JPH0550721A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To provide an image forming apparatus capable of easily adjusting the density of an output image desired by an operator. CONSTITUTION:A paper feed roller is driven in timing 4a and a resist roller is subsequently driven in timing 4b. Then, the irradiation with laser modulation beam is started in timing 4c and high developing voltage is changed from '0' V to predetermined voltage V1 in timing 4d and successively changed to voltage V2 in timing 4f. By this constitution, printing density is adjusted from laser modulation data d1 to laser modulation data d10 and printing can be performed in respectively different densities.

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, and more particularly to an image forming apparatus having a self-test image printing function and a print density adjusting function.

[0002]

2. Description of the Related Art In recent years, laser beam printers (hereinafter referred to as "L
Since electrophotographic printers such as "BP") can print at high resolution and high speed, they have become widely accepted in the market.

The resolution of this LBP is 300d.
Pi (300 dots per inch) is widely accepted in the market. On the other hand, there is much demand for higher resolution, and 600 dpi LBP has recently been introduced.

As this resolution increases, it becomes difficult to increase the relative accuracy of the size of one dot (dot diameter). In the LBP, the dot diameter depends on various parameters such as the beam diameter and beam intensity of the laser beam, the sensitivity of the photoconductor, the mechanical accuracy of the developing machine, and the value of the developing high pressure. However, the higher the resolution, the more difficult it becomes to suppress the variation in dot diameter between the LBP devices.

In order to solve this problem, conventionally, a mechanism for adjusting the dot diameter, that is, adjusting the print density has been provided. For example, attach a variable resistor to LBP,
By changing the resistance value of the variable resistor, the developing high pressure or the laser light amount is changed.

[0006]

However, in the above-mentioned conventional example, in order to print at the density the operator prefers, the operator adjusts the value of the variable resistor many times and repeatedly performs the printing operation. It was necessary to find the position of the variable resistance machine corresponding to the print density of.

Further, due to its life, it is necessary to adjust the variable resistor even when the photoconductor or the developing machine is replaced.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus capable of easily adjusting the density of an output image preferred by an operator.

[0009]

[Means for Solving the Problems] and

In order to achieve the above object, the image forming apparatus of the present invention is an image forming apparatus having a function of printing a test image and a function of adjusting the print density, and an output means for outputting the test image. And a density adjusting unit for adjusting the print density of the image output by the output unit, and a test image having the density adjusted by the density adjusting unit is output.

Preferably, the density adjusting means adjusts the print density by controlling the developing high pressure when developing the formed image.

More preferably, the density adjusting means adjusts the print density by changing the amount of light for scanning.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the drawings.

<Description of Configuration> FIG. 1 is a block diagram showing the circuit configuration of the image forming apparatus in this embodiment. Further, FIG. 2 is a view showing a mechanical sectional view of a laser beam printer (LBP) which is a printer unit in this embodiment.

In FIG. 1, 17 is an external information processing device, and 18 is an operation panel including a display section and a key input section. Reference numerals 19, 20, 28, 29, 30, and 31 are interface circuits each including an input / output buffer and a latch circuit. 25 is a microprocessor that controls all LBP sequences and image processing (hereinafter referred to as “MPU”)
Is. Reference numeral 21 denotes a RAM that stores code information received from the external information processing device 17 (hereinafter referred to as “code storage RAM”).
Is described). Reference numeral 22 denotes a RAM that stores image data developed based on code information (hereinafter referred to as “image data storage RAM”);
OM (hereinafter referred to as "test pattern storage ROM"). Reference numeral 24 denotes a ROM (hereinafter referred to as "control storage ROM") that stores LBP sequences, character or graphic information. Reference numeral 26 is an internal control bus such as an address bus, a data bus, and a controller bus.

Now, when the code information is received from the external information processing device 17 through the interface circuit 19, the MPU
25 stores the code information in the code storage RAM 21. Similarly, the data stored in the code storage RAM 21 is expanded into binary image data bit-mapped according to the program in the control storage ROM 24, and the image data storage R
Store in AM22. After that, when the code information for one page is received and similarly developed into the image data for one page, the DMA
The controller 27 is operated. Here, the DMA controller 27 reads the data stored in the image data storage RAM 22 sequentially from a predetermined address in accordance with a request from the raster conversion circuit 32, and transfers the data to the raster conversion circuit 32. The raster conversion circuit 32 converts the data received from the DMA controller 27 into a serialized image signal and outputs a request signal to the DMA controller 27 according to the horizontal synchronizing signal 43 received from the beam position detection circuit 33. In this way, the code information sent from the external information processing device 17 is converted into a serialized image signal. This state of data flow is called "online mode".

On the other hand, this apparatus also has an "offline test mode" in which data exchange with the external information processing equipment 17 is stopped and a test image is generated by itself, and the operation panel 18 is used.
It is possible to perform various tests by shifting the device to the offline test mode by a command from. In this mode, the MPU 25 generates a bit image on the image data storage RAM 22 according to the test image information stored in the test pattern storage ROM 23. Then, similarly to the “online mode”, the DMA controller 27 and the raster conversion circuit 32 are operated to operate the image data storage RAM 2
The test image information stored in 2 is converted into a serialized image signal.

In the "offline test mode",
A test image as shown in FIG. 3 is generated on the bitmap memory of the image data storage RAM 22. As shown in the figure, it can be seen that the same test pattern is repeatedly generated in a block shape. The test patterns in the same block are composed of vertical lines, horizontal lines, and lattice patterns, and different identification images are generated for the same test pattern. In this example, the identification images are density 1, dens
It is density 2, ..., Density 10.

<Description of Printing Operation> Next, the operation of printing the test image shown in FIG. 3 will be described below with reference to FIGS. 1 and 2.

As described above, when the code data for one page is expanded into the image data, the MPU 25 rotates the laser scanner 3 and the photosensitive drum 2 shown in FIG. When the rotation speed of the laser scanner 3 reaches a specified value, the laser drive circuit 35 is operated via the interface circuit 28. At this time, the output value of the DA converter 34 becomes the minimum value, and the forced drive signal 45 becomes active. This causes the laser drive circuit 35 to forcibly turn on the laser 38 with a low light amount. The laser beam output from the laser 38 is applied to the laser scanner 3 and a part of the laser beam is directly applied to the photodiode 39. At this time, a current substantially proportional to the amount of laser light flows through the photodiode 39,
The current is converted into an analog voltage by the laser light amount detection circuit 37. Then, the analog voltage is applied to the AD converter 3
6, converted into digital data, and the MPU 25 receives the digital data via the interface circuit 29. In this way, the MPU 25 can detect the laser light amount. Further, the MPU 25 monitors the laser light amount while monitoring the interface circuit 28 and the DA converter 3
4. The amount of laser light is gradually increased through the laser drive circuit 35, and when the amount of laser light reaches a specified value, the amount of light is controlled to be maintained.

The laser beam scanned by the laser scanner 3 is applied to the reflection mirror 4 and
The beam position detector 33 is also irradiated. Then, each time a beam is incident on the beam position detector 33, the beam position detector 33 outputs a pulse signal. The pulse is input to the raster conversion circuit 32 as the horizontal synchronization signal 43. The raster conversion circuit 32 uses the horizontal synchronization signal 43.
Request data from the DMA controller 27 in synchronization with
The data received from the DMA controller 27 is converted into serial raster data. Then, the raster data is output to the laser drive circuit 35 as an image signal 44. In this way, the image data stored in the image data storage RAM 22 is converted into rasterized laser-modulated light having a constant peak light amount.

As described above, the modulated laser light is scanned by the laser scanner 3, the scanning light is irradiated on the reflecting mirror 4, and the reflected light scans the surface of the photosensitive drum 2. The surface of the photoconductor drum 2 is charged by the primary charging roller 5, and the laser beam scans the charged surface of the photoconductor drum 2 to scan the photoconductor drum 2.
A charged image is formed on the surface of the. Then, the charged image is converted into a toner image by the developing roller 7. here,
A developing unit 6 has a toner 8 and a developing roller 7 therein. The developing roller 7 is a cylindrical magnet, and by applying a high voltage, the toner 8 attached to the developing roller 7 can be carried to the surface of the photosensitive drum 2. The toner image thus formed is further carried to the transfer roller 10.

After the image data for one page is generated and the laser scanner 3 and the photosensitive drum 2 are rotated, the paper 13 loaded in the paper cassette 14 is fed to the paper feed roller 1.
The sheet is conveyed to the registration roller 11 by 2. Here, the fed paper hits the registration roller 11,
After a predetermined time, the registration roller 11 starts to rotate, and the conveyed paper is conveyed toward the transfer roller 10. Next, the toner image generated by the developing roller 7 is transferred to the transfer roller 10.
Is transferred to the transport paper. The conveying paper to which the toner image is attached passes through the fixing roller 15, and the fixing roller 15 fixes the toner image on the conveying paper. Then, the conveyed paper passes through the paper discharge roller 16 and is discharged to the outside of the apparatus.

The toner 8 on the surface of the photosensitive drum 2 which cannot be transferred by the transfer roller 10 is collected by the cleaner 9.

<Description of First Control Method> The test image shown in FIG. 3 is printed as described above. In this embodiment, the high voltage value applied to the developing roller 7 is set as follows. Are changing. The method of controlling the developing high pressure will be described below with reference to the timing chart shown in FIG.

First, the sheet feeding roller 12 is driven at the timing of 4a, and then the registration roller 1 is driven at the timing of 4b.
Drive 1 Then, the irradiation of the laser modulated light is started at the timing of 4c. In the figure, d1 to d10 are data respectively corresponding to the areas d1 to d10 shown in FIG. In this way, the identification image is added to the test image, and d
It outputs in order from 1 to d10.

In this control method, the developing high voltage is changed from "0" V to a predetermined voltage V1 at the timing of 4d, and the MPU 25 makes DA through the interface circuit 31.
This can be achieved by changing the data input to the converter 41. The DA converter 41 is the interface circuit 3
The data received from 1 is converted into an analog voltage, and the analog voltage is input to the developing high voltage output circuit 42. The developing high voltage output circuit 42 outputs a high voltage proportional to the input analog voltage to the developing roller 7. However, M
The PU 25 can change the developing high voltage by changing the data input to the interface circuit 31.

Here, the time from 4b to 4c in FIG. 4 is substantially the same as the time when the photosensitive drum 2 shown in FIG. 2 rotates from 2a to 2b. After the developing high pressure is set to V1 in 4d of FIG. 4, the developing high pressure is slightly raised to V2 in 4f. The time from this 4d to 4f is 4
Equal to the time from c to 4e.

In this way, the image of d1 is developed with the developing high pressure of V1, and the image of d2 is developed with the developing high pressure of V2. In other words, the higher the developing voltage, the higher the print density,
With the control method as described above, images from d1 to d10 can be printed with different densities. In this control method, the density is gradually increased from d1 to d10.

By the control method described above, it is possible to add an identification image to the same test pattern and print with different densities.

Further, this device can be switched to various modes by the key switch provided on the operation panel 18. For example, in the "offline" state, the operator can set the "concentration setting mode" with the corresponding key switch. In the "density setting mode", the operator can select the density from d1 to d10 already described. Then, the MPU 25 stores the set state and the input data of the DA converter 41 corresponding thereto in the code storage RAM 21.

When the "online" state is entered and the image data for one page is received from the external information processing device 17, the printing operation is started. The difference between the "online" printing operation and the test image printing operation described above is the method of controlling the developing high pressure. In the "online mode", the voltage input to the developing high voltage output circuit 42 is set to a constant value. This makes it uniform over one page. The MPU 25 causes the DA converter 41 to input the density set value already stored in the code storage RAM 21. Thus, the data from the external information processing device 17 can be printed according to the density set by the operator.

In the above-described embodiment, the case of application to a laser beam printer has been described as an example, but the present invention is not limited to this, and for example, the laser drive circuit 35 and the laser scanner 3 may be replaced with an LED array head or an LCD. LED printer and L can be easily replaced by replacing the head.
It can also be applied to a CD printer.

<Description of Second Control Method> In the control method described above, the density is adjusted by changing the developing high pressure, but it is also possible to change the laser light amount.

In this control method, the interface circuit 28, the DA converter 34, and the laser drive circuit 35 of FIG. 1 are driven to cause the laser 38 to emit light, and the photodiode 39, the laser light amount detection circuit 37, the AD converter 36, and the interface. By detecting the amount of light emission by the circuit 29, the laser current value of the laser 38 is controlled to be a predetermined value. Here, the drive current of the laser required to obtain a predetermined amount of laser light is previously stored in the code storage RAM 21.
It is something to remember. That is, A of the AD converter 36
The data to be input to the DA converter 34 corresponding to the D output value is detected, the detected data is stored as a table in the code storage RAM 21, and the data input to the DA converter 34 by the MPU 25 according to the data in the table is detected. The density is adjusted by gradually changing it.

FIG. 5 is a timing chart for printing a test image by changing the amount of laser light. 5 shown in FIG.
The paper feed roller 12 is driven at the timing of a, and the registration roller is driven at 5b. Then, at 5c, the output of the laser beam modulated by the test pattern of d1 is started.
At this time, DA is set according to the table stored in the code storage RAM 21 so that the peak value of the laser light amount becomes p1.
Data is input to the converter 34. Next, the peak light amount of the laser 38 is set to p2 at the timing of 5d, and the laser beam modulated by the test pattern of d2 is output at the timing of 5e. In this way, the test patterns from d1 to d10 can be output with different peak light amounts, that is, printed with different densities. Here, the developing high pressure changes from "0" to Vd at a timing of 5 g, and d1
The test patterns from d to d10 are printed at the same developing high pressure.

Therefore, according to the second control method, the same test pattern can be printed at different densities in the "offline" test image printing mode. In the "online mode" in which the information received from the external device 17 is printed, the density is designated by the operation panel 18, as in the first control method described above.

As described above, according to this embodiment,
By repeatedly printing the same test pattern with different densities, various density patterns can be discriminated. Further, by adding an identification image to the test patterns having different densities and selecting a density corresponding to the identification image, the image information received from the external device can be printed at a desired density.

In addition to the LBP, the present invention is not limited to the LED.
It can be applied to an LED printer by using an array head and changing the peak light emission amount of the LED array. Further, it can be applied to an LCD printer by changing the light emission amount of the LCD shutter and the fluorescent tube.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. It goes without saying that the present invention can also be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0040]

As described above, according to the present invention,
It is possible for the operator to easily adjust the density of the output image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an image forming apparatus in this embodiment.

FIG. 2 is a diagram showing a mechanical cross section of a printer unit in the present embodiment.

FIG. 3 is a diagram showing a test print image in the present embodiment.

FIG. 4 is a timing chart for explaining density adjustment by the first control method.

FIG. 5 is a timing chart for explaining density adjustment by the second control method.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B41J 29/46 D 8804-2C G06K 15/00 2116-5L (72) Inventor Hideki Suzuki 3 Shimomaruko Ota-ku, Tokyo Chome 30-2 Canon Inc.

Claims (3)

[Claims] 1. An image forming apparatus having a function of printing a test image and a function of adjusting print density, comprising: output means for outputting a test image; and print density of an image output by the output means. And a concentration adjusting means for adjusting,
An image forming apparatus, which outputs a test image having a density adjusted by the density adjusting means. 2. The image forming apparatus according to claim 1, wherein the density adjusting unit adjusts the print density by controlling the developing high pressure when developing the formed image. 3. The image forming apparatus according to claim 1, wherein the density adjusting unit adjusts the print density by changing the amount of light to be scanned.