JP2002149034A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where the service life of an LD array can be prolonged by focusing on a toner save mode where the amount of toner attached to an electrostatic latent image in development is reduced. SOLUTION: In the image forming device provided with a scanner part 1, a printer part 4 having an LD array 21, a CPU 7 to carry out total control and further provided with the toner save mode, the CPU 7 has a function to thin out by reducing the lit time of light emitting elements which require the largest amount of current among the light emitting elements of the LD array 21 when the toner save mode is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading means for optically reading data of an original image and converting the read data into image information, an image processing means for processing the read image information, and an image having a toner save mode. The present invention relates to an image forming apparatus including processing means, image forming means for forming a latent image on a photoreceptor by a plurality of light emitting elements based on processed image information, and main body control means for controlling the whole.

[0002]

2. Description of the Related Art In a digital image forming apparatus such as a digital copying machine or a laser printer, a laser modulated by an image signal is emitted from a semiconductor laser (LD; light emitting element) and written on a photoreceptor by a polygon mirror. To form an electrostatic latent image (latent image), further develop this electrostatic latent image with toner to obtain a toner image, transfer this toner image to transfer paper, and perform final image formation. It is supposed to do.

In order to increase the speed of digital copiers and laser printers while suppressing the number of rotations of a polygon motor, a multi-beam laser is being used. More specifically, there is a technique for simultaneously writing a plurality of lines of image data on a photoconductor using an LD array.

[0004]

Here, in an image forming apparatus for simultaneously writing a plurality of lines of image data on a photosensitive member using an LD array, a plurality of LDs on the LD array are required.
If even one of the (light emitting elements) deteriorates and normal operation becomes impossible, it is necessary to replace the LD array even if another LD can be used.

As means for judging LD deterioration in a copying machine, the amount of current required when the LD outputs a certain amount of light is monitored as needed, and if the amount of current exceeds a set value, it is determined that the LD has deteriorated. There are things that we try to consider.

Factors that cause LD degradation include inrush current generated when image data is turned on, and degradation over time caused by the total lighting time of the LD. LD arrays are expensive, and it is desired to extend the life of the LD arrays.
Japanese Patent No. 4368 discloses a technique for shortening a lighting time by shortening a synchronization detection signal output timing and extending a life of an LD.

The present invention focuses on a toner save mode for reducing the amount of toner attached to an electrostatic latent image during development,
It is an object of the present invention to provide an image forming apparatus capable of extending the life of an LD array.

[0008]

According to a first aspect of the present invention, there is provided an image reading means for optically reading original image data and converting the read data into image information. Processing means for processing the processed image information and having a toner save mode, image forming means for forming a latent image on a photoreceptor by a plurality of light emitting elements based on the processed image information, and main body control means for controlling the whole Wherein the main body control means has a function of performing a thinning-out operation to reduce the lighting time of the light emitting element requiring the most current when the toner save mode is selected. The present invention relates to an image forming apparatus.

According to a second aspect of the present invention, an operation means for selecting a toner mode is connected to the main body control means, and the image forming means includes a semiconductor laser array comprising a plurality of light emitting elements, a semiconductor laser drive circuit, A control circuit for controlling the semiconductor laser drive circuit, current detection means for detecting a current value required for light emission of each light emitting element, and a comparison operation means for comparing the current value required for light emission of each light emitting element, 2. The image forming apparatus according to claim 1, wherein the main body control means performs the thinning-out processing via the control circuit based on a comparison operation result of the comparison operation means.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein in the toner save mode, a light emitting element for thinning out one transfer sheet is fixed.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein a light emitting element for thinning out is fixed in one copy operation job in the toner save mode.

According to the first and second aspects of the present invention, in the toner save mode, the light emitting element for thinning out light emission is the light emitting element requiring the most current for light emission. And the life of the semiconductor laser array is extended. By extending the life of the semiconductor laser array, cost reduction during service can be expected. Further, since the synchronous detection operation is performed with the smallest current value, energy can be saved.

According to the third aspect of the present invention, since the light emitting elements for thinning out are fixed on one transfer sheet, the mask pattern used for toner save is not changed in one print original. That is, uneven image formation caused by changing the mask pattern is prevented.

According to the fourth aspect of the present invention, the light emitting elements for thinning out are fixed in one copy operation job. Therefore, when a plurality of copies are made, uneven image formation due to a change in the light emitting elements for thinning out, Density unevenness is prevented.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of a digital copying machine. This digital copying machine controls a scanner unit 1 for reading a document image, a VPU 2 for A / D converting a read signal to perform black offset correction, shading correction, and pixel position correction, an IPU 3 for performing image processing, and a printer unit 4. GAVD 5, an LD control unit 6 for controlling a semiconductor laser (LD), an LD array 21 for forming electrostatic latent image data on a photosensitive drum, and a C for controlling the entire apparatus.
PU 7, ROM 8 storing a control program, RAM 9 used temporarily by the control program, image memory 10 storing read images, system bus 11 for exchanging data between devices, system buses 11 and I
It comprises an I / F unit 12 for interfacing between the PUs 3, an operation unit 13 for giving an instruction from a user, and the like.
The boards of the VPU 2 and the IPU 3 are incorporated in the scanner unit 1.

FIG. 2 is a schematic diagram of the writing unit.
The writing unit is included in the printer unit 4 of FIG. 1 and has a unit that will be described below in conjunction with the operation. LD
The laser beam emitted from the front of the array 21 is collimated by a collimator lens (not shown) and deflected by a deflector 22 composed of a rotating polygon mirror.
3 forms an image on the surface of the photosensitive drum 24 uniformly charged by the charger.

Then, the image forming spot repeatedly moves in the axial direction of the photosensitive drum 24 by the rotation of the deflector 22, and at the same time, the photosensitive drum 24 rotates. Thus, an electrostatic latent image is formed on the photosensitive drum 24 in the main scanning direction and the sub-scanning direction.

The photodetector 25 is provided outside the information writing area and detects a laser beam deflected by the deflector 22 to generate a synchronization detection signal. The GAVD 5 applies an information signal to the semiconductor laser drive circuit 26, and controls its timing with a synchronization signal from the photodetector 25.

The semiconductor laser drive circuit 26 has a GAVD5
The LD array 21 is driven through a current detection circuit 29 to be described later by the information signal from the
An electrostatic latent image is formed thereon. This electrostatic latent image is developed by a developing device and transferred to a transfer paper by a transfer device.

The laser beam emitted backward from the LD array 21 is incident on the PD 27 and its light intensity is detected. The control circuit (a) 28 controls the semiconductor laser drive circuit 26 in accordance with the output signal of the PD 27. By controlling, the output light quantity of the LD array 21 is controlled to be constant (APC control).

Specifically, the driving power supply of each light emitting element is adjusted and held by an external signal so that the output light quantity of each light emitting element of the LD array 21 becomes constant. A current detection circuit 29 is provided for each light emitting element. Here, the current value of each light emitting element during APC control is detected, and which light emitting element has the least current, resulting in LD deterioration. It is determined whether or not the process has proceeded, and the information is given to the GAVD5.

FIG. 3 is a detailed diagram of the current detection circuit. FIG.
The current detection circuit 29 includes an operational amplifier 31, an A / D conversion circuit 32, and a control circuit (b) 33. The current flowing through the resistor between the semiconductor laser drive circuit 26 and the LD array 21 is converted into a current-voltage signal by the operational amplifier 31.
The data is converted into a digital value by the D converter 32,
The conversion data is sent to the control circuit (b) 33. The control circuit (b) 33 determines which of the light emitting elements has the greatest deterioration from the transmitted data of each light emitting element, and sends the information to the GAVD 5.

FIG. 4 is a diagram showing the state of thinning out of image formation in the toner save mode. The image data sent from the IPU 3 is rearranged into raster information in the GAVD 5 (a). The reordered image information is “4
(B) are sequentially referred to in a size of (× 4) (one block).

Here, when the image information of one block is all black, the image information of the block is thinned out using a preset mask pattern. An AND operation with the mask pattern is performed for each dot, and as a result, the n-th block is converted into the information shown in (c).

After the processing for the n-th block is completed, (n
The processing is sequentially performed on the (+1) th block and the (n + 2) th block. As a result, the image information of (a) is processed into the image information of (d). In the example shown here, 75% thinning is performed only on the solid black portion, but the thinning amount is SP.
It can be changed at any time in a special mode called a mode.

FIG. 5 is a flowchart for calculating which of the light emitting elements is most deteriorated. First, any c
h (channel) to check if APC is operating (S
1) If not in operation, return. In the case of operation, when the light intensity reaches the expected value, the current value at that time is obtained and the data is stored (S2). The time from the start of the APC operation to the time when the light intensity reaches the expected value is obtained in advance, and when data is read after a certain period of time, or when the read timing is determined from the operation of the control circuit (a) 28, it is determined. Is also good.

Next, when there are n light emitting elements, the APC operation is performed in each channel, so that the APC operation is performed n times in total. This is set as one mode, and the current value of each channel is stored until the APC operation completes (Y in S3). After one cycle of the APC operation, the selection result of the number of the light emitting element having the largest current value is stored (S4).

FIG. 6 is a flowchart of a process for determining a mask pattern used in the toner save mode and masking image information. First, it is determined whether the mode is the toner save mode (S1). If the mode is not the toner save mode, the process returns. In the case of the toner save mode, the ch obtained from the flowchart shown in FIG.
Data is read (S2).

Subsequently, a mask pattern to be masked is read (S3). The information to be read here is
This is information on the mask pattern of “4 × 4” and the channel to which the thinning rate is high. This may be calculated by the GAVD 5 from the mask pattern.

Next, it is confirmed whether the channel with the largest thinning rate in the mask pattern is the same as the channel with the most deterioration (S4), and if they are the same, the image information is masked (S5). . If they are not the same, the mask pattern is rotated (ch with high thinning rate fluctuates simultaneously with the rotation)
(S6) The comparison is performed again in S4. The operation of S4 is continued until the channel having the largest thinning rate in the mask pattern is the same as the channel having the most deterioration.

FIGS. 7 and 8 are views showing the manner of rotation of the mask pattern. FIG. 7A shows a reference mask pattern in the 75% toner save mode. Here, the channels with large thinning are 2ch and 4ch. This reference mask pattern is subjected to the process of step S6 in FIG.
h mask information is 2ch, 2ch mask information is 3c
h, the mask information of 3ch is rotated (moved) to 4ch, and the mask information of 4ch is rotated (moved) to 1ch.
The mask pattern after the change shown in FIG. Here, the channels with large thinning are 1ch and 3ch.

FIG. 8A shows a reference mask pattern in the 69% toner save mode. Here, the channel with the largest thinning is 3ch. If this is subjected to a rotation process to obtain the mask pattern shown in FIG.
ch. When the rotation processing is further performed to obtain the mask pattern shown in (c), the channel with large thinning is 1ch. Here, the reference mask pattern means GAV according to each%.
D5 is prepared in advance.

FIG. 9 is a timing chart of the APC operation and the measurement and storage of the current value of each light emitting element. (1) The current value of each light emitting element is measured and stored from the APC operation immediately before the start of image formation. In this example, the APC operation of all the channels is performed per synchronization detection. A method of performing the APC operation of any one channel for each synchronization detection may be adopted. (2) Image data output when FGATE = H. (3) After the end of the image data output, the APC operation is continuously performed at a position where the photosensitive drum 24 is not affected. (4) The current value of each LD is measured and stored again from the APC operation immediately before the start of image formation. (5) Image formation starts again.

Here, in the toner save mode, in order to fix the light emitting element for thinning out on one sheet of transfer paper,
The APC operation immediately before the FGATE signal becomes H may be used to determine the light-emitting element having the largest deterioration. As another method, a method in which the selected channel is not rewritten while the FGATE signal is “High” may be selected.

In the toner save mode, copy operation 1
Fixing the light emitting elements for thinning out in a job can be achieved by separately providing a flag that sets H at the start of one job operation and L at the end of the job, and using the flag as an alternative to the FGATE signal.

[0036]

According to the first and second aspects of the present invention, in the toner save mode, the light emitting element that thins out light emission is the light emitting element that requires the most current for light emission. It is possible to eliminate the bias between the semiconductor laser arrays and extend the life of the semiconductor laser array. Also, by extending the life of the semiconductor laser array, cost reduction during service can be expected. In addition, since the synchronous detection operation is performed with the smallest current value, energy can be saved.

According to the third aspect of the present invention, the light emitting element for thinning out is fixed on one sheet of transfer paper.
The mask pattern used for toner save is not changed in one printed document. That is, it is possible to prevent uneven image formation caused by changing the mask pattern.

According to the fourth aspect of the present invention, the light emitting elements for thinning out are fixed in one copy operation job. Therefore, when a plurality of copies are made, the light emitting elements for thinning out are changed to cause uneven image formation. , Uneven density can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a digital copying machine.

FIG. 2 is a schematic diagram of a writing unit.

FIG. 3 is a detailed diagram of a current detection circuit.

FIG. 4 is a diagram showing a state of thinning out of image formation in a toner save mode.

FIG. 5 is a flowchart for calculating which light emitting element is most deteriorated.

FIG. 6 is a flowchart of a process of determining a mask pattern used in the toner save mode and masking image information.

FIG. 7 is a diagram illustrating a state of rotation of a mask pattern.

FIG. 8 is a diagram showing a state of rotation of a mask pattern.

FIG. 9 is a timing chart of APC operation, current value measurement and storage of each light emitting element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanner part 4 Printer part 7 CPU 21 LD array

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/00 384 H04N 1/29

Claims (4)

[Claims] 1. An original image data is read optically,
Image reading means for converting the read data into image information; image processing means for processing the read image information and having a toner save mode; and a latent image on a photoreceptor by a plurality of light emitting elements based on the processed image information. An image forming apparatus comprising: an image forming unit that forms an image; and a main body control unit that controls the entirety. The main body control unit includes a light emitting element that requires the most current when the toner save mode is selected. An image forming apparatus having a function of performing thinning to reduce a lighting time. 2. An operation means for selecting a toner mode is connected to the main body control means, and the image forming means controls a semiconductor laser array including a plurality of light emitting elements, a semiconductor laser drive circuit, and a semiconductor laser drive circuit. Control circuit, a current detection means for detecting a current value required for light emission of each light emitting element, and a comparison operation means for comparing a current value required for light emission of each light emitting element, wherein the main body control means 2. The image forming apparatus according to claim 1, wherein the thinning process is performed via the control circuit based on a result of the comparison operation of the operation unit. 3. The image forming apparatus according to claim 1, wherein in the toner save mode, the light emitting element for thinning out one transfer sheet is fixed. 4. The image forming apparatus according to claim 1, wherein in the toner save mode, the light emitting element for thinning out is fixed in one copy operation job.