JPH10202945A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the full use of the output characteristics of a photosensor on a detection means for the detection of a horizontal synchronous signal due to a change in the light intensity of a laser beam. SOLUTION: A variable resistance 41 is installed on the outside of a photo IC (photosensor) 40 on a synchronous detector (a detection means for detecting a horizontal synchronous signal) and thereby, the gain resistance value (circuit constant) of the variable resistance 41 is made changeable for the variation of the incident light intensity of a laser beam. In addition, it is possible to make changeable the gain resistance value of the variable resistance 41 through a control signal inside the image forming device or an operating signal from an operating part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a digital copying machine, a digital multifunction peripheral, a facsimile machine, a laser printer and the like.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a laser printer, dust of a polyhedral rotating reflecting mirror (polygon mirror) and a reflecting mirror (BD mirror) for detecting a horizontal synchronizing signal, which are caused by long-term use. It was not possible to know a decrease in the amount of laser light due to contamination due to laser light or deterioration of the laser diode (LD) itself until a horizontal synchronization signal detection error occurred.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 8-258330, when the value of the light intensity of the laser beam for image exposure decreases to a predetermined level which does not lead to a horizontal synchronization detection error, the user is required to make an earlier decision. A warning has been proposed to perform a maintenance of the optical system so that an unusable state due to a horizontal synchronization signal detection error can be appropriately avoided.

[0004]

However, when the value of the light intensity of the laser beam decreases and reaches a level immediately before a horizontal synchronization detection error, the user must use the apparatus for maintenance of the optical system. Suspend, replace LD,
It is still necessary to clean the BD mirror. That is, there is a problem in that a warning is issued without fully (maximally) utilizing the life characteristics of the LD and the output characteristics of the photosensor of the detection means for detecting the horizontal synchronization signal.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to make full use of the output characteristics of a photosensor as a detecting means for detecting a horizontal synchronizing signal due to a change in light intensity of laser light. With the goal.

[0006]

In order to achieve the above object, the present invention provides a laser light generating means (laser diode) as a light source for image exposure, and a polyhedral rotary reflecting mirror emitted from the laser light generating means. In an image forming apparatus having a detection means for detecting a horizontal synchronization signal for detecting a laser beam scanned by a (polygon mirror), a circuit constant changing means for changing a circuit constant in the detection means for detecting a horizontal synchronization signal is provided. Things.

The circuit constant changing means may be a means for changing the circuit constant by a control signal inside the image forming apparatus, or a means for changing the circuit constant by an operation signal from an operation unit.

According to the image forming apparatus of the present invention, since the circuit constant (gain resistance value) of the detecting means for detecting the horizontal synchronizing signal can be changed, the detecting means for detecting the horizontal synchronizing signal based on the change in the light intensity of the laser beam. This makes it possible to make full use of the output characteristics of the photosensor, thereby reducing the frequency of maintenance.

By making the circuit constants changeable by a control signal inside the image forming apparatus (in this case, the changed contents of the circuit constants are incorporated in a control program or the like), the frequency of maintenance can be further reduced. it can. Alternatively, by allowing the circuit constant to be changed by an operation signal from the operation unit, it is possible to allow the user to change the circuit constant and determine the maintenance.

[0010]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 2 is a configuration diagram showing an example of a main part of a digital copying machine embodying the present invention.

The digital copying machine 1 includes a scanner unit (image reading unit) 2 for reading an image of a document (not shown), a signal processing unit 3 for performing various processes on the image data read by the image reading unit 2, A printer unit (image printing unit) 4 that prints (prints) image data output from the signal processing unit 3 on printing paper (not shown) is sequentially connected.

The scanner unit 2 includes a line light source 6 and a reflection mirror 7 which are elongated in the main scanning direction below the contact glass 5.
And a second scanning unit 11 composed of a pair of reflecting mirrors 9 and 10 movably supported in the sub-scanning direction so that the speed ratio becomes 2: 1. The system 12 and the CCD sensor 13 are sequentially arranged.

The signal processing unit 3 includes an amplifier 14 for amplifying image data (analog value) from the CCD sensor 13 of the scanner unit 2 and an A / D converter for converting the image data from the amplifier 14 from an analog value to a digital value. 15 and A
An image processing unit 16 that performs predetermined image processing on image data from the / D converter 15 and a buffer memory 17 that temporarily stores image data from the image processing unit 16 are provided.

The print control unit 18 controls the read start timing of the image data in the buffer memory 17 (light emission start timing of the laser diode 20), and outputs the read image data at that timing. And an LD modulator 19 for controlling the light emission of an LD (laser diode) based on the image data.

The printer section 4 reflects the light reflected by a polygon mirror 23 rotatable in the main scanning direction via a collimator lens 21 and a cylindrical lens 22 onto an emission optical path of an LD 20 connected to an LD modulation section 19 of the signal processing section 3. The surface of the photosensitive drum 26 is rotatable in the sub-scanning direction via an fθ lens 24 and a reflection mirror 25 on the main scanning optical path of the polygon mirror 23.

In the printer section 4, the laser light scanned by the polygon mirror 23 is
A synchronization detector 27 (detection means for detecting a horizontal synchronization signal) composed of a photo sensor or the like described below at a position immediately before the light enters the light source 6.
The output terminal of the synchronization detector 27 is connected to the print control unit 18 of the signal processing unit 3 by feedback.

In the digital copying machine 1 constructed as described above, the image data of the document read by the scanner unit 2 is printed out on a printing paper by the printer unit 4, and in this process, the image data is subjected to signal processing. The input speed (reading speed) of the scanner unit 2 and the output speed of the printer unit 4 are temporarily stored in the unit 3 to arbitrate.

More specifically, in the digital copying machine 1, when an image of a document is copied onto printing paper, the scanner unit 2 scans the image of the document placed on the contact glass 5 with the first and second scanning units. The scanning is performed by reading in the sub-scanning direction by 8 and 11, and the CCD sensor 13 is controlled by the imaging optical system 12.
The CCD sensor 13 outputs dot matrix image data to the signal processing unit 3 line by line as main scanning lines that are continuous in the sub-scanning direction.

At this time, the CCD sensor 13 outputs one line of image data one pixel at a time in the main scanning direction at a predetermined image clock after resetting the address by the line synchronization signal LSYNC. 1, line by line is output to the signal processing unit 3 at a predetermined line synchronization caused by the scanning speed of the second scanning units 8, 11 and the reading cycle of the CCD sensor 13.

The signal processing unit 3 amplifies the image data input line by line by an amplifier 14 and converts the analog data into a digital value by an A / D converter 15. After performing various image processing such as double processing and editing processing, the image data is input to the buffer memory 17. Then, since the print control unit 18 outputs a timing control signal to the buffer memory 17 as described later, the image data in the buffer memory 17 is read according to the timing control signal, and is input to the print control unit 18.

When image data is input, the print control unit 18 performs various processes such as range limitation and pattern synthesis, and outputs the image data to the LD modulation unit 19. Reference numeral 19 outputs a drive current modulated in accordance with the image data to the LD 20 of the printer unit 4.

The printer unit 4 converges outgoing light of the LD 20 driven in accordance with image data by various lenses 21 and 22 and deflects and scans the light by the polygon mirror 23. The scanning light is corrected by the fθ lens 24. An image is formed on the surface to be scanned of the photosensitive drum 26 that moves in the sub-scanning direction. As a result, an electrostatic latent image of a dot matrix is formed on the scanned surface of the photosensitive drum 26. The latent image is developed with toner (not shown) and transferred to a printing paper, thereby performing image printing.

Here, in the printer section 4, since the main scanning light from the polygon mirror 23 is incident on the synchronization detector 27 before being incident on the photosensitive drum 26, the synchronization detector 27 receives the synchronization detection signal ( The print control unit 18 of the signal processing unit 3 outputs a timing control signal to the buffer memory 17 in synchronization with the input (detection) of the synchronization detection signal. As a result, the image data temporarily stored in the buffer memory 17 is sequentially read at an appropriate timing for the print output of the printer unit 4.

FIG. 3 is a block diagram showing a configuration example of a control system of the entire digital copying machine. The control unit of the digital copying machine stores a scanner drive control unit 31 for driving and controlling each unit of the scanner unit 2, a printer drive control unit 32 for driving and controlling each unit of the printer unit 4, and various data. It comprises a memory section 33 and a main control section 34 using a microcomputer for controlling the entire digital copying machine.

The operation unit 35 displays the number of copies (prints),
It is provided with various keys for setting various conditions such as paper size and enlargement / reduction mode, clearing the set conditions, and instructing start / stop of operation. The scanner drive control unit 3
1, the printer drive control unit 32 and the memory unit 33 function as the signal processing unit 3 in FIG. Although not shown, the digital copying machine 1 of this embodiment is assumed to be equipped with an automatic document feeder (ADF).

In this digital copying machine 1, when a desired number of copies of a plurality of originals are to be copied, the plurality of originals are set on the ADF platen first, and the desired number of copies are input by operating the keys on the operation unit 35. After that, when the start key is pressed, the main control unit 34 outputs a command signal to the scanner drive control unit 31 to feed only one document on the document table of the ADF onto the contact glass 5.

Then, the image of the document is read by the scanner unit 2, the image data is stored in the memory unit 33 (buffer memory 17), and the read document is discharged to a discharge tray (not shown). The scanner unit 2 is temporarily stopped. Next, an instruction signal is output to the printer drive control unit 32 to cause the printer unit 4 to start a printing operation. Thereafter, by repeating this series of operations, the set number of copies are made for each original set on the original platen.

FIG. 1 is a circuit diagram showing a configuration example of the synchronization detector 27. In the synchronization detector 27, reference numeral 40 (portion surrounded by a broken line) denotes a general-purpose photo IC, which includes an input terminal 42, a power supply terminal 43, a gain resistance terminal 44, and an output terminal 4.
5 and a ground terminal 46. A variable resistor 41 as a circuit constant changing means is externally connected between the power supply terminal 43 and the gain resistor terminal 44, and its gain resistance value Ro (a circuit constant that affects the state of the output signal Vo of the photo IC 40). Can be changed.

A power supply voltage Vcc is applied to the power supply terminal 43, and a ground terminal 46 is connected to the ground. Photo I
A photosensor (photodiode) 4 is provided in C40.
7, current amplifier 48, comparison amplifier (Schmitt circuit) 4
9 and a resistor 50 are provided.
Is connected to the input terminal 42 and the input terminal of the current amplifier 48, and its cathode is connected to the power supply terminal 43.

The output terminal of the current amplifier 48 is connected to the gain resistance terminal 44 and the non-inverting input terminal (+) of the comparison amplifier 49. The reference voltage Vref is applied to the inverting input terminal (-) of the comparison amplifier 49, and an output signal Vo having a waveform as shown in FIG. A resistor 50 (resistance value 10) is provided between the output terminal 45 and the power supply terminal 43.
kΩ).

In the synchronous detector 27 configured as described above, when a laser beam is incident on the photo sensor 47 of the photo IC 40, a current corresponding to the incident light intensity Pi flows through the current amplifier 48, and the current value becomes The corresponding voltage is input to the non-inverting input terminal (+) of the comparison amplifier 49. Comparison amplifier 4
Reference numeral 9 compares the voltage with a reference voltage Vref input to the inverting input terminal (-), and outputs a pulse-like output signal Vo corresponding to the comparison result.

Here, when the incident light intensity Pi of the laser light on the photosensor 47 becomes high (incident light amount increases), the current flowing through the current amplifier 48 increases and the input voltage of the comparison amplifier 49 increases, so that the output Output signal V from terminal 45
The width o (low-level period) To increases. Conversely, when the incident light intensity Pi of the laser light on the photosensor 47 decreases (the incident light amount decreases), the current flowing through the current amplifier 48 decreases, and the input voltage of the comparison amplifier 49 decreases. The width To narrows.

On the other hand, when the gain resistance Ro of the variable resistor 41 decreases, the current flowing therethrough increases and the comparison amplifier 4
9, the width To of the output signal Vo increases. Conversely, when the gain resistance Ro of the variable resistor 41 increases, the current flowing therethrough decreases, and the input voltage of the comparison amplifier 49 decreases, so that the width To of the output signal Vo decreases.

Generally, the photo I of the synchronous detector
A fixed resistor is connected outside C, and the gain resistance value Ro is uniquely determined in accordance with the incident light intensity Pi of various laser beams so that the width To of the output signal Vo can be obtained under optimum conditions. (See the example of the Ro-Pi curve in FIG. 4).
That is, the fixed resistor is replaced each time depending on the type of the image forming apparatus.

However, as shown in FIG. 1, by connecting the variable resistor 41 to the photo IC 40 of the synchronization detector 27, the gain resistance value Ro can be freely changed with respect to the variation of the incident light intensity Pi of the laser beam. This makes it possible to make full use of the output characteristics of the photo IC 40 (photo sensor 47) due to the change in the light intensity of the laser light, thereby reducing the frequency of maintenance. Along with this, it becomes possible to cope with the incident light intensity of the laser light which differs depending on the type of the digital copying machine (image forming apparatus), and the work of replacing an external fixed resistor (gain resistor) is also omitted.

The gain resistance value Ro of the variable resistor 41
Can be changed by providing a volume switch or the like in the synchronization detector 27, but the change can be made by using other means such as a dip switch.

FIG. 5 is a diagram showing an example of the configuration of the synchronization detector 27 shown in FIG. 1 and means for changing the gain resistance value Ro (circuit constant) of the variable resistor 41 which is the circuit constant changing means. . In this example, the gain resistance value R of the variable resistor 41 is
o can be changed by a control signal (electric switch) inside the digital copying machine.

In this example, the width T of the output signal Vo with respect to the change in the intensity Pi of the laser light incident on the photosensor 47 is shown.
The corresponding data of o is stored in the memory (ROM or EEPROM) 54 in advance as a conversion table shown in Table 1. Further, the output signal Vo of the photo IC 40 is supplied to a C / C converter via a peak hold circuit (PH) 51 and an A / D converter 52.
Since the input signal is input to the PU 53, the CPU 53 stores the output signal Vo in an internal memory as data for a certain incident light.

The CPU 53 determines a gain resistance value R at which an output signal Vo having an optimum width To can be obtained based on these data.
is obtained, the gain resistance Ro is given to the selector 55 connected to the variable resistor 41 of the synchronization detector 27, and the output thereof uniquely determines the gain resistance Ro of the variable resistor 41.

For example, the photo IC 40 of the synchronization detector 27
When it is desired to set the width To of the output signal Vo to 300 (ns), the incident light intensity P of the laser light to the photosensor 47 is
i can be any value as long as Pi = 2.0 (mW) from the conversion table of Table 1. When Pi is 2.0 (mW), the gain resistance value Ro is approximately 1.4 kΩ from the example of FIG.
Becomes This value is transferred by the CPU 53 to the selector 55 connected to the variable resistor 41 of the synchronization detector 27, and the output thereof controls the gain resistor Ro of the variable resistor 41 to be changed to 1.4 kΩ.

[0041]

[Table 1]

As described above, if the means for changing the circuit constant (gain resistance value Ro of the variable resistor 41) in the synchronization detector 27 is incorporated in hardware and software, the frequency of maintenance can be further reduced. Becomes It is generally known that the relationship between the incident light intensity Pi and the gain resistance Ro is not limited to the Ro-Pi curve as shown in FIG.

Since the control board on which the CPU 53 and the memory 54 are mounted and the synchronization detector 27 are generally connected by a harness wire or the like via a connector in many cases, the selector 55 is connected to the synchronization detector 27 or the CPU.
Although it will be mounted on any of the control boards including 53, it may be provided on either side for convenience of use.

FIG. 6 is a diagram showing another configuration example of the synchronization detector 27 shown in FIG. 1 and a means for changing the gain resistance value Ro (circuit constant) of the variable resistor 41 which is a circuit constant changing means thereof. The same reference numerals are given to portions corresponding to FIG. In this example, the gain resistance Ro of the variable resistor 41 is
Can be changed by an operation signal from the operation unit 35.

Also in this example, the data corresponding to the width To of the output signal Vo with respect to the change in the incident light intensity Pi of the laser light is shown in Table 1.
Is stored in the memory 54 in advance as a conversion table shown in FIG. The output signal Vo of the photo IC 40 is supplied to the CPU 53 via the peak hold circuit 51 and the A / D converter 52.
The CPU 53 stores the output signal Vo in the internal memory as data for a certain incident light in the internal memory, and then outputs the information calculated based on the contents of the conversion table in the memory 54 and the characteristics of FIG. Display on the display.

Accordingly, the user (user) can input an arbitrary value as the gain resistance value Ro using the numeric keypad of the operation unit 35 while viewing these displayed contents.
When the input is made, the control unit of the operation unit 35 outputs a signal (operation signal) indicating the input value, and sets (changes) the gain resistance value Ro of the variable resistor 41 to the input value. When the user is allowed to set the gain resistance value Ro, it is preferable to provide a plurality of keys with options for executing the setting, canceling the setting, and the like.

As described above, the circuit constant (the gain resistance value Ro of the variable resistor 41) of the synchronization detector 27 is changed by the operation unit 35.
By making the change in response to an operation signal from the user, the change of the circuit constant and the judgment on the maintenance can be left to the user. Although the embodiment in which the present invention is applied to a digital copying machine has been described above, the present invention is not limited to this, but is also applicable to other electrophotographic image forming apparatuses such as a digital multifunction peripheral, a facsimile machine, and a laser printer. What you get.

[0048]

As described above, according to the image forming apparatus of the present invention, the photo sensor (photo I) of the detecting means for detecting the horizontal synchronizing signal based on the change in the light intensity of the laser beam.
The output characteristics of C) can be fully utilized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of a synchronization detector 27 of FIG.

FIG. 2 is a configuration diagram showing an example of a main part of a digital copying machine embodying the present invention.

FIG. 3 is a block diagram illustrating a configuration example of a control system of the entire digital copying machine illustrated in FIG. 2;

FIG. 4 is a diagram showing a relationship between an incident light intensity Pi of laser light to the photo sensor 47 of FIG. 1 and a gain resistance value Ro (circuit constant) of a variable resistor 41;

FIG. 5 is a diagram showing a configuration example of a means for changing a gain resistance value Ro of a synchronous detector 27 and a variable resistor 41 shown in FIG. 1;

FIG. 6 is a diagram showing another configuration example of the means for changing the gain resistance value Ro of the synchronous detector 27 and the variable resistor 41 thereof.

[Explanation of symbols]

 1: Digital copier 2: Scanner unit 3: Signal processing unit 4: Printer unit 18: Print control unit 19: LD modulation unit 20: LD 23: Polygon mirror 26: Photoconductor drum 27: Synchronous detector 31: Scanner drive control Unit 32: Printer drive control unit 33: Memory unit 34: Main control unit 35: Operation unit 40: Photo IC 41: Variable resistor 42: Input terminal 43: Power supply terminal 44: Gain resistance terminal 45: Output terminal 46: Ground terminal 47 : Photo sensor 48: Current amplifier 49: Comparison amplifier 50: Resistance 51: Peak hold circuit 52: A / D converter 53: CPU 54: Memory 55: Selector

Claims (3)

[Claims] 1. A laser light generating means as a light source for image exposure, and a detecting means for detecting a horizontal synchronizing signal for detecting a laser light emitted from the laser light generating means and scanned by a polygon mirror. An image forming apparatus, comprising: a circuit constant changing unit that changes a circuit constant in the detecting unit for detecting the horizontal synchronization signal. 2. The image forming apparatus according to claim 1, wherein
An image forming apparatus according to claim 1, wherein said circuit constant changing means is means for changing said circuit constant by a control signal inside said apparatus. 3. The image forming apparatus according to claim 1, wherein
The image forming apparatus according to claim 1, wherein the circuit constant changing unit changes the circuit constant according to an operation signal from an operation unit.