JPH0943943A - Image forming device - Google Patents

Abstract

(57) An object of the present invention is to provide an image forming apparatus capable of performing highly reliable exposure amount control at low cost. SOLUTION: At the start of a copy routine, an optical sensor 3
7, the amount of reflected light of n originals is read and A / D converted. The main control system 42 averages the data of x higher-order originals from the A / D-converted data, obtains the average value of the reflected light amount read values of the background portion of the original document, and compares it with the initial value. If the read value is below the initial value as a result of this comparison calculation, the exposure lamp voltage is corrected according to the degree.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to a lamp exposure amount correction technique.

[0002]

2. Description of the Related Art An original document on a document table (contact glass) is illuminated by an exposure lamp, and reflected light from the document is directly illuminated on a photoconductor through an optical system to form an electrostatic latent image. A digital image in which an electrostatic latent image is formed by photoelectrically converting image information by reflected light from an image forming apparatus or a document with a CCD, modulating a laser beam, and writing on the photoconductor with the modulated laser beam. In any of the forming apparatuses, there is a problem in that the exposure light amount is reduced due to deterioration of the exposure lamp over time, stains on the optical system, etc., and image quality is deteriorated.

Therefore, various exposure light amount correction techniques have been conventionally proposed. Specifically, the technique of increasing the exposure light amount at regular intervals (operating time and the number of copies), assuming the amount of decrease in the light amount due to the contamination of the optical system and the deterioration of the exposure lamp over time, and the potential near the surface of the photoconductor A technique in which a sensor or an optical sensor is arranged, a reference latent image pattern or an image pattern formed on the surface of the photoconductor is detected by these sensors, and the exposure light amount is controlled based on the detection output (for example, Japanese Patent Laid-Open No. 63-63 No. 169672,169673) is generally used.

[0004]

However, the former of the above prior arts does not take into account the fact that the degree of contamination of the optical system differs depending on the use environment conditions, copy conditions, and the like, so that appropriate light amount correction is always performed. Not limited to this, the background may be soiled due to insufficient light quantity, or the image may be blurred due to excessive light quantity. The latter uses a potential sensor and an optical sensor in close proximity to the photoreceptor surface,
There is a disadvantage that the cost is high.

The present invention has been made in view of such a background, and an object thereof is to provide an image forming apparatus capable of performing highly reliable exposure amount control at low cost.

[0006]

In order to achieve the above object, the present invention reads an amount of light reflected from an original by an exposure lamp for irradiating the original and corrects the voltage of the exposure lamp according to the amount of the reflected light. The apparatus is provided with reading means for reading the amount of reflected light from the original at the defocus position of the exposure optical system, and correction means for correcting the exposure lamp voltage based on the output signal of the reading means at the start of the copy routine. And

Further, in the above description, the reading means reads the amount of reflected light from a plurality of originals for every fixed number of sheets, and the correcting means samples the output signal of the reading means and determines the voltage of the exposure lamp according to the output signal. It is characterized by correction.

Further, in the above, the correction means corrects the voltage of the exposure lamp on the basis of the average value of the upper several output signals of the sampling output signals from the plurality of originals.

In such means, at the start of the copy routine, the reading means (optical sensor) reads the reflected light quantity of a plurality of (n) originals, more specifically, the reflected light quantity (density) of the background portion of the original, A / D convert. The correction means (main control system) averages data of x (x <n) originals higher than the A / D converted data to obtain an average value of the reflected light amount readings of the background of the original, Performs comparison operation with the initial value (reference value). If the read value is below the initial value as a result of this comparison calculation, the exposure lamp voltage is corrected according to the degree.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Referring to the accompanying drawings,
An embodiment of the present invention will be described in detail. FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus according to the present invention.
As shown in FIG. 1, around the drum-shaped photoreceptor 11,
Charging corona charger 12, slit exposure device 13, eraser 14, developing device 24, transfer corona charger 28, and separation corona charger 2 in the order of the image forming process.
9, a separation claw 30, a cleaning device 34, and a static eliminator 35 are arranged.

The slit exposure device 13 includes an exposure lamp 16, a first, a second, and a third reflecting mirrors 17, 18 and 19, an image forming lens 20, a fourth, a fifth and a third, which are provided directly below a document table 15. Six reflection mirrors 21, 22, 23 are provided. The exposure lamp 16, the first, second, and third reflecting mirrors 1
7, 18, and 19 form a first carriage, and the fourth, fifth, and sixth reflection mirrors 21, 22, and 23 form a second carriage.

The paper is fed from the paper feed device 25 or the manual feed table 27 toward the registration rollers 26, and is sent to the fixing device 32 by the conveying device 31 via the transfer / separation unit to fix the unfixed toner image. The paper is discharged to the paper discharge tray 33.

FIG. 2 is a perspective view showing a main part of the slit exposure device 13. As shown in FIG. 2, an optical sensor 37 for reading the reflected light from the original, specifically, the reflected light from the third mirror 19 is arranged at the defocus position of the exposure optical system.

Next, the operation of the image forming apparatus having such a configuration will be described. During the image forming operation (copying operation), the photoconductor 11 is rotationally driven by a main motor, which will be described later, and is uniformly charged by the charging corona charger 12, and thereafter, image exposure is performed by the slit exposure device 13 and the photoconductor is exposed. An electrostatic latent image is formed on 11, and the eraser 14 eliminates unnecessary areas of the electrostatic latent image. The electrostatic latent image on the photoconductor 11 from which the unnecessary area is discharged is developed by the developing device 24 to become a toner image.

On the other hand, a sheet is fed from either the sheet feeding device 25 or the manual feed table 27, and the registration roller 2
Sent to 6. The registration roller 26 sends out the sheet to the transfer unit in accordance with the toner image on the photoconductor 11.

On the sheet sent to the transfer portion, the toner image on the photoconductor 11 is transferred by the transfer corona charger 28, separated from the photoconductor 11 by the separating corona charger 29 and the separating claw 30, and the conveying device 31. Are conveyed to the fixing device 32. Then, after the toner image is fixed by the fixing device 32, the toner image is discharged to the discharge tray 33 as a hard copy.

After the paper is separated, the photoconductor 11 is cleaned by the cleaning device 34 to remove the residual toner, and the static eliminator 35 removes the electric charge to prepare for the next image forming operation.

By the way, in the slit exposure device 13, it is well known that the first carriage and the second carriage reciprocate in the scanning range at a speed of 2: 1 by a scanner motor described later, but in the present invention, In the scanning process, the reflected light of the original is received by the optical sensor 37 by the third reflecting mirror 19 as shown in FIG. The exposure amount is controlled based on the read data of the optical sensor 37 as described later.

FIG. 3 is a block diagram showing an embodiment of a control block of the image forming apparatus according to the present invention. As shown in FIG. 3, this control block includes an AC control system 38, a power supply 40,
The main control system 42 is provided. The AC control system 38 is connected to the exposure lamp 16, the heater 32 a of the fixing device 32, and the main motor 41.

The main control system 42 includes the optical sensor 3
7, two high pressure system 43, 44, ADS (automatic concentration adjustment)
The sensor 45, the operation system 46, the scanner motor 47, and the developing motor 48 are connected. The high voltage system 43 applies a high voltage to the charging corona charger 12 and the developing sleeve 24a, and the high voltage system 44 applies a high voltage to the transfer corona charger 28 and the separation corona charger 29.

More specifically, the AC control system 38
AC power is supplied from a commercial AC power source via a main switch, and the AC power supplies the heater 32a of the fixing device 32 with electricity and drives the exposure lamp 16 and the main motor 41 in accordance with a command from the main control system 42. To do.

The power supply 40 generates a predetermined DC voltage from the AC power supplied via the main switch and the AC control system 38 and applies it to the main control system 42 and other parts. The main control system 42 controls each part of the image forming apparatus to start the above-described copying operation by turning on a start switch (not shown) of the operation system 46, and is set by the operation system 46. The copying operation is continuously repeated for the specified number of times.

The main control system 42 takes in input signals from the operation system 46, the optical sensor 37, etc., and the AC control system 3
8, and controls the high voltage systems 43 and 44, the scanner motor 47, the developing motor 48 that drives the developing device 24, and the like. Further, the main control system 42 controls an image forming condition, for example, a developing bias voltage, via the high voltage system 43 according to an input signal from the ADS sensor 45 in order to automatically set the image density.

Further, the main control system 42 has a function as a correction means for correcting the voltage of the exposure lamp 16 according to the output signal of the optical sensor 37, and carries out the processing shown in FIG. The ADS sensor 45 reads the density of the leading edge of the document on the document table 15, and the operation system 46 is operated by the user.

FIG. 4 is a flow chart showing an embodiment of the exposure amount control method according to the present invention. This flowchart shows the control contents of the main control system 42. That is, the main control system 42 confirms at step 101 at the start of the copy routine whether or not the correction flag is set, and if the correction flag is set, at step 102, the AC control system 38 is exposed to the exposure lamp. 16 voltage 1
Increase V. If the correction flag is not set, the process directly proceeds to step 103.

Next, the main control system 42 proceeds to step 10
At step 3, the AC control system 38 turns on the exposure lamp 16 to control each part of the image forming apparatus to perform the copying operation as described above. Then, the main control system 42 proceeds to step 104.
Then, an input signal (a reading value of the background portion of the original document) from the optical sensor 37 that receives the reflected light from the original document and detects the amount of the reflected light is read for a plurality (n) of the original documents and A / D converted.
Then, in steps 105 and 106, the upper x sheets of the input signal data read from n sheets are averaged to obtain the average value of the read values of the background portion of the document. Here, n is normally about 20, for example, and the top 5 of them are averaged.

Next, the main control system 42 proceeds to step 10
In step 7, the average value of the read values of the background portion of the original document is compared with the initial original document (blank paper), and in step 108, the corrected exposure lamp voltage is determined by the following equation.

Corrected exposure lamp voltage = {initial white pattern read value-current white pattern read value (average value)}
/ K

Here, K is the voltage of the exposure lamp 16 of 1V.
It is a constant required to increase. In the experiment, when a 5V input A / D converter was used, the value of K was 0.1 to 0.2.
It is about V.

Next, the main control system 42 proceeds to step 10
In step 9, it is checked whether the corrected exposure lamp voltage is 1 V or higher. If the corrected exposure lamp voltage is 1 V or higher, a correction flag is set in step 110, and if the corrected exposure lamp voltage is lower than 1 V, the step is set. At 111, the correction flag is reset. This completes one cycle of the image forming operation, and the main control system 42, if the correction flag is set as described above at the start of the next image forming operation,
The AC control system 38 increases the voltage of the exposure lamp 16 by 1V.

According to the embodiment of the present invention, since the optical sensor 37 is arranged at the defocus position near the exposure optical system, the sensitivity deterioration of the photoconductor 11 and the characteristics of the developing device 24 and the characteristics of the toner are affected. Without this, the exposure lamp voltage can be properly corrected. Moreover, the exposure lamp voltage that is constantly corrected is a small voltage of 1 V, and when the corrected exposure lamp voltage is 0 V, the exposure lamp voltage is not corrected. Therefore, the copy image density before and after the correction of the exposure lamp voltage is large. Change can be eliminated.

In reading the background density of the document from the amount of reflected light of the document incident on the optical sensor 37, a large number (n
Since the original data of (sheets) is read and the plurality of (x) original document data of the higher order are averaged, the reliability of the read data becomes very high.

[0033]

According to the first aspect of the invention, the amount of light reflected from the original is read at the defocus position of the exposure optical system, and the exposure lamp voltage is corrected with time based on this value. The exposure lamp voltage can be properly corrected without being affected by the use environment conditions, the copy conditions, the presence or absence of sensitivity deterioration of the photoconductor, the characteristics of the developing device, the characteristics of the toner, and the like. As a result, a stable, high-quality image can always be obtained.

According to the second and third aspects of the present invention, the output signal from the reading means based on the reflected light amount from a plurality of originals is sampled for every certain number of sheets, and the upper several of the plurality of output signals are sampled. By correcting the exposure lamp voltage with the average value of the output signals, in addition to the above effects, it is possible to reduce the error due to the variation in the background density of the document.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a perspective view showing a main part of a slit exposure apparatus.

FIG. 3 is a configuration diagram showing an embodiment of a control block of the image forming apparatus according to the present invention.

FIG. 4 is a flowchart showing an embodiment of an exposure amount control method according to the present invention.

[Explanation of symbols]

 16 exposure lamp 37 optical sensor 42 main control system

Claims (3)

[Claims] 1. An image forming apparatus that reads the amount of light reflected from an original by an exposure lamp that irradiates the original, and corrects the voltage of the exposure lamp according to the amount of the reflected light, in the defocus position of the exposure optical system. An image forming apparatus comprising: a reading unit that reads the amount of reflected light; and a correcting unit that corrects the exposure lamp voltage based on an output signal of the reading unit at the start of a copy routine. 2. The image forming apparatus according to claim 1, wherein
The reading unit reads the amount of reflected light from a plurality of originals for every fixed number of sheets, and the correction unit samples the output signal of the reading unit and corrects the voltage of the exposure lamp according to the output signal. A characteristic image forming apparatus. 3. The image forming apparatus according to claim 2,
The image forming apparatus is characterized in that the correction means corrects the voltage of the exposure lamp based on an average value of several higher order output signals among the sampling output signals from the plurality of originals.