording method in which a latent image is formed based on an image signal, and toner is attached to the latent image under an electric field to form a dot-configured image. In particular, the present invention relates to an image recording apparatus that can specify the type of image to be recorded and reproduce and record it under conditions that match 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 has been known.

This recording device uses a signal processing device 1 to process image data obtained from signals input from a document image sensor or other equipment, or from data in a data storage unit.
An image signal (hereinafter referred to as a binary image) composed of binary (black and white) pixel data is obtained, and the pixel data of this binary image is used to generate a laser, an acousto-optic modulator, and a lens device.

A laser writing device 2 consisting of a rotating polygon mirror or the like is turned on and off for each pixel, rotates in the direction of the arrow, and charges a charger 4.
The surface of the photoreceptor drum 3, which is uniformly charged, is subjected to image exposure using a laser beam (K), and the electrostatic latent image formed thereby is exposed to a developing device 5 as shown in FIG. 2 in detail.
The toner is deposited under an electric field, and the resulting toner image is transferred by the transfer device 6 to the recording paper P that is fed in synchronization with the rotation of the photoreceptor drum 3 so as to be in contact with the surface. The recording paper P on which the image has been transferred is separated from the surface of the photosensitive drum 3 by the separator 7, and then the toner image is fixed by the roller fixing device 8, and the recording paper P is discharged outside the machine, and the toner image is transferred thereto. The surface of the photoreceptor drum 3 is covered with a static eliminator 9
The developing device shown in FIG. 2 will be described with reference to FIG. 2, in which the remaining toner is removed by the cleaning device 10 after the static electricity is removed by the cleaning device 10, and the image recording process of - times is completed.

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
The developing sleeve 51 is stationary or rotates to the left, and the magnet body 52 rotates to the right and remains stationary, so that 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 both rotations cause it to move counterclockwise. The amount of the developer transported in this manner is regulated by the layer thickness regulating blade 54 to form a developer layer with a uniform layer thickness, and the developer layer is formed in a developing area where an electric field is generated by a bias voltage. The electrostatic latent image on the photosensitive drum 3 is developed. The remaining developer layer that has passed through the developing area is removed from the surface of the developing sleeve 51 by a cleaning blade 55 and placed in a developer reservoir 5.
The developer in the developer reservoir 53 is reduced to
The signal processing method in the signal processing device 1 of the conventional image recording apparatus is multi-valued or continuous. The image data is converted into a binary image by comparing each pixel data of the image data with gradation with a preset threshold value. This processing method uses the same threshold value for all pixels. (hereinafter referred to as a simple binarization method) and a method in which each pixel is set to a different value (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 represent halftones in a pseudo manner by the density of the spatial distribution of black dots, 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. Process 1 sets the density level of the pixel to 16
Input image data expressed in stages, R1 is a predetermined threshold matrix, and Sl is 0" or 0" depending on whether the density level of the pixel is below or above the threshold by comparing the pixels of the input image data E1 with the corresponding threshold of the threshold matrix R1. This is the output image data with "1'".If this 0" is white and "1" is black, this output image data S1 is "O".

Although the distribution of "1"s can represent gradations in a pseudo manner (5), 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, and other suitable methods may be used, such as randomly setting a threshold value of "1 to 16" for each pixel, or setting a threshold of "1 to 16" randomly for each pixel, or It is possible to obtain a binary image with excellent gradation reproducibility even when using a method that sets data. However, compared to these other methods, the systematic dither method has faster calculation speed.
Moreover, it is excellent in that it has good halftone reproducibility.

In contrast to the above dithering method, in the case of the simple binarization method, the threshold value is set to "9", and the input image data E1 is similarly "
When binarized into θ″ or “1”, the arrangement of “10″′ in input image data E1 becomes \”1. It becomes a black pixel of II, and its distribution makes the gradation appear smooth. On the other hand, the resolution of the input image data E1 can be maintained.

On the other hand, if the input image data is already binarized, such as a halftone photograph, and the halftones are reproduced in a pseudo manner, it is more advantageous to use the dither method. In general, it cannot be said that there is (6). 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. It may be better to process halftone photographs and the like by simple binarization.

As explained above, if a binary image is formed using an appropriate signal processing method depending on the type of input image data I, an excellent recorded image can be obtained.

However, in conventional image recording devices, regardless of the type of image to be recorded, the laser writing device 2 performs image exposure with a laser spot of the same diameter, and the electrostatic latent image formed thereby remains the same unless it is specifically changed. Developing was carried out under an electric field using a bias voltage. As a result, the recorded image was always composed of dots of the same size. The problems caused by this will be 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, line 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 so that they 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 continuous gradation plane or a gradation plane composed of halftone dots, the dots may be arranged as shown in FIG. It is desirable to record in the arrangement shown in (a).

However, as mentioned above, conventional image recording devices record dots of a fixed size regardless of the type of image, making it extremely difficult to obtain both excellent line drawings and gradation surfaces. there were.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and provides an image recording system in which recorded images with excellent resolution, sharpness, halftones, smoothness, etc. can always be obtained depending on the type of image to be recorded. It provides equipment.

[Structure of the invention]

The present invention provides an image recording apparatus that forms a latent image based on an image signal and forms an image with a dot configuration by attaching toner to the latent image under an electric field. The present invention provides an image recording apparatus characterized in that the image recording apparatus is configured to switch the image recording apparatus, and with this configuration, the above object is achieved.

First, the basic principle of the present invention is explained in Figs. 5 and 6.
This will be explained using figures.

5 and 6 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 (9) shown in FIG. 3 shows changes in the development characteristics with respect to the amplitude VaO of the AC component and the frequency f, that is, the reciprocal of the period, of the bias voltage having the following values. In FIGS. 6 and 7, the surface potential of the photosensitive drum 3 is expressed as (1) the DC component of the s1 bias voltage is Vdc.

As is clear from FIGS. 6 and 7, the larger the amplitude VaO of the AC bias is, the smaller the frequency f, that is, the greater 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, when 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.

The image recording apparatus of the present invention utilizes the above principle.

FIG. 7 shows an example of the image recording device of the present invention, and FIG. 110) The same reference numerals as in FIG. 1 indicate the same functional members.

In the recording device shown in FIG. 7, the image reading device 12
The COD image sensor reads the original and outputs the image data to the signal processing device 1, and at the same time or prior to that, the operator determines whether the image data identified by the image reading device 12 is a line drawing or a gradation image. The identification signal is output to the control device 13 which is the control section of the recording apparatus.

Thereby, the control device 13 outputs the control signal C to the bias power supply 11.

On the other hand, the signal processing device 1 converts the image data into a binary image and outputs it to the laser writing device 2.

Therefore, the laser writing device 2 performs image exposure on the photoreceptor drum 3 with a laser spot according to the image data.

The electrostatic latent image formed by image exposure is
Therefore, in the case of a line drawing, development is performed under an electric field in which at least one cycle of the amplitude of the alternating current component is increased, and in the case of a gradation drawing, the amplitude of the alternating current component, FM
At least one of the stages is developed under a reduced electric field.

The rest of the recording operation is performed in the same way as described in connection with Figure 1.The recorded images obtained by this image recording device are images with high resolution and sharpness in the case of line drawings, and images with high resolution and sharpness in the case of gradation drawings. This is an image that reproduces smoothness and smoothness.

The present invention is not limited to an image recording device that switches only the developing bias depending on whether it is a line drawing or a gradation drawing, as in the image recording device shown in FIG. You can also do this.

FIG. 8 shows an example of such a device. The difference from the device shown in FIG. 7 is that the signal processing device 1. Control signals 01 and 02°C3 are transmitted from the control device 13 to the laser writing device 2° bias power supply 11, respectively.

Based on this, the signal processing method, laser spot diameter, and developing bias are switched as shown in Table 1, and image formation is performed. However, the developing process is performed by reversal development in which toner is attached to the area irradiated with light.

Table 1 〔Example〕 Next, a specific embodiment of the present invention will be described.

Embodiment 1 In an image recording apparatus as shown in FIG.
outputs the control signal C to the bias power supply 11, the signal processing device 1 converts the image data E by a simple binarization method,
The bias power supply 11 applied the bias voltages shown in Table 2.

/IQ1 Table 2 (Note) The amplitude is 14 from peak to peak.

The photoreceptor drum 3 has a Se photoreceptor layer on the surface and has a diameter of 120M, and the rotation in the direction of the arrow is at a circumferential speed of 12M.
0 sm/880% Charge to 600V with charger 4. 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 to spot-expose the charged surface of the photoreceptor drum 3 at a density of 12 dots/fin. do. The developing device 5 has a developing sleeve 51 with a diameter of 30 fins, and a photosensitive drum 3.
The gap between the
The magnetic body 52 rotates counterclockwise (14) at a circumferential speed of /sea, and the magnet body 52 rotates clockwise at a circumferential speed of 80 rpm. It is assumed that the layer thickness is formed 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 and gradation drawings were recorded using the image recording device under the above conditions, the recorded images obtained in both cases 1 and 2 showed that the line drawings had noticeable skipped dots and uneven lines. Embodiment 2 In the image recording apparatus shown in FIG. 8, the image reading device 12 reads the original is a line drawing, gradation drawing, or halftone drawing, and based on the identification signal, control device B sends control signals 01.03 to signal processing device 1. Bias power supply 1
1. Furthermore, in the signal processing device 1,
When the original is a line drawing or a halftone image, a simple binarization method is used, and when the original is a gradation drawing, a binary image is formed using the dither method. The bias power supply 11 applies the bias voltage shown in Table 3 to the sleeve in accordance with control signal No. 0. Other conditions were set the same as in the example.

Table 3 (Note) Amplitude is from peak to peak.

The recorded images obtained in both cases 1 and 2 are sharp with no noticeable dot skipping or line irregularities for line drawings, and have good midtone reproducibility for gradation images and halftone images. It was good and smooth.

Embodiment 3 In an image recording apparatus as shown in FIG. 8, the image reading device 12 outputs a video signal as image data, and when the control device 13 receives an identification signal, it outputs control signals 02 and 03. are output to the laser writing device 2 and the bias power supply 11, respectively, and the laser writing device 2 selects a lens according to the control signal C2, and performs exposure with a laser spot with a diameter of 100 μm in the case of line drawing designation, and in the case of gradation side designation. Exposure was performed using a laser spot with a diameter of 70 μm, and the bias power supply 11 applied the bias voltages shown in Table 4.

Table 4 (Note) Amplitude is peak-to-peak.

(17) The signal processing device 1 is configured to convert image data by the dither method, regardless of whether it is a line drawing or a gradation drawing. The developing device 5 uses a developer in which the toner becomes positively charged by frictional electrification, and the gap between the developing sleeve 51 of the developing device 5 and the photoreceptor drum 3 is set to 0.511111, and the layer thickness of the developer layer is set to Q.
, 6 mm, and the development is so-called reversal development in which toner is attached to the exposed portion of the photosensitive drum 3. Other conditions were the same as those in Example 1.

When line drawings and gradation drawings were recorded using the image recording device under the above conditions, the recorded images obtained had no noticeable dot skipping or line unevenness in both cases of 1V and 11°2. The image was sharp, and the halftone reproducibility of the gradation image was good.

〔Effect of the invention〕

According to the image recording apparatus of the present invention, it is possible to obtain a recorded image with a dot structure that has high resolution and sharpness in the case of a line drawing, and is smooth and has excellent halftone reproducibility in the case of a gradation drawing.

The present invention is applicable not only to image recording apparatuses that perform laser writing on electrophotographic photoreceptors (18), but also to image recording apparatuses that form images composed of approximately dots using electrostatic recording methods or magnetic recording methods. 0 applicable to

[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, and Figs. 5 and 6 are graphs showing how the development characteristics change when the amplitude and frequency of the AC bias are changed, respectively. , 7 and 8 are schematic configuration diagrams showing an example of the image recording apparatus of the present invention. ■...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, 54... Layer thickness regulating blade, Process 1...Input image data, R1...Threshold value matrix, Sl...Output image data, VaC...Amplitude, f...Frequency, Vs...Photosensitive drum surface potential, Vdo... DC component, 12... image reading device,
13...Control device, D...Identification signal, 0.01~
C3...control signal. Patent Applicant Roku Konishi Photo Industry Co., Ltd. Soi Sankeishi Figure 7 Procedural Amendment April 7, 1980 Kazuo Wakasugi, Commissioner of the Patent Office 1, Indication of Case 1982 Patent Application No. 48246 2 and 4” 0 Name Image Recording Device 3, Relationship with the person making the amendment Patent applicant fE”+W 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo
Name) (127) Konishi Roku Photo Industry Co., Ltd. 8, "However, conventional" in the first line of page 9 of the statement of contents of the amendment was changed to "However, this point was overlooked without being noticed, and the conventional" I am corrected. (2)

Claims (2)

[Claims] (1) In an image recording device that forms a latent image based on an image signal and causes toner to adhere to the latent image under an electric field to form a dot-structured image, the electric field is controlled depending on the type of image to be recorded. An image recording device characterized by being configured to switch. (2) The electric field includes an alternating current component, and at least one of its amplitude and synchronization is large when the image to be recorded is a line drawing, and small when the image to be recorded is a gradation plane. 1
The image recording device described in Section 1.