JPS59114971A - Electrostatic printer - Google Patents

Abstract

PURPOSE:To obtain a recorded matter having a prescribed gradation with a simple constitution by comparing the density of an original picture with a reproduced curve set separately from a relation curve of picture density which are formed on a photosensitive body to calculate the correction value and correcting the density of the original picture. CONSTITUTION:The optical density data of an original picture which is read by an original density reader is stored in a picture memory part. The characteristic curve of a photosensitive body which is previously measured, i.e., a relation curve of optical density of a picture is fed and stored to a photosensitive body characteristic memory part. While the gradation to be reproduced in this system is fed and stored to a reproduced gradation setting part. Then a comparison/ arithmetic part compares the characteristic curve of the photosensitive body with the reproduced gradation set value to calculate the difference of reproduction density at each original picture density point. Then a correcting operation is carried out to the density difference at a correction arithmetic part, and the result of this operation is supplied to an AOM driving part to control the luminous flux given from a gas laser. In such a way, a reproduction exactly similar to an original picture can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatographic printer that records continuous l@ tone images, and more particularly to a scanning electrostatographic printer with improved tonal reproducibility. .

Electrostatographic printers that use electrostatic photography currently on the market control an optical modulator in response to image signals generated from an electronic computer, etc., and modulate the original beam generated from a light source such as a laser. An image is written on a photoconductive photoreceptor to form an electrostatic latent image, which is then developed and transferred to obtain a recorded matter. It's almost limited to things that don't exist.

Although there are many practical demands for reproducing and recording original images such as photographs with continuous gradation using printers such as those mentioned above, there is no one that satisfies this requirement, and development of an electrostatic printer with good MWi reproducibility is required. desired.

[Prior art]

In electrostatic printers such as those described above, the image is output in the form of small dots on the scanning edge, and the screen is represented by a collection of dots. The images formed on photoconductive photoreceptors, which are normally used for electrostatic recording, have extremely high contrast and are suitable for reproducing and recording figures that do not have a gradation level, such as characters and line drawings. Yes, but is it a series of photos etc.? In order to record a continuous tone image using an electrostatic printer, the original image is usually scanned with a light sensor to read its optical density, and then the electrical signal is However, if the intensity of the light flux is simply made proportional to the optical density of the original image, the image formed will have a significantly high contrast. The richness of the original drawings
z M II 'v impossible to reproduce.

In order to reproduce and record continuous gradations using the above-mentioned printer, it has been proposed to change the dot spacing and density depending on the density of the original image. In this case, the density of each dot is set to the maximum density, and the density va is determined by the sparse S of the array.
Although it has the advantage of being unaffected by the gradation characteristics of the photoreceptor, it is necessary to two-dimensionally control the interval and density of the output dots, so the input image density CCD In the case of a multi-pixel one-dimensional line sensor such as an element, the technical difficulty is extremely high.

Although it is technically easy to create gradations by changing the density of dots by changing the intensity of the exposure source flux without changing the density of the dots, as mentioned above, it is difficult to This cannot be avoided, and only a reproduced image with extremely poor gradation and high contrast can be obtained.

[Purpose of the invention]

The object of the present invention is to have good continuous tone reproducibility! - To provide an electrostatic printer having a relatively simple configuration.

[Structure of the invention]

The purpose of the above is to provide a means to memorize the izunoka that has been read,
means for storing the photographic gradation characteristics of the photoconductive photoreceptor; means for inputting and setting data of the gradation to be reproduced; and means for storing the photographic gradation characteristics of the photoreceptor and the data of the gradation to be reproduced. This has been achieved by an electrostatic printer characterized by having arithmetic means for comparing and calculating a correction value, correcting the original image density value, and outputting the corrected image density value to the light modulation means. As a means for reading the optical density of the original image, it is preferable to use a line sensor using a COD element or an MC8 type element. It is preferable to use HS, various gas lasers, and semiconductor lasers as the exposure light source for the photoreceptor, and as the one-dimensional modulation means, A.
An original modulator such as an OM (acousto-optic modulator) can be used. Photoconductors include inorganic photoconductors such as selenium-based, zinc oxide-based, and amorphous silicon-based photoconductors, various organic photoconductors, PIP & photoconductors, and various photoconductive photosensitive materials used in electrostatic photography. You can use your body. In addition, the read original image density, photographic gradation characteristics of the photoreceptor, storage means for setting data of the gradation to be reproduced, and photographic gradation characteristics of the photoreceptor are compared with the setting data of the gradation to be reproduced. As the arithmetic means for calculating the correction value and correcting the original image density value, various electronic storage elements and arithmetic elements commonly used in data processing can be used.

[Function and effect of the invention]

The present invention calculates a correction value by comparing a pre-measured photographic gradation curve of a photoconductor, that is, a relational curve between the original image density and the image density formed on the photoconductor, with a separately set desired reproduction curve. Correct the original image density read by
By controlling the intensity of the light beam scanning the photoreceptor, the desired gradation level 7 can be achieved.
The shading of the image is formed by changes in the density of each dot, and is not expressed by the density of the dots.

FIG. 1 is a block diagram showing an embodiment of the present invention. Original density reading device such as original sensor that scans the original drawing! The optical density data of the original image read by is stored in the image storage section in time series. The characteristic curve storage section inputs and stores a previously measured characteristic curve of the photoreceptor, that is, a relationship curve between the optical density of an image obtained from the exposure device and the photoreceptor (FIG. 2A).

The reproduction tone setting value includes the tone to be reproduced by this system,
That is, the relationship between the original image density and the density to be obtained on the copy (FIG. 2 B1 curve b)'&large input is stored. If this relationship is made into a 45° linear relationship on Figure 2B, the original and the reproduction will have the same gradation, but for practical purposes, it is possible to obtain a reproduction with a more preferable gradation. It is desirable to configure the system so that any relationship can be set.

The comparison calculation unit compares the photoreceptor characteristic curve described above with the reproduction gradation setting value to calculate the difference in copy density at each original image density point, and the correction calculation unit performs correction calculation for this density difference. When a semiconductor laser is used as a light source by inputting it to a driving section and controlling the luminous flux from a gas laser, the amount of light emitted can be controlled by inputting it to its output control section.

In the above system, the photosensitive characteristics of the photoreceptor are shown in Figure 2A.
In this case, if the density signal of the original is inputted to the dot signal control section without being corrected as usual, the relationship between the optical density of the obtained copy and the optical density of the original is exactly as in 2Fg, which is the inversion of FIG. 2A: It becomes curve a of iB, which faithfully reproduces the original drawing 4
There is a big difference from the 5° straight line B and b in Figure 2.

Difference at each density point of these two curves (28th Jc)'Y
In addition to the corresponding density of the image signal, if the exposure light flux is controlled by inputting the relationship as shown in Figure 2 B and curve C in advance, it is possible to offset the gradation characteristics of the photoreceptor and obtain a reproduction faithful to the original image. .

Furthermore, by performing the above procedure while changing the set angles of the lines B and b in FIG. 2 as necessary, it is possible to freely adjust the contrast of the copy and obtain a copy with a preferable contrast.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2A
is a characteristic curve of the photoreceptor, B is a relationship curve between the original image density and the initial density of the copy, and C is a relationship curve between the original image density and the correction amount for n. Agent Umi Kuwahara Figure 2

Claims (1)

[Claims] (1) A means for scanning a continuous tone original image with a light receiving head to read the optical density of the original image, a means for scanning a photoconductive photoreceptor with a beam of light from a laser or the like as a light source, and a means for scanning the optical density of the original image using the light beam as a light source. In an electrostatic printer having a light modulating means for modulating the light based on the output of the means, and a photoconductive photoreceptor that is scanned and exposed by the light beam to form an electrostatic latent image, a storage means for storing the density of the read original; ” means for storing photographic gradation characteristics of the photoconductive photoreceptor; means for inputting and generally defining data of the gradation to be reproduced; and means for storing the photographic gradation characteristics of the photoreceptor and the predetermined gradation reproduction data. calculation means V for calculating a correction value by comparing the values, correcting the original image density value, and outputting the corrected image density value to the light modulation means.