JPH07314768A - Image forming device and method thereof - Google Patents

Abstract

PURPOSE:To provide an image forming device, which can obtain a high quality formed image irrespective of input image data. CONSTITUTION:In a generating part 390, in which pulse width modulation is performed, the image data sent from an inputting part 310 is modulated with a certain period into an image signal so as to form a latent image through the burning controlling of a semiconductor laser 330 in response to the pulse- width-modulated signal at a controlling part 350. At this time, the image data are compared at a comparator 320 with the threshold data stored in a storage part 300. The deterioration of light output is prevented from developing by improving the responsiveness of an image forming device through the application of a bias current source 370, which can supply ordinary bias value to the semiconductor laser 330 when the inputted image data are larger than the threshold value, and through the application of a bias current source 370, which can supply current bias different from and higher than the ordinary bias value when the inputted image data are smaller than the threshold value.

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 method, for example, a digital copying machine, a laser beam printer, or the like, which converts data of image data (for example, PWM modulation) and turns on a laser to form a latent image. The present invention relates to an image forming apparatus and method suitable for forming an image.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as a digital copying machine, a latent image is formed by PWM-modulating image data and turning on a laser according to the signal. Also,
A method is widely used in which a constant bias current is applied to a laser in advance to improve the response of the laser to a PWM signal.

[0003]

However, the laser lighting requires a large current in order to accurately perform on / off in a short time such as small image data. Also, the higher the current applied to the laser, the shorter the life of the laser itself. For this reason, in the conventional laser lighting, a large bias current is not applied in advance to the laser.

Therefore, a sufficient light output cannot be obtained for data of a short pulse width corresponding to small image data, and as a result, it appears as image deterioration of the latent image in the case of small image data. There was a problem.

[0005]

The present invention has been made to solve the above-mentioned problems, and in order to solve the above-mentioned problems and obtain a high quality formed image regardless of input image data, for example, the following configuration is used. Equipped with. That is, an image forming apparatus including a light emitting light source, which forms a latent image by the light emitted from the light emitting light source and forms an image based on the formed latent image, wherein input image data is used for controlling light emission from the light emitting light source. Data conversion means for converting to suitable data, a first current source for applying a predetermined current to the light emitting light source in advance, a comparison means for comparing the input image data with a predetermined threshold value, and a comparison result of the comparison means. Control means for controlling the first current source to change the current applied to the light emitting light source, and a second current source for causing the light emitting light source to emit light according to the conversion data in the data converting means. Is characterized by.

Further, there is provided an image forming apparatus which comprises a light emitting source, forms a latent image by the light emitted from the light emitting source, and forms an image based on the formed latent image, wherein input image data is transmitted from the light emitting source. Data conversion means for converting into data suitable for light emission control, a first current source for causing the light emission light source to emit light according to the converted data in the data conversion means, and comparison means for comparing the input image data with a predetermined threshold value. And a control unit that controls the first current source based on the comparison result of the comparison unit to change the current applied to the light emitting source.
A second current source that applies a predetermined current to the light emitting source in advance is provided.

[0007] For example, in both configurations, the light emitting source is a laser, and the control means increases the current applied to the light emitting source when the input image data value is small. And Alternatively, the control means gradually decreases the current applied to the light emitting light source when the input image data value is large.

[0008]

With the above construction, a high quality formed image can be obtained regardless of the input image data.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings. In the following description, the case where the present embodiment is applied to a digital copying apparatus will be described as an example. However, the present invention is not limited to the above example, and it goes without saying that it can be applied to any device as long as it is a device that forms an image.

[First Embodiment] First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a sectional view showing the structure of an embodiment according to the present invention. In FIG. 1, reference numeral 1 denotes a document feeding device serving as a document feeding means, and one or two read documents placed on the document feeding device 1 are continuously placed at a predetermined position on a platen glass surface 2. To send. 3 is a document table glass surface 2 by the document feeder 1
When it is placed on the document, the document is reciprocally scanned in a predetermined direction and the reflected light of the document passes through the lens 8 through the scanning mirrors 5 to 7 to form an image on the image sensor unit 101. It is a configured scanner.

Reference numeral 10 is an exposure control unit composed of a laser scanner, and the exposure control unit 10 is a controller unit CONT.
The light beam modulated on the basis of the image data output from the image signal controller is irradiated onto the photoconductor 11. 12, 1
Reference numeral 3 is a developing device for visualizing the electrostatic latent image formed on the photoconductor 11 with a developer (toner) of a predetermined color, and reference numerals 14 and 15 are stacking and storing recording media of a fixed size, and a registration roller driven by a feeding roller. It is a transferred paper stacking unit that is fed to an arrangement position and is re-fed in a state where the image leading edge is aligned with the image formed on the photoconductor 11.

Reference numeral 16 is a transfer / separation charger, which is a photosensitive member 11.
After the toner image developed on the transfer paper is transferred to the transfer paper, it is separated from the photoconductor 11. The transfer paper on which the original image is transferred is
The image is transferred to the fixing unit 17 via the conveyor belt, and the transferred image is fixed there. Reference numeral 18 denotes a paper ejection roller for stacking and ejecting the transfer-receiving paper on which the image formation has been completed on the tray 26, 19 a paper ejection sensor for detecting conveyance of the transfer-receiving paper, and 20 for ejecting the transfer paper on which the image formation has been completed. A tray, 21 is a direction flapper that is provided for a multiplex / double-sided image forming process by switching the carrying direction of the transfer-receiving paper on which image formation has been completed to the paper discharge port and the internal carrying direction.

An image forming operation on a recording medium in the present embodiment having the above-mentioned structure will be described below. The image signal input to the image sensor unit 101 reaches the printer control unit 206 after being subjected to predetermined image processing by the image control unit 203 in the controller unit CONT described later. The signal input to the printer control unit 206 is converted into an optical signal corresponding to the image signal by the exposure control unit 10, and the photoconductor 11 is irradiated with the signal. An electrostatic latent image corresponding to the input image signal is formed on the photoconductor 11 by the irradiation light. The latent image formed on the photoconductor 11 is the developing device 12 or the developing device 13.
Developed by.

The transfer sheet is conveyed from the transfer sheet stacking unit 14 or the transfer sheet stacking unit 15 in synchronization with the latent image timing, and in the transfer unit 16, the developed image is transferred from the photoconductor 11 to the transfer sheet. Transcribed. The transferred image is
After being fixed to the transfer paper by the fixing unit 17, the paper discharge roller 1
8 is discharged to the outside of the apparatus. Further, at the time of double-sided recording, after the transfer target paper passes the paper discharge sensor 19, the paper discharge unit roller 18 is rotated in the direction opposite to the paper discharge direction. At the same time, the flapper 21 is raised upward to store the copied transfer paper in the intermediate tray 24 via the transport paths 22 and 23. At the time of next back surface recording, the transfer paper stored in the intermediate tray 24 is fed and the back surface is transferred.

Further, at the time of multiplex recording, the flapper 21 is raised and the copied transfer paper is stored in the intermediate tray 24 via the conveying paths 22 and 23. In the next multiplex recording, the transfer paper stored in the intermediate tray 24 is fed and multiplex transfer is performed. FIG. 2 is a diagram showing an operation unit for making various settings such as editing and copying in the copying machine shown in FIG. 1 of the present embodiment. First, the functions and the like of various keys on the operation panel will be described.

In FIG. 2, reference numeral 5001 denotes a power switch for controlling energization of the image processing apparatus. A reset key 5002 operates as a key for returning the settings of various modes to the standard mode during standby. 5003 is a copy start key. A clear key 5004 is used to clear the set numerical value. 500
Reference numeral 5 denotes an ID key. This ID key 5005 enables a copying operation for a specific operator, and for operators other than the above, the copying operation can be prohibited unless an ID is input by the ID key. It will be possible.

A stop key 5006 is used when the copying operation is interrupted or stopped. Reference numeral 5007 is a guide key, which is used when it is desired to know the contents of each function. Reference numerals 5008 and 5009 denote up and down cursor keys, respectively, which move the pointer up and down on each function setting screen. Similarly,
Reference numerals 5011 and 5010 denote left and right cursor keys, which move the pointer to the left and right on each setting screen.

Reference numeral 5012 is an OK key, and in each function setting screen, the setting is performed by pressing this key when the setting state displayed on the screen is acceptable. 5013
In each function setting screen, press the key to execute the output on the lower right of the screen of 5052. 5014
Is a standard reduction key and is used when reducing a standard size to another standard size. Reference numeral 5015 is used when selecting the same size copy. Reference numeral 5016 is a standard enlargement key, which is used to enlarge a standard size to another standard size.

Reference numeral 5017 is a cassette selection key for selecting the cassette stage of the transfer paper to be copied. A copy density selection key 5018 is used to reduce the copy density. An AE key 5019 automatically adjusts the copy density with respect to the density of the original. A copy density selection key 5020 is used to increase the copy density. A sorter key 5021 is a key for designating an operation mode of the sorter. 5022 is a preheat key,
Used to turn on / off the preheat mode.

Reference numeral 5023 is an interrupt key, which is pressed to interrupt copying during copying and perform copying. Reference numeral 5024 is a ten-key pad, which is used when inputting a numerical value. 5
Reference numeral 025 is a marker processing key for setting trimming, masking, and partial processing (contour, mesh, shadow, negative / positive). Reference numeral 5026 denotes a patterning key, which is used when a color is expressed as a pattern or a color is expressed as a density difference. Reference numeral 5027 is a color erasing key, which is used when it is desired to erase a specific color by the processing described later.

An image quality key 5028 is used when setting the image quality. Reference numeral 5029 is a negative / positive, which is used when the negative / positive is performed. Reference numeral 5030 denotes an image create key, which is pressed when performing contouring, shadowing processing, halftone processing, italics, mirror image, and image repeat. A trimming key 5031 is used when the area is designated and trimming is performed. 5032 is a masking key,
Used when specifying an area and masking.

Reference numeral 5033 is a partial processing key for designating an area and then setting partial processing (contour, mesh, lower limit, negative / positive, etc.). Reference numeral 5034 denotes a frame erasing key, which is used to erase the frame according to the mode. The modes are: sheet frame erase (creates a frame for the sheet size), original frame erase (creates a frame according to the original size. Original size is specified), book frame erase (frame according to the book spread size) And create a blank in the center. There is a book spread size specification). 5035 is a binding margin key,
Used when you want to create a binding margin at one end of the paper.

Reference numeral 5036 is a move key which is used when the user wants to move. The movement includes parallel movement (up and down, left and right), center movement, corner movement, and designated movement (point movement). Reference numeral 5037 denotes a zoom key, which can set the copy magnification from 25% to 400% in 1% increments. or,
Main scanning and sub scanning can be set independently. Reference numeral 5038 denotes an automatic scaling key, which automatically enlarges or reduces the size of the transfer paper in accordance with the size. Also, the main scanning and the sub-scanning can be automatically scaled independently. Reference numeral 5039 denotes an enlargement continuous shooting key, which is used when an original is enlarged to a plurality of sheets for copying.

Reference numeral 5040 is a reduction layout key,
It is used when copying two originals by enlarging or reducing them into one. It is also used when enlarging / reducing four originals for copying. Reference numeral 5043 denotes a continuous shooting key, which is used when the copying area on the platen glass surface is divided into two, and it is desired to carry out continuous copying in which two sheets are automatically answered (page continuous shooting, double-sided continuous shooting). Reference numeral 5044 denotes a double-sided key, which is used when it is desired to output both sides (single-sided double-sided, page continuous shooting both-sided, double-sided both-sided).

Reference numeral 5045 denotes a multiplex key, which is used when it is desired to perform multiplex (multiplex, page continuous multiplex). 5046
Is an MC key, which is used when using a memory card. Reference numeral 5047 is a projector key, which is used when the projector is used. Reference numeral 5048 is a printer key, which is used when setting at the time of printing. Fifty
Reference numeral 50 denotes a document mixed loading key, which is used when document sizes are mixed when copying is performed using the feeder.
Reference numeral 5051 denotes a mode memory key, which is used for registering the copy mode set for copy or for calling the registered copy mode.

Reference numeral 5052 is a display screen for displaying the status of the device,
The number of copies, copy ratio, copy paper size are displayed, and the setting contents are displayed while the copy mode is set. Reference numeral 5053 is a system preheat key, which is used to turn on / off the system preheat mode in which only the external interface and its peripheral circuits are operated and the control unit for copying is stopped. 505
A power display unit 4 is turned on when the main switch 5001 is in the ON state and turned off when the main switch 5001 is in the OFF state.

FIG. 3 is a diagram for explaining the system concept in this embodiment. FIG. 3A is a conceptual diagram of a conventional system, in which the PWM modulation circuit 101 modulates image data into an image signal at a constant cycle based on the image data from the image data 100, and the PWM signal is converted into the PWM signal. The corresponding laser is turned on by the laser lighting circuit 102 to form a latent image. On the other hand, FIG. 3B is a system conceptual diagram in this embodiment. In this embodiment, in comparison with the conventional system configuration shown in (a), the comparator 130 compares the image data input from 110 with the threshold data set in the threshold data 120, and the result is (S
The ELECT signal) 140 is used to control the current value of the current source for driving the laser.

FIG. 4 is a diagram showing an example of optical output obtained by turning on a laser for image data. As shown in FIG. 4A, when the input image data is large (the input image data [Vin] is the reference image data [Vin]
larger than ref]), a sufficient optical output corresponding to the input data can be obtained. However, when the input image data is short as shown in FIG. 4B, an imperfect optical output as shown by the solid line in FIG. 4 appears.

This is because in a system in which a constant current is applied as a bias in advance in order to improve the laser response, the response becomes slow because the bias current applied is low, and in the case of a short pulse. This is because it cannot show sufficient responsiveness. This bias value is set in consideration of the case where the laser is fully turned on. Further, when the bias value is set to be high, the response is improved, but since a high bias current is constantly applied to the laser, there is a drawback that the life of the laser itself is shortened.

Therefore, in the present embodiment, in consideration of the above points, when the input data is small, a higher current bias different from the normal bias value is applied to improve the responsiveness, thereby deteriorating the optical output. Preventing and increasing the resolution on the highlight side of the resulting image by obtaining the light output as shown by the dotted line in FIG. In order to achieve the above, the present embodiment has the configuration shown in FIG. In FIG.
Reference numeral 310 is an input unit for image data, and 300 is an input unit 3.
An image data storage unit 390 serving as a reference for comparison with the image data input from 10 is a generation unit that generates a PWM (pulse width modulation) waveform according to the image data from the storage unit input unit 310. 330 is a laser, PWM
Is connected to a constant current source 380. Reference numeral 350 denotes a control unit that performs on / off control of the laser 330, and the generation unit 3
On / off control of the laser is performed according to the PWM signal from 90 to control the lighting of the laser.

Reference numerals 360 and 370 denote bias current sources having different set values, and 340 denotes the bias current sources 360 and 3.
It is a selector that switches any one of 70 to connect to the laser 330. The bias current sources 360 and 370 are
For example, the bias current source 360 = normal current bias value (applicable to the entire lighting range) bias current source 370 = higher current bias value than the bias current source of 360 (applied when the image data is small) Data of the input image from 310 and the reference data stored in the storage unit 300 are compared by the comparator 320, and based on the resulting SELECT signal, the selector 340 switches the bias current sources 360 and 370 to the laser. Bias current is applied.

With the configuration shown in FIG. 5, when the input image data 310 is larger than the reference image data preset in the storage unit 300, the normal bias source 360 is used.
, And conversely, when smaller, a bias source 370 higher than 360 is selected. In the above explanation,
Although the configuration including the two bias current sources has been described, the present invention is not limited to the above example, and the configuration including the three or more current sources may be further applied to the laser 330 depending on the input image data value. The bias current value may be finely controlled. Of course, this case is also included in the present invention.

By controlling as described above, it is possible to improve the responsiveness of the light output, and it is possible to obtain a high quality formed image regardless of the input image data without significantly shortening the life of the laser. [Second Embodiment] In the first embodiment described above,
An example has been described in which two bias current sources are provided and two bias current sources are selected according to input image data to improve the responsiveness of light output. However, the present invention is not limited to the above example, and as another method for achieving the same effect as the above-described first embodiment, one bias current source is provided and the current value of this current source is selected. It may be configured as possible. A second embodiment according to the present invention having such a configuration will be described below.

Also in the second embodiment, the basic structure is the same as that of the first embodiment described above, and the circuit structure shown in FIG. 5 of the first embodiment becomes the structure shown in FIG. 6 in the second embodiment. Is different. 6, the same components as those in the first embodiment shown in FIG. 5 described above are denoted by the same reference numerals and detailed description thereof will be omitted.
FIG. 6 is a diagram showing the configuration of a laser 330 drive controller of the second embodiment according to the present invention. 6, the current value of the current bias source 410 applied to the laser is set to a high value in advance (for example, a current value value equivalent to that of the bias current source 370 in the first embodiment shown in FIG. 5). As a result, the response characteristic of the light output when the image data is small can be improved.

However, since there is a problem such as the above-mentioned life as it is, the bias current source 4 is used in the second embodiment.
A current regulator 400 is provided between the laser 10 and the laser 330, and the adjustment level of the current regulator 400 is compared with the comparator 32.
It is adjusted by 0. The current regulator 400 is, for example, a digital variable resistor. With this configuration, the current regulator 40 is responsive to the output SELECT signal of the comparator 320.
0 is controlled, and when the input image data is larger than the reference value, a large resistance value is set to prevent a large current from being applied to the laser as a bias current, and when the input data is small, the resistance value is set small. By setting it, a high bias current can be applied to the laser to improve the optical output.

As described above, according to the second embodiment,
By making the current regulator 400 adjustable in multiple stages,
It is possible to control the bias current value for each input data, and it is possible to obtain the responsivity of the laser which is finer and more uniform than the first embodiment described above. [Third Embodiment] In the first and second embodiments described above, an example has been described in which the response of the optical output is improved by controlling the bias current value flowing in the laser 330 according to the input image data. However, the present invention is not limited to the above example, and the current value of the constant current source 380 for PWM can be controlled according to the input image data as another method for achieving the same effect as each of the above-described embodiments. You may comprise. The third embodiment according to the present invention having the above-described structure will be described below.

The basic structure of the third embodiment is similar to that of the first embodiment described above, and the circuit structure of the first embodiment shown in FIG. 5 is changed to the structure shown in FIG. 7 of the third embodiment. Is different. 7, the same components as those in the first embodiment shown in FIG. 5 described above are denoted by the same reference numerals and detailed description thereof will be omitted.
In the third embodiment, it is proposed to control the laser drive current using two constant current sources for PWM.

FIG. 7 shows a block diagram of the laser drive control unit in the third embodiment. As shown in FIG. 7, there is one current bias source (360) in the third embodiment, and its set value is also a standard value which is not set higher considering the life of the laser and the like. . On the other hand, unlike the above-described embodiment, the third embodiment has a configuration including two constant current sources 380 and 500 for PWM. Then, for example, the constant current source 380
Is a current source set to a normal current value, and a constant current source 50
0 is set to a current value higher than that of the constant current source 380.
Reference numeral 510 is a selector for switching and connecting the two constant current sources 380 and 500 based on the SELECT signal from the comparator 320.

In the above structure, the PW of the laser 330 is
Switching of the current source when M is turned on is performed by the above-mentioned first and second
Similar to the embodiment, the selector 510 uses the SELECT signal from the comparator 320. As a result, when the input data is higher than normal (when it is not small), it operates as a constant current source similar to the conventional one, and when the input data is small, PWM lighting is performed using the current source set to a higher current value. A high quality formed image can be obtained regardless of the input image data without significantly shortening the life of the laser.

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

[0041]

As described above, according to the present invention, P
In an image forming apparatus using a laser using WM modulation,
The deterioration of the optical output when the input pulse width is short can be compensated for by changing the current value of the applied current source, and the gradation of the image at the time of highlight output can be improved, and the life of the laser can be shortened. It is possible to obtain a high-quality formed image without shrinking regardless of the input image data.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an entire system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an operation unit of the present embodiment.

FIG. 3 is a diagram for explaining a system concept in the present embodiment.

FIG. 4 is a diagram showing an example of a light output obtained by turning on a laser for image data.

FIG. 5 is a diagram showing a configuration of a laser drive control unit in the present embodiment.

FIG. 6 is a diagram showing a configuration of a laser drive control unit in a second embodiment according to the present invention.

FIG. 7 is a diagram showing a configuration of a laser drive control unit in a third embodiment according to the present invention.

[Explanation of symbols]

 1 Document Feeding Device 2 Document Platen Glass Surface 3 Scanner 5-7 Scanning Mirror 8 Lens 10 Exposure Control Section 11 Photosensitive Body 12, 13 Developing Device 14, 15 Transferred Paper Loading Section 16 Transfer Separation Charger 17 Fixing Section 18 Paper Ejection Roller 19 Paper discharge sensor 20 Paper discharge tray 21 Direction flapper 24 Intermediate tray 101 Image sensor unit 203 Image control unit 206 Printer control unit 300 Image data storage unit 310 Image data input unit 320 Comparator 330 Laser 340510 Selector 350 Control unit 360 , 370,410 Bias current source 380,500 Constant current source for PWM 390 Generator 5003 Copy start key 5004 Clear key 5052 Display screen

Claims (9)

[Claims] 1. An image forming apparatus comprising a light emitting light source, which forms a latent image by light emitted from the light emitting light source and forms an image based on the formed latent image, wherein input image data is generated from the light emitting light source. Data conversion means for converting data suitable for light emission control, a first current source for applying a predetermined current to the light emitting light source in advance, comparison means for comparing the input image data with a predetermined threshold value, comparison of the comparison means Control means for controlling the first current source based on the result to change the applied current to the light emitting light source; and a second current source for causing the light emitting light source to emit light according to the conversion data in the data converting means. An image forming apparatus comprising: 2. An image forming apparatus comprising a light emitting light source, which forms a latent image by the light emitted from the light emitting light source and forms an image based on the formed latent image, wherein input image data is generated from the light emitting light source. Data conversion means for converting into data suitable for light emission control, a first current source for causing the light emitting light source to emit light according to the converted data in the data conversion means, and comparison means for comparing the input image data with a predetermined threshold value. A control unit for controlling the first current source based on a comparison result of the comparison unit to change an applied current to the light emitting light source; and a second current source for applying a predetermined current to the light emitting light source in advance. An image forming apparatus comprising: 3. The image forming apparatus according to claim 1, wherein the light emitting source is a laser. 4. The image forming apparatus according to claim 1, wherein the control unit increases the current applied to the light emitting light source when the input image data value is small. . 5. The image forming apparatus according to claim 1, wherein the control unit gradually decreases the current applied to the light emitting light source when the input image data value is large. . 6. A light emitting light source, a first current source for applying a predetermined current to the light emitting light source in advance, data conversion means for converting input image data into data suitable for light emission control by the light emitting light source, An image forming a latent image by forming a latent image by the emitted light from the light emitting source, and a second current source for emitting the light emitting source according to the converted data in the data converting means. An image forming method in a forming apparatus, wherein the input image data is compared with a predetermined threshold value, and the first current source is controlled based on the comparison result to change the current applied to the light emitting light source. Image forming method. 7. A light emitting light source, a first current source for applying a predetermined current to the light emitting light source in advance, data conversion means for converting input image data into data suitable for light emission control by the light emitting light source, An image forming a latent image by forming a latent image by the emitted light from the light emitting source, and a second current source for emitting the light emitting source according to the converted data in the data converting means. An image forming method in a forming apparatus, wherein the input image data is compared with a predetermined threshold value, and the second current source is controlled based on the comparison result to change the current applied to the light emitting light source. Image forming method. 8. The image forming method according to claim 6, wherein the current applied to the light emitting source is increased when the input image data value is small. 9. The image forming method according to claim 6, wherein when the input image data value is large, the current applied to the light emitting light source is gradually reduced.