JPH081992A - Optical writing apparatus - Google Patents

Abstract

PURPOSE:To provide an optical writing apparatus in which a linear density gradation can be realized without necessity of a special circuit. CONSTITUTION:The optical writing apparatus is so formed as to simultaneously scan a plurality of electron beams in the width direction of a photosensitive member by dividing the photosensitive member width direction 13 of a fluorescent layer 10 into sections corresponding to the number of the beams so that a plurality of light emitting dots of the respective beams are differentiated at any of the areas, emitting light wavelengths and light emitting efficiency from those of the adjacent dots and to impinge the beams to the desired dot of the direction 13 by a deflecting electrode 7 as deflecting angle control means and deflecting angle control circuit 8, thereby realizing a linear gradation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing apparatus used in an image forming apparatus such as a copying machine, a facsimile, a laser beam printer, etc., which forms an image by an electrophotographic method, and more particularly, it emits an electron beam. The present invention relates to an optical writing device that uses a phosphor that emits light as a light source.

[0002]

2. Description of the Related Art As an optical writing device in an electrophotographic image forming apparatus, there is an LED print head in which LED chips are arrayed, as described in Electrophotographic Society of Japan, Vol. 30, No. 4, etc. .

FIG. 8 shows a general structure of an optical writing head using an LED print head. 18 is a photoconductor, 1
Reference numeral 9 denotes an LED array, which is configured by arranging LED chips, which are minute light sources, at equal intervals in the width direction [direction of arrow 13] of the photoconductor 18 in an array. Reference numeral 17 denotes a microlens array, which images the light emitted from the LED array 19 on the photoconductor 18. The arrow 12 indicates the feeding direction of the photoconductor 18.

The LED print head thus constructed gives an ON signal in accordance with an image signal to cause the LED chips of the LED array 19 to emit light and form an electrostatic latent image on the photoconductor 18. Therefore, each light emitting dot forms one pixel on the photoconductor 18 as its image forming pattern.

[0005]

When gradation is expressed in units of one pixel in such an optical writing device, the light emission time is changed to change the light projection time to the photoconductor 18 to obtain the gradation. Is being expressed. Therefore, it is necessary to add a modulation circuit, and the control of the projection time requires a special circuit for guaranteeing the linearity characteristic in accordance with the sensitivity characteristic of the process.

An object of the present invention is to provide an optical writing device capable of realizing gradation expression with linearity adapted to the characteristics of a photoconductor without using a special circuit.

[0007]

According to a first aspect of the present invention, there is provided an optical writing device in which a plurality of electron beams modulated according to an image signal are made to collide with a phosphor layer, and the photoconductor is exposed to light by the emission of the phosphor layer. An optical writing device, wherein the phosphor layer comprises a plurality of light emitting dots for each of the electron beams, and a deflection angle scanning means for projecting the electron beam at a desired position of the plurality of light emitting dots. Is provided.

According to a second aspect of the present invention, there is provided an optical writing device including a cathode for generating electrons, and a back electrode for controlling an emission direction of the electrons generated from the cathode to improve electron utilization efficiency.
A control electrode having a plurality of control holes through which the electrons pass for converting the electrons into a plurality of electron beams; a focusing electrode for focusing the electron beam formed by the control electrodes into a desired size; Signal modulating means for controlling the passing amount of the beam, deflection electrodes for simultaneously deflecting the plurality of electron beams in the width direction of the photoconductor, and deflection angles of the electron beams deflected by the deflection electrodes are set to desired angles. Deflection angle control means, a phosphor layer that emits light when the electron beam strikes, an anode that accelerates the velocity of the electron beam, at least the cathode, the back electrode, the control electrode, the focusing electrode, The electron beam is provided in front of the signal modulation electrode, the deflection electrode, the phosphor layer, and a vacuum container that can hold a vacuum in the anode. The photoconductor width direction of the phosphor layer is divided into sections according to the number of the electron beams, and the photoconductor width direction is simultaneously scanned. It is characterized in that the electron beam is projected and emitted at a desired position in the width direction, and the photoconductor is exposed.

[0009]

According to the structure of the first aspect, the electron beam can be projected by the deflection angle scanning means to a desired position among the plurality of light emitting dots provided for each electron beam. Therefore, a linear density gradation can be obtained by making the emission characteristics of a plurality of emission dots provided for each electron beam different for each emission dot and selecting the position of impact of each electron beam on the emission dot. .

According to the second aspect of the invention, shower-like thermoelectrons generated by heating the filament to a constant temperature are passed through the plurality of control holes of the control electrode to form a desired number of electron generation sources. The same number of electron beams as the control holes generated by passing through the control electrode are focused to a desired size by the focusing electrode. A plurality of electron beams generated at the same intervals as the control holes of the control electrode impinge on the phosphor layer divided into sections according to the number of the electron beams to emit light. The deflecting electrodes cause the respective electron beams to scan the phosphor with a desired scanning width, thereby causing the entire width of the phosphor corresponding to the width direction of the photoconductor to emit light. The phosphor is turned on and off by controlling the passage of the electron beam by controlling the voltage applied to the signal modulation electrode by the modulation circuit, and the turning position of the phosphor is selected by the deflection angle control means. Is controlled by controlling the voltage applied to the electron beam and setting the deflection angle of the electron beam to a desired angle.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical writing apparatus of the present invention will be described below with reference to FIGS.
It will be described based on. It should be noted that components having the same functions as those of the conventional example shown in FIG.

FIG. 1 shows a first embodiment. Reference numeral 1 is a cathode, which generates electrons by heating the filament. Reference numeral 2 is a back electrode for controlling the emission direction of electrons, and 3 is a control electrode, which has n (n> 1, integer) control holes 3a through which electrons generated from the cathode 1 pass, and makes the electrons into a beam shape. . 4 is a focusing electrode for narrowing the electron beam to a desired size, and 5 is a signal modulation electrode for controlling the passing amount of the electron beam for each of the n electron beams. Reference numeral 6 denotes a modulation circuit, which controls the voltage applied to the signal modulation electrode 5 by selecting the position of the signal modulation electrode 5 in the width direction of the photoconductor in order to control the passing amount of the electron beam. Reference numeral 7 is a deflection electrode for scanning n electron beams with a desired scanning width, and 8 is a deflection angle control circuit, which controls a voltage applied to the deflection electrode 7 in order to set the deflection angle of the electron beam to a desired angle. . Reference numeral 9 is an anode to which a high voltage is applied to accelerate the speed of the electron beam, and 10 is a phosphor layer, which is formed on the surface of the anode 9 on the cathode 1 side and emits light when the electron beam collides with it. .

The above-mentioned components are the vacuum container main body 11a.
And a vacuum container lid 11b, and the inside is enclosed in a vacuum container whose interior is kept in vacuum. The vacuum container body 11a
At least the window 11c is made of, for example, a transparent member such as glass so that the light emitted from the phosphor layer 10 is transmitted. The arrow 12 indicates the feeding direction of the photoconductor 18,
Reference numeral 13 indicates the width direction of the photoconductor 18.

The operation of the optical writing device composed of such components will be described with reference to FIGS. 2 and 3.
FIG. 2 is a conceptual diagram showing the operating state of the optical writing device.
In FIG. 2, reference numeral 14 is an optical head unit in which the above-mentioned constituent members are combined into a unit, 15 is an electron beam of n lines, and 16 is an electron beam.
Is a light emitting dot which emits light when n electron beams 15 are sequentially scanned in the direction from A to B at the same time. In FIG. 2, each electron beam 15 is composed of seven light emitting dots 16a to 16g. L is a scanning width scanned by one electron beam, and p is a dot pitch representing a center-to-center distance between adjacent light emitting dots 16.

Each of the n electron beams 15 exposes the entire width of the photoconductor by causing "L / p" light emitting dots 16 to emit light in the width of the scanning width L. Which one of the light emitting dots 16a to 16g is to selectively emit light is determined by controlling the voltage applied to the deflection electrode 7 based on the signal generated by the deflection angle control circuit 8 and scanning the electron beam. 15 emits dots of a desired phosphor. As shown in FIG. 3, the light emitted from the optical writing device of the present invention is imaged on the photoconductor 18 by the microlens array 17.

By optimally applying the dots of this phosphor in accordance with (1) dot area, (2) emission wavelength, and (3) emission efficiency in accordance with the sensitivity of the photoconductor, the light energy for obtaining an output image of a desired density is obtained. Obtainable. The principle of this optimum coating is shown in Figs.
This will be described with reference to FIG.

(1) When changing the dot area As shown in FIG. 4, the process sensitivity characteristic of the photoconductor 18 is
The image density, which is the output sensitivity with respect to the projected light power, has a non-linear relationship. To correct this non-linearity,
The light emission characteristic of the optical writing device is such that the dot area of the light emitting dot 16 is changed in the width direction 13 of the photoconductor 18. Specifically, like the coating state of the phosphor shown by 10a in FIG.
The areas of the light emitting dots 16a ... S1, S2, S3, S
4, when the density D2 is twice the density of D1 is desired, the dots applied in the area S2 are emitted, and when the density three times is desired, the dots applied in the area S3 are emitted. .

In the case of changing the emission wavelength of (2) As shown in FIG.
Luminescent dots 16 with which desired densities can be obtained in the same manner as in the case where the phosphors E1, E2, E3, E4, and E5 having different emission wavelengths are applied so that the densities are linearly output and the dot area is changed in (1) To emit light selectively.

In the case of changing the luminous efficiency of (3) As shown in FIG. 6, phosphors F1, F2 having different luminous efficiencies,
By applying F3, F4, and F5, similarly to the case where the dot area of (1) is changed, the light emitting dots 16 that can obtain a desired density are selectively emitted.

By just setting the deflection angle control circuit 8 in this way, it is possible to realize a writing device which conforms to the process characteristics and guarantees the linearity of gradation without using a special circuit.

FIG. 7 shows a second embodiment. The components with the same numbers as in FIG. 1 are the same components as those of the first embodiment. In the second embodiment, the phosphor is applied uniformly over the entire light emitting surface (uniformly in the width direction 13 of the photoconductor 18) as in the phosphor application state shown in 10b, and the phosphor is blackened. Stripes 20a, 20b, 20c, 20
d, ..., and the luminous dots 16a, 16b having a desired area,
.........

The black stripe 20 referred to here
a, 20b, 20c, 20d, ... Are light absorbing black paints. The optical writing device configured as described above can easily change the desired light emitting area as compared with the case of applying the phosphor by changing the area as in the first embodiment.

[0023]

As described above, according to the present invention, a cathode for generating electrons, a back electrode for controlling the emission direction of electrons generated from the cathode to improve the utilization efficiency of electrons, and a plurality of electron beams for electrons are used. Therefore, a control electrode having a plurality of control holes through which electrons pass, a focusing electrode for focusing the electron beam formed by the control electrode to a desired size, a signal modulating means for controlling the passing amount of the electron beam, and a plurality of A deflection electrode for simultaneously deflecting the electron beam in the width direction of the photoconductor, a deflection angle control means for setting a deflection angle of the electron beam deflected by the deflection electrode to a desired angle, and a phosphor by the electron beam colliding with the phosphor. A layer, an anode for accelerating the speed of the electron beam, and at least a cathode, a back electrode, a control electrode, a focusing electrode, a signal modulation electrode, a deflection electrode, a phosphor layer and an anode. And a vacuum container capable of maintaining a vacuum inside, and a plurality of electron beams divide the width direction of the photoconductor of the phosphor layer into sections according to the number of electron beams, and the width direction of the photoconductor is divided. And the deflection angle control means so that the electron beam can be projected onto a desired position in the width direction of the photoconductor of the phosphor layer by means of the deflection angle control means. By changing the wavelength or the luminous efficiency according to the process sensitivity, it is possible to change the gradation of density linearly without requiring a special circuit.

[Brief description of drawings]

FIG. 1 is a development view of components of a first embodiment of an optical writing device according to the present invention.

FIG. 2 is a conceptual diagram showing an operating state of the embodiment.

FIG. 3 is a configuration diagram when a latent image is formed on a photoconductor using the optical writing device according to the embodiment.

FIG. 4 is a diagram showing the relationship between the process sensitivity characteristic of the photoconductor and the light emission characteristic of the optical writing device.

FIG. 5 is a relationship diagram between the process sensitivity characteristic of the photoconductor and the wavelength sensitivity characteristic of the photoconductor.

FIG. 6 is a diagram showing the relationship between the process sensitivity characteristic of the photoconductor and the luminous efficiency characteristic of the phosphor.

FIG. 7 is a development view of components of the second embodiment.

FIG. 8 is a configuration diagram of a conventional LED print head optical system.

[Explanation of symbols]

 1 cathode 2 back electrode 3 control electrode 4 focusing electrode 5 signal modulation electrode 6 modulation circuit 7 deflection circuit 8 deflection angle control circuit 9 anode 10 phosphor layer 10a phosphor coating state 10b phosphor coating state 11a vacuum container body 11b vacuum Container lid 12 Feeding direction of photoconductor 13 Width direction of photoconductor 14 Optical head unit 15 Electron beam 16, 16a, 16b, ... Emission dot 17 Microlens array 18 Photoconductor

Claims (7)

[Claims] 1. An optical writing device in which a plurality of electron beams modulated according to an image signal are made to collide with a phosphor layer, and a photoconductor is exposed to light by the emission of the phosphor layer. Consists of multiple emission dots for each electron beam,
An optical writing device provided with deflection angle scanning means for projecting the electron beam at a desired position among the plurality of light emitting dots. 2. A cathode that generates electrons, a back electrode that controls the emission direction of the electrons generated from the cathode to improve the utilization efficiency of the electrons, and a plurality of electrons through which the electrons pass to form the electrons into a plurality of electron beams. A control electrode having a control hole, a focusing electrode for focusing the electron beam formed by the control electrode to a desired size, a signal modulating means for controlling the passing amount of the electron beam, and the plurality of electrons. A deflection electrode for deflecting the beam in the width direction of the photoconductor at the same time,
Deflection angle control means for setting the deflection angle of the electron beam deflected by the deflection electrode to a desired angle, a phosphor layer that emits light when the electron beam strikes, and the speed of the electron beam is accelerated. An anode, and a vacuum container capable of containing at least the cathode, the back electrode, the control electrode, the focusing electrode, the signal modulation electrode, the deflection electrode, the phosphor layer and the anode inside and maintaining a vacuum. The electron beam is divided into sections according to the number of the electron beam in the width direction of the photoconductor of the phosphor layer, and the electron beam is simultaneously scanned in the width direction of the photoconductor.
An optical writing device in which the deflection angle scanning means irradiates the electron beam at a desired position in the phosphor width direction of the phosphor layer to emit light, and the photoconductor is exposed. 3. The phosphor layer corresponds to the minimum emission dot,
The optical writing device according to claim 1 or 2, wherein the optical writing device is applied independently. 4. The optical writing device according to claim 1, wherein the coating areas of the phosphor layers independently coated in units of light emitting dots are different between adjacent ones. 5. The optical writing according to claim 1, claim 2, claim 3 or claim 4, wherein the phosphor layers independently applied in units of emission dots have mutually different emission wavelengths. apparatus. 6. The phosphor layers independently coated in a unit of luminous dot have different luminous efficiencies between adjacent phosphor layers, claim 1, claim 2, claim 3, claim 4 or claim 5. The optical writing device described. 7. The phosphor layer uniformly coated on the entire surface scanned by an electron beam is divided into black dots for each emission dot unit, and the area of division is changed between adjacent ones. The optical writing device according to claim 2.