JPH0594079A - Electrostatic recorder - Google Patents

Abstract

PURPOSE:To obtain a satisfactory image by preventing irregularities in image density caused by irregularities in electrification and irregularities in development. CONSTITUTION:When a value V detected by a density sensor 17 as an image forming information detecting means 21 for detecting image forming information on a photosensitive body 2 is inputted, a correcting arithmetic means 22 carries out an arithmetic operation for correcting the emitting light quantity of an optical writing head H composed of plural light emitting elements. Then, an emitting light quantity control means 23 outputs an emitting light quantity control signal A1 to the optical writing head based on the corrected value T obtained by the arithmetic operation and the photosensitive body is irradiated with the corrected emitting light quantity H1, thereby obtaining a satisfactory image having uniform density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing head to which a light emitting element such as a fluorescent display tube which forms an electrostatic latent image by selectively irradiating light on a photoconductor such as a digital copying machine or a printer. The present invention relates to an electrostatic recording apparatus used, and particularly to an electrostatic recording apparatus suitable for obtaining a uniform image density.

[0002]

2. Description of the Related Art FIG. 10 is provided with an optical writing head H for selectively emitting light from a plurality of dots of light emitting elements, which are arranged in an array in the main scanning direction and which are applied with a uniform amount of light emission, to which a fluorescent display is applied. The schematic configuration of the main part of the electrostatic recording device is shown. This type of apparatus includes a photoconductor 2 for forming an electrostatic latent image and a toner image. Around the photoconductor 2, a charging charger 1, an optical writing head H, a developing unit 4, a transfer charger 5, and a cleaner unit 8 are arranged. The electrostatic latent image on the photoconductor 2 is developed as a toner image by the developing unit 4 and then transferred by the transfer charger 5 to the conveyed paper 6. The sheet 6 onto which the toner image is transferred is fixed in the fixing unit 7.
The toner is fixed on the sheet and is discharged onto the discharge tray 9.

The optical writing head H includes an optical writing element 0
And a rod lens array 3 and the like. Light from the optical writing element 0 passes through the rod lens array 3 and is charged by the charging charger 1 into the photoconductor 2
An image is formed on the surface to form an electrostatic latent image. Conventionally, as a method of correcting the light amount of the optical writing head H used in this type of electrostatic recording apparatus, for example, those disclosed in Japanese Patent Laid-Open Nos. 63-172287 and 63-222869 are known. .. According to these correction methods, the light emission time or the current value of each dot is adjusted so that the amount of light received on each photoconductor becomes constant according to the light emission intensity of each dot in the uncorrected state that is turned on under a constant driving condition. Are in control.

[0004]

However, due to the inclination of the distance between the charging charger 1 and the photoconductor 2,
When the charging variation occurs on the photoconductor 2, even if the exposure is performed by the optical writing head whose light amount is uniformly corrected,
It is not possible to obtain a high-quality image with uniform density. Also,
Even if uniform charging and exposure are obtained, the developing unit 4
If the density of the toner image developed in step 1 is uneven, it is not possible to obtain a high quality image as described above. Therefore, the conventional electrostatic recording device has a problem that it may not be possible to obtain a high-quality image having a uniform density even if the amount of light emitted from the optical writing head is uniform. SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic recording apparatus which can prevent uneven image density due to uneven charging and uneven development and can obtain a high quality image.

[0005]

In order to achieve the above object, the present invention is an electrostatic recording apparatus provided with an optical writing head for selectively emitting light from a plurality of dot light emitting elements arranged in an array in the main scanning direction. In the above, an image formation information detection means for detecting information on image formation on the photoconductor by the optical writing head, and a correction calculation for making a predetermined calculation by inputting a detection value by the detection means to obtain a light amount correction value of the light emitting element. And a light emission amount control device for controlling the light emission amount of the optical writing head based on the correction value.
The image formation information detection means is a density sensor that detects the density of the toner image on the photoconductor or a potential sensor that detects the latent image potential on the photoconductor. Further, the image formation information detecting means is configured to be movable in the main scanning direction in parallel with the surface of the photoconductor.

[0006]

The detection value detected by the image formation information detecting means is calculated according to a predetermined rule shown in FIGS. 6 and 7,
The correction calculation means determines a correction value that makes the image density uniform. The light emission amount control means controls the light emission amount of the optical writing head based on the correction value.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows the configuration of the electrostatic recording device of the present invention. The optical writing head H is a same-magnification imaging optical element as the optical writing element 0 that selectively emits light from a plurality of dots of light emitting elements, which are arranged in an array in the main scanning direction and are applied in a main scanning direction by applying a fluorescent display tube. It is composed of a rod lens array 3 which is a system. As shown in FIG. 3, the write head H has a sealed case 10 having a transparent partition wall 15 whose inside is evacuated, and an anode electrode pattern 11 is formed in the sealed case, and an upper surface of one end of the anode electrode pattern 11 is formed. Phosphor 1
2 is applied, and a filament cathode 13 is provided directly below the transparent partition wall 15. Cathode 13
When an electric current is applied to and heat is applied, thermoelectrons fly out from the cathode 13. The thermoelectrons are grounded at the cathode 13 and attracted by the positive voltage applied to the grid electrode 14, the selection electrode 16 and the anode electrode pattern 11, are narrowed down and collide with the phosphor 12 to emit light.

On the photoconductor 2 charged by the charging charger 1, the light from the optical writing element 0 whose amount of light is uniformly corrected is imaged through the rod lens array 3 and drawn electrostatic latent image. The image is developed as a toner image by the developing unit 4. As shown in FIG. 5, the density of the toner image 17c is determined by irradiating the surface of the photoconductor 2 with light from a light source 17a such as an LED or a semiconductor laser, and capturing the reflected light 17d with a photodiode 17b. It is measured by the density sensor 17 which outputs a voltage signal. Sensor 17
As shown in FIG. 4, the sensor driving device 18 is movably mounted in the main scanning direction and scans the surface of the photoconductor 2 in parallel at a constant distance.

Next, the light emission amount control for making the image density uniform will be described. FIG. 1 shows a block diagram for controlling the light emission amount of the optical writing head. 6 and 7 are flow charts. If the adjustment mode button on the operation panel is selected when the printed image is visually ununiform, the sensor driving device 18 operates and the density sensor 17 starts scanning in the main scanning direction (S).
1). The density sensor 17 receives the reflected light 17d from the photoconductor 2.
Is captured by the photodiode 17b, and the voltage data V is output to the correction calculation unit 22 by using the concentration as a voltage signal (S
2). The correction value calculation means 22 averages the voltage data of a plurality of areas in the scanning direction for each area, and then converts the voltage data into a relative exposure amount (S3).

The relationship between the output voltage value of the photodiode and the exposure amount of the optical writing head has been previously obtained by experiments. FIG. 8 shows that the toner image is formed by changing the exposure amount of the optical writing head under the same development and charging conditions as the actual electrostatic recording device, and the density is measured as a voltage signal by the density sensor. The relationship is represented by a calibration curve. Therefore, in step S3, the exposure amount of the optical writing head corresponding to the voltage value output from the density sensor is obtained by checking the calibration curve, and the voltage data V corresponding to the density is converted into the relative exposure amount E. Next, the minimum value Emin is found from the relative exposure amount E (S4), and the ratio t of each relative exposure amount E to this Emin is found.
(= Emin / E) is obtained (S5). The obtained relative ratio t is ranked in, for example, 16 steps shown in FIG. When ranking, round up, round down,
Alternatively, it may be rounded off.

Next, as an example, the ranking by rounding down will be described in detail. Here, the number of ranks is 16 steps, and in order to decide which rank of 16 steps is to be located, first rank 16 (hereinafter, the rank is referred to as “R”) is set (S6), and the relative ratio t is set to the threshold value T.
16 is compared (S7). R1 if smaller
The threshold value Tn is lowered to 5. When it is smaller, the threshold value Tn is successively lowered to R14 (n = n-1) (S8), and when the relative ratio t is between Tn + 1 and Tn (Tn + 1> t).
The threshold value Tn of ≧ Tn) is determined as the correction value T of the relative ratio t. By repeating the processing of S5 to S8, the correction value is determined for each data.

The correction value T (T
n → T) is output to the light emission amount control means 23 in order to control the relative light emission amounts of all the dots included in the area to which the correction value is given. The light emission amount control means 23 outputs a signal A1 for applying a predetermined pulse width to the light emitting element for each region based on the correction value, controls the relative light emission time of the optical writing head H, and outputs the corrected light amount. Light H1 to photoconductor 2
(S9). The light emission time is controlled by changing the pulse width of the voltage applied to the selection electrode 15 in the optical writing element O. According to this embodiment, since the pulse width is determined by the correction value T, it is possible to obtain a uniform image density in the main scanning direction. In the above-described embodiment, the light emission amount control of the optical writing head is configured to be performed by the operation of the selection means such as the adjustment button. However, the automatic adjustment may be performed such that the operation is periodically performed at a certain fixed time. good.
Further, although the start of the light emission amount control of the optical writing head is instructed by the operation of the selecting means, the operation may be automatically instructed immediately after the power is turned on or the preheat is released.

[0013]

According to the present invention, the image forming information detecting means detects the image density unevenness due to the charging unevenness or the development unevenness, and the light emission head is controlled by the light emission amount controlling means based on the correction value calculated from the detected value. By controlling the light emission amount of, it is possible to always obtain a good image with uniform image density.

[Brief description of drawings]

FIG. 1 is a block diagram for controlling a light emission amount of an optical writing head.

FIG. 2 is a schematic configuration diagram of a main part of an electrostatic recording device including the optical writing head of the present invention.

FIG. 3 is a side sectional view of an optical writing element.

FIG. 4 is a perspective view of a main part of the electrostatic recording apparatus shown in FIG.

5 is a perspective view of a schematic configuration of image forming information detecting means applied to the electrostatic recording apparatus shown in FIG.

FIG. 6 is a flowchart of light emission amount control.

FIG. 7 is a flowchart of light emission amount control.

FIG. 8 is a diagram showing a relationship between an exposure amount of an optical writing head and a voltage output value of a density sensor.

FIG. 9 is a diagram showing an example of ranking relative ratios.

FIG. 10 is an explanatory diagram of a schematic configuration of a main part of an electrostatic recording device including a conventional optical writing head.

[Explanation of symbols]

H light writing head, O light writing element, 1 charging charger, 2 photoconductor, 3 rod lens array, 4 developing unit, 5 transfer charger, 6 paper, 7 fixing unit, 8 cleaner unit, 9
Output tray, 17 Concentration sensor, 17a Light source, 17b
Photodiode sensor, 17c toner image, 18
Sensor scan driving device, 21 Image formation information detecting means, 22 Correction value calculating means, 23 Light emission amount controlling means

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takeo Kakinuma 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Zero Tux Co., Ltd.

Claims (4)

[Claims] 1. An electrostatic recording apparatus having an optical writing head for selectively emitting light from a plurality of light emitting elements arranged in an array in the main scanning direction, and information relating to image formation on a photoconductor by the optical writing head. Image formation information detection means, a correction calculation means for inputting a detection value by the detection means and performing a predetermined calculation to obtain a light amount correction value of the light emitting element, and a light emission amount of the optical writing head based on the correction value. An electrostatic recording device comprising a light emission amount control means for controlling. 2. The electrostatic recording apparatus according to claim 1, wherein the image forming information detecting means is a density sensor for detecting the density of the toner image on the photoconductor. 3. The electrostatic recording apparatus according to claim 1, wherein the image formation information detecting means is a potential sensor for detecting a latent image potential on the photoconductor. 4. The electrostatic recording apparatus according to claim 1, wherein the image formation information detecting means is configured to be movable in the main scanning direction in parallel with the surface of the photoconductor.