JP2000111817A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect defects of plural lasers at low cost by generating a horizontal synchronizing signal error signal if horizontal synchronizing signals as many as the plural lasers are not counted within a horizontal signal permissible range. SOLUTION: A video controller 102 transmits a VDO signal of image data of one line to a laser driving circuit 104 in synchronism with a BDO signal. A laser driving circuit 104 turns on and off a laser diode 105 according to the VDO signal to form an electrostatic latent image on a photosensitive drum. In an engine controller 103, a BD signal counting means 112 is provided and counts the pulses of the BD signal sent from an optical sensor 111. The engine controller 103 counts the pulses of the BD signal inputted within a BD permissible range to make the horizontal synchronizing signal ready when two BD signals are inputted within the BD permissible range and generates a horizontal synchronizing signal error when only one BD signal is inputted within the BD permissible range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error detection of a horizontal synchronizing signal in an image forming apparatus using a multi-beam laser as a light source for image exposure.

[0002]

2. Description of the Related Art Conventionally, a laser printer has been known as this type of image forming apparatus.

An explanation will be given of error detection of a horizontal synchronizing signal when a single beam laser is used as a light source for image exposure.

In FIG. 2, reference numeral 202 denotes a video controller, which converts image data from a host computer 201 into a video signal (VDO) for driving a laser, and transmits the video signal to a laser driving circuit 204. The laser drive circuit 204 is controlled by the engine controller 203. The laser drive circuit 204 turns on / off the laser diode 205 in response to the video signal, and irradiates the polygon mirror on the scanner motor 206 with laser light. The polygon mirror reflects the laser beam while rotating, and scans in the horizontal direction at a constant speed. Laser light is fθ lens 207
, Is reflected by the turning mirror 208, is irradiated on the photosensitive drum 209, and an electrostatic latent image is formed on the surface of the photosensitive drum 209. An optical sensor 211 is disposed in a non-image area where the reflected light of the laser does not hit the photosensitive drum, and the laser light is reflected and folded by the reflecting mirror 210,
When input to the optical sensor 211, the horizontal synchronizing signal BD
A (Beam Detect) signal is output and transmitted to the engine controller 203.

The engine controller 203 shapes the waveform of the BD signal, generates a BDO (BD Out) signal, and transmits the signal to the video controller 202.

The video controller transmits a VDO signal of one line of image data to the laser drive circuit 204 in synchronization with the BDO signal.

[0007] The laser drive circuit 204 turns on and off the laser diode in response to the VDO signal, and forms an electrostatic latent image on the photosensitive drum.

This situation will be described with reference to FIG.

In FIG. 3, LON is a signal for controlling the laser drive circuit 204 by the engine controller 203, and is a signal for forcibly emitting the laser diode at the L (Low) level.

The ENB signal is output from the engine controller 20
3 is a signal that is generated and output to the laser drive circuit 204, and a signal that permits turning on and off the laser diode based on the VDO signal sent from the video controller 202 to the laser drive circuit 204.
Permission is given at the OW level, indicating that this period is an image area. Also, a non-image area is shown at the H (High) level. The logic circuit for this is a laser drive circuit 20.
4 is incorporated. The laser drive circuit 204
When the ON signal is at the LOW level and when the ENB signal is at the LOW level
The laser diode emits light when the level and the DATA signal are at the LOW level.

The engine controller 203 first sets B
In order to detect the D signal, the LON signal is set to the LOW level to cause laser emission. (T1) BD is detected (t
2), the engine controller 203 immediately generates a BDO signal and transmits it to the video controller 202. The video controller 202 transmits a VDO signal for one laser scan to the laser drive circuit 204 a predetermined time after the BD signal, or after ta in the example of FIG. Engine controller 2
03 sets the ENB signal to the LOW level at the timing (t4) of the image area, and permits laser emission by the VDO signal.

The laser drive circuit 204 turns on and off the laser diode based on the VDO signal, and
An electrostatic latent image is formed thereon.

Then, at a timing (t6) when the laser scanning position becomes a non-image area, the engine controller 203 sets the ENB signal to the HIGH level and inhibits laser emission by the VDO signal.

Next, the engine controller 203 sets the LON signal to the LOW level to detect the next BD signal, causes the laser to emit light (t1 '), and detects the next BD (t2'). Repeat.

In this manner, the BD is detected for each line, the image data for one line is transmitted to the laser drive circuit 204 in synchronization with the BD signal, and the laser diode is turned on / off based on the signal. By repeating the operation described above, an image of a print sheet as shown in FIG. 3, that is, an image of a vertical line in this description is formed.

During such a series of image forming operations,
If a BD signal is generated at an erroneous timing due to extraneous noise, or if a BD signal is not generated due to a trouble such as a laser failure, a printed image will be a defective image. Therefore, the engine controller 203
It is necessary to detect whether the signal is always generated at a regular timing.

Conventionally, as shown in FIG. 4, an allowable range of a BD signal is set, and if a BD signal is generated within the allowable range of the BD, the normal print operation is continued as BDRDY (BD ready), and the BD If no BD signal is generated within the range, or if a BD signal is generated outside the allowable BD range, a BDERR (BD error) is set, and the engine controller 203 restarts the printing operation from the beginning or, in some cases, fails. Or inform the user.

The description so far has dealt with the case where there is one laser diode for image exposure.

Recently, there has been an increasing demand for a higher printing speed of a printer and a higher resolution of a printed image. Therefore, as a light source for image exposure, for example, a multi-beam comprising two or four laser diodes is used. A laser may be used.

When such a multi-beam laser is used, a VDO signal must be output at the same timing for each laser, so a BD signal is required for each laser. Although it is conceivable to provide an optical sensor for each laser, it is often the case that one optical sensor generates BD signals of a plurality of lasers for cost reduction.

In this case, a plurality of BD signals are transmitted to the engine controller 203 through one signal line.

The printer having such a configuration also needs to detect BDERR.

An example of BDERR detection of a two-beam laser will be described below.

As shown in FIG. 5, a BD allowable range is set so as to straddle both of the two BD signals, and B is set within the BD allowable range.
BDRDY is set when a D signal is generated, and BDERR is set when a BD signal is not generated within the BD allowable range or when a BD signal is generated outside the BD allowable range.

Alternatively, as shown in FIG.
In some cases, a BD allowable range corresponding to each signal is provided.

[0026]

However, in the example of the prior art shown in FIG. 5, if either one of the BD signals is not detected even if one of the BD signals is not detected, BDRDY and As a result, since a BD is not actually output, there is a problem that a defective image cannot be detected. Further, in the example shown in FIG. 6, since the BD allowable range is set for each laser, the number of circuits for setting the BD allowable range is increased, which causes a problem that the cost is increased.

An object of the present invention is to provide an image forming apparatus capable of detecting a defect of each of a plurality of lasers at low cost.

[0028]

According to the present invention, there is provided an image forming apparatus comprising: a plurality of laser emission sources as image exposure light sources;
Means for modulating laser light emitted from the plurality of laser light sources in accordance with an image signal; optical scanning means for causing the plurality of laser lights to scan the image carrier; and disposing in a non-image area on the laser light scanning path. A light scanning position detecting means for sequentially outputting a horizontal synchronizing signal for detecting a horizontal image writing timing when each of the plurality of laser beams scans with a time difference, and from the light scanning position detecting means. The same number of horizontal synchronization signals as the number of the laser
Means for generating a signal indicating one horizontal synchronizing signal allowable range including a time at which the plurality of lasers are expected to scan the optical scanning position detecting means; Horizontal synchronization signal counting means for counting the number of signals; and means for generating a horizontal synchronization signal error signal when the same number of horizontal synchronization signals as the plurality of lasers are not counted within the horizontal synchronization signal allowable range. It is characterized by the following.

Further, the image forming apparatus according to the present invention comprises a plurality of laser light sources as image light sources, means for modulating laser light emitted from the plurality of laser light sources according to image signals, Light scanning means for scanning the image carrier with laser light, and a non-image area on the laser light scanning path for detecting a horizontal image writing timing when each of the plurality of laser lights scans with a time difference. An optical scanning position detecting means for sequentially outputting horizontal synchronizing signals, and transmitting the same number of horizontal synchronizing signals as the laser light emitting sources output from the optical scanning position detecting means through one signal line. Means for generating a signal representing one horizontal synchronizing signal allowable range including a time at which the plurality of lasers are expected to scan the optical scanning position detecting means; When the signal allowable range starts, the operation of turning on the lighting signal of a certain laser light source, turning off the lighting signal when the horizontal synchronization signal is detected, and turning on the lighting signal of the next laser light source starts. Are sequentially performed from the laser light source, and when this operation is not completed for all of the plurality of laser light sources until the horizontal synchronization signal allowable range ends, the horizontal position of the laser light source whose corresponding lighting signal is on is turned on. Means for generating a synchronization signal error signal.

Further, according to the image forming apparatus of the present invention, in the above-mentioned image forming apparatus, any one of the horizontal synchronizing signals is used.
Control means for controlling the light scanning means using one cycle, and when the horizontal synchronization signal error signal is that of the horizontal synchronization signal used by the control means, the corresponding laser emission source is synchronized with the horizontal synchronization signal. Means for forcibly emitting light until a signal cycle can be measured, and if not, means for not forcing any of the plurality of laser emission sources to emit light.

[0031]

[First Embodiment] FIG. 1 is a diagram showing an image forming apparatus according to a first embodiment of the present invention. In FIG. 1, reference numeral 102 denotes a video controller which transmits image data from a host computer 101. The signal is converted into a video signal (VDO) for laser driving and transmitted to the laser driving circuit 104. The laser drive circuit 104 is controlled by the engine controller 103. The laser drive circuit 104 turns on / off the laser diode 105 in response to the video signal, and irradiates the polygon mirror on the scanner motor 106 with laser light. The laser diode 1
Reference numeral 05 denotes a two-beam laser. The polygon mirror reflects the laser beam while rotating, and scans in the horizontal direction at a constant speed. The laser beam passes through the fθ lens 107,
The photosensitive drum 1 is reflected by the folding mirror 108 and
9, an electrostatic latent image is formed on the surface of the photosensitive drum 109. An optical sensor 111 is arranged in a non-image area where the reflected light of the laser does not hit the photosensitive drum 109, and the laser light is reflected and folded by the reflecting mirror 110,
When input to the optical sensor 111, a BD which is a horizontal synchronizing signal
A (Beam Detect) signal is output and transmitted to the engine controller 103.

The engine controller 103 shapes the waveform of the BD signal, generates a BDO (BD Out) signal, and transmits the signal to the video controller 102.

The video controller 102 transmits a VDO signal of one line of image data to the laser drive circuit 104 in synchronization with the BDO signal.

The laser drive circuit turns on and off the laser diode 105 in response to the VDO signal, and forms an electrostatic latent image on the photosensitive drum.

The engine controller 103 includes a BD
The signal counting means 112 has a function of counting the number of pulses of the BD signal transmitted from the optical sensor 111.

The engine controller 103 counts the number of pulses of the BD signal input within the BD allowable range, and when two BD signals are input within the BD allowable range as shown in FIG. As shown on the right side of FIG. 8, when only one BD signal is input within the BD allowable range, the BDERR is set.

The operation of the engine controller 103 is shown in the flowchart of FIG.

Referring to FIG. 9, in step S901,
Wait until the BD tolerance is reached. If it is within the BD allowable range, the process exits the loop of step S901 and returns to step S90.
Proceeding to 2, the BD signal counting means 112 starts counting the BD signal. In step S903, it is determined whether or not the count value of the BD signal counting unit 112 is 2, and if so, the process proceeds to step S904; otherwise, the process proceeds to step S905. In step S904, the BDR
DY is generated. In step S905, it is still BD
It is determined whether it is within the allowable range, and if so, the process returns to step S903; otherwise, the process proceeds to step S906.
To generate a BDERR.

As described above, according to the present embodiment, in a laser printer for transmitting two BD signals through one signal line, the BD configuration of the two BD signals is simple.
ERR detection can be performed.

[Second Embodiment] A second embodiment will be described with reference to the timing chart of FIG. 10 and the flowchart of FIG.

In FIG. 10, LON1 is a forced light emission signal of the laser diode (hereinafter referred to as LD1) which is scanned first in the main scanning direction among the two laser diodes.
LON2 is the laser diode (L
D2).

The engine controller 103 sets LON1 to LOW level in order to detect BD1 which is a horizontal synchronization signal of LD1 (t101).

After a predetermined time (t103) since BD1 is detected (t102), LON1 is set to HIGH level to turn off LD1, and LON2 is set to LOW level to turn on LD2.

After a predetermined time (t105) since BD2 is detected (t104), LON2 is set to the HIGH level and LD2 is turned off.

Hereinafter, this operation is repeated.

In this embodiment, first, the LD 1 is turned on,
LD1 is turned off when D1 is detected, then LD2 is turned on, and BD2 is detected.
Therefore, when a BDERR occurs, the B
It becomes possible to detect whether it is DERR.

This will be described with reference to FIGS.

In FIG. 12, at the end of the BD allowable range (t12
6 '), a BDERR occurs, and at this time, LON1
W level.

This is because, since BD1 cannot be detected, LO
This is because N1 cannot be turned off. Therefore, it is understood that this BDERR is the BDERR of BD1.

In FIG. 13, when BDERR occurs (t
136 '), LON2 is at the LOW level. This is because LON2 cannot be turned off because BD2 cannot be detected. Therefore, this BDERR
Is the BDERR of BD2.

Therefore, in this embodiment, the BDERR
Depending on which of LON1 and LON2 was on at the time of occurrence, it is the error of BD1 of LD1 or the BD of LD2.
2 can be determined.

By extending this embodiment,
It is possible to cope with a case where the laser diode 105 has three or more beam lasers.

The operation of the engine controller 103 in the second embodiment is shown in the flowchart of FIG. FIG.
Referring to FIG. 1, in step S1101, the process waits until the BD allowable range is reached.
Proceeding to 02, LON1 is turned on (LOW). Next, the process proceeds to step S1104, where it is determined whether or not a BD signal is present. If so, the process proceeds to step S1105; otherwise, the process proceeds to step S1110. Step S1
At 110, it is determined whether the BD is still within the allowable range,
If so, the process returns to step S1104; otherwise, the process proceeds to step S1112.

In step S1105, LON1 is turned off (HIGH). In the next step S1106, LON1 is turned off.
N2 is turned on (LOW). Next, step S1107
It is determined whether a BD signal is coming or not, and if so, the process proceeds to step S1108; otherwise, the process proceeds to step S1111. BD is still in step 1111
It is determined whether it is within the allowable range, and if so, the process returns to step S1107;
Proceed to.

In step S1108, LON2 is turned off (HIGH).
Generate DRDY.

In step S1112, a BDERR is generated. In the next step S1113, it is determined whether or not LON1 is ON (LOW). If so, the flow advances to step S1114 to generate a BDERR of BD1,
Otherwise, the process proceeds to step S1115 and the BD of BD2
Generate ERR.

[Embodiment 3] FIG. 14 and FIG.
This will be described with reference to the timing chart of FIG. 5 and the flowchart of FIG.

Scanner motor 106 for scanning laser light
In some cases, the cycle of the BD signal is used for the rotation control of. In other words, the BD cycle is measured, and the number of revolutions of the scanner motor 106 is detected from the cycle, and control is performed to adjust the BD cycle to a predetermined cycle so that the number of revolutions of the scanner motor becomes a constant speed. When performing such control,
When the BDERR occurs, the BD cycle cannot be measured, and the rotation of the scanner motor cannot be controlled.

Therefore, when the BDERR occurs, the laser is normally forcibly emitted even when the laser scanning position enters the image area, and the operation of detecting the BD cycle is usually performed.

When a two-beam laser is used as a light source for image exposure and two BD signals BD1 and BD2 are detected, one of BD1 and BD2 may be used for BD cycle measurement.

In this embodiment, the BD 1 is used for controlling the rotation of the scanner motor.

FIG. 14 shows the operation of the second embodiment.
6 is a timing chart for explaining the subsequent operation when it is detected that BDER is detected.

In FIG. 14, when BDERR occurs (t1
406), LON1 is ON.

Therefore, it can be seen that the BDERR of BD1. Since BD1 is used for controlling the rotation of the scanner motor, if the period of BD1 is not known, the rotation of the scanner motor cannot be controlled.

Therefore, even after the occurrence of the BDERR, LON1 is kept at the LOW level, that is, LD1 is kept emitting light.
The light emission of LD1 is continued until two signals are detected in total and the cycle of BD1 can be measured. During this time, the light emission of the LD 1 is continued also in the image area (t1408 to t1409).

Next, FIG. 15 is a timing chart for explaining the subsequent operation when it is detected that BD2 is BDERR by the operation of the second embodiment.

In FIG. 15, when BDERR occurs (t1
506), LON2 is ON.

Therefore, it is understood that the BDERR of BD2. BD2 is not used for controlling the rotation of the scanner motor. Therefore, even if the period of BD2 is not known,
There is no problem in controlling the rotation of the scanner. Therefore, even if BDERR occurs, LON2
Is turned off immediately (t1507) so that the image area is not irradiated with laser light.

FIG. 16 is a flowchart showing the above description.

Referring to FIG. 16, step S1601
If the BDERR has not occurred in the loop of, the process waits.
Proceed to step S1602. In step S1602,
It is determined whether or not LON1 is ON (LOW). If so, the process proceeds to step S1603; otherwise, the process proceeds to step S1608.

In step S1603, the BD1 of BD1 is
Generate RR. In the next loop of step S1604, the process waits until BD1 is detected. If BD1 is detected, the process proceeds to step S1605, and waits until BD1 is further detected in the loop of step S1605. If BD1 is detected, the process proceeds to step S1601, and the period of BD1 is measured from the time interval between BD1 detected in step 1604 and BD1 detected in step 1605. Next step S
At 1607, LON1 is turned off (HIGH).

In step S1608, the BDER of BD2 is
Generate R. In the next S1609, LON2 is turned off (HIGH).

According to the present embodiment, when BDERR occurs,
The BD cycle measurement mode is set only when the BD signal of the BD signal used for the rotation control of the scanner is used, so that only the minimum necessary laser emission is required, and unnecessary laser emission can be prevented. .

[0074]

As described above, according to the present invention, a plurality of horizontal synchronizing signals are transmitted by a single signal line using a plurality of laser diodes as a light source for image exposure. Synchronous signal error detection can be performed in only one horizontal synchronous signal allowable range,
Circuits for setting the allowable range can be minimized.

When the horizontal synchronizing signal is used for controlling the rotation of the scanner motor, unnecessary emission of the laser diode can be prevented when an error occurs in the horizontal synchronizing signal.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of an image forming apparatus according to a conventional example.

FIG. 3 is a timing chart illustrating an operation of the image forming apparatus of FIG. 2;

FIG. 4 is a timing chart illustrating the operation of the image forming apparatus of FIG. 2;

FIG. 5 is a timing chart illustrating an operation when the image forming apparatus in FIG. 2 is a multi-beam type.

FIG. 6 is a timing chart illustrating an operation when the image forming apparatus in FIG. 2 is a multi-beam type.

FIG. 7 is a timing chart illustrating Embodiment 1 according to the present invention.

FIG. 8 is a timing chart illustrating Embodiment 1 according to the present invention.

FIG. 9 is a flowchart illustrating Embodiment 1 according to the present invention.

FIG. 10 is a timing chart illustrating Embodiment 2 according to the present invention.

FIG. 11 is a flowchart illustrating a second embodiment according to the present invention.

FIG. 12 is a timing chart illustrating Embodiment 2 according to the present invention.

FIG. 13 is a timing chart illustrating Embodiment 2 according to the present invention.

FIG. 14 is a timing chart illustrating Embodiment 3 according to the present invention.

FIG. 15 is a timing chart illustrating Embodiment 3 according to the present invention.

FIG. 16 is a flowchart illustrating a second embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Host computer 102 Video controller 103 Engine controller 104 Laser drive circuit 105 2-beam laser diode 106 Scanner motor 107 fθ lens 108 Folding mirror 109 Photosensitive drum 110 Reflecting mirror 111 Optical sensor 112 Horizontal synchronization signal counting means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C362 AA74 BA56 BA69 BB31 BB33 BB34 EA04 EA07 2H027 DA07 DA41 DA50 DE02 ED04 ED07 EF09 2H045 AA01 AA52 CA88 CA97 5C072 AA03 BA20 CA06 HA02 HA06 HB08 HB11 UA20

Claims (3)

[Claims] 1. A plurality of laser light sources as image light sources, means for modulating laser light emitted from the plurality of laser light sources in accordance with an image signal, and an image carrier on the image carrier. An optical scanning means for scanning the laser light scanning path, and sequentially outputting a horizontal synchronization signal for detecting a horizontal image writing timing when each of the plurality of laser lights scans with a time difference. An optical scanning position detecting unit that transmits the same number of horizontal synchronization signals as the number of laser emission sources output from the optical scanning position detecting unit through one signal line, wherein the plurality of lasers are A means for generating a signal indicating one horizontal synchronizing signal allowable range including a time expected to scan the optical scanning position detecting means; and a horizontal synchronizing means for counting the number of the horizontal synchronizing signals. Image forming means for generating a horizontal synchronizing signal error signal when the same number of horizontal synchronizing signals as the plurality of lasers are not counted within the horizontal synchronizing signal allowable range. apparatus. 2. A plurality of laser light sources as light sources for image exposure, means for modulating laser light emitted from the plurality of laser light sources in accordance with an image signal, and an image carrier on the image carrier. An optical scanning means for scanning the laser light scanning path, and sequentially outputting a horizontal synchronization signal for detecting a horizontal image writing timing when each of the plurality of laser lights scans with a time difference. An optical scanning position detecting unit that transmits the same number of horizontal synchronization signals as the number of laser emission sources output from the optical scanning position detecting unit through one signal line, wherein the plurality of lasers are A means for generating a signal representing one horizontal synchronization signal allowable range including a time expected to scan the optical scanning position detection means; and The lighting signal of a certain laser light source is turned on, the light signal is turned off when the horizontal synchronization signal is detected, and the operation of turning on the lighting signal of the next laser light source is sequentially performed from the first laser light source. If this operation is not completed for all of the plurality of laser light sources until the horizontal synchronization signal allowable range ends, a horizontal synchronization signal error signal of the laser light source whose corresponding lighting signal is on is generated. And an image forming apparatus. 3. The image forming apparatus according to claim 2, wherein the control unit controls the optical scanning unit by using any one cycle of the horizontal synchronization signal, and the control unit controls the error of the horizontal synchronization signal. If the means is for a horizontal synchronization signal to be used, the corresponding laser emission source is forced to emit light until the cycle of the horizontal synchronization signal can be measured; otherwise, any one of the plurality of laser emission sources is used. An image forming apparatus further comprising means for not forcibly emitting light.